NBSIR 85-3193

AlllOb 034513

Preliminary Recommendations for

Maintenance of Factory Coated

Metal Siding and Roofing

Mary C. McKnight

Robert G. Mathey

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Materials Division

Gaithersburg, MD 20899

and

Richard W. Drisko

Naval Civil Engineering Laboratory

Port Hueneme, California 93043

June 1985

QC

100

U56

85-3193

1985

sponsored by:

\ir Force Engineering and Services Center

Tyndall Air Force Base, Florida 32403

NBSIR 85-3193

NATIONAL

AF STANDARD*

. LIBRARY &S-, — /U<gC

> Q. C ^

/OD

PRELIMINARY RECOMMENDATIONS FOR

MAINTENANCE OF FACTORY COATED

METAL SIDING AND ROOFING

Mary C. McKnight

Robert G. Mathey

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Materials Division

Gaithersburg, MD 20899

and

Richard W. Drisko

Naval Civil Engineering Laboratory

Port Hueneme, California 93043

June 1985

Sponsored by:

Air Force Engineering and Services Center

Tyndall Air Force Base, Florida 32403

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director

ABSTRACT

Recommendations and guidelines are presented for condition assessment and

maintenance of the exterior surfaces of factory coated metal siding and

roofing. The metal siding and roofing products commonly encountered on Air

Force installations are addressed. The types of deterioration of metal buildings and appropriate methods of repair and maintenance procedures are related

to the materials and construction practices used. The results of field

observations of the condition of many types of coatings on metal siding and

roofing in varying states of deterioration are reported.

A quantitative condition assessment procedure was developed for exterior

surfaces of metal buildings and consists of two parts. First, the condition

of the siding and roofing of the building is evaluated using inspection forms,

visual standards, and descriptions of levels of deterioration. In the second

part, recommended maintenance procedures are determined using the evaluation

data and analytical procedures which were developed. Visual standards and

detailed coating failure descriptions were developed in order to identify

and categorize the condition of the metal siding and roofing of buildings.

Preliminary repair and coating maintenance system recommendations were made

for frequently encountered problem conditions observed during inspections of

buildings with metal siding and roofing on Air Force bases. The preliminary

recommendations include those for surface preparation and selection of maintenance coatings. The recommendations were based on the types of existing

coatings and metal materials, their condition, and whether the selected

maintenance coatings are compatible with the existing coatings and selected

surface preparation procedures.

Keywords: coating; condition assessment; maintenance coatings; metal roofing;

metal siding; roofing; siding; surface preparation; visual

standards

.

iii
ACKNOWLEDGMENT

This report was sponsored by the Air Force Engineering and Services Center,

Tyndall Air Force Base, Florida. Technical coordination with the Air Force

Engineering and Services Center was provided by Mr. Jesse Neal whose

assistance and encouragement the authors gratefully acknowledge.

Special thanks are expressed to Mr. Jesse Neal and Mr. Harry R. Marien, Air

Force Engineering and Services Center, and Dr. Robert L. Alumbaugh, Naval Civil

Engineering Laboratory, for their many valuable comments and suggestions in

the planning of this study. Also, their assistance and recommendations in

conducting a field study to obtain information about the condition of metal

siding and roofing at Air Force bases are appreciated.

iv
TABLE OF CONTENTS

Page

ABSTRACT iii

ACKNOWLEDGMENT iv

LIST OF TABLES viii

LIST OF FIGURES ix

1. INTRODUCTION 1

1.1 BACKGROUND 1 1.2 OBJECTIVE AND SCOPE OF THE STUDY 1 1.3 SCOPE OF THIS REPORT 2 1.4 BENEFITS OF A SYSTEMATIC MAINTENANCE PROGRAM 3

2. METAL SIDING AND ROOFING MATERIALS COMMONLY ENCOUNTERED ON

AIR FORCE BASES 4

3. CONDITION OF METAL SIDING AND ROOFING OBSERVED IN THE FIELD 8

3.1 CONDITIONS REQUIRING REPAIR BEFORE RECOATING 8

3.2 CONDITIONS RELATED TO COATING PROTECTION 11

3.2.1 Metal Siding and Roofing without Maintenance Coatings 11

3.2.2 Metal Siding and Roofing Having Maintenance Coatings 15

4. DESIGN, CONSTRUCTION, AND MAINTENANCE PRACTICES AFFECTING COATING

DETERIORATION AND METAL CORROSION 24

4.1 BUILDING LOCATION 24

4.2 BUILDING DESIGN 24

4.3 SURFACE CONFIGURATION AND TEXTURE 25

4.4 SELECTION OF MATERIALS 25

5. CONDITION ASSESSMENT PROCEDURE 29

5.1 CONDITION EVALUATION 29

5.1.1 Initial Check-Off Inspection 29

5.1.2 Detailed Inspection 31

5. 1.2.1 Conditions Requiring Repair 31

5. 1.2.

2

Detailed Inspection of Conditions Related to

Coating Protection Problems 34

5. 1.2.

3

Characterization of Existing Coatings 37

5.2 ANALYSIS OF CONDITION EVALUATION INFORMATION 41

5.2.1 Information from Initial Check-Off Evaluation 41

v
TABLE OF CONTENTS (Continued)

Page

5.2.2 Information from Detailed Evaluation 41

5. 2 .2.1 Conditions Requiring Repair 41

5 .2 .2 .2 Conditions Related to Coating Deterioration 42

5 .2 .2 .3 Characterization of Existing Coating 43

5.3 SELECTION OF TYPE OF MAINTENANCE PROCEDURE 43

5.4 RECORD KEEPING 43

5.5 SUGGESTED CONDITION RATING PROCEDURE FOR EXTERIOR SURFACES OF

METAL BUILDINGS 45

6 . PRELIMINARY RECOMMENDED MAINTENANCE PROCEDURES 47

6.1 INSPECTION SCHEDULES 47

6.2 REPAIR PROCEDURES 48

6.2.1 Complete Replacement of Panels 48

6.2.2 Repair of Perforated or Severely Impact Damaged Panels 48

6 .2 .3 Repair of Leaks 48

6 .2 .4 Repair of Fasteners 48

6.2.5 Repair of Drainage Systems 49

6.3 MAINTENANCE COATING PROCEDURES 49

6.3.1 Coating Maintenance Systems for Metal Protected by

Galvanizing without an Organic Coating 49

6. 3. 1.1 Total Recoat 49

6. 3. 1.2 Spot Recoat 53

6.3.2 Coating Maintenance Systems for Steel Panels Protected

by Galvanizing and an Organic Maintenance Coating 53

6. 3. 2.1 Total Recoat 53

6 .3 .2 .2 Spot Recoat 53

6.3.3 Coating Maintenance Systems for Steel Panels Protected

by a Bituminous Coating 54

6. 3 .3.1 Total Recoat 54

6. 3. 3. 2 Spot Recoat 54

6.3.4 Coating Maintenance Systems for Steel Panels Protected

by Thin Organic Factory Coatings with or without a Maintenance Coating 55

vi
TABLE OF CONTENTS (Continued)

Page

6. 3 .4.1 Total Recoat 55

6.3 .4 .2 Spot Recoat 55

6.3.5 Maintenance Coating Systems for Buildings with Only

Surface Coating Deterioration 55

7 . SUMMARY 56

8 . REFERENCES 58

APPENDIX A. GLOSSARY OF TERMS A-l

APPENDIX B. VISUAL STANDARDS AND DESCRIPTIONS OF LEVELS OF DETERIORATION B-l

APPENDIX C. SURFACE PREPARATION AND MAINTENANCE COATING SYSTEMS C-l

C.l SURFACE PREPARATION C-l

C.2 MAINTENANCE COATING SYSTEMS C-2

C.3 REFERENCES C~3

vii
LIST OF TABLES

Page

Table 1. Metal Siding and Roofing Materials Commonly Encountered 5

Table 2. Systems of Maintenance Coatings Over Metal Siding and Roofing

and Observed Problems Associated with Each System 19

Table 3. List of Generally Acceptable and Poor Practices in Design,

Construction, and Maintenance of Siding and Roofing in Metal

Buildings 27

Table 4. Initial Check-Off Inspection, Inspection Form 1 32

Table 5. Detailed Inspection of Panels, Fasteners, and Drainage Systems,

Inspection Form 2 33

Table 6. Detailed Evaluation of Conditions Related to Coating Protection,

Inspection Forms 3 and 3A 35

Table 7. Illustration of Analysis Procedure 38

Table 8. Characterization of Existing Coating, Inspection Form 4 39

Table 9. Record Keeping Form 44

Table 10. Maintenance Coating Procedures for Steel Panels Protected by

Galvanizing and Non-bituminous Maintenance Coating 50

Table 11. Maintenance Coating Procedures for Steel Panels Protected with

Bituminous Factory Coating or Bituminous Maintenance Coating with

or without Non-bituminous Topcoat 51

Table 12. Maintenance Coating Procedures for Steel Panels Protected by

Thin Organic Factory Coatings with or without Non-bituminous

Maintenance Coating 52

viii
LIST OF FIGURES

Page

Figure 1 . Configurations of typical metal siding and roofing 7

Figure 2. Illustration of loss of metal at bottom edges of panels 9

Figure 3. Illustration of loss of metal at top edges of panels under

the eave 9

Figure 4. Illustration of corrosion of metal at laps 10

Figure 5. Bituminous mastic material used on roof to cover fasteners .. 10

Figure 6. Thick fibrated bituminous roof coatings 12

Figure 7. Impact damage of metal panels 12

Figure 8. Deterioration of drainage system 13

Figure 9. Corroded gutter hangers 13

Figure 10. Corroded fasteners with associated corrosion of the metal

panels 14

Figure 11. Loose fasteners 14

Figure 12. Corrosion of galvanized steel panels 16

Figure 13. Cracking of bituminous coating 16

Figure 14. Cracking of topcoated bituminous coating systems 17

Figure 15. Fibers of reinforcing fabric showing on surface of

deteriorated bituminous coating 17

Figure 16. Corrosion along factory formed bends of steel panels protected

by a thin organic coating 18

Figure 17. Corrosion of steel at edges of panels protected by a thin

organic coating 18

Figure 18. Peeling of alkyd coating from galvanized steel panels 2()

Figure 19. Red rust showing through aluminum pigmented bituminous

coating on steel roof panels 20

Figure 20. Severe cracking of bituminous roof coating 1

IX
LIST OF FIGURES (continued)

Page

Figure 21. Elatomeric roof coating about two years old, a piece had

been cut away to show the paint layers 21

Figure 22. Peeling of bituminous factory coating system recoated with

a mineral spirit solvent paint 23

Figure 23. Adhesion failure of maintenance coating to a thin organic

factory coating 23

Figure 24. Condition assessment procedure 30

Figure B.l. Visual standards for flat surface corrosion B-4

Figure B.2. Visual standards for edge corrosion at vertical and

horizontal laps and at the top and bottom of metal panels . . B-5

Figure B.3. Visual standards for bend corrosion B-6

Figure B.4. Visual standards for undercutting B-7

Figure B.5. Visual standards for peeling/blistering B-8

Figure B.6. Visual standards for cracking B-9

x
1. INTRODUCTION

1 .1 BACKGROUND

Since the early 1950's, the Air Force has built a large number of buildings

with factory coated sheet metal siding and roofing. Although exact figures

are not available, it is estimated by the Air Force Engineering and Services

Center that the surface area of the metal siding and roofing on these types of

buildings at Air Force Bases exceeds 400 million square feet. Annual maintenance cost for periodic corrosion control and aesthetic recoating of this

amount of metal siding and roofing is estimated to exceed $40 million. Current

Air Force directives and guidance do not directly address the problems associated

with metal roofing and siding. As a result, Air Force bases are using various

coating systems that often fail prematurely, inadequately protect the metal,

or are not aesthetically pleasing. The advancing age of many of the metal

buildings increases the severity of the problems encountered with these types

of buildings. Because of the problems experienced with metal buildings, the

Air Force requested that the National Bureau of Standards (NBS) develop guidelines for coating maintenance of metal siding and roofing. The Naval Civil

Engineering Laboratory (NCEL) was requested to provide technical assistance

and to prepare a manual for use by Air Force personnel in the field for the

maintenance of metal buildings. This report and other information resulting

from this investigation will be used as the basis for the manual.

Preliminary recommendations for coating maintenance of metal buildings given in

this report are intended for use by base level personnel for identification and

assessment of coating deficiencies, repair of metal siding and roofing, substrate

preparation prior to recoating, and selection of maintenance coatings that will

predictably protect the metal during the expected service life of the coating.

These preliminary recommendations are based on information from the literature,

coating manufacturers, metal building manufacturers, and the condition of

metal siding and roofing observed in the field. It is planned that the preliminary recommendations will be revised and interim criteria developed for

selection of maintenance coating systems upon completion of another phase of

this study which deals with laboratory and field evaluations of coating systems .

1 .2 OBJECTIVE AND SCOPE OF THE STUDY

The objective of this study is to assist the Air Force in developing criteria

for recoating metal siding and roofing on buildings at Air Force bases. The

research is divided into two phases. In Phase I, the objective is to develop

general field guidance for condition assessment and maintenance of the exterior

surfaces of metal siding and roofing. Laboratory and field tests will be

conducted in Phase II to evaluate potential maintenance coatings and surface

preparation techniques. This report describes the work completed in Phase I and includes preliminary recommendations and guidance for the maintenance <>t metal buildings. The preliminary recommendations address condition assessment

of metal siding and roofing, repair procedures, substrate preparation, arid

coating selection. The preliminary recommendations and guidance are limited r exterior metal siding, roofing, necessary fasteners, and drainage systems used

on industrial-type buildings.

1
The steps taken in carrying out Phase I included obtaining information from

personnel at Air Force bases regarding the condition of the metal buldings at

particular locations. Field surveys were conducted by NBS and NCEL personnel

to observe the condition of many different types of coatings on metal siding

and roofing in varying states of deterioration. Photographs were taken of

various types of coating failures and of different degrees of each type of

failure in order to develop a technical basis for preliminary visual standards.

Information was obtained from the literature, coating manufacturers, metal

building manufacturers, and building owners regarding condition assessment,

substrate preparation, and maintenance coating selection.

Visual standards and detailed coating failure descriptions will assist inspectors

in their attempts to identify and categorize the condition of the surfaces of

metal buildings or their components. The results of Phase I described in this

report will be used as the basis for a manual to be prepared by NCEL with the

assistance of NBS. The manual is intended to provide field personnel with a relatively simple but complete procedure for quantatively defining the conditions of painted exterior metal surfaces and then using the determined condition

to select the most economical and practical method of maintaining an acceptable

level of coating appearance and protection of the metal.

The objective of Phase II is to improve the preliminary guidelines by providing

the needed technical support data through laboratory and field tests. Laboratory and field test methods will be selected and candidate maintenance coating

systems along with application methods will be tested and evaluated. Surface

preparation techniques will also be evaluated taking into consideration the

type and condition of the substrate. To the extent feasible, factorial design

experiments will be carried out with the parameters being initial surface

condition, surface preparation techniques, coating materials, and application

methods

By using the results of the laboratory tests, the initial results of the field

tests, and the information in this report, interim criteria will be prepared.

These criteria will include procedures for assessing exterior surface conditions

of existing metal buildings and selecting appropriate surface preparation

procedures, coating systems, and application methods for a range of condition

categories. It is recommended that the performance of the coatings in the

field tests be assessed for a period of at least 3 years before preparation of

final maintenance criteria.

