AD-A244 074 _ 1111l~ II1 IIrl © 

U.S. Army Corps of Engineers

US Army Corps Technology Transfer

of Engineers Test Bed Program

Omaha District

Considerations For The Use Of

Exterior Insulation & Finish Systems

(EIFS) On U.S. Army Facilities

DTIC

!JA 0 6 1992

92-00155

DEPARTMENT OF THE ARMY

OMAHA DISTRICT, CORPS OF ENGINEERS

OMAHA, NEBRASKA

December 1991

Contributors:

Kenney I Williams I Williams Inc.

Maple Glen, PA US Army Corps of Engineers

Construction Engineering Omaha, NE Research Laboratory

Approved for public release; distribution is unlimited.
The contents of this report are not to be used for advertising, publication,

or promotional purposes. Citation of trade names does not constitute an

official endorsement or approval of the use of such commercial products.

The findings of this report are not to be construed as an official Department of the Army position, unless so designated by other authorized

documents.

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1. AGENCY USE ONLY (Leave Blank) 12. RPRT DATE T3.. REPORT TYPE AND DATES COVERED

SRE November 1991 Final

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Considerations for the Use of Exterior Insulation and Finish Systems (EIFS)

on U.S. Army Facilities ,3B

6. AUTHOR(S)

Kenney, Williams, Williams, Incorporated

Maple Glen, Pennsylvania

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION

REPORT NUMBER

USACERL U.S. Army Engineer District, Omaha

PO Box 9005 215 N. 17th Street MROED-001

Champaign, IL 61826-9005 Omaha, NE 68102-4978

9. SPONSORINGMONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

USACE

ATTN: CEMP-EA

20 Massachusetts Avenue, NW.

Washington, DC 20314-1000

11. SUPPLEMENTARY NOTES

Copies are available from the National Technical Information Service, 5285 Port Royal Road,

Springfield, VA 22161

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Approved for public release; distribution is unlimited.

13. ABSTRACT (Maximm 200 words)

Numerous U.S. Army and Air Force buildings clad with exterior insulation and finish systems (EIFS) have

recently experienced maintenance problems, localized deterioration, and outright failure. In cases of major

failures, remedial work may cost more than $1 million.

This report provides technical information and guidance for specifying, reviewing, and/or inspecting EIFS

claddings. It also contains a brief history of EIFS, describes EIFS components and different types of EIFS

claddings, lists considerations for EIFS selection, and details typical EIFS failure modes. Figures show

successful and unsuccessful EIFS condition on military and private sector buildings.

14. SUBJECT TERMS 15. NUMBER OF PAGES

Exterior Insulation and Finish Systems (EIFS) 88

maintenance 16. PRICE CODE

materials performance

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT

OF REPORT OF THIS PAGE OF ABSTRACT

Unclassified Unclassified Unclassified SAR

NSN 7540-01-280-SS00 SWicd Fon 298 (Re. 2-8

Preacibed by ANSI Sal 239-18

2W-102
FOREWORD

This work was performed for the U.S. Army Corps of Engineers (USACE) as coordinated jointly

by the U.S. Army Construction Engineering Research Laboratory (USACERL), Champaign, Illinois, and

the U.S. Army Corps of Engineers, Omaha District, Omaha, Nebraska. Funding was provided through

the Corps of Engineers National Alternate Construction Technology Team (CENACTT) as part of the U.S.

Army Corps of Engineers Technology Transfer Test Bed Program ('TTrB).

Over the course of this effort, the USACE Omaha District Project Managers were Jennifer Young

and Jeff Skog. Richard Lampo from USACERL was the project technical coordinator. The Headquarters,

USACE Technical Monitor was Rodger Seeman, CEMP-ES. Leo A. Daly, c/o Raymond Madsen, Omaha,

Nebraska. and Kenney, Williams and Williams, Inc. (KWW), c/o Mark Williams, Maple Gle,, Pennsylvania, were contractors in this effort.

Acknowledgement is given to the following individuals who also helped compose, review avI/or

edit this report: Richard Lewis, Omaha District; Barbara Williams and Mary Straney, KNN W, Inc.; and

Richard Rundus and Jonathan Trovillion, USACERL.

Acesion Fo."

" -NTIS Io ,A..I . .. ..

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2
CONTENTS Page

ABSTRACF ........................................................ 1

FOREWORD ....................................................... 2

LIST OF FIGURES .................................................. 5

INTRODUCTION ................................................... 9

Background ..................................................... 9

Objectives ....................................................... 9

Approach ....................................................... 9

Report Overview .................................................. 9

2 HISTORY ........................................................ 10

Overview ...................................................... 10

Europe ....................................................... it).