1 .3 SCOPE OF THIS REPORT

This report is not intended for use in procuring or recommending materials or design information for new metal buildings. The report does, however, address

the types of metal siding and roofing commonly encountered on Air Force installations, since both the type of deterioration and appropriate methods of repair

are directly related to the types of materials and construction practices

used. This report is also intended to describe design features that may attribute to accelerated coating and metal deterioration. Thus, special attention

should be given during inspection for early signs of deterioration and in

maintenance activities where modifications can reduce further deterioration.

2
Basically, the guidelines and recommendations are intended to provide a procedure to obtain, on a prescribed schedule a rating of the condition of

existing metal building exterior surfaces. This rating is to be used both as

a data base for later reference and for determining present necessary maintenance actions. The rating data are to be filed and analyzed according to

prescribed procedures to determine necessary maintenance actions, establish

their priority, and to determine in detail how this is best achieved. The

recommended actions may include no action, simple cleaning of the painted

exterior, spot or limited recoating, repair or replacement of a limited number

of metal siding or roofing panels, and total recoating. The tightening of

loose fasteners and replacement of missing fasteners is addresssed, since in some cases, deterioration of fasteners is much greater than deterioration of

siding or roofing. In all areas to be considered, the guidelines and recommendations are intended to be as simple and concise as possible, while providing

the necessary information for effective coating maintenance of metal buildings.

1 .4 BENEFITS OF A SYSTEMATIC MAINTENANCE PROGRAM

A systematic maintenance program approach will not only benefit the Air Force,

but also other owners of metal buildings. It provides a record of existing

conditions that can be used to determine which metal buildings require maintenance actions, the nature of the appropriate actions, and how to achieve them

technically and economically. This simplifies the work of the base engineer by

assisting in technical decisions on maintenance of metal buildings. It also

assists in establishing priorities for maintenance actions, and in providing

lead time for timely and economical maintenance. Effectively implemented, it can provide for attractive working and living areas on bases, extend the service

life of metal buildings, and economically maintain operationally ready facilities.

3
2 METAL SIDING AND ROOFING MATERIALS COMMONLY ENCOUNTERED ON AIR FORCE BASES

There are many metal siding and roofing products presently in use at Air Force

bases. Buildings fabricated with metal panels may have metal siding or cladding,

they may have metal roofing, or they may have both. Those with both metal

siding and roofing are generally referred to as metal building systems. A

metal building system, as defined by the Metal Building Manufacturers Association, "consists of a group of coordinated components, including structural

members, exterior covering panels, fastening devices and accessories which

have been designed for specific loads, which will work together compatibly and

which have been engineered so that they may be mass produced and assembled in

various combinations with various collateral materials, to provide an enclosed

or partially enclosed structure" [1].

Two types of metal siding may be found on buildings at Air Force bases. One

is used on industrial-type buildings and the other is used on residences.

Industrial-type metal siding has vertical ribs or corrugations and seams in

contrast to residential siding which usually has horizontal seams and configurations. This report deals only with metal siding and roofing used on industrialtype buildings including hangars, warehouses, dormitories, and recreational

facilities such as gymnasiums and bowling alleys.

The metal siding and roofing panels used in buildings are generally roll-formed

from either steel or aluminum and are covered with some form of factory-applied

organic coating sytem. Most of the siding and roofing panels in use at Air Force

bases are hot-dipped galvanized (zinc coated) steel with an organic coating.

The panels are usually cold-rolled from high-strength low-alloy sheet steel.

The organic coatings on the panels fall into three categories: liquid-process

coatings, dry-film laminates, and protected metal [2], Liquid-process coatings

consist of one or more films of synthetic resin coating materials applied as a liquid to the substrate and then heat cured. A dry-film laminate is a dry

film coating material bonded to the metal substrate with an adhesive. Protected

metal is referred to as a galvanized steel substrate coated with a relatively

thick coating of an asphaltic material, with or without an inert mineral filler

addition, which itself may be covered with a thin decorative coating.

The thickness or weight of the galvanized coating on the steel panels may be

varied, as well as the thickness of the sheet itself. This depends on the

requirements and the specifications used to procure the panels when the building

was constructed. Requirements for metal buildings depend on the intended use

of the building and the environment to which they will be exposed.

Table 1 summarizes information about the metal siding and roofing materials

commonly encountered on Air Force bases. Also included in the table are maintenance coatings which are used periodically to recoat the siding

and roofing for aesthetic reasons and to protect the steel from corrosion.

Figures in brackets indicate references listed in Chapter 8.

4
Table 1. Metal Siding and Roofing Materials Commonly Encountered

Categories or Properties

of Materials

Sheet Metal Types

Sheet Steel Types

Steel Sheet Rolling

Processes

Types of Materials

steel, aluminum

carbon, high strength low alloy, alloy

hot rolled, cold rolled

Metal Coatings on Sheet

Steel

none, galvanized (zinc), aluminum,

zinc/aluminum

Metal Siding and Roofing

Configurations

corrugated, V-crimp, V-beam, ribbed,

standing seam

Metal Surface Treatments primer, phosphate, chromate

Organic Factory Coatings

Surface Characteristics

of Metal Panels

Fasteners for Sheet Steel

Maintenance Coatings

none, thermosetting acrylics, solution

vinyls, silicone modified (alkyds,

polyesters, and acrylics), plastics and

organosols (vinyls), fluocarbons, polyvinyl fluoride), poly (vinylidene fluoride),

heavy build elastomeric, fluorocarbon

film laminate, acrylic film laminate,

poly (vinyl chloride) laminate, bitumen,

bitumen with asbestos fibers,

bitumen with asbestos fabrics, bitumen

with top coat (polyester)

smooth, texured

steel, blued/acid treated steel, metal

coated, galvanized, plastic cap over steel

Zn/ZnO alkyd (TT-P-641)*, latex, elastomeric,

alkyd, epoxy, urethane, bitumen, aluminumpigmented bitumen, bitumen with fibers,

and aluminum-pigmented bitumen with fibers

Federal Specification

5
Additional information about metallic and organic coatings for metal siding

and roofing and methods for fastening coil coated steels is reported in reference [3]. Sketches of configurations of typical metal siding and roofing

panels commonly encountered are shown in figure 1. It is noted that the size

and spacing of the configurations and the thickness and length of the panels

may vary from one building to another depending on the building design with

regard to appearance, construction details, and anticipated loads. Standing

seams are often encountered in roofing applications but are in general not

found in siding applications. The other configurations of metal panels shown

in figure 1 are usually encountered in siding and also are often included in

roofing applications.

There are many possible combinations of metallic coatings, panel configurations,

organic factory applied coatings, and maintenance coatings that may be used to

produce and to maintain metal siding and roofing panels (table 1). The newer

types of siding and roofing are coil coated or roll coated with thin organic

coatings about 1 mil or 0.001 in. (0.025 mm) thick. Most of the older metal

buildings and some newer ones are of the protected metal type. These buildings

have panels of steel, usually galvanized, coated with a relatively thick,

about 25 mils or 0.025 in. (0.625 mm) bituminous material with mineral fillers,

and in some cases, covered with a thin decorative coating. In addition, some

of the older thick factory applied bituminous coatings (usually asphalt) may

contain asbestos fibers or asbestos fabric.

Over a period of time, the factory applied organic coatings deteriorate due to

weathering. Therefore, periodically, the panels need to be recoated. There

are many types of maintenance coatings listed in table 1.

6
Figure 1. Configurations of typical metal siding and roofing (not to scale)

7
3. CONDITION OF METAL SIDING AND ROOFING OBSERVED IN THE FIELD

A field study was conducted to obtain information about the condition of metal

siding and roofing at twelve Air Force bases in various geographic locations

in the United States. The intent of the field study, in addition to assessing

the condition of various steel siding and roofing products, was to identify

problems with factory coated panels which had been exposed to weathering over different periods of time, and to assess the performance of the various types

of factory applied and maintenance coatings. Observations during the field

study also included the condition of fasteners and drainage systems, the extent

and locations of corrosion of metal siding and roofing panels, and the

effectiveness of different types of maintenance coatings. Many of the civil

engineering staff at the bases visited, provided information about their

experience regarding performance of factory applied coatings and maintenance

coatings used on galvanized and non-galvanized sheet steel exterior panels.

The inspection of buildings on Air Force bases indicated that most of the metal

siding and roofing was steel and that the condition of the metal siding and

roofing tended to fall into one of several classifications. The condition of

the siding and roofing resulting from in-service exposure varied depending on

the extent of deterioration, damage, or loss of coating protection. The

different classifications of the conditions of the metal siding and roofing

which were observed are described and illustrated with photographs in this

section of the report. This information will assist Air Force personnel in

the inspection of the condition of metal siding and roofing and acquaint them

with conditions they are likely to see.

The problem conditions identified with the metal siding and roofing were divided

into two major classifications. One classification addressed problems with

metal panels and building systems which needed repair before recoating, and

the other addressed problems related to the integrity of the coating protection.

The two major classifications are further divided into several subclassifications

which are discussed in sections 3.1 and 3.2.

3.1 CONDITIONS REQUIRING REPAIR BEFORE RECOATING

Although the overall condition of metal panels, fasteners, and drainage systems

of most buildings observed during the study was generally considered to be good, some problems were observed that require repair before coating. A discussion

of these problems with illustrations follows:

a. Loss of Metal

Metal loss due to corrosion was observed mostly at the following locations:

at the bottom edges of the panels near the ground, just under the eaves, or

at laps and seams (figures 2, 3, and 4). On one roof, corrosion of the

metal was not visible from the top, however, severe loss of metal at most laps

could be seen from the inside of the building.

8
Figure 2 . Illustration of loss of metal at bottom edges of panels

Figure 3. Illustration of loss of metal at top edges of panels

under the eave

9
Figure 4. Illustration of corrosion of metal at laps

Figure 5. Bituminous mastic material used on roof to cover fasteners

10
b. Roof Leaks

In many instances, roof repairs were observed. One type of repair

frequently observed, particularly on roofs with relatively little slope, was the use of bituminous mastic material to cover fasteners (figure 5).

It was reported by base personnel that leaking often occurred at these

fastener locations. Another type of repair was the use of thick bituminous

coatings at the junction between two different types of roofing systems

such as encountered with building modifications, additions, or repairs

(figure 6).

c. Impact Damage

Dents or severe localized bending of sheet metal was often observed

(figure 7). This damage was attributed primarily to vehicles bumping into

the buildings.

d. Gutter or Drainage Problems

Many problems with gutters or other parts of drainage systems were observed.

These problems included deterioration of valleys, gutters, and downspouts

(figure 8), and corroded gutter hangers (figure 9).

e. Loose, Missing, or Corroded Fasteners

The extent of fastener corrosion ranged from slight to severe. In some cases where fasteners were badly corroded, the sheet steel adjacent to the

fasteners was also corroded (figure 10). Some fasteners had pulled out

of the panels (figure 11), and others were loose or missing. It appeared

that in some instances the loose fasteners were never securely attached to

the panels or support structures.

3.2 CONDITIONS RELATED TO COATING PROTECTION

The condition of the metal substrates of the panels and the protective organic

coatings was observed to vary from good to severely deteriorated. This was expected since the ages of the metal buildings ranged from nearly new to more

than 40 years old. The problems associated with coating protection are divided

into two parts. One part deals with buildings which did not have maintenance

coatings and the other pertains to buildings which had been repainted.

3.2.1 Metal Siding and Roofing without Maintenance Coatings

The condition of metal siding and roofing panels not having maintenance coatings

depended to some extent on the type of panel. The types of panels fall into

the following three groups: metal panels without organic coating, steel or galvanized steel panels with a bituminous protective coating (protected metal),

and steel panels with a thin 1 to 2 mil or 0.001 to 0.002 in. (0.025 to

0.050 mm), organic coating.

11
Figure 6. Thick fibrated bituminous roof coatings

/

Figure 7 . Impact damage of metal panels

12
Figure 8. Deterioration of drainage system

Figure 9. Corroded gutter hangers

13
Figure 10. Corroded fasteners with associated corrosion of

the metal panels

Figure 11. Loose fasteners

14
a. Metal Panels without Organic Coating

Galvanized steel panels were the most commonly observed material in this

group. Anodized aluminum was also observed in a few instances. Most of

the galvanized steel panels which were observed had either white rusting or moderate red rusting (corrosion of the base steel). A typical example of

red rusting of galvanized steel is shown in figure 12.

b. Metal Panels Protected with a Bituminous Coating

Bituminous coatings both with and without fibers and with and without factory

applied topcoats were observed. All of the panels with bituminous coatings

were more than 15 years old. These types of coating systems generally

exhibited cracking. In cases where the bituminous coating was not topcoated,

the cracks or breaks in the coating tended to extend to the metal substrate

(figure 13). When the bituminous coating was topcoated, the cracks or breaks

tended to be found only in the topcoat (figure 14). The topcoats were sometimes chalked and faded. The appearance of some buildings, without a topcoat,

that were about 25 years old had an overall whitish cast. This was due to

loss of the bituminous coating, and subsequent exposure of the white fibers

in the reinforcing fabric which was in the coating (figure 15).

c. Metal Panels Protected with Thin Organic Coatings

Most of the buildings constructed with metal panels having thin organic

coatings, about 1 mil or 0.001 in. (0.025 mm), that were observed were less

than 10 years old. The metal panels of these buildings were in general in

excellent condition. However, deterioration was noted in some cases at the

factory formed bends (figure 16) and at the edges of the siding and roofing

panels (figure 17). Red rusting was detected at these locations. The

deterioration for these noted cases was in some instances severe enough

that recoating was needed. In a few cases, pin point rusting over flat

surfaces was observed. Pin point rusting is characterized by tiny holes in

the coating with rust staining extending from the holes. Fading, chalking,

and mildew were also observed. The fading and chalking tended to be found

together and was observed on the older buildings, those more than 10 years

old.

3.2.2 Metal Siding and Roofing Having Maintenance Coatings

Many combinations of siding and roofing products and maintenance coatings were

observed. The combinations that were frequently observed and the problems most

commonly associated with those particular combinations of materials involved

are listed in table 2. Paint peeling from galvanized steel was the most

extensive and frequently observed problem. Thus, it is listed first in the

table. The remainder of the systems of maintenance coatings over metal siding

and roofing listed in the table are not in any particular order with regard to

the performance of metal siding and roofing.

15
Figure 12. Corrosion of galvanized steel panels

Figure 13. Cracking of bituminous coating

16
Figure 14. Cracking of topcoated bituminous coating systems

Figure 15. Fibers of reinforcing fabric showing on surface

of deteriorated bituminous coating

17

>\\\\W>
Figure 16 . Corrosion along factory formed bends of steel panels protected

by a thin organic coating

Figure 17 . Corrosion of steel at the edges of panels protected by a thin organic coating

18
Table 2. Systems of Maintenance Coatings Over Metal Siding And Roofing

and Observed Problems Associated with Each System

System of Maintenance Coating

Over Metal Siding and Roofing Observed Problems

Galvanized steel and non-bituminous Peeling paint, poor adhesion,

maintenance coating corrosion of substrate

Galvanized steel and bituminous Bleeding and cracking of thick

maintenance coating coating, corrosion of substrate

Galvanized steel and bituminous Peeling and cracking of coatings,

factory coating and organic corrosion of substrate

maintenance coating

Galvanized steel and thin organic Peeling paint, corrosion of

factory coating and organic substrate

maintenance coating

The types of maintenance coatings that were observed on galvanized steel included

zinc pigmented alkyd primers (e.g., TT-P-641) with an alkyd topcoat, red lead

pigmented alkyd primers with either alkyd or acrylic topcoats, vinyl wash primer

(e.g., MIL-P-15328) with alkyd or other topcoats, and acrylic or bituminous

coatings with and without aluminum pigment. The condition of the maintenance

coatings varied. It was often noted that alkyd systems either experienced

peeling (figure 18) or they could be easily removed with tape after making an X-cut in the coating with a knife.