United States ................................................... 10

3 SYSTEM COMPONENTS ........................................... 12

Overview ...................................................... 12

Lamina ..................................................... 12

Rigid Insulation Board ......................................... 12

Attachment .................................................. 12

Substrate ................................................... 12

Finish Coat ..................................................... 13

Weathering Surface ............................................ .13

Color and Texture ............................................ 14

Reinforcement .................................................. 15

External Reinforcement ........................................ 15

Internal Reinforcement ........................................ 16

Base Coat .................................................... 16

Insulation ................................................... 17

MEPS Insulation ............................................. 18

XEPS Insulation ............................................. 18

Attachment ................................................... 19

Adhesive Attachment .......................................... 19

Mechanical Attachment................................ 19

Substrate ..................................................... 20

Sealant joints ................................................... 21

Materials.................................................. 21

Design and Application........................................ 21

Sealant Joint Failure .......................................... 22

4 COMPARISON OF EIFS TYPES ...................................... 23

Overvie I.. .................................................... 23

ClassPBSystems..............................................23

Class PM Systems ............................................... 24

5 EISSLCIN................................................. 28

3
CONTENTS (Cont'd)

Page

6 TYPICAL EIFS FAILURE MODES.................................... 30

Overview ..................................... ............... 30

C racking ..................................................... 32

Spalling/CZracking ............................................... 52

Impact Damage ................................................ 56

Inadequate Closure .............................................. 61

System Detachment .............................................. 74

Surface Degradation ............................................. 78

7 SUMMARY AND RECOMMENDATIONS............................... 83

Recommendations ............................................... 83

INDEX......................................................... 85

DISTRIBIbTION

4
FIGURES

Number Page

1 Typical Class PB System 13

2 Typical Class PM System 25

3 Crack in EIFS lamina due to a failure to abut the insulation boards 33

4a Cracking which follows the outline of the insulation boards is a sign of failure to

abut boards 33

4b Closeup of cracking in Figure 4a 34

5 Adhesive between EPS boards - improper 34

6 Incorrect backwrap between EPS boards 35

7 EPS outside comer - interlock omitted 35

8 Vertical and horizontal crack intersection shows the omission of a running bond

pattern 36

9 Cracking in "V" groove articulation 38

10 Exposed mesh in "U" groove articulation 38

11 Cracking in "V" groove articulation 39

12 Cracking in "U" groove articulation 39

13 Crack at window head; diagonal mesh omitted 40

14 Diagonal crack at window sill 41

15 Vertical crack at window head showing improper alignment of insulation board joint

at window head 41

16 Dryvit: Wall Fenetration Details 42

17 Crack due to control joint omission 44

18 Control joint omission at substrate change 44

19 Impingement at control joint - crack 45

20 Premature control joint termination 45

5
FIGURES (cotit'd)

Page

21 Premature control joint termination 46

22 Premature control joint termination at sill 46

23 Premature control joint termination 47

24 Impioper control joint termination 47

25 Vinyl contrci joint failure 48

26 Vinyl control joint failure 48

27 Dry,,A: Expansion joint location drawing 49

28 Expansion joint omission at comer 50

29 Omission of expansion joint between buildings 50

30 Successful expansion joint at building base 51

31 Spalling of base coat due to improper application 53

32 Insufficient mesh embedment 53

33 Insufficient mesh embedment 54

34 Ultraiolet EPS board damage 54

35 EIFS lataina failure due to application over improper substrate 55

36 Closeup of ElFS lamina failure shown in Figure 35 55

37 Inadeqnate material applicat, ., 57

38 Impact damage at loading are% 57

39 impact Oamage at service area 58

40 Doorstop prevents mpact damage 58

41 Impact damage due to door hardware 59

42 Impact damage due to lawn maintenance 59

43 Base detail to accommodate lawn equipment 60

6
FIGURES (cont'd)

Page

44 Gravel border around building perimeter 60

45 Inadequate closure - EIFS/metal sill 61

46 Inadequate closure at metal sill 62

47 Inadequate closure at metal sill 62

48 Inadequate closure at window sill 63

49 Inadequate closure at pipe 63

50 Inadequate closure at pipe 64

51 Inadequate closure at pipe 64

52 Inadequate closure at pipe 65

53 Improper .vering of pipe 65

54 Inadequate closure at hose bib 66

55 Inadequate closure at through-wall cable 66

56 Good termination at door jamb 67

57 Poor parapet termination - insufficient slope 68

58 Poor EIFS termination behind gutter 69

59 Poor EIFS termination at downspout 69

60 Poor EIFS termination at grade 70

61 Good EIFS termination - incorrect backwrap 70

62 Improper tooling 72

63 EIFS/sealant - cohesive EIFS lamina failure 72

64 Cohesive and adhesive sealant failure 73

65 EIFS/sealant - adhesive failure 73

66 Insufficient adhesive attachment 74

7
FIGURES (cont'd)

Page

67 Insufficient adhesive attachment 75

68 Catastrophic system detachment 75

69 Improper mechanical fastener spacing 76

70 Improper mechanical fastener application 76

71 Improper mechanical fastener coating 77

72 Water intrusion - deteriorated exterior gypsum 77

73 Faded finish coat 78

74 Stains due to leaks in gutter 79

75 Stains due to laundry room exhaust 79

76 Stains due to leaks in gutter 80

77 Mildew at grade 80

78 Mildew at mid-wall section 81

79 Mildew at grade 81

80 Stains due to finish coat impurities 82

8
CONSIDERATIONS FOR THE USE OF

EXTERIOR INSULATION AND FINISH SYSTEMS

(EIFS) ON U.S. ARMY FACILITIES

1 INTRODUCTION

Background

In recent years, exterior insulation and finish systems (EIFS) have been used as a cladding on U.S.

Army and Air Force buildings. Field feedback indicated numerous EIFS-clad buildings were experiencing

maintenance problems, localized deterioration, and outright failure. In a couple of cases of major failures,

remedial work may cost more than $1 million. Consequently, the U.S. Army Corps of Engineers undertook a material properties and performance investigation to understand how EIFS is best utilized.

Objectives

The objective of this effort was to provide technical information and guidance to Corps personnel

responsible for specifying, reviewing, and/or inspecting EIFS claddings.

Appnroach

To meet the project objective, the following data collection approaches were used:

- Field survey of nearly 50 EIFS clad buildings from various military posts to assess and document

conditions

" Compilation of information on EIFS definition, classification, and material performance

" Survey of EIFS manufacturers in the United States for additional input on system composition

and performance.

Report Overview

Chapter 2 contains a brief history of EIlS. Chapter 3 describes EllS components. Chapter 4

identifies different types of EIFS claddings and their respective advantages and disadvantages. Chapter

5 discusses considerations for EIFS selection. Chapter 6 lists typical EIFS failure modes. Photographs

are included that document successful and unsuccessful EIFS conditions on military and private sector

buildings. Chapter 7 presents summary and recommendations.

9
2 HISTORY

Overview

Exterior insulation and finish systems (EIFS) are exterior wall claddings consisti;:g of insulation and

wet-applied finishes. Finishes are composed of cementitious and/or synthetic matenals. ElFS function

as a building skin, protecting the building structure from moisture and thermal changes. These systems

are "barrier type" claddings. By design, "barrier" walls must shed water and prevent moisture from

penetrating into the building itself. Hence, all EIFS must perform as waterproofing systems. Moisture

protection is attained by providing an integrated system of EIFS layers in which each component serves

specific and unique functions.

Different terms have been used to refer to EIFS, including "synthetic stucco," and "soft" and "hard"

coat systems. As these systems gained acceptance in the construction industry, the need for a clear

terminology to describe types of EIFS and their related components became apparent. Manufacturers,

distributors, and users, under the auspices of the Exterior Insulation Manufacturers Association (EIMA),

designated "exterior insulation and finish systems" as the official name for these cladding systems. EIMA

also classified various types of EIFS (see Chapter 4).

The benefits of EIFS for both retrofit and new construction are many. Moisture and weather

protection as well as insulating properties are obtained in one integrated system. EIFS is less expensive

than many conventional building materials. Structurally lightweight, EIFS places only slight additional

loads on the building foundation and structural supports. Retrofit work can be completed without

disturbing occupants because the cladding is attached to the outside of the building. Optimal floor space

is realized in all types of construction, and exteriors are relatively maintenance-free. With ongoing

manufacturers' refinements, EIFS offers an increasing range of colors and finishes as well as prefabrication options.

Europe

EIFS originated in Europe as an outgrowth of the painting and plastering trades more than 30 years

ago. Following World War II, building professionals began to use a combination of remedial coatings

and rigid insulation to upgrade existing building facades. With the success of retrofit use, Europeans also

applied these systems to new construction projects. To date, however, retrofit application represents the

predominant use of EIFS in Europe.

Interested manufacturers "formalized" the practices of building contractors by supporting research

and development efforts. Manufacturers and professionals in West Germany led in the development of

EIFS technology. Manufacturing advances enhanced the basic notion of combining syntheticlcementitious

coatings and rigid insulation, and fostered widespread acceptance of EIFS.