Fibrated bituminous maintenance coating systems, some containing aluminum

pigment, were observed on many galvanized steel roofs. Some of the problems

with these roofs included red rust (figure 19), severe cracking (figure 20),

bleeding of bituminous material which produced a nonuniform appearance, and

heavy build-up of material, e.g., about 0.5 in. (12.7 mm). Two types of thick,

15 - 30 mils or 0.015-0.030 in. (0.375-0. 750 mm) elastomeric systems, acrylic

and urethane, had also been applied as maintenance coatings over some of the

galvanized steel roofs. These systems had been applied about two years prior

to the field study and were judged in good condition (figure 21). It can be seen in this figure that a portion of the coating has been cut to show the

paint layers.

On one large metal building, a paint containing mineral spirits had been applied

to a bituminous factory coating with a polyester type of topcoat. During

inspection of this building it was observed that the bituminous coating had

Federal specification.

Military specification.

19
Figure 18 . Peeling of alkyd coating from galvanized steel panels

Figure 19. Red rust showing through aluminum pigmented

bituminous coating on steel roof panels

20

*
Figure 20. Severe cracking of bituminous roof coating

Figure 21. Elastomeric roof coating about two years old, a piece had been cut away to show the paint layers

21
peeled extensively from the metal siding (figure 22). The solvent in the

maintenance coating had likely weakened the bond between the bituminous coating

and the metal.

Latex paints (e.g., acrylics) were also observed as maintenance coatings over bituminous factory coatings. In these cases, the condition of the latex

coatings was good two years after their application. Maintenance coatings

had been applied to only a few of the observed metal buildings with thin

organic factory coatings. In one case, a new building had been painted with

an acrylic latex paint. After one year, the adhesion was very good and the

overall condition was good. A potential problem with maintenance coatings over thin organic factory applied coatings is illustrated in figure 23. The

maintenance coating on this building did not adhere to the thin organic factory

coating and adhesion failure was observed at the interface between coating

layers. Bituminous maintenance coatings were also observed to have been

applied over roofs with thin organic factory coatings. Some of these maintenance coatings over thin organic factory coatings had performed satisfactorily

while others had exhibited adhesion failure between coating layers during the

short time they had been in service. There is the potential for similar

problems to occur where bituminous maintenance coatings are used over galvanized

steel

22
Figure 22. Peeling of bituminous factory coating system

recoated with a mineral spirit solvent paint

Figure 23. Adhesion failure of maintenance coating to a thin

organic factory coating

23
4 . DESIGN, CONSTRUCTION, AND MAINTENANCE PRACTICES AFFECTING COATING

DETERIORATION AND METAL CORROSION

There are many design, construction, and maintenance practices that can adversely affect the performance of coated metal siding and roofing. Poor

practices may introduce conditions promoting deterioration of the coating,

corrosion of the metal, or both. It is important in the maintenance of metal

buildings to be aware of practices that may result in problems affecting the

performance of siding and roofing. Problems resulting from poor practices

should receive special attention during periodic maintenance inspections of

buildings. This chapter is intended to aquaint maintenance personnel with some acceptable and poor practices in the design, construction, and maintenance of

exterior metal siding, roofing, fasteners, and drainage systems. Problems

resulting from poor practices can be identified and in many cases corrected or alleviated by modification, repair, or by appropriate maintenance practices.

Some of the problems associated with poor practices are discussed in sections

4.1 through 4.4 along with some acceptable practices for metal buildings.

These practices deal with building location, building design, surface con- figuration and texture, and selection of materials. Table 3 summarizes many

acceptable and poor practices discussed in this chapter.

4 .1 BUILDING LOCATION

Although it is not usually possible to change the geographical location of a building, some sites on a particular military installation may have less

aggressive environments than others. Locations close to coastal waters,

particularly where there is appreciable salt spray, should be avoided as much

as possible. Similarly, metal buildings should be located away from industrial

areas or other areas emitting air pollutants. Industrial air pollution may

cause early soiling of coated surfaces, as well as coating deterioration and

metal corrosion. The direction of prevailing winds may also be important with

regard to carrying salt spray, industrial air pollution, or sand particles.

Windborne sand and dirt can cause coating erosion and soiling of coated

metal siding and roofing.

4 .2 BUILDING DESIGN

The design and layout of buildings, particularly industrial type buildings, can influence the durability of coated metal components. If the buildings have

stacks, the stacks should be high and located so that contact of the emissions

with the building and other structures is minimal. This applies to emissions

of steam as well as smoke and particulates.

The roof design should provide a system with enough slope and capacity for

complete drainage while requiring minimal maintenance. The drainage should be

through gutters, conduits, and downspouts rather than down the side of the

building. If the siding or roofing of a building remains wet for long periods

of time it promotes coating deterioration, underfilm corrosion, and growth of

mildew organisms. It is obvious that leaks in roofing or siding should be

24
repaired as soon as possible using recommended methods rather than adhesive

cement or putty type products that provide incomplete or temporary repair.

If buildings are air-conditioned using window units, water from window airconditioners should not be allowed to drain down the side of the building or

to drip from upper stories onto awnings or other appertunances located below

them. Building components that remain wet for long periods of time are subject

to deterioration, corrosion, and mildew.

Common procedures for joining panels of metal buildings include bolting,

riveting, and screwed or friction fasteners. Of major concern is the joining

of components of dissimilar metals which may result in galvanic corrosion (see

section 4.4) and the formation of crevices with resultant crevice corrosion,

a form of concentration cell corrosion. If rivets or bolts are used to join

dissimilar metal structural components or to attach siding and roofing panels

of dissimilar metals, electrical insulators can be used to minimize

corrosion. The insulators, however, should not be a type of material that

will absorb or retain water.

4 .3 SURFACE CONFIGURATION AND TEXTURE

Roofing and siding panels are corrugated, formed, bent, or grooved in some manner to produce a product that is pleasing in appearance and provides strength,

stiffness, and other desirable features. Some panels are produced that have an embossed or textured surface. While these products with textured surfaces may

be pleasing in appearance, their surfaces tend to collect water, salt, dirt,

mildew spores, and other undesirable contaminants. Textured surfaces are also

more difficult to coat with a continuous film of coating having a uniform

thickness. Thus, it is preferred that siding and roofing panels have a smooth

surface consistent with fastening and interlocking requirements.

4 .4 SELECTION OF MATERIALS

There is a wide choice of structural members, siding and roofing panels, and

coating materials available for metal buildings. It is important that the

materials and products used in metal buildings be wisely selected for appropriateness and for compatibility with each other.

One of the most important considerations in the selection of materials and

products for metal buildings is the contact of dissimilar metal components,

including fasteners, that may result in rapid galvanic corrosion. Galvanic

corrosion occurs in the presence of an electrolyte, usually water, because of

the differences in electrochemical potential between two different metals or alloys. Contact of dissimilar metals should be avoided. It is preferred that

the same type of metal or metals with very similar electrochemical potentials

be used whenever metal connections are necessary. When this is not possible,

electrical insulators that do not absorb water should be used between two

metal components which are of different metals. Conventional organic coat in/s

provide little if any electrical insulation because they are thin and easily

damaged or broken. Fasteners should be of the same material as the metal tli.-v

25
are joining, slightly cathodic to it, or well coated with an appropriate

metallic coating.

Aluminum is attacked by alkali, and thus aluminum components should not be

allowed to come in contact with concrete. On the other hand, steel is com- patible with concrete and these two materials may be used together. Steel can

be protected from corrosion by galvanizing. The duration of the protection

provided for steel by galvanizing in a given environment is directly proportional to the thickness of the zinc coating. Galvanizing by the hot dip process can provide for relatively thick zinc coatings. Thus, it is preferable

that galvanizing of steel building components be from the hot dip process

rather than from electrodeposition which results in a relatively thin zinc

coating

There are many different types of coating systems available for coating

previously unpainted metal panels or for recoating damaged or deteriorated

panels having factory-applied coatings. It is suggested that the recommendations presented in this report be followed when selecting coating materials

because of possible incompatibility problems and because coating performance

may vary widely with different types of coating systems. As an example, alkyd

coatings are not compatible with galvanized steel. Further, there are wide

differences in the weathering characteristics of coatings of different generic

types. Epoxy coatings are known to chalk over relatively short periods of

time due to sunlight, and blue and pinks colors are known to fade more rapidly

than other colors. It is noted that, while sunlight causes coatings to chalk

and fade to various degrees, shade permits retention of moisture that can accelerate corrosion and mildew growth.

26
Table 3. List of Generally Acceptable and Poor Practices in Design,

Construction, and Maintenance of Siding and Roofing in Metal

Buildings

Acceptable Practices Poor Practices

Locate building away from salt spray

and wind-borne particulates or industrial pollution

Locate buildings in any environment

Complete roof drainage through easily

maintained conduits

Incomplete roof drainage or drainage

down side of building

Scheduled roof inspection and

maintenance program

Repair roof leaks as they are reported

Permanent roof repairs according to

Air Force guidance

Temporary repair of roof leaks with

putty or plastic cement

Water from window air-conditioners

conducted away from building

Water from window air-conditioners

running down side of building

Use of closed type structural

members or open type beams oriented

so as not to collect water

Beams with open design oriented to

collect water

Use of electrical insulators in

nonwelded joints to eliminate

crevices

Crevices in riveted or bolted joints

Metal panels with smooth surfaces

except for interlocks

Metal panel surfaces with textured or embossed appearance

Contacts of similar metals or separation of dissimilar metals

with electrical insulators to

prevent galvanic corrosion

Contacts of dissimilar metals

Fasteners of same material as metal

being joined; or slightly cathodic

to joined metal; or well coated with

an appropriate metallic coating

Fasteners of dissimilar metal compared

to metal being joined, or inappropriate

metallic coating

Use of washers with fasteners to

prevent damage to metal being joined

Washers not used with fasteners

Aluminum isolated from concrete Aluminum in contact with concrete

Hot dipped galvanizing Electroplated galvanizing

27
Table 3. List of Generally Acceptable and Poor Practices in Design,

Construction, and Maintenance of Siding and Roofing in Metal

Buildings (Continued)

Acceptable Practices

Use of recommended compatible coatings

for repair

Use of weather-resistant recommended

coating systems

Coatings with white, earth tone, or other fade-resistant colors

Poor Practices

Repair of damaged or deteriorated

coatings with available materials

Finish coating of epoxy or other

freely chalking product

Coatings of blue, pink, or other colors

that fade rapidly in sunlight

28
5 . CONDITION ASSESSMENT PROCEDURE

The effectiveness of building maintenance procedures and base maintenance

programs depends upon the quality of the assessment of the condition of building components and systems. Condition assessment takes into account both the

evaluation process which includes visual inspections and use of visual

standards and other criteria, and the analysis of the evaluation data to obtain

a numerical rating or quantitative assessment of the condition of the building

or of its components. To have an effective and reliable maintenance procedure

in a cost-effective maintenance program, the assessment procedure must provide

a quantitative description of condition which is reproducible and repeatable.

Further, the procedure should be relatively simple, fast to conduct, and provide

enough information to select an appropriate maintenance procedure. Methods

of evaluating, and in some cases rating, the condition of the substrate and

coating, have been described in the literature [4]

However, most of these

methods are subjective and require an experienced inspector to obtain reliable

information. To satisfy the necessary attributes listed above for a condition

asssessment procedure, detailed inspection forms, visual standards illustrating

commonly occurring deterioration conditions, and definitions have been developed

for use in condition evaluation. Analytical procedures have been developed to

evaluate the condition assessment data and to provide the basis for recommendations for maintenance procedures.

The condition evaluation procedure developed in this study involves a relatively

quick, initial visual check of the condition of metal siding and roofing panels

and, if indicated from this initial inspection, a more detailed inspection

may be necessary. Based on the initial inspection, no further inspection is

needed if either the siding and roofing are in good condition and maintenance

is not needed or total replacement of metal panels is indicated. If deterioration of the metal panels, fasteners, drainage systems, or the coating is

observed during the initial inspection and total panel replacement is not

necessary, then a detailed inspection of the building is required. The purpose

of the detailed inspection is to determine the type and level of the deterioration and to characterize the type of the existing coating on the metal panels.

The detailed evaluation procedure is designed to give quantitative information

on the condition of the building with respect to several mechanisms of deterioration. Hence, considerable numeric information may be obtained and a procedure to incorporate this information is required so that the overall

condition of the siding and roofing is assessed. A summary of the condition

assessment procedure is shown in a flow diagram in figure 24.

5.1 CONDITION EVALUATION

5.1.1 Initial Check-off Inspection

The initial check-off inspection is a relatively quick look at the build in)'.

The objective of this inspection is to determine the general condition of t h •

• metal siding, roofing, fasteners, and drainage systems. As a result of this

inspection, it should be known whether the building components have esscnt i 1 1 1 v no deterioration, some deterioration, or severe deterioration.

29
CONDITION ASSESSMENT PROCEDURE

Figure 24. Condition assessment procedure

30
Inspection Form 1 (table 4) is used in carrying out this initial inspection.

The terms listed in the left-hand column are defined in the glossary in

Appendix A. Many of the conditions listed in Inspection Form 1 (table 4) are illustrated in chapter 3. In the initial check-off inspection, the only

type of deterioration for which a quantitative estimate is required is

panel perforation. This requirement is made so that further inspection will

not be necessary when panels are badly perforated.

The recommended procedure is:

a. View each side of the building and the roof from a distance sufficient to

obtain an overall view. Note any areas that appear to be substantially

more deteriorated than other areas of the building.

b. Inspect the sides from close-up by walking around the entire building and

looking for conditions listed on the initial check-off inspection form.

Pay particular attention to suspect areas identified from a distance and

to the condition of the metal panels, coatings, fasteners, downspouts,

and underside of gutters.

c. Conduct a roof-top inspection for all conditions listed in the initial

check-off inspection form. (It is necessary to be on the roof part of

the time to do this inspection.) Particular attention should be paid to

the condition of the metal at the laps, both on top and underneath, and

the condition of the drainage systems, fasteners, and other construction

details. Investigate areas where leaks were reported by the building

occupants or evidence of leaks is present.

5.1.2 Detailed Inspection

When items in Section I of Inspection Form 1 (table 4) are checked, then a detailed inspection of the conditions requiring repair is needed; and when

items in Section II are checked, then both a detailed inspection of these

conditions and characterization of the existing coating are required.

These inspection procedures are described in this section. When only the

items in Section III are checked, further inspection is not required.

5. 1.2.1 Conditions Requiring Repair

When conditions requiring repair (i.e., those listed in Section I of the

initial check-off inspection form) are observed, then a detailed inspection

of the siding or roofing metal panels for that condition is required. These

conditions include severe deterioration of panels (perforations in the

panel or erosion of the metal at the edges) and roof leaks that may be

associated with the panel laps, fasteners, and slope or drainage. In addition, inspection to determine the extent of plastic mastic material along

laps and over fasteners will be required since this information is necess.irv

in selecting a surface preparation procedure. Inspection Form 2 (table >) is used to guide this inspection. Terms found in this form are also defim-d

in the glossary in Appendix A.