United Sta!e.s

EIFS were first introduced in the United States in 1969. The Dryvit Corporation is generally

credited with being the first to import the system concepts from West Germany and adapt them for use

in the United States. Estimates indicate that EIFS have been used in over 100,000 major projects-both

10
new and renovated-since their introduction to North America. According to EIMA, the EIFS industry

is growing more than 25 percent a year. To date, applications have primarily involved nonresidential

buildings: office and retail developments, hotels, schools, and hospitals. However, residential use is

reportedly increasing.

Although U.S. systems retained the basic components of European systems, certain modifications

were made to reduce costs and accommodate the practices of the North American construction industry.

Significant modifications were made in the kinds of substrate material used, and the methods of system

application and detailing. These differences are discussed in greater depth throughout this report.

11
3 SYSTEM COMPONENTS

Overview

EIMA defines EIFS as nonload bearing exterior cladding systems and classifies these systems as

Class PB (polymer based) or Class PM (polymer modified). EIFS chemical formulation varies by class

as well as manufacturer. The current EIMA classification differentiates system types largely by base coat

thickness and the method of installing system reinforcement. The EIMA classification is endorsed by

virtually all EIFS manufacturers.

EIMA describes these systems as generally consisting of an insulation board, an adhesive and/or

mechanical attachment of the insulation board to the substrate, an integrally reinforced base coat on the

face of the insulation board, and a textured, protective finish. Each EIFS component serves specific

functions integral to the overall performance of the exterior wall. A brief discussion of each system

component as well as related materials is provided below.

Lamina

Lamina is a composite layer consisting of three parts: finish coat, base coat, and reinforcement.

Finish coat is the system's outermost surface and provides color and texture to the building. Base coat

is the foundation for the finish coat, holds the system reinforcement, and most importantly, serves as the

wall assembly's primary barrier against water penetration. EIFS reinforcement can be external, either

fiberglass mesh or metal lath, which may be combined with internal fiber reinforcement mixed in the base

coat.

Rigid Insulation Board

Rigid insulation board provides thermal resistance and reduces potential for system cracking by

isolating the lamina from the substrate. Typical kinds of insulation used in EIFS include molded expanded

polystyrene (MEPS), extruded expanded polystyrene (XEPS), semi-rigid fiberglass, and mineral/rock wool.

The type and density of insulation used vary by individual manufacturer.

Attachment

EIFS is attached to the building substrate by adhesives, mechanical fasteners, or a combination of

both. For adhesively attached systems, base coat material or a special adhesive compound is used to

adhere insulation board to the substrate.

Substrate

Although not a component of EIFS, substrate is integral to system performance because it is the

innermost point of contact between the system and building. Gypsum sheathing with steel studs is used

most often in U.S. commercial installations. Masonry and cementitious board are alternate substrates.

For reference, Figure 1 presents the components of a typical Class PB system.

12
Finish coat-, .

Base coat . "- Y."! . " "..

Reinforcing ''" :: '

Metal stud mesh

Sheathing

,. H H , 

': .

Adhesive

MEPS insulation .. ..y .,. y: ... 1 .-. ,

Figure Class;- 1. Typical S,.s.,e. , I1 . ., :... ...**... ,.

, ." ... ,....-.. ,... :, .,.. . ... . . . . . ........ . ... ,,,,; ..

-:,' ..-... . -':,.. . .' ,; .. . . ,. -. -

Figure 1. Typical Class PB System.

Finish Coat

Finish coats typically contain some percent of polymer compound together with silica sand or other

aggregate, antifungicides, and additives to enhance workability and resistance to freeze-thaw cycles.

Depending on the manufacturer, the finish coat can also contain portland cement. As the outermost EIFS

surface, the finish coat provides a weathering surface, color, and texture for the exterior wall.

Weathering Surface

EIFS must serve as a moisture and weather barrier, since a durable weathering surface is necessary

for overall system performance. The finish coat is the initial surface of contact for elements of moisture

and weather. To ensure the system's success, the finish coat must be thick enough to adequately cover

the underlying base coat. In practice, the actual thickness of finish coats varies according to the chemical

and physical properties of particular products. Cementitious material or stone aggregates in the finish coat

increase the specified thickness.

13
Although primarily used in retrofit situations, elastomeric coatings are occasionally applied over the

finish coat to enhance weather resistance. However, these coatings are generally unnecessary if the system

is properly installed. As with all system components, adherence to the manufacturer's recommendations

for finish coat selection and application is important.

As the outermost surface of the system, the finish coat "telegraphs" imperfections in underlying

layers, specifically imperfections in the substrate, insulation, or base coat. Fissures or micro-cracks in the

finish coat signal a potential threat to the "moisture security" of EIFS. Regular inspection and expeditious

maintenance of small cracks prevent minor defects from developing into major problems.