31
Table 4. Initial Check-off Inspection

INSPECTION FORM 1

Building No. Date

Inspector

Section I. Conditions requiring

repair

sides

absent present

roof

absent present

perforations (including

corrosion and serious impact

damage)

percent of panels that are perforated

leaks

deterioration of drainage system

lost, damaged, or loose fasteners

Section II. Conditions related to sides roof

coating protection problems

(absent or present) north

corrosion

flat surface

south east west

edge

bend

undercutting

peeling/blistering

cracking

Section III. Conditions related to sides roof

coating surface deterioration absent

chalking

present absent present

fading

mildew

bleeding/ soiling

32
Table 5. Detailed Inspection of Panels, Fasteners, and Drainage Systems

INSPECTION FORM 2

Building No. Date _

Inspector

Sides Roof

yes

Leaks, problems associated with

slope

no yes no

drainage

fasteners

seams (plastic mastic material over

fasteners, seams, etc)

other, describe

Drainage systems, problems associated with

slope

gutter capacity

downspout capacity

other, describe

Fasteners

corroded with corrosion limited

to fasteners

corroded with corrosion extending

to panel

washers cracked, degraded, or missing

fasteners loose, damaged, or missing

33
Since leaking roofs may be associated with several conditions related to design,

guidelines associated with these conditions are included in this section. The

design requirements for roof slope and drainage capacity were taken from the

Tri-Service Manual, "Maintenance and Repair of Roofs" [5] and the Architectural

Sheet Metal Manual [6], For lap seam corrugated sheet metal roofs, a slope of

at least 4 inches per foot is required. For standing seam roofs, a slope of

at least 3 inches per foot is required. When these seams are soldered or a sealant is used, the requirements may change (less slope required). The manuals

referenced above should be consulted for information on particular cases. Drainage system slope requirements depend on many factors, such as, anticipated

rainfall intensities, slope of the roof, style of gutters, and downspout outlet

opening area. Problems with drainage systems are detected by inspecting the

gutters and downspouts for deterioration and the surface area adjacent to the

drainage system for localized deterioration. Design criteria for particular

cases can be determined from tables in the Architectural Sheet Metal Manual

[6]. When roofs from adjacent buildings drain into the same gutter system,

the capacity should be twice as large as the gutter criteria noted above [7].

Leaking roofs or siding panels can be associated with fasteners. Both the

location of fasteners in the panels, and the condition of the fasteners and

substrate adjacent to them affect maintenance decisions. This is particularly

important for roofs since conditions exist which make them more susceptible to

leaking than the walls of buildings. Inspection should include identification

of location, type, and level of deterioration.

5. 1.2. 2 Detailed Inspection of Conditions Related to Coating Protection Problems

When conditions relating to coating deterioration are present (Section II,

Inspection Form 1), a detailed inspection to determine the extent of the

deterioration is required. Inspection Form 3 (table 6) and the visual standards and descriptions of the levels of deterioration (Appendix B) are used in

this inspection.

To obtain quantitative and reproducible inspection data for the condition of

buildings, well-defined standard procedures are needed. Since visual standards

are successfully used to rate the level of deterioration of panels in laboratory

experiments [8], the use of visual standards to provide a means of quantitative

assessment of the condition of coated metal panels was considered and selected.

Industry consensus visual standards for corrosion, blistering, and cracking

were considered, but after comparing the types of deterioration observed during

field inspections and those illustrated in the industry consensus visual

standards, it was concluded that, with the exception of corrosion on flat

surfaces, these standards did not represent the types of deterioration of

coated metal panels seen in the field. Further, the photographs in the industry

visual standards are of small areas (that is, the association between photograph

and sample is approximately one to one) . But since some of the types of

deterioration observed can only be represented by photographs of large areas

of siding or roofing, standards which represent larger areas are needed.

Hence, special visual standards which include sketches and photographs were developed for use in condition assessment of buildings with metal siding or roofs. The six sets of visual standards developed in this study are: 1) for

34
Table 6. Detailed Evaluation of Conditions Related to Coating Protection

INSPECTION FORM 3

Building No. Date

Inspector

Problem Condition (Type of Deterioration)

Ratio (R) of Length of Building to Width of Building

Side

or Roof

Level of Deterioration* Fraction of Area** Localized Rating Condition Rating

of Sides and Roof

G = E + F WorstA

Typical

B Worst

C

Typical

D

Worst

E=AxC

Typical

F=BxD

North

Side

East

Side

South

Side

West

Side

Roof

Localized Condition Rating of Sides of Building

(Average of Worst Ratings of Sides)J_/

OVERALL CONDITION RATING OF SIDES OF BUILDING

(Average of Condition Ratings of SidesXL^

* Determined from visual standards and descriptions of levels of deterioration

(Appendix B)

** Fraction of area having this particular type of deterioration (problem condition)

for a given side or roof of the building

i/use formula (1) if necessary, see 5 .2 .2 .2

FORM 3A

(Used when side or roof is divided into sections)

Section

Level of Deterioration Fraction of Area Localized Rating Condition Rating

of Sections

G - E + F

Worst

A

Typical

B Worst

C

Typical

D

Worst

E=AxC

Typical

F=BxD

12

3

4

5 Localized Condition Rating of Side or Roof

(Average of Worst Ratings of Sections)

Overall Condition Rating of Side or Roof

(Average of Condition Ratings of Sections) *

*Enter into appropriate block in Inspection Form 3

35
corrosion on flat surfaces, 2) for corrosion along bends, 3) for corrosion

along edges, 4) for undercutting (under film corrosion), 5) for peeling and

blistering, and 6) for cracking. Three sketches and one photograph are used

to describe each condition. The photograph is used to illustrate moderate

deterioration (level of deterioration of 5) and the three sketches illustrate

slight, moderate, and severe deterioration (that is, levels of 8 , 5 and 2 respectively) . Sketches are not included in the visual standards for the

conditions which represent no deterioration (level of 10).

A detailed inspection is done for each condition related to coating protection

(Inspection Form 1, Section II) found present during the initial inspection. A

separate form (Inspection Form 3) is used for each condition related to coating

protection. As can be observed from Inspection Form 3, each side of the building and the roof is inspected separately. The following procedure is recom- mended :

a. Determine the ratio of length to width of the building (R). For cases where the ratio of length to width (R) is 3 or greater, divide

the side and roof into sections of about the same size and follow the

inspection procedure separately for each section.

b. View a side, roof, or section of the building from a distance and

identify sample areas, about 3x3 ft (lxl m), that appear to be

the worst and typical condition, with respect to the type of deterioration being considered for the evaluation. When sections of a side or roof are inspected separately, record information for each section in

Form 3A (table 6). Additional forms (Form 3A) may be required during

the inspection of a building.

c. Confirm that these choices of sample areas correspond to worst and

typical areas for the particular type of deterioration being evaluated

by inspecting the surface from a close distance.

d. For each side, roof, or section of the building, rate the two 3 x 3 ft

(1 x 1 m) areas numerically using the visual standards (figures B.l

through B.6) and descriptions of level of deterioration (Appendix B)

to determine the level of a particular type of deterioration. To

evaluate the extent of undercutting at corroded areas, use a knife to remove loose coating. The distance the coating can easily be removed

is the measure of undercutting. This is explained in the description

of the level of deterioration for undercutting and shown in the visual

standard (figure B.4).

e. For each side, roof, or section of the building, estimate the fraction

of area that has a condition similar to the worst sample area and

estimate the fraction of area that has a condition similar to the

typical sample area. Make these estimates (decimal fractions) to the

nearest tenth and record them on Inspection Form 3 or Form 3A. When

there is doubt about whether an area should be classified as worst or typical, classify the area as worst. The sum of the decimal fractions

entered on Inspection Form 3 may not always equal one.

36
f. Repeat this evaluation procedure for all conditions checked present in

Section II of the initial check-off form (Inspection Form 1).

An example is given (table 7) for determining the level of deterioration and

corresponding fraction of area information which is entered on Inspection Form

3 or 3A. In this example, the condition of peeling/blistering was observed as present in the initial inspection (Inspection Form 1). In evaluating the

north side of the building, the sample area of this side representing the

most severe peeling (worst) had a level of 2 (visual standards and descriptions

of level of deterioration, Appendix B) and the sample area representing the

typical condition of the north side of the building with respect to peeling

had a level of 8 (visual standards and descriptions of level of deterioration).

The portion of the area of the north side that was similar to the worst area

was 20 percent or 0.2, and for the typical area, the portion of area of the

north side was 70 percent or 0.7. Therefore, in this example, 10 percent or 0.1

of the area of the north side of the building was in better condition than the

typical area.

5. 1.2. 3 Characterization of Existing Coatings

Maintenance coatings should be compatible with existing coatings and they should

only be used to recoat existing coatings that have good adhesion to the substrate

or previously applied coatings and are of acceptable thickness. Therefore, it

is required that the type, thickness, and adhesion of the existing coating be

determined. Procedures for determining these properties are described below.

The information about the properties of the existing coating is recorded on Inspection Form 4 (table 8).

Information regarding the age of the building, type of metal substrate, type

of existing coating, and whether a maintenance coating had been applied should

be available from the records. However, if this information is not available,

the following procedures can be used.

Substrate Type

Place a magnet on the metal panel. If it adheres, the substrate is not

aluminum and is likely steel. To determine if steel is galvanized, scrape

small area of coating and look for spangles (large crystals) on the metal

surface which are characteristic of a zinc coating.

Type of Existing Coating

In order to select a maintenance coating that is compatible with the

existing coating, it is necessary to identify the existing coating.

Procedures for selecting maintenance coatings are discussed in section

6.3. Information about the type of existing coating, if not readily

identifiable, can be obtained quickly from a relatively simple field test or in more detail from a laboratory test. In the field test, the category

of paint finish can be determined by rubbing the painted surface with a cotton-tipped swab stick wetted with methyl ethyl ketone (MEK), a common

paint solvent. The Director of Bioenvironmental Safety at the base

37
Table 7 . Illustration of Analysis Procedure

INSPECTION FORM 3

Building No. 483 Date 1/30/85

Inspector MK

Problem Condition (Type of Deterioration) Peeling/ Blistering

Ratio (R) of Length of Building to Width of Building 3

Side

or Roof

Level of Deterioration* Fraction of Area** Localized Rating Condition Rating

of Sides and Roof

G = E + F

Worst

A

Typical

B Worst

C

Typical

D

Worst

E=AxC

Typical

F=BxD

North

Side 2 8 0.2 0.7 0.4 5.6 6.0

East

Side divided into sections, see Form 3A 0.5 5.7

South

Side

r i

5 | 10 0.1 0.8 0.5 8.0 8.5

West

Side divided into sections, not shown 0.2 7.0

Roof divided into sections, not shown 0.5 7.1

Localized Condition Rating of Sides of Building

(Average of Worst Ratings of Sides).!./ 0.4

OVERALL CONDITION RATING OF SIDES OF BUILDING

(Average of Condition Ratings of Sides).!./ 6.6

JL/ Use formula (1) if necessary, see 5 .2 .2 .2

Overall Condition Rating =

6 + 3(5.7) + 8.5 + 3(7.0)

= 6 .6

FORM 3

(Used when side or roof is divided into sections)

Section

Level of Deterioration Fraction of Area Localized Rating Condition Rating

Worst of Sections

A

Typical

B Worst

C

Typical

D

Worst

E=AxC

Typical

F=BxD G = E + F

1 2 8 0.1 0.9 0.2 7.2 7.4

2 5 8 0.2 0.7 1 .0 5.6 6.6

3 2 5 0.1 0.8 0.2 4.0 4.2

4

5 Localized Condition Rating of Side or Roof

(Average of Worst Ratings of Sections) 0.5

Overall Condition Rating of Side or Roof

(Average of Condition Ratings of Sections) * 5.7

*Enter into appropriate block in Inspection Form 3

38
Table 8. Characterization of Existing Coating

INSPECTION FORM 4

Building No.

Age of Building Date

Date of Last Coating Application Inspector

Panel/ Coating Characteristics Siding Roof

Metal substrate (check)

steel

galvanized steel

aluminum

Factory Coating Type (check)

thermosetting

thermoplastic

bituminous

Maintenance Coating TypeJ_/ (check)

thermosetting

thermoplastic

bituminous

Total Coating Thickness (in mils)

Adhesion Rating (section 5.1 .2.3)

rating

position of failure

1 If more than one maintenance coating present,

the type for each layer.

record the number of layers and

39
should be consulted about the use of methyl ethyl ketone and other

solvents prior to any work where these solvents may be involved.

If the paint finish is unaffected by MEK the general category is

thermosetting; if the swab picks up some of the finish without a dark

brown discoloration the category is thermoplastic, and if the swab

picks up a dark brown stain, the category is bituminous. Bituminous

coatings are usually very thick compared to other organic coatings

and are either black or aluminum pigmented; thus coatings with these

characteristics should be suspected of containing bituminous material.

The laboratory test is used to determine if the existing coating is

of the thermoplastic or thermosetting type and whether it contains

bituminous material. This information can be obtained in the following

way. Take a small sample of the coating that represents its entire

thickness and place it in a glass container. Add a small amount of

mineral spirit solvent to the sample. If the solvent turns into a dark

color, the coating most likely contains bituminous material. Using one layer of the existing coating at a time, place the sample in mineral

spirit solvent. If the layer dissolves, it is a thermoplastic type

coating. However, it may be a thermoplastic type coating and not dissolve

in mineral spirits but in some other solvent. To further test this

coating, obtain two more samples. Again using one layer at a time, add

toluene to the container having one sample and methyl ethyl ketone to

the container having the other sample of coating. As a result of this

further test, if the layer dissolves in either of these two solvents it

is a thermoplastic type coating; if the coating does not dissolve and

only softens slightly, it is a thermosetting type coating [9], Repeat

the procedure for all layers. In some cases after weathering,

thermoplastic coatings may change properties so that they are insoluable in the two solvents, thus from this test method they appear to

be a thermosetting type coating. For maintenance purposes, these

weathered thermoplastic coatings may be treated as a thermosetting

type coating. It may not always be possible to test just one layer

because it may be difficult to separate one layer from another, but an effort should be made to test each layer of coating. Report the type of

factory coating and maintenance coating. If more than one maintenance

coating had been applied, information on the type of each of them should

be obtained and recorded in Inspection Form 4.

Adhesion Rating

The adhesion rating of the existing coating is determined according to a procedure described in ASTM D 3359. This procedure is described in the

following way. First, using a sharp knife, make cuts in the shape of an

"X” in the coating. Make sure that the cuts extend through the coating to

the metal substrate. The length of each cut should be about 1 inch and

the smaller angle between the cuts should be about 30 degrees. Probe a point of the cut within the 30 degree angle with the pointed end of a knife to determine if the coating can be readily removed. Apply a piece of pressure-sensitive adhesive type of tape across the cut area in

the direction in which the 30 degree angles point. Rub over the tape

40
and press firmly with a finger. Remove the tape by peeling it as close to an angle of 180 degrees as possible or as close to parallel to

the substrate as possible. When the tape removes coating more than one third the distance from the cut intersection to the end of the cut, the

adhesion is judged to be poor. Otherwise the adhesion is considered to

be good. Also determine the location of the interface at which the

failure occured , that is at the metal substrate or between coating layers.

Record both the adhesion rating (good or poor) and the position of failure

on Inspection Form 4 (table 8). Make at least two adhesion measurements

on each side, roof, or section of the building when determining the

properties of the existing coating.

Thickness Measurement

This measurement can either be made with a magnetic thickness guage [10]

(providing that the substrate is magnetic) or by removing a sample of

coating and measuring the thickness with a micrometer. Record the

measurement in mils (thousands of an inch). This measurement represents

the entire thickness of the existing coating. If more than one maintenance coating is present, record the number of layers on Inspection

Form 4 ( table 8) .

5 .2 ANALYSIS OF CONDITION EVALUATION INFORMATION

5.2.1 Information From Initial Check-Off Evaluation

The recommendations for maintenance of metal siding and roofing are made based

on the inspection of the condition of the building and the analysis of condition evaluation information. When a sizable portion of the panels in the

building (about 25 percent) are perforated (this includes deterioration at the

edges and damage), then total replacement of the siding and/or roofing panels

is recommended. This approximate percentage or sizable portion of panels will

depend on considerations such as desired service life of the building and

likelihood of other panels soon needing replacement. As noted previously,

when other problems listed in Sections I or II of Inspection Form 1 are checked,

then detailed inspections are required. When conditions listed in Section

III of Inspection Form 1 are present, then the decision to recoat is based

solely upon aesthetic reasons. If the decision is made to recoat, then

characterization of the existing coating as to type and other properties

(Inspection Form 4) is required so that a compatible maintenance coating system

may be selected.

5.2.2 Information from Detailed Evaluation

5. 2. 2.1 Conditions Requiring Repair

From the inspection of the condition of metal panels, fasteners, and drainu>usystems as noted in Inspection Form 2, the type and extent of problems is

determined. The information regarding the type and extent of problems is us<-<1 without further analysis to select the proper maintenance repair procedm. .

41
5 .2 .2 .2 Conditions Related to Coating Deterioration

Because of the amount of data that may be accumulated in this part of the

inspection (Inspection Form 3) some analysis of the data is needed before

decisions can be made regarding selection of maintenance systems. The objective of this analysis is to determine whether total recoating or spot

recoating is needed, as well as to determine the degree of surface preparation

required

The following analysis is recommended when using Inspection Form 3.

For each side of the building and for the roof, multiply the level of

deterioration of the worst sample area (Column A) by the fraction of area represented by the worst sample area (Column C) and enter in Column E.

Next, multiply the level of deterioration of the typical sample area (Column B) by the fraction of area represented by the typical sample area (Column D) and enter in Column F. Sum these two numbers for each

side and for the roof (Inspection Form 3).

When the sides or roof are divided into sections of about the same size

during the detailed inspection, the evaluation of condition is done

separately for each section (Form 3A) . The condition rating of a side or roof (Column G, Form 3) is the average value for the condition ratings of

the sections (Form 3A)

The next step is to determine the overall condition rating of the sides

or the roof of the building for a given problem condition. If the length

of the building is less than twice the width, the overall condition rating

of the sides is the average of the condition rating for each side. If the

length of the building is twice or more than the width, a weighted overall

condition rating of the sides is determined by the following expression:

(Li x R) + (L2 x R) + Wx + W2 2R + 2

where = L2 =

»1 = w2 = R =

condition rating for one long side,

condition rating for other long side,

condition rating for one short side,

condition rating for other short side, and

ratio of length of building, where R is closest

width

integer

The overall condition rating for the sides and the roof are kept separate.

The conditions are often different and maintenance and repair procedures

may vary.

Repeat this evaluation for each condition (Section II of Inspection Form 1)

for which a detailed inspection was carried out.

42
An illustration of the analysis procedure of the example partly described

in Section 5. 1.2 .2 is found in table 7.

5 .2 .2 .3 Characterization of Existing Coating

As was the case for the information obtained in the detailed inspection of the

panels, fasteners, and drainage system, no further reduction of the data

obtained in the characterization of the existing coating is needed. This

information will be used directly in determining the recommended maintenance

procedure to ensure the selection of compatible coatings and application over

sound existing coatings.

5 .3 SELECTION OF TYPE OF MAINTENANCE PROCEDURE

As stated above, the condition assessment procedure was designed so that

decisions could be made regarding the type and extent of maintenance procedure

required. The following procedures for selection of the type of maintenance

are recommended. From the initial check-off inspection, one of the following

actions is necessary: 1) if no maintenance required, reinspect in one year, 2)

detailed inspection of conditions requiring repair before recoating, or 3)

detailed inspection of conditions relating to coating deterioration.

When any of the conditions requiring repair are present (Inspection Form 2)

the condition should be corrected. Recommended specific maintenance procedures

are discussed in Chapter 6

The rating of problems related to coating deterioration is used to select the

coating procedure in the following way. If the overall rating for any of the

six types of deterioration related to coating protection as identified in

Section II of Inspection Form 1 , for the sides or roof as determined in

(Column G, Inspection Form 3) is less than 8, then total recoating of the

sides or roof is recommended. If the overall ratings for all six types of

deterioration are greater than 8 (Column G, Inspection Form 3) and any of the

localized worst ratings (Column E) , are greater than or equal to 0.2, then

spot repainting of the sides or roof is recommended. If all the overall

ratings for all six types of deterioration are 8 or greater and the localized

worst ratings are all less than 0.2, then maintenance coatings are not

recommended and reinspection is necessary in one year. Information from the

characterization of existing coatings (inspection Form 4) is used in the

selection of a maintenance coating system.

5 .4 RECORDKEEPING

Two kinds of records should be kept. One relates to the assessment and the

other to the maintenance. Following the condition assessment, the first part

of the record form (table 9) should be completed. The maintenance that was performed should be described in the second part of the record form. Careful

record keeping will, in time, contribute to more cost effective selection of

maintenance procedures

43
Table 9. Record Keeping Form

Building No. Inspector

Age of Building Date

Information from Inspection/Assessment Side Roof

Metal Panels

metal substrate (steel, galvanized steel, or aluminum)

perforations/impact damage

leaks in panels or at laps

replacement recommended

other

Fasteners

corroded

corroded with corroded adjacent panel

loose, damaged, or missing

cracked, degraded, or missing washers

leaks at fasteners

other

Drainage system

deteriorated gutters

deteriorated supports for gutters and downspouts

deteriorated downspouts

other

Coating

factory coating type

maintenance coating type(s)

date of most recent recoating

total thickness of coating (mils)

adhesion of coating (good or poor)

coating surface deterioration

chalking

fading

mildew

soiling

other

Rating of substrate and coating condition

corrosion - flat surface

corrosion - bend

corrosion - edge

corrosion - undercutting

pee ling/ blistering

cracking

Description of Maintenance Procedure

Repairs (narrative description)

Maintenance coating

total or spot recoating

surface preparation

primer type and thickness

topcoat type and thickness

Describe problems encountered during maintenance

44
5 .5 SUGGESTED CONDITION RATING PROCEDURE FOR EXTERIOR SURFACES OF METAL

BUILDINGS

A procedure is suggested or proposed to determine a condition rating for the

exterior surfaces of coated metal buildings. This suggested procedure takes

into consideration repairs, all six types of deterioration related to coating

protection (Section II or Inspection Form 1), fasteners, drainage systems, and

the appearance of coated metal panels. The condition ratings previously

discussed (sections 5 .2 .2 .2 and 5.3) pertain to only one type of deterioration

related to coating protection for the sides or the roof. Procedure to incorporate

all the factors to be considered in assessment of the condition of the exterior

surfaces of metal buildings were not found in the literature. The suggested

condition rating procedure may be useful as a guide for maintenance program

planning at the base or command level since it takes into account the factors

affecting the condition of the exterior surfaces of metal building systems.

Rating schemes have been devised to obtain overall condition ratings for other

systems such as roofing and paving [11, 12]. The overall condition ratings are being used in maintenance management programs. Since the overall ratings for

these two systems are base on a scale of 100 (very good condition) to 0 (very

poor condition), a scale of 100 to 0 was considered appropriate for the

suggested condition rating for the exterior of coated metal buildings.

Because of the number and range of conditions requiring repair and also the

number and range of conditions related to coating protection, it is difficult

to determine a method to combine the individual condition assessment ratings

and findings into one rating which represents the overall condition of a building. The major problem in selecting a procedure for combining the condition ratings for all the problem conditions for which the condition assessment

is carried out for metal siding and roofing into an overall rating is weighting

or determining the relative importance of the types of deterioration. The

procedure described below for determining the overall condition rating of

buildings with metal siding and/or roofing using the information from the

condition assessment is based upon the limited inspections done in conjunction

with this project. It is suggested as a starting point for determining

an overall building rating and it is expected that the procedure will be

improved as condition assessment data become available. This procedure was

not used in the condition assessment presented in this report. It is proposed

for possible future consideration in maintenance management programs.

Each group of problem conditions listed in the initial check-off inspection

form (Inspection Form 1) will be used to determine the overall rating.

Starting with 100, subtract assigned numbers based on the condition assessment

data to determine the overall building condition rating. This preliminary

procedure is described below:

° Start with a value of 100 for the condition rating.

- subtract 30 if there are leaks.

- subtract 10 if there are problems with the drainage system.

- subtract 10 if there are problems with the fasteners that i nv !

.

problems with the adjacent metal panels.

45
- subtract 5 if there are problems with the fasteners that do not

involve problems with the adjacent metal panels.

(If it is thought that leaks and problems associated with drainage

systems or fasteners are minor, then the numbers subtracted from

100 can be less than those used above.)

- subtract twice the difference between 10 and the condition rating

for all four types of deterioration listed in section II of the

initial check-off inspection form (Inspection Form 1) that are related to corrosion. Do this separately for the sides and roof.

If a detailed inspection was not done for a particular type of

deterioration, because that type of deterioration was not present,

then the rating for that type of deterioration is taken as 10.

- subtract the difference between 10 and the condition rating

for peeling/blistering and cracking. Do this separately for the

sides and roof.

- subtract 5 from the overall building rating obtained above if

chalking and/or fading is present.

- subtract 5 if mildew is present.

- subtract 5 if the surface is discolored by bleeding or soiling.

Using this procedure, the overall rating could be less than zero. However,

this situation is not likely. Using this procedure, the overall rating may

be skewed toward 100 and an overall rating of 80 or less may indicate that

the building requires maintenance.

46
6. PRELIMINARY RECOMMENDED MAINTENANCE PROCEDURES

In this chapter, preliminary repair and coating maintenance system recommendations

are made for frequently encountered problem conditions observed during inspections of buildings with metal siding and roofing on Air Force Bases. It is

planned that these preliminary recommendations will be revised and interim

criteria developed for the selection of maintenance coating systems upon com- pletion of another phase of this study which deals with laboratory and field

evaluations of coating systems. These preliminary recommendations are based

on information currently available. No testing has been done to validate

these recommendations. This information was primarily obtained from the literature, current government documents, manufacturers' recommendations, and from

field surveys of the condition of metal siding and roofing.

These preliminary recommendations were based on the following assumptions and

requirements: 1) a desired ten year service life (assumming no extraordinary

circumstances), 2) environmentally acceptable and readily available procedures

and materials, and 3) maintainable systems. Since most of the siding and roofing

panels observed at Air Force bases during the field study were factory coated

steel with or without maintenance coatings, these preliminary recommendations

address these types of panels. Many factors, such as materials, labor, downtime of buildings, service-life of maintenance procedures, aesthetic requirements, and desired service-life of buildings enter into the overall cost of

maintenance procedures. Cost analyses were beyond the scope of this study.

Information on economic studies cam be found in references 13 and 14.

In this chapter, maintenance procedures for each of the problem conditions

discussed in Chapter 5 are included. These procedures are in the following

order: inspection schedules, repair procedures, and coating maintenance

procedures. Coating procedures for buildings that have and have not had maintenance type coatings are grouped together because many of the procedures are

the same. Based on the assessment of the condition of the metal siding and

roofing and existing coating characteristics, the appropriate section in this

chapter can be consulted to determine the recommended maintenance procedures

For example, if it is determined from the condition assessment that the

building needs recoating, and that the metal panels are galvanized and have an organic maintenance coating, recommendations for this condition would be

found in section 6 .3 .2 .

6.1 INSPECTION SCHEDULES

It is recommended that buildings be inspected at least once a year. Exceptions

to this recommendation are for buildings somewhat deteriorated, that is the

overall rating (Inspection Form 3) is 8 or slightly greater, and for buildings

located in a particulary corrosive environment, then a six month interval

between inspections is recommended.

47
6

.2

REPAIR PROCEDURES

6.2.1 Complete Replacement of Panels

When the decision to replace siding or roofing panels is made, new construction

design specifications should be used for selection of materials and design

criteria [ 15-18 ] .

6 .2 .2 Repair of Perforated or Severely Impact Damaged Panels

When a panel is perforated or in any way degraded to the extent that metal is

missing, then the panel should be repaired or replaced depending on the extent

of the perforations or damage. Replacement panels should be of similar con- figuration and material. When recoating of the entire building is the only

way to match the appearance of the replacement panels with the existing panels,

follow appropriate recommendations given in this chapter. These recommendations

depend on the condition of the existing panels.

6.2.3 Repair of Leaks

Although sides of buildings can leak, the problem is usually associated with

the roof and recommendations in this section are oriented towards roof leaks.

However, appropriate recommendations could also be applicable for siding leaks.

The cause of roof leaks is usually associated with the slope of the roof, fasteners, drainage systems, and perforations in the roof panels. Recommendations

for repair of perforated panels were made in the previous section (Section 6.2.2)

For leaks associated with inadequate slope of the roof, it is recommended that

the roof be replaced with a type that is designed for low slope. Because of

lapped seams and fasteners in some types of low-sloped metal roofs, leaks may

occur if water is allowed to stand on the roof. When replacement is not possible

a possible temporary solution is to use glass fabric set in an elastomeric

coating over areas associated with leaks, such as at fasteners and lapped seams (coating system 1, Appendix C.2). Another possible temporary solution is to

adhere an elastic sheet material over the areas with leaks.

The use of sprayed polyurethane foam roofing systems has been suggested for use

in some instances by the Naval Civil Engineering Laboratory [19,20]. Control

and quality of materials and workmanship is essential in the application of

these systems. It has been reported that properly applied polyurethane foam

roofing systems can provide maximum roof integrity and thermal efficiency [19].

6.2.4 Repair of Fasteners

Leaks at fasteners are usually associated with loose or missing fasteners,

missing or deteriorated washers, deteriorated fasteners, or rusted metal

panels around the fasteners. If there is no rust of the metal panels at

the fasteners, replace missing or deteriorated washers and tighten or replace

missing fasteners. When rubber washers are used care should be taken to not

over-tighten the fasteners. When localized rust of metal panels is evident at

fastener locations, surface preparation is required to remove rust (surface

48
preparation procedure 1, Appendix C.l) and an appropriate primer, and topcoat if

necessary, (tables 10, 11 and 12) should be applied at these areas before following repair procedures given above. For cases of severe rusting of metal

panels at fasteners, panel replacement is necessary. Temporary repairs could

be made using glass fabric and elastomeric coating or an adhered elastic sheet

described in previous section.

6.2.5 Repair of Drainage Systems

When drainage systems are found to be inadequate to remove water quickly,

corrections should be made. A determination must be made as to whether the

problem is due to gutter or downspout capacity or gutter slope. Guidelines

for design of drainage systems are given in the Architectural Sheet Metal

Manual [6]. When components of drainage systems, such as gutter, downspouts,

supports or hangers, are severely corroded they must be replaced with components

having adequate capacity. Deteriorated, damaged, loose, or missing components

or sections of these components should be repaired or replaced depending on their

condition.

6.3 MAINTENANCE COATING PROCEDURES

The selection of a maintenance coating system which includes substrate

preparation depends upon the condition of the existing coating and the metal

substrate. Generally, when surface corrosion and coating deterioration are present a maintenance system dealing with corrosion must be considered. For

example, if there is overall surface corrosion, it is recommended that the

existing coating be removed regardless of its condition.

As indicated in figure 24 (condition assessment procedure) either spot or total

recoating is recommended depending on the detailed inspection and condition

ratings (Inspection Form 3). Spot recoating is defined as spot surface preparation, priming, and topcoating. Total recoating includes surface preparation

and either spot priming and total recoating or total priming and topcoating.

Preliminary recommendations for surface preparation and maintenance coating

selection for conditions commonly found at Air Force Bases are briefly described

in sections 6.3.1 through 6.3.5 and listed in tables 10 through 12. Surface

preparation procedures and maintenance coating systems are described in detail

in Appendix C.l and C.2 respectively.