One characteristic of noncementitious finish coats is their tendency to soften when exposed to

moisture for an extended time. This softening leads to delamination such that the finish coat pulls away

from the base coat and reinforcing mesh. Class PB sealant joints are particularly vulnerable to delamination since most systems rely on the finish coat as the sealant substrate. With moisture-induced softening,

it appears that the bond between the finish coat and sealant material is stronger than the bond between the

finish and base coats. Cohesive EIFS lamina failure at sealant joints is the result. Use of open-cell backup rod aggravates this condition by absorbing moisture which enters the joint.

An added factor in the delamination process is the presence of voids within the finish coat. These

microscopic pockets serve as "conduits" that carry unwanted moisture into the EIFS finish coat and bring

about softening. Finish coat softening and voids help explain why the base coat is the primary barrier

against moisture in EIFS claddings.

Color and Texture

Aside from its function as a weathering surface, the finish coat also provides the exterior wall with

an aesthetically pleasing appearance of lasting color and texture. A wide range of colors, from light to

dark, are available. Some manufacturers offer more than 350 standard colors from which to choose.

Custom colors are also available from virtually every manufacturer.

Most manufacturers state that unlike some traditional stuccos which require periodic repainting, EIFS

do not. EIFS colors are integral to the system finish and usually are not affected by sun or mildew.

However, there is some evidence that dark colors tend to fade and chalk with time, and that some finish

coats tend to support mildew growth, particularly on north-facing facades. Periodic recoating of dark

coiors or mildew removal may be required to maintain the origi-nal facade appearance. In addition,

impurities in finish coat materials-small particles of iron, for example-can oxidize and appear as rust

colored streaks on the facade. Removing these impurities and recoating the finish surface is the remedial

action of choice.

Color has a direct effect on thermal joint movement. Light and heat are reflected by pale colors and

absorbed by dark ones. The absorption properties of dark colors increase thermally induced movement

which, in tum, strains sealant joints. Sealant joint design should take into consideration the reflection

value of the selected color. The higher the reflectivity, the less a particular color is affected by thermal

factors. For this reason, pale or light colors are preferred. If dark colors are used, it may be necessary

to limit panel size, increase the number of joints, or enlarge joint width.

Finish coat texture ranges from relatively smooth to coarse, depending on the type and size of

aggregate used. For example, natural stone finishes containing colored aggregates of marble or quartz are

available. These finishes emulate the appearance of exposed granite, marble, or building stone.

14
The aggregate composition has a direct bearing on finish coat porosity and compaction, both of

which influence moisture retention. Aggregate composition is a factor of particle size and gradation as

reflected in the granulometric curve (proportion and distribution of different-sized aggregate particles).

Some EIFS finish coats are "gap graded"-predominantly large and small aggregate particles; others are

continuously graded with a complete range of large-medium-small particles. "Gap graded" materials do

not compact well, resulting in an open finish coat with voids. In addition, the tooling of sealant against

a "gap graded" material is more difficult.

Aside from a wide range of available colors, manufacturers typically offer texture and pattern

choices similar to those of traditional portland cement stucco-sand finish and swirls, among others. The

use of three-dimensional shapes to enhance the appearance of doors, windows, and facade details further

expands the aesthetic possibilities of EIFS. The design flexibility inherent in the many colors, textures,

and finish options of EIFS is a major reason for the increasing use of these claddings.

Reinforcement

EIFS reinforcement is classified as external and internal. External reinforcement includes fiberglass

mesh and metal lath; internal reinforcement is incorporated in the base coat, usually by the manufacturer.

Whatever the reinforcement used, this component is central to EIFS performance because it increases

durability, tensile strength, and impact resistance. For all types of EIFS, not only must the reinforcement

be compatible with other materials in the system, but it must also meet the building's usage needs.

Manufacturers provide recommendations and guidelines for reinforcement selection and use. The

particulars of any given end use must be assessed by building professionals before reinforcement selection

and installation.

External Reinforcement

This is the most popular kind of EIFS reinforcement. Typically, it is a balanced, open fiberglass

mesh fabric coated with a polymeric finish for compatibility with other system materials. Class PB

systems always incorporate fiberglass mesh, while Class PM systems sometimes use this kind of reinforcement.

Usually fiberglass mesh is adhesively attached in Class PB systems by working and completely

embedding the mesh into the wet base coat during the application process. Exposed or partially embedded

mesh is especially problematic. Such conditions could allow water to enter this reinforced base coat layer.

Retained water leads to finish coat softening by keeping finish coat surfaces moist. Retained water may

also lead to chemical attack and weakening of the fiberglass mesh. Furthermore, partially embedded mesh

diminishes the system's integrity by simply weakening system fortification. Class PB systems must be

"backwrapped" at all exposed edges of the insulation board; that is, the lamina is returned from the system

face, over the edge and to the back of the insulation board. Backwrapping helps prevent moisture from

entering EIFS layers by eliminating lamina discontinuities at areas exposed to the weather.