6.3.1 Coating Maintenance Systems for Metal Protected by Galvanizing

without an Organic Coating

6. 3. 1.1 Total Recoat

Red rust is the type of deterioriation generally expected for galvanized metal

panels without an organic coating. The recommendation for surface preparation

is to spot abrasive blast or to power tool clean (surface preparation pron-dur'-

1, Appendix C.l) the surface to remove localized corrosion products or abrasiv

blast (surface preparation procedure 2, Appendix C.l) to remove general overul 1 corrosion. A recommended coating system is an organic zinc-rich primer and

49
Table

10.

Maintenance

Coating

Procedures

for

Steel

Panels

Protected

by

Galvanizing

and

Non-bituminous

Maintenance

Coating

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a 4-J -X 4-J o QJ

4-J 4-J qj e E Q) QJ QJ 4-J cO •rH QJ be •H o CO CO CO 40 co

CO COL c c 40 40

X o 4-J CJd 4-J Ci Pn E Pn

X 4-J •H o Pc QJ QJ 4-J 4-J 4J <4H CJ cti O •rH On CO CO d c u H 40 4= •rH •rH *rH o QJ Ct Ci 4-J o 4-» QJ d

QJ 4J 4-J QJ QJ QJ Ci CTJ CL CO CJd bO •H bC CL QJ

4-J CO

a o o dd 0) 40

CJ QJ CO CO QJ 0) Cl o Ci •H •H 4-J •H

X 3

03 Ci bO QJ Ci Ci CL) QJ 4-J 4-J CO 4-J c c 0) d d o CL 40 QJ 40 CT3 cO 4d CO rH CM

03 o '—1 C •H -X <4H 4-Ja 4-JCO 4-JO rH

40 •H •H QJ 4-J CJ QJ QJ o d o CTJ CJ CJ •H QJ CJ c 4-J 03 i i 1 rH qj co •rH 40 CJ CL CO 3 Ci o 03 Mh i i 1 CO 3 o 40 CO d 0) QJ d 0) 3

bC •H

a 4-J 4_Ja 4-J

X 4H • QJ • Ci

O CO CJ QJX

(0 C/3 o <4-1 QJ QJ QJ C4 QJ 4-J QJ CL

d QJd

O QJ •H qj hJ o B 40 QJ > 3 rH d rH co E co •H CJ

4-J 40

X

O CO 40 •rH 40 QJ

d c o O

<0

X bO 4-J E CO cO CJ QJ o QJ 43 Cl o < d X X X C Ci QJ QJ 4-J E 4-) CO 4-) d 4-» CJ CL

CJ •H o o o o o d Cl CO <4-1

dd

4-J o o o o o QJ QJ QJ QJ QJ Ci •H CO •H QJ Q)

03 bO bO bC CL CL -d QJ 40 40 40 40 3 CO QJ CO

X CO oo 5 40 H 4-J H 4-J CO 2 p-1 E H co

cO JO CJ

X 0) Q-l bo 43

50
Table

11.

Maintenance

Coating

Procedures

for

Steel

Panels

Protected

with

Bituminous

Factory

Coating

or

Bituminous

Maintenance

Coating

with

or

without

Non-bituminous

Topcoat

<D X

<D x

XC

C

XX •3 CO

X

D c 2* 3 X a) • CO

CDa

X CO

X

So

X

X

C c x X X X o CD X X co X X X CJ CO S X 0) X CO e CJ X X 0) o cO X • X X 3 X Li X

4-1

X bO

X CO c

CO CO

X

C CO 3 <D

a c TJ

x <D Li

X e o c X Li * o X o u O

cj

X

a <D

X c 3

*H

X CO

D

so 3 E V

X Li 3 X c CD CO c O C o X CD <D CO cj X E <D E

CD o o 3 X E

CO s u

O

X

O

co 0) a CD

uX CJ

cj

X CO

X

X

D

X

X o > X

X

x o o CL c

CO

X l-l CD CO CO o CL co 3 CO X s C a 3 X X o C CO c O X CD CO CD X X X CJ E

CO COX

— CO CD 3 c C c X X

CDO

X Li o Li CO

C

X

X

O

X 3 >%

X

X E X CO CO CO E co O o X c CJ X Li CD bo

CD

X • c L

X c

4-1

X CD

X CD

O

X

X

<D E X

u CO CJ

X 3 O X <D D C CO a Li X D o

CD J-lO

a o X CJ

X <D o l-i * X • X CL CO X 3 X X So X X CO C X 3 CO <D a CO X X 3 c X c CD <D o X o X • o 3 X • X CO X ,—4 X 3 LJ bo X X • X •* 3 c c CO CD co o QJ • X CO <D <D X c X •3 CM 3 E CJ CO 4-) o X c X X • c CD O <D CO X CD X X 'O o X X X O X X 3* a X CL Qcj co o CD c X o

-3

O CO CD

X <D Li 3 CO bO C X CJ CO a. 3 X CL c X c D X D X CL c X CO X s l-i CL, < <D bo X

4-1

g CD CL Li c 3 CO

CO o CO c c aD

X CD 3 X o CO U X X < X X X X X (D X CO LJ cO 00

(D • X CL, c 3 3 c D o 3 CD bO X CD D X X u X u X C So c E X X 5 CO u X X X X CO X 3 X ^ x X X CO X D l-l <D CD o X X * CO C •3 a> X CJ X u 3 3 O X <D CO X e CO CO

CO

a E X CL <D CD l-l CD

X

X

bO

X CO

X 3 CJ

u *rH c c bO X (D CD CO CD La CO CD X C <D X l-l X <D CD X D X X X X X CO rH l-i 3 X > 5

CO

X

a <DX COX CD 0) O CO X CO 3 D 3 CO CJ 3 a X D S CO L-i CO D X x X CD CO CD CO o CD X 3

CD CD CO

X

X E Li c X

X

C

CJX CO CD 3 CO

X 3 CD c CD CO X 3 E CO CO E

CO

XC CO <D CD CD

C E C X o CO a X o V O

<D

X <D bo CO o CO CO

X CJ 4J C X X C i-i E 3 X D C •X CO 3 X bO CL CO C X X X *3 X c X CD c

CO i—I

CO CD CO

X c bo

x CL CD CO E CO CL CJ O X o c OJ X X X CD O CJ co X X X 3 * X X X X O LJ LJ CO CM O <D CL CL CD a CO co 3 • X CM X U La o X E f—1 E

So CO CD

X c La CO

u CD

X CD Q)

x E X CD CO CD c. CO

X 5 X

X

X COX c X CD <D c CO 3 CO

H COX

X

D

X l-i

U (0 >>

D 3 So

X 3 l-l

O

X

O C- c CD CO CJ

D CO

X o 3 a CG E •rH CJ X c CO X <D c bO O O bO

4-1

X • • CJD

O c 3 X c

CO

B aj QJ E CD CO

X c •rH CJ D.

X

CL 3 CO

XXX

C •'*>»

X LJ E X D X D X L. X CO CO D CD CO o X X CO X 03 3 CO CD O X CO o

CJ

X

H

X

H

X

C/3

r >•u

HX CJ

CO

XU 3 D »X bO

X

X

CO X

CLbOcXx333

CD iJ

CO3X

CO>

0) ^ c

<D bo CO C O X X

LJ

U

COO

X

U CDE

bo

x

C

x

x a. X

CO uh X O X

<D <da

<u to X X x V

SI si 3 co

<D X 3C • X CD 3 X Q.

a> co <d X CL "O EO X

X CJ CJ

a) a;

x

>i Cl (U 5

CO COX

CO -u

Q) CO

L JC T3

O c cj 5 x

CD

C CO

CO

CJ CO 3O

CD bo co u C C CO X o CM X X X

O

CD_

_ 3

CD CO CO a. co 3 SO X

a) do li

u

SI 01 CO

u ^ 3 QJ >% X

.—I 0) C CD o e > CO O J= S x

CDX CO

<D

O

X

x 33

CO CD

CD CJ x o 3 X 3 a.

x

CD c C/3 o

CD • >X X x O

CJ 5

CD

U-i CD x s:

S*

O

•3 CD d co u to X SI o a. a

CD c

a. i-» co c x 0 co - x a. x 01 D C

COX

X

O 1 a co -h

<0 4-* a oj u co u u to u

co jC

x

(XX 4J x

0) 3 CO

cj cox

co a; x >% e 3 C X

X

C/5 o Q- 4J •nJC h

51

“Coating

systems 4

and 5

will

be

investigated

in

Phase

II

of

the

study.

"Maintenance

procedures

for

this

condition

will

be

investigated

during

Phase

II

of

the

study
Table

12.

Maintenance

Coating

Procedures

for

Steel

Panels

Protected

by

Thin

Organic

Factory

Coatings

with

or

without

Non-bituminous

Maintenance

Coating

CO 0)

01

B

G OJ CN CO CN CNI CO 3 4-1 CO

0)CJ CO g CJ 4-J

X

X

X

cg bO cO 0) OJ OJ 3 c O 4-J 4-J 4J

01 •H o CJ CO

X CO cO

X o 4-J •H P- rH 0) rH X OJ c 03 4-J o 4-J \ \ 4-J

CT3 o o.

H c CO c C

G c u •H N 1—1

Csl

N

X

0)g

G 1 —v 1 1 4-) CJ OJ kN X pG >n

X c CO B X OJ X X OJ •H 0) •H o 4-J o O X

03

Q

Ga CT3

a CL CO s CL OJ rH OJ QJ i—1

TJ 3 OJ TO n G -C

X c c 3 CO CO

OJ o T3 1 e •H 0) t—H G G I B 4-J CJ O O 1 o CO o a G G CN CN

0) 03 CL OZ

OJ •H Pn G C 0) g CL, o 4-J CO •H c C o 3 0) 4J CO CO c

•H o a OJ OJ 4-J e CO •rH rH rH bO b0 O

•H 4-4

g CJ CJ OJ 0) o

rH

g CJ > > mg

OJ 3 CO 4-J 4-J o O

(-1 CO OJ o o B E 0)

Cl,

Q

aa 0) OJ OJ

CO CO

GG 3

4-J CO •H bO

rH

C Mh 4H PC •H O o \ x c C 3

bO CJ o o \ 0) c cO c c CO CO Pn

•H

G OJ 0)

w r—1

CJ pn Pn c OJ o 0) G

•H CL

O

•H

C

TP o 4h c OJ •rH o O a CO c

cj CO o CO MH G o o OJ CO o B G G c G PG OJ c

OJ 3 O PG '—1

CO

U o OJ G bo

Cl, TO 4-4 4-1 W c o o o CO CO c G G •H 0) OJ „ \ o O CO Pb CO CO c o 0) OJ T3 G Pn Pg c G

OJ

O

PC CJ

4-J 3

4-J cO

CO OJ rH

CA be CO

a o c o o G

GG

•H •H E B OJ OJ OJ

4-J 4-J 0)

GG -C _c

x

CO CO

a OJ OJ 4-J 4-1 4-J •H O >1 JG X •H •H *H g C_J H 4-J 4-J OJ OJ OJ

OJ

cj OJ

ctf

G

t-i c 3

ctf o rH Pg bO

40 •H •H i i 1 PgG c

c_> 3 4-) CO i i 1 c o •H O CO U-i i i 1 CO X 4-J bO •H CJ CJ CT3 c CO o ML 03 o

•H 0)

X

O 4-1 CJ

CTJ T3 bO o < C X) X> X)

G

G

u •H o o o o o

4-J o o o o o

cO bO bO bo

a Cl

(G o CP QJ 3 3

Ml •G CJ

X •x

CD 3 3 O X TP 3 3 G

TP QJ 3 B

a

TP 0)

X OJ 3

OJ

XP coX

O 3 > •G •rH 3 G X o G rL •G •G X E CJ 3 >

OJ CO CO E 3 X G OJ c 3 o

TP o 3 . OJ H TP X

M

X COX bO 3 3 M c H 3 3 3

TP o TP •G

G 3

rH •H

C

X

r 3 3 GJ O CJ 3 O 3 O •H CJ 3 O 3 X X TP X •G CL

CO c E 3 3 G o OJ CO O O bO X CJ rH G 3

•HX

X

G 3 •H

CO o o O ,—1 G

— E G CJ

X 3

OJ

a 3 X TP /G rH CO X •G E -C Ml O o rH TP E o o a 3 G G 3 3 X O a CO 3 3 3 3

LO c CLG

X 3

Ml o bO

X . O •rH 3 3 3 3 o X X TP CJ > —y CO CO X 3 3 • 3 c * X c o •H G 3 G 3

•H •HX • O

O 3 X

GJ E x

X •G 3 o CO O CJ X ,—1

or c cj a)

X 3 3 X o •G # •n 3 G X •G • X OJ o 3 O X 5 o E TJ X G CD •G O 3 X Cl 3 G 3 G G CJ GJ G 3 3 3 O CO G QJ a X X P-N 0) O X 3 s 3

COx 0) Ml

x co TP

X 1—1 GJ xz •G CO

•G GJ CO ml bOG E G C O 3 3 3 3 O CG-I O • O •G G X O ml o •H W • I *G X 3 3

co

X IX • X 3 TP

O

CO

M cO CJ • •G

O 3 X e M tp a) CNl TP O 3 bO 3 o C co X • 3 O 3 O •H QJ 0) CO •iH CJ O X G G X GJ CO E X TP CJ O Pl rH

cO CO CO E CL CP

X 3

TP xz o QJ •H 3 pT, TP 3 c C Cl a c CL TP X X 3 CL

CO 0) QJ *H CL CP

X •G 3 X E C G < OJ G 3

GJ E •rH TP Cl

G 3 TP

X o Pg OJ CP CL 3 > 3 X

OJ CJ TJ

G

X •G < X 3 X

G 0) 0) CO CO

X 3 3 O G GJ C QJ TJ CP 3 3 rH E CO •G X QJ •G X 3 G 3

PH OJ E X 5 OO

CO

G GJ •G 0) •G TJ

•rH CO rH

X

G OJ 3 3 X 3 c OJ QJ O X CJ TJ TP >

bO •rH Xl

G

X CO •G 3 3 3 O

CB CL

X OJ

G 3 3 X E

•H •H >“H •G TP CJ

G CL 3

GJ rH rH QJ S CO 3 3 3 G

CO OJ •HG 0) QJ

X TP •G

O

G 5 CO CO

G TP

X

O

CJ

a E CO •G 3 3 X

CD CO OJ OJ TP

O CJ bO OJ 0) E Gl CO G G 3 3 C G G 0) CO QJ CO O X X 3

*H co 3 x Pg

G 3 3 G

G

GJ TP co co 3 CO

G 3 3

CO CO OJ Pg TP E 3 3 3 TP

•H c CJ co bO OJ QJ 3 CL 3 X o O CP CJ X X 3 3 CJ

OJ •H

G bO -G

O CO 3 G

X o

4-J CL CP

x

G Pg E CL

XG

Ml

G CO CL co CL

OU

Gx

O

X 3 3

0) cO CJ CP bO •G CJ 3 3

COa

OO CP • 3 X

O

CO OJ 4-J CJ

G •G •G

X 3 X •G

OJ

G o OJX

X 3 G

G

X c a QJ X CO CO X 3 3 CNJ 3

.X CJ

X

G o X TP 3 G

CJ OJ • CP

O cO CJ 3 • 3 3

•H CJ a) cO CL 3 a

X 3 G CL J3 co i—i

CP OJ QJ 3 o O 3 3 3

GJ • Ml QJ • G CJ 3 G o TP

G

bCGX QJ

a 3 3 CL 3 •G 3 CL

OJ

C 3 4JC

X CO E OX CJ

X •G CO •G

X OJ 3 bO •G CJO 3

GJ GJ (U CO CO CJ OJ o c X •G

G CJ

CO 0) x. E X co

X 3 •G

a

G CL 3 C O CO 4-J Ml 3 LJ 3 X X

OJ

u OJ OJ QJG •G 3 3 1—1 3 3 G

X OJ J= c X

X 3 CO 3 o 3 3 3 3 S G H •H H X cn S P>M CJ cn G 3p cn

CO -Q CJ CP OJ cG bo

X • G

52
an acrylic latex topcoat (coating system 2, Appendix C.2). If it is desired

to coat the galvanized steel when there is no red rust, and if the galvanized

surface has been exposed to the weather for more than one year, then a latex

maintenance primer and topcoat (coating system 3, Appendix C.2) may be used.