Fiberglass mesh is generally available in three weights: regular, intermediate, and heavy. Regular

or "standard grade" mesh serves as the basic system reinforcement and weighs about 4.5 ounces per square

yard. Intermediate weight mesh has threads up to three times heavier than regular grade and weighs about

12 ounces per square yard. Heavy mesh offers the most impact resistance and weighs about 20 ounces

15
per square yard. Fiberglass detail mesh is another type of reinfo.cement, one which is usually specified

in Class PB systems for application around openings and at terminations.

In broad terms, standard grade fiberglass mesh is typically used for wall areas which have limited

exposure to impact. Heavyweight mesh, on the other hand, may be needed at high impact areas such as

the base of buildings or entrance areas. The edges of heavy mesh are usually abutted and embedded in

the base coat. Standard reinforcing mesh, also embedded in the base coat, is applied over the top to cover

tie seam. This procedure ensures that system coatings function as one cohesive unit.

A second kind of external reinforcement is metal lath. It is fabricated in expanded, wire-woven and

wire-welded forms. Metal lath is the traditional reinforcement for portland cement stucco. It can be used

in certain Class PM systems, but is never used in Class PB systems. Metal lath is always mechanically

attached and is generally available in various configurations to accommodate finish situations.

Internal Reinforcement

This reinforcement is internally incorporated in the base coat compound during manufacture. Internal fiber strands such as chopped random fibers are one kind of internal reinforcement. Compared to

external reinforcement, internal EIFS reinforcement is less common. Its use is limited largely to Class

PM systems, which usually incorporate a chopped random fiber form in conjunction with external

reinforcement.

Base Coat

Base coat composition varies from manufacturer to manufacturer. Most base coats contain polymer,

portland cement, and fillers. A few manufacturers offer a 100 percent polymer-based product. "Pure"

polymer base coats come ready-mixed, whereas cementitious base coats are generally mixed in the field.

The polymer and fillers of cementitious base coats are typically combined by the manufacturer and

shipped in 5-gallon containers to the site, where portland cement and a small amount of water are added.

Some products are intended to be used as a base coat only; others are designed to serve two

purposes: to adhere the insulation to the substrate and to provide the system's base or "ground" coat.

This kind of dual purpose product is incorporated in many Class PB systems available in the United States

today.

The base coat serves multiple, interrelated functions within EIFS. First, it is the primary barrier for

stopping water from penetrating into other wall components. Second, it holds or "embeds" the external

reinforcing mesh and/or actually contains the internal reinforcement material. Third, the base coat receives

the finish coat and is thus the foundation for the system's outermost layer.

Since the base coat is the system's primary defense against moisture penetration, its application and

detailing are critical aspects of the installation process. Application and detailing are especially important

in Class PB systems which require the base coat to be applied in the correct thickness for proper

performance. In the United States, a nominal base coat thickness of 1/16 to 1/4 inch is the standard

requirement for many Class PB systems. Class PM systems in the United States use a thicker babe coat,

ranging between a nominal 1/4 to 3/8 inch.

16
Deviations from the recommended base coat thickness can lead to EIFS deterioration. An

insufficient applicatio, of base coat will not protect and/or hold the reinforcement. A base coat that is

too thin or too thick will result in cracking and exposure of the reinforcing mesh to moisture. With time,

the exposure of fiberglass mesh to moisture and alkalinity from the system matrix (especially with

cementitious base coats) could diminish i's reinforcing strength.

In Class PB systems with fiberglass mesh, the base coat should fully encapsulate the reinforcing

mesh so that the mesh is free from contact with the insulation on the bottom and the finish coat on the

top. It is interesting to note that European systems typically incorporate a skim or "key coat" of base

material on top of an initial base coat layer. This double base coat is applied in two layers, a procedure

which facilitates the correct positioning of the reinforcing mesh in the base coat. Applicators are able to

focus on the placement of mesh during the initial base coat, and attend to possible inconsistencies in base

coat coverage on :he top of the mesh when the skim coat is applied. By contrast, the one-step base coat

procedure generally employed in the United States requires greater skill in order to fully embed or

encapsulate the reinforcing mesh.

The specified mixing proportions for the base coat are intended to promote the best possible

performance of the exterior wall. The manufacturer's recommended ratio of components should be strictly

followed. Deviation from these proportions can jeopardize the success of the system. For example, if the

amount of cement in the base mix is increased, or the polymer decreased, the resulting material will be

stiff and prone to cracking.

The correct degree of mixing is equally important. Over-mixing yields unsatisfactory results. Such

practices introduce unwanted air into the formulation, creating air voids or "pockets." These pockets

permit moisture to pass through the base coat layer and increase the likelihood of exterior wall problems.

Again, manufacturers provide specific mixing instructions for base coat preparation. Climatic conditions

are also significant factors in a successful base coat installation. Temperatures or humidity levels outside

the range sanctioned by the product manufacturer can adversely affect the base coat. Applied in a wet,

workable state, the base coat undergoes a series of chemical and physical changes to achieve a solid, rigid

state. Should the outside temperature fall below prescribed limits before a solid state is fully attained

(typically 40 'F), the overall integrity of the system is endangered.

Less than prescribed climatic conditions can slow the reaction between polymers and portland

cement, extending the setting time or causing incomplete setting altogether. For "pure" polymer base

coats, application in other than manufacturer-specified conditions can lead to curing problems. Whether

the base coat is cementitious or pure polymer, it must be fully cured prior to the application of finish coat.

Some system manufacturers recommend a primer on top of the base coat. Primers function as

adhesion intermediaries and eliminate the adverse effect of efflorescence due to base coat cement content.

To facilitate application, a wet primer is often applied before finish coats with large aggregates.

Insulation

Insulation is an essential component of EIFS. Rigid insulation board provides thermal resistance

and isolates the base coat from the substrate. Where applicable, insulation also provides a surface for the

system's adhesive attachment to the substrate. The specific type and density of insulation vary in accordance with the requirements of proprietary systems.

17
Typical kinds of insulation used in EIFS include MEPS, XEPS, semi-rigid fiberglass, and mineral/

rock wool. Polyisocyanurate and polyurethane boards are additional types of insulation. MEPS is the

insulation used most often in U.S. EIFS applications; XEPS is second in frequency of use. Both MEPS

and XEPS are discussed below. Semi-rigid fiberglass is used in European systems, with only limited use

in this country. Mineral/rock wool, a traditional insulation material also used in Europe, is not typically

used in the United States. Some U.S. manufacturers are assessing mineral/rock wool insulation for

domestic application because of its high fire rcsistant and low smoke generation properties. Polyisocyanurate and polyurethane boards are used primarily in Europe and infrequently in the United States.

MEPS Insulation

Compared to XEPS, MEPS insulation offers a lower initial cost. Virtually all Class PB systems use

MEPS insulation and adhesive attachment, alhough adhesive and mechanical attachment may be combined. MEPS is installed in 2 x 4 foot panels, using a running bond ,dttem with staggered vertical joints.

MEPS inisulation boards must be a minimurr of I-pound per cubi. foot in density. Higher densities

are available and specified for some applications. Throughout the United States, the average thickness

of installed MEPS insulation is about 1.5 inches. Depending; on the R-value desired, it can be installed

in thicknesses of up to 4 inches for 1-pound density board. Building codes generally allow a maximum

MEPS thickness of 4 inciez.

As a result of manufacturers' production methods and qtality control procedures, MEPS boards can

vary .,ignificantly in their physical and performance characteristics. The actual density of boards and their

dimensional characteristics (length, width, thickness, squareness, and planar flatness) significantly affect

EIFS performance. Poor quality MEPS board allows moisture to percolate freely between beads, lessening

the insulation value of the board. MEPS boards must b tightly butted to avoid gaps. Gaps between

boards represent a lapse in the system's support and result in ciacking of the overlying finish and/or base

coats. Where gaps exmst. slivers of insulation should be inserted. Gaps should never be filled with

adhesive or other non-insulating material.

Before applying the base coat, the surface of the MEPS insulation must be properly prepared. Site

dirt, ultra-violet (UV) degradation and unevenness should be corrected by rasping the sirface. Yellowed

surfaces damaged by UV exposure should be rasped until the surface is 100 percent white.

XEPS Insulation

Most Class PM systems use XEPS insulation. Compared to MEPS, XEPS insulation typically has

a higher density, a greater compressive strength, artid-because of its closed-cell construction-less vapor

permeability. Overall, XEPS insulation is manufactured in accordance with tighter dimensional tolerances.

A tongue and groove is provided on two edges of the board for alignment purposes. The cost of this

insulation is about double that of MEPS.

The minimum density for XEPS insulation in U.S. EIFS applications is 1.6 pounds per cubic foot,

although the densities of many products are closer to 2.0 pounds. XEPS insulation has excellent water

resistant properties because of its closed-cell construction and continuous skin. As discussed in Section

IV, this closed-cell XEPS construction influences the vapor transmission process within EIFS claddings

and requires special design consideration.

18
Attachment

Attachment is the means by which EIFS, specifically its insulation cojiponent, is held to the

building structure or substrate. Attachment may be adhesive, mechanical, or a combination of the two.