If exposed less than one year, treat the surface with a wash primer (MIL-P15328) and apply latex maintenance primer and topcoat. The recommended surface

preparation for new or weathered rust free galvanizing is to water wash the

surface or if an oily or greasy film is present to solvent wash the surface

followed by washing with water.

6. 3. 1.2 Spot Recoat

If localized rust is present and it seems appropriate to only recoat those areas (because of, for example, limited desired service life or limited

resources), then the recommendation is to spot abrasive blast or power tool

clean the areas that are rusted and apply a zinc-rich epoxy coating. The

overall recoated appearance may be uneven in texture and differ in color com- pared to other areas of the metal panels.

6.3.2 Coating Maintenance Systems for Steel Panels Protected by Galvanizing

and an Organic Maintenance Coating

6 .3 .2.1 Total Recoat

Peeling of existing coatings is the most likely problem encountered in this

category. In most cases, the maintenance organic coating should be removed.

Several alternatives are suggested for coating removal. They include con- trolled or careful abrasive blasting (which will remove some of the galvanizing) , water blasting (which does not always remove all the organic coating), a com- bination of abrasive and water blasting, and chemical removal. Each of these

three procedures have limitations and will be investigated in phase II of this

project. It is noted that galvanizing protects steel from corrosion and

generally should not be removed. However, when there is some corrosion of the

steel panel, then abrasive blasting may be the best choice to remove the

corrosion and coating. If the coating adhesion is poor, then water blasting

is probably the best choice. If abrasive blasting is not permitted because of

environmental restraints, then chemical removal may be considered. The Director

of Bioenvironmental Safety at the base should be consulted about chemical

removal prior to any work involving chemicals.

Preliminary recommendations for coating maintenance procedures are summarized

in table 10. These maintenance coating systems and others will be tested in

Phase II of this project.

6 .3 .2

.2

Spot Recoat

When peeling of loose maintenance coating is localized, then hand scrap ini' ' remove the peeling coating is recommended. If there is no red rust, then .1 latex system is recommended. When there is localized corrosion of the

steel, then spot abrasive blasting or power tool cleaning is recommend < !.

53
the galvanizing is lost or removed, a zinc-rich epoxy primer is recommended.

The topcoat should be the same type as the existing coating or a latex coating.

The area of existing coating overlapped by spot recoating should be compatible

with the maintenance primer or maintenance topcoat if applied over the existing

coating. Do not use zinc-rich epoxy over coatings soluble in methyle ethyl ketone

(thermoplastic type coatings, see section 5. 1.2. 3), instead use wash primer

MIL-P-15238 with TT-P-645 primer when existing coating is soluble in methyl ethyl

ketone

6.3.3 Coating Maintenance Systems for Steel Panels Protected by a Bituminous

Coating

6 .3 .3.1 Total Recoat

When metal panels that are protected with bituminous factory coatings

are to be recoated, it must be determined whether these existing coatings contain asbestos. The Director of Bioenvironmental Safety at the base should be

consulted in order to identify if coatings contain asbestos, and prior to any

work dealing with coatings containing asbestos. The surface preparation for

coatings containing asbestos may be different (surface preparation will

also depend on the adhesion rating and coating thickness) than for those that

do not contain asbestos. If a decision is made to remove asbestos containing

coatings, regulations concerning asbestos removal must be followed. Presently,

there is limited information on the performance of primers for use over minimally

prepared rusty metal surfaces that are compatible with bituminous containing

coatings. Primers for this application will be identified and tested in phase

II of this project.

Several maintenance coating systems have been recommended for use with bituminous

coated panels. Recommendations for surface preparation and maintenance coatings

for various conditions are given in table 11. In this table, recommendations

are made with the assumption that asbestos containing material will not be

removed during surface preparation.

6 .3 .3 .2 Spot Recoat

The following surface preparations and maintenance coatings are recommended

for spot recoating of panels containing bituminous material:

When the coating does not contain asbestos, loose coating material and/or

corrosion products should be removed by hand cleaning, power tools, or spot

water or abrasive blasting (surface preparation procedure 1, Appendix C.l).

When the coating contains asbestos, then localized surface preparation can only be done in accordance with safety requirements and approval of the

Director of Bioenvironmental Safety at the base. After removal of rust

and loose coating, a maintenance latex primer is recommended. When there is no surface preparation or it is minimal, due to the existing coating containing

asbestos, an over-rust primer should be used at locations where corrosion is

present. It is important that this primer be compatible with bituminous coatings.

A latex topcoat is recommended to minimize incompatibility of the new topcoat

54
with existing bituminous material. Organic solvents and topcoats tend to

reduce the adhesive and cohesive properties of existing bituminous coatings .

6.3.4 Coating Maintenance Systems for Steel Panels Protected By Thin Organic

Factory Coatings with or without a Maintenance Coating

6. 3 .4.1 Total Recoat

The systems described in table 12 are recommended for maintenance of metal

panels with thin organic factory coatings. Corrosion at bends in the panels

was the most often observed problem. Improved techniques for removing corrosion need to be developed and current technology will be evaluated during

Phase II of the project. The use of power tools or water blast for removal of

corrosion at bends is recommended at this time. Prime areas where corrosion

was removed prior to total recoating.

6 .3 .4 .2 Spot Recoat

The preliminary recommended procedure for spot recoating metal panels protected

by a thin organic factory coating is removal of corrosion products, dirt, and

grease (surface preparation procedure 1, Appendix C.l), application of a primer

over the base metal, and a topcoat. The topcoat should be compatible with and

match the factory applied coating. The applicable maintenance coating procedures are given in table 12. In case a matching topcoat cannot be found,

then total recoating may be necessary.

6.3.5 Maintenance Coating Systems for Buildings with Only Surface Coating

Deterioration

From the initial check-off inspection (Inspection Form 1), it will be determined if the coating surface is deteriorated (chalking, fading, mildew, or bleeding/soiling). Surface preparation for deteriorated coatings where

corrosion is not present is given in surface preparation procedure 1

,

Appendix C.l. After proper surface preparation, application of a maintenance

acrylic latex coating is recommended. Satisfactory performance of acrylic

latex coatings over urethanes, thermosetting factory coatings, polyesters, and

bituminous coatings were observed during the field study. Other coating

systems will be evaluated in phase II of this project.

55
7 . SUMMARY

The Air Force has a large number of buildings with factory coated sheet

metal siding and roofing. Although annual maintenance costs may exceed $40

million, there are no current directives for exterior maintenance of these

buildings. Hence, various maintenance coating sytems are being used and some

of these fail prematurely. This work was initiated to provide guidance in

maintenance of these types of buildings. The objective of the work is to

assist the Air Force in developing criteria for recoating buildings constructed

with factory coated metal siding and roofing. The work was divided into two

phases. The objective of the first phase is to 1) develop standard procedures

for assessing the condition of the exterior surfaces of buildings and 2) make

preliminary recommendations, based on existing information, for maintenance

coatings procedures. The results of Phase I described in this report will be

used as a basis of a manual for field use which will be prepared by the Naval

Civil Engineering Laboratory. The objective of the second phase is to modify

the condition assessement procedures, as indicated by field use, perform

laboratory and field tests to evaluate and revise the preliminary maintenance

recommendations and to evaluate other candidate maintenance procedures and

materials, and develop interim criteria for the selection of maintenance

coating systems.

The types of metal siding and roofing materials commonly encountered at Air

Force bases are described. Most of the siding and roofing panels were hotdipped galvanized (zinc coated) steel with an organic coating. A field study was conducted to obtain information about the condition of metal siding and

roofing at many Air Force bases in various geograhic locations in the United

States. Problems were identified with coated metal panels on buildings which

had been exposed to weathering over different periods of time. The performance

of various types of factory applied and maintenance coatings was assessed.

The condition of fasteners and drainage systems was also observed and

determined

Procedures to identify or characterize existing coatings on metal panels are recommended. Visual standards which include sketches and photographs were developed for use in condition assessment of coated metal siding and roofing.

Industry standards for corrosion, blistering, and cracking did not represent

the types of deterioration of coated metal panels observed in the field.

The quantitative condition assessment procedure that was developed is divided

into two parts. First, the condition of the siding and roofing of the

building is evaluated from one site inspections using inspection forms, visual

standards, and descriptions of levels of deterioration; and second, based on the evaluation data and analytical procedures which were developed, appropriate

maintenance procedures are determined. The preliminary recommended maintenance

procedures include those for the repair of panels, fasteners, and drainage

systems, and for maintenance coating selection. Maintenance procedures include

selection of appropriate surface preparations and primers for a wide range of

existing coatings, problem conditions, and maintenance coatings.

56
The benefits of the quantitative, reproducible condition assessment procedure

includes improved data for use by base engineers to prioritize maintenance

work, more effective use of engineering time, accumulation of data to determine

service-life of maintenance procedures, and selection of proper maintenance

procedures

57
8 . REFERENCES

1. Metal Building Systems Manual, Metal Building Manufacturers Association,

Cleveland, Ohio, 1981.

2. Sleater, Gerald A., Performance of Industrial-Type Cladding Materials,

NBSIR 73-134, National Bureau of Standards, March 1973.

3. Mock, John A., Introduction to Prefinished Metals, Technomic Publishing

Co., Inc., Lancaster, Pennsylvania, 1983.

4. Thompson, S. P., "Managing a Maintenance Painting Program to Reduce Costs,"

Materials Performance, Oct, 1982, p. 48; and Appleman, B. R., "Maintenance

Repainting of Structural Steel: Chemistry and Criteria," J. Protective

Coatings and Linings, Vol. 1, August 1984, p. 20.

5. Facilities Engineering Maintenance and Repair of Roofs, Army TM5-617,

Navy NAVFAC MO-113, Air force AFM 91-31 and Marine Corps MCO PI 1014. 9,

January 1974.

6. Architectural Sheet Metal Manual, Sheet Metal and Air Conditioning

Contractors National Association, Inc., Vienna, Va., 1979.

7. Private Communication with H. Marien, AFESC/DEMM, Tyndall AFB, FL.

8. ASTM D714, Standard Method of Evaluating Degree of Blistering of Paints;

ASTM D660, Standard Method of Evaluating Degree of Cracking of Exterior

Paints; 1984 Annual Book of ASTM Standards, Vol 6.01, American Society

for Testing and Materials, Philadelphia, PA 19103. ISO 4628, parts 1-6,

Evaluation of Degradation of Paint Coatings —Designation of Intensity,

Quantity and Size of Common Types of Defect, International Standard

Organization, 1 rue de Varembe, CH-1211, Geneva 20, Switzerland.

9. Field Identification of Weathered Paints, NCEL Techdata Sheet, Naval

Civil Engineering Laboratory, November 1972.

10. Tator, K. B., and Trimber, K. A., "Inspection," in Good Painting

Practices, Steel Structures Painting Manual, Vol. 1, Steel Structures

Painting Council Pittsburg, PA, p. 183, 1982.

11. Built-up Roof Management Program, Department of the Air Force,

AFM 91-36, September 1980.

12. Pavement Maintenance Management, (PAVER), U.S. Army Corps of Engineers,

Army TM5-623, November 1982.

13. Roebuck, A. H. and Brevoort, G. H. , "Coating Work Costs and Estimating,"

Materials Performance, January 1983, p. 43.

58
14 . Sline, M. R., Brevoort , G. H., Feinberg, R., B., and Oechsle, S. J.,

"Comparative Painting Costs," Good Painting Practice, Steel Structures

Painting Manual, Vol 1, Steel Structures Painting Council, Pittsburg, PA,

1982, p. 222.

15. Guide Specification, NAVFAC TS-13121, Section 13121, Pre-Engineered

Metal Buildings (Rigid Frame), Department of the Navy, Naval Facilities

Engineering Command, June 1979.

16. Guide Specification, NFGS-07410, Section 07410, Preformed Metal [Roofing]

[And] [siding], Department of the Navy, Naval Facilities Engineering

Command, May 1983.

17. Guide Specification for Military Construction, CE-201 .1 , Notice 38,

Metal Buildings, Department of the Army, Corps of Engineers, Office

of Chief of Engineers, January 1984.

18. Guide Specification for Military Construction, CE-222 .02 , Notice 24,

Metal Roofing and Siding, Factory-Color- Finished , Department of the Army,

Corps of Engineers, Office of Chief of Engineers, December 1983.

19. Sprayed Polyurethane Foam Roofing System, Techdata Sheet 82-17, Naval Civil

Engineering Laboratory, October 1982.

20. Alumbaugh, R. L., Conklin, S. R., and Zarate, D. A., "Preliminary

Guidelines for Maintenance of Polyurethane Foam (PUF) Roofing Systems,"

TN NO: N1691, Naval Civil Engineering Laboroatory, March 1984.