The type and method of attachment is determined by specific system requirements, manufacturer

guidelines and, to some extent, user discretion.

Adhesive Attachment

Since EIFS was introduced !o the U.S. market in the late 1960s, the majority of installations have

used adhesive attachment only. As noted ea,!,%er, a single product may be used for both adhesive

attachment fi'.d base coat application, deperding on the proprietary system selected. Similar to base coat

compounds, tdhesive materials are eit&.r ready-mixed by the manufacturer .r prepared on-site by the

applicator. Adhesive attachment entails the placement of base coat materi: or a special 100 percent

polymer-based mixture on insulation boards, which are then pressed to the substrate. Adhesives are

typically applied by one of two methods, as discussed below.

The first method is termed "ribbon-and-dab" application. Ribbons of ac2hesive are placed around

the perimeter of the insulation board, and dabs of adhesive are placed within. This method is particularly

useful in cases of uneven substrate such as existing masonry or concrete surfaces. Not all manufacturers

officially endorse this method of application. There is concern that a consistent application of adhesive

is more difficult to achieve with the "ribbon-and-dab" method. An added concern is that this method

provides less protection for the substrate should water penetrate the system. Moisture can run between

dabs of adhesive and have direct contact with the substrate, heightening the potential for deterioration.

For the above reasons, an alternative method of application known as "notched trowel" is specified

by some manufacturers. This method involves use of a notched trowel to cover the entire back of the

insulation board with adhesive in an evenly distributed layer. Notched trowels of various sizes are

recommended by manufacturers to control the dimensions of adhesive ribbon. The notched trowel method

works well on even substrates such as sheathing boards. Depending on the adhesive used, notched trowel

application is preferred by some manufacturers because it offers water resistant qualities. Should moisture

penetrate the system barrier, the overall coat of adhesive applied by the notched trowel method provides

an additional layer of protection.

Mechanical Attachment

Mechanical fasteners are available in a range of shapes and sizes, and vary by manufacturer. In

general, fasteners are nail-like forms which are driven into the substrate/framing. A recent report' noted

that the use of mechanical fasteners-alone or in combination with adhesives-is increasing. Mechanical

fasteners are reportedly being added to manufacturers' standard lines of adhesively attached EIFS.

Specifiers now have the option of using mechanical fasteners in combination with adhesives, an option

which provides additional security with respect to system attachment.

When mechanical fasteners are used in Class PM systems, the insulation is typically spot fastened

to the substrate. Then, the system reinforcement is attached using the remaining fasteners. Spacing of

'Doyle. M. 'Trends in Specifying EIFS," Building Design and Construction (August 1988), pp 60-61.

19
the fasteners is important and is generally specified by the manufacturers. When mechanical fasteners are

used in Class PB systems, they are typically countersunk and plugged with insulation board to avoid

telegraphing the presence of the fastener through the base/finish coats.

Mechanical fasteners are available in a wide variety of pull-out strengths depending on substrate

material, fastener material, and depth of fastener penetration. Advantages of mechanical fastener

installation include secure attachment to questionable substrates and ease of construction.

Substrate

The substrate represents the inpi:riost point of contact between the cladding and the building.

Although not a component of EIFS as such, the substrate is nonetheless significant simply because it is

the foundation for EIFS attachment.

While EIFS can be applied over almost any sound substrate, surface preparation and the proposed

method of attachment are important considerations. The preparation of existing substrate surfaces with

cleaners, sand blasting, or other measures may be necessary. Some EIFS claddings use primers which

serve as adhesion intermediaries between the system and the substrate. Generally, any surface

contamination that might interfere with adhesive bonding must be removed.

The selection of substrate material for new construction must be coordinated with the requirements

of specific EIFS claddings. Retrofit projects seeking to u'e EIFS should be examined for overall wall

integrity. Where adhesive attachment is to be used, consideration of the existing substrate is critical.

EIFS should not be adhesively installed over substrates of questionable integrity unless bond tests are first

undertaken. In questionable cases, mechanical fasteners may be the only means of attachment. An

alternative for extremely poor substrates is the use of mechanically attached metal lath over a bond breaker

such as building paper. The lath and bond breaker form a physical link between the existing substrate and

the EIFS system. Lath reinforces the cladding while mechanical fasteners assure attachment. The bond

breaker also provides a second barrier against moisture penetration.

For most U.S. commercial installations--both Class PB and Class PM-exterior grade gypsum board

on steel studs serves as the substrate. Low cost, good workability, and high fire resistant properties

account for the prevalent use of this substrate material. Gypsum board is easily installed, carries minimal

deadweight, allows stud space for wiring or additional insulation, and accommodates framing for interior

finishes. Other substrates