59

APPENDIX A. GLOSSARY OF TERMS

abrasive material used for blast-cleaning, such as sand, grit, or shot

adhesion bonding strength; adherence of coating to substrate

asphalt a dark brown to black cementitious material in which the

predominating constituents are bitumens which occur in

nature or are obtained in petroleum processing

bend corrosion corrosion of the base metal that can be seen from the

top side of the paint film that is associated with the

factory formed bends

binder resin; non-volitale part of vehicle; film forming portion

of paint

bitumen a class of amorphous, black or dark-colored cementitious

substances, natural or manufactured, composed principally

of high molecular weight hydrocarbons, soluble in carbon

disulfide, and bound in asphalts, tars pitches and

asphaltites

bituminous containing or treated with bitumen

blast cleaning cleaning by abrasives which are propelled at high speed

and can be done either dry or with abrasive in a water

stream (wet blasting)

bleeding movement of colored extractables from subsurface layers

of coating film to exposed surface

blistering formation of dome shaped projections in paint film from

local loss of adhesion and lifting of paint film from

the underlying surface

chalking formation of loose powdery material on the surface of

cured paint film caused by deterioration of the binder

due to weathering

checkings light breaks in the film which do not penetrate to the

previously applied coating or substrate

condition

assessment

systematic evaluation of condition of a building, and

incorporation of evaluation information to determine

overall assessment rating

A-l
corrosion oxidation of metal to form salts, e.g., for steel, iron

oxide salts commonly called rust

cracking breaks in paint film which extend through to the

structural surface (for example to the surface of the

metal in sheet siding)

delamination peeling of one or more coats of paint film from undercoat

or base substrate

dry film thickness depth of cured film on substrate, usually expressed in

mils, (.001 in); often written as DFT

edge corrosion corrosion of base metal that can be seen from top side

of the paint film and is confined to areas near the edges

of the metal panels

emulsion paint paint with resin dispersed in water vehicle, often called

latex paint

erosion gradual wearing away

fading reduction in brightness or change in color as a result

of weathering

feathered edge tapering of edge of paint film to produce smooth

transition from top of paint film to adjacent substrate

flaking paint delamination in thin scale-like particles

flash rusting rusting of steel shortly after cleaning

flat surface

corrosion

general corrosion over all or a portion of the surface;

corrosion not localized along edges or bends

flexibility elongation; extent to which a material will stretch

before undergoing permanent damage

fog coat thin or mist coat (about 0.5 mil dry film thickness)

galvanized steel zinc coated steel, from dipping in molten zinc or by

electrocoating

gloss luster; sheen; brightness

hydroblasting water blasting; cleaning with water at extremely high

pressures
incompatibility inability of a coating to perform well over another

coating because of bleeding, poor bonding, or lifting of

old coating; inability of a coating to perform well on a substrate

latex natural or synthetic binder for water emulsion paints

mildew fungal growth on paint film that can cause discoloration,

usually a dark brown or black, and ultimate decomposition

of a coating’s binder

millscale bluish layer or iron oxide formed on surface of steel by

hot rolling

mistcoat fog coat; a thin coat (about 0.5 mil dry film thickness)

applied to existing paint for bonding of a subsequently

applied topcoat

near-white blast a good grade of abrasive blast cleaning

needle gun hand held pneumatic tool containing small needles which

are driven against metal surface to remove paint,

corrosion products, etc

nonvolatile vehicle resin; binder; film-forming componenets of all paints

organic coating coating (paint) with organic binder, generally of

petroleum or vegetable origin

overall rating rating describing overall condition of building, to be

used in determining priority of maintenance work

peeling paint curling or stripping from substrate

perforations small holes in metal panels caused by corrosion, impact

damage, etc

pigment solid, opaque, frequently colored component of paint

pitting formation of small, deep or shallow cavities formed in

steel by rusting

pinholing formation of small holes through coating from improper

application of paint

plastic mastic repair material often used to fix leaks on roofs around

fasteners and lap joints

polymer large molecule formed by reaction of smaller molecules;

often makes up binder
pot life time interval after mixing of components during which

the coating can be satisfactorily applied

primer prime coat; first coat on a substrate, formulated to

provide good adhesion and usually containing inhibitive

pigments when formulated for metals

rotary-peening

machine

portable, pneumatic, power driven tool for removing paint

and corrosion from metal surfaces using a rotating head

fitted with tungsten carbide-tipped flaps

spangles the flowery crystals formed in galvanizing or hot

dipped zinc coatings on the surface of sheet steel; their

size, luster, and smoothness may vary depending on galvanizing conditions

spreading rate area covered by a unit volume of a coating at a specified

thickness

standing seam

roof

metal sheets are fastened to the roof deck by means of

cleats which are attached to roof deck at one end of a sheet and folded into the seam (unsoldered) at the end

of another sheet

thermoplastic

coating

coating type in which the binder does not chemically

react to form a cross-linked film

thermosetting

coating

coating type in which the binder reacts with another

component of the binder to form a cross-linked film

undercutting blistering and/or peeling of paint from underfilm corrosion

in areas of a paint defect

vehicle liquid portion of paint; resin and solvent components of

a paint

wash primer a thin primer with phosphoric acid and rust inhibitor

for improving adhesion of a primer to metal or as a hold

coat after blasting
APPENDIX B. VISUAL STANDARDS AND DESCRIPTIONS OF LEVELS OF DETERIORATION

For each of the problem conditions listed in Section II of the initial checkoff inspection form (Inspection Form 1) there is a set of visual standards.

The visual standards are complemented by a brief description for each level of

deterioration of each problem condition category. Presented in this appendix

are six visual standards (figures B.l through B.6) and corresponding descriptions of levels of deterioration for problem conditions dealing with flat

surface corrosion, edge corrosion, bend corrosion, undercutting, peeling/

blistering, and cracking. The level of deterioration of a particular problem

condition determined from the visual standards and the description of levels

of deterioration are used in the detailed evaluation of the condition of

metal panels (Inspection Form 3).

For each set of visual standards, there is a photograph that illustrates

moderate deterioration (rating or level of deterioration of 5) for a particular

problem condition and sketchs of three levels of deterioration. The levels of

deterioration or the extent of the problem represented by the sketches are severe or "2" level, moderate or "5" rating, and slight or ”8" rating. There

are not any sketches in the visual standards for the "10" rating since by

definition the "10" rating corresponds to no visible deterioration.

The descriptions for each level of deterioration for problem condition

categories flat surface corrosion, edge surface corrosion, bend corrosion,

undercutting, peeling/blistering, and cracking are given below.

Flat Surface Corrosion

Level of Deterioration Description of Level of Deterioration

10 no corrosion is visible on surface of

coating or substrate and no corrosion is

present on substrate when film is removed

8 a rating of 8 corresponds to slight corrosion

(fraction of area corroded is 0.03%)

visible on surface of coating or substrate

5 a rating of 5 corresponds to moderate

corrosion (fraction of area corroded is

0.3%) visible on surface of coating or substrate

2 a rating of 2 corresponds to severe corrosi n (fraction of area corroded is 3%) visible

on surface of coating or substrate

B-l
Edge Corrosion

Level or Deterioration Description of Level of Deterioration

10 no corrosion of edges visible from surface

or when coating is removed

8 discontinuous corrosion along edges,

1/16 in. (1.6 mm) or less in width

5 continuous corrosion along edges, 1/16 in.

(1.6 mm) or less in width

2 continuous corrosion along edges, 1/16 in.

(1.6 mm) or more in width

Bend Corrosion

10 no corrosion associated with the factory

formed bends that is visible from the

surface

8 discontinuous corrosion 1/16 in. (1.6 mm) or less in width on 25% of bends

5 discontinuous corrosion 1/16 to 1/8 in.

(1.6 to 3.2 mm) in width on 50% of bends

2 continuous corrosion 1/8 in. (3. 2 mm) in

width on 50% of bends

Undercutting

10 paint film is adhered tightly to metal

substrate adjacent to defect.

8 adjacent to coating defect, paint film can

be removed for a distance of 1/16 in.

(1.6 mm) or less from defect.

5 adjacent to coating defect, paint film can

be removed for a distance of 1/16 to

1/8 in. (1.6 to 3.2 mm) from defect

2 adjacent to coating defect, paint film can

be removed for distance greater than

1/8 in. (3. 2 mm) from defect

B-2
Peeling/ Blistering

Level or Deterioration Description of Level of Deterioration

10 no peeling or blistering of paint film

8 peeling and/or blistering of paint film

that is confined to 0.05% of the area

5 peeling and/or blistering of paint film

that is confined to 0.5% of the area

2

Cracking

peeling and/or blistering of paint film

that is confinded to 5% of the area

10 no cracking of paint film visible to naked

eye

8 slight cracking of paint film, cracks do

not extend to substrate and cover 0.05% of

the area

5 moderate cracking of paint film, cracks

do not extend to the substrate and cover

0.5% of the area

2 severe cracking of paint film, cracks

extend to the substrate and cover 5% of

the area
Level 8, (0.03% of area) Level 5, (0.3% of area)

Figure B.l. Visual standards for flat surface corrosion

(sketches actual scale)

B-4
Vertical lap

Horizontal lap

Level 8, discontinuous corrosion

1/16 in. or less in width

Vertical lap

Horizontal lap

Level 5, continuous corrosion

1/16 in. or less in width

Vertical lap

Horizontal lap

Level 2, continuous corrosion

1/16 in. or more in width

Figure B.2. Visual standards for edge corrosion at vertical and hori / mil .1 laps and at the top and bottom of metal panels

(sketches actual size)

B-5
Level 8, discontinuous corrosion

1/16 in. or less in width on 25%

of blends

Level 5, discontinuous corrosion

1/16 to 1/8 in. width on 50% of

blends

Level 2, continuous corrosion Level 5, photograph

1/8 in. or more in width on 50%

of bends

Figure B.3. Visual standards for bend corrosion (not to scale)

B-6
Level 8, paint film can be removed Level 5, paint film can be removed

1/16 in. from defect from between 1/16 and 1/8 in. from defect

Level 2, paint film can be removed Level 5, photograph

1/8 in. from defect

Figure B.4. Visual standards for undercutting. In the evaluation of tin- condition of metal panels, undercutting may affect the level

of deterioration of the types of deterioration shown in tin- other visual standards, figures B.l, B.2, B.3, B.5 and R.t .

B-7
1

1

1

•

1

1 1

•

1 1

1

1 1

Level 8, (0.05% of area) Level 5, (0.5% of area)

Level 5, photograph

Figure B.5. Visual standards for peeling/blistering (sketches actual scale)

B-8
Level 8, (0.05% of area)

Figure B.6. Visual standards for cracking (sketchs actual seal--)

B-9

APPENDIX C. SURFACE PREPARATION AND MAINTENANCE COATING SYSTEMS

C.l SURFACE PREPARATION

Procedure 1 - This procedure is used to remove localized loose paint, localized

corrosion products, dirt, grease, chalk and mildew from metal panels. For

example, this system could be used to clean along bends of metal panels when

deterioration is confined to the bend area. Removal of localized corrosion

products and loose paint can be done either by spot abrasive blasting or by

using power tools. The types of power tools used include needle guns, rotarypeening machines, and power sanders. In addition to localized abrasive blasting

or power tool cleaning, it is necessary to remove dirt, grease, chalk, and

mildew from the remaining coating surface before recoating. Dirt and chalk

can usually be removed by water blasting. If blasting with water does not remove the dirt and chalk, and if environmental regulations permit, a 5% solution of trisodium phosphate can be substituted for the water. Solvent washing

is generally used to remove grease. It is noted that the use and disposal of

solvents, cleaning solutions, and paint materials should meet the approval of

the Director of Bioenvironmental Safety for the base. Mildew can be removed by

washing the surface with a 1% solution of sodium hypochlorite. A combination

of spot abrasive blasting or power tool cleaning and water blasting has been

reported to be effective in most cases for surface preparation of metal

substrates with localized corrosion or peeling [Cl].*

Procedure 2 - Complete removal of coatings and corrosion products is usally

done by abrasive blasting [ C2 ] . The desired degree of coating and corrosion

removal is usually specified using surface preparation standards of the Steel

Structures Painting Council's Standards (SSPC)[C3] or the National Association

of Corrosion Engineers Standards (NACE) [C4],

Procedure 3 - Water blasting, either with or without abrasive, is also used to remove corrosion products and existing coatings [ C5 ] . Rust inhibitors are usually added to the water to prevent flash rusting. SSPC or NACE standards

are used to specify the degree of surface cleaning desired.

Procedure 4 - This surface preparation system is for removing loose paint from

galvanized surfaces. When there is no evidence of corrosion of the base steel,

it is desirable not to remove the protective zinc coating. Surface preparation

procedures currently being used for this condition include blasting with soft

abrasives such as walnut shells, chemical removal, and water blasting. These

procedures will be investigated during phase II of this project.

Procedure 5 - This system is for the special case when just the outer layer *t existing coating film is peeling from the adjacent layer and there is essentially no corrosion of the base metal. Water blasting is sometimes used in

this situation and will be investigated in phase II of the project.

Figures in brackets preceeded by C indicate references listed at the < 1

< ! : this appendix.

C-l
C. 2 MAINTENACE COATING SYSTEMS

System 1. Elastomeric - This coating system may be used on roofs and is

usually applied to obtain a 20-30 mils or 0.020-0.030 in. ( 0 . 500-0 . 750 mm)

dry film thickness. In cases where leaks have occurred at fasteners and

laps, the use of a glass fabric set in a 20-30 mil or 0. 020-0. 030in. (0.500-

0.750 mm) layer of elastomeric coating is recommended at these locations

prior to application of an elastomeric coating over the entire surface. The

binders in these types of elastomeric coatings are commonly acrylics or urethanes

System 2. Epoxy-zinc/acrylic latex topcoat - This system consists of an epoxy-zinc (zinc-rich epoxy) primer (Naval Ship Technical Manual, Chapter 631)

and an acrylic latex maintenance topcoat (MIL-P-28578)*. Each of these

coatings should be applied to obtain a 2-3 mil or 0.002-0.003 in.

(0.050-0.075 mm) dry film thickness.

System 3. Acrylic latex maintenance primer and topcoat - This system consists

of an acrylic latex maintenance primer (MIL-P-28577)* and an acrylic latex

topcoat (MIL-P-28578)*. The dry film thickness of each coating should be

from 2 to 3 mils or 0.002-0.003 in. (0.050-0.075 mm).

System 4. Over-rust primer- When surface preparation is minimal, the use of an over-rust primer may be appropriate. Primers for use over rusty steel are available. Their performance will be evaluated for use with existing

bituminous containing coatings in Phase II of the project. Compatible topcoats will also be tested in Phase II.

System 5. Moisture curing urethane primer and aliphatic urethane topcoat - When environmental conditions, low temperature below 50° F (32° C), do not

permit the use of latex systems, a urethane system may be used in some cases

as a maintenance coating.

* Military specification
C.3 REFERENCES

Cl. Delahunt, J. F., "Maintenance Paint Surveys of Refineries and Petrochemical

Plants," J. of Protective Coatings and Liners, Vol . 1, No. 7, p. 22,

December 1984

C2 . Painting of Facilities, Air Force Manual, AFESC/DEMM, Tyndall AFB, FL

32403, 1983.

C3 . Pictorial Surface Preparation Standards for Painting Steel Surfaces,

SSPC-VIS-1, Steel Structures Painting Council, 4400 Fifth Avenue, Pittsburg,

PA 15213, 1967.

C4 . TM-01-70 Visual Standards for Surfaces of New Steel Air-Blast Cleaned

with Sand Abrasive, National Association of Corrosion Engineers, P .0 . Box

218340, Houston, TX 77218, 1970.

C5 . Bennett, J., "Water Blast Cleaning," in Good Painting Practices Steel

Structures Painting Manual, Vol. 1, Steel Structures Painting Council,

4400 Fifth Avenue, Pittsburg, PA 15213, 1982, p. 64.

C-3

HBS-114A (REV. 2-6C ) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO. NBSIR-85/3193

2. Performing Organ. Report No. 3. Publication Date

JUNE 1985

4. TITLE AND SUBTITLE

Preliminary Recommendations for Maintenance of Factory Coated Metal Siding and Roofing

5. AUTHOR(S)

Mary E. McKnight, Robert G. Mathey, and Richard W. Drisko

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Qrant No.

8 . Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, State. ZIP)

Air Force Engineering and Services Center

Tyndall Air Force Base, Florida 32403

10. SUPPLEMENTARY NOTES

J Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bl iography or literature survey, mention it here) Recommendations and guidelines are presented for condition assessment and maintenance

of the exterior surfaces of factory coated metal siding and roofing. The metal siding

and roofing products commonly encountered on Air Force installations are addressed.

The types of deterioration of metal buildings and appropriate methods of repair and

maintenance procedures are related to the materials and construction practices used.

The results of field observations of the condition of many types of coatings on metal

siding and roofing in varying states of deterioration are reported. A quantitative

condition assessment procedure was developed for exterior surfaces of metal buildings

and consists of two parts. First, the condition of the siding and roofing of the

building is evaluated using inspection forms, visual standards, and descriptions of

levels of deterioration. In the second part, recommended maintenance procedures are determined using the evaluation data and analytical procedures which were developed.

Visual standards and detailed coating failure descriptions were developed in order to

identify and catergorize the condition of the metal siding and roofing of buildings. Preliminary repair and coating maintenance system recommendations were made for frequently encountered problem conditions observed during inspections of buildings with

metal siding and roofing on Air Force bases. The preliminary recommendations include

those for surface preparation and selection of maintenance coatings. The recommendations were based on the types of existing coatings and metal materials, their condition

and whether the selected maintenance coatings are compatible with the existing coatings

and selected surface preparation procedures.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon > / Coating; condition assessment; maintenance coatings; metal roofing; metal siding;

roofing; siding; surface preparation; visual standards

13. AVAILABILITY

En Uni imited

I I For Official Distribution. Do Not Release to NTIS

Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Order From National T echnical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

86

15. Price

$11.50

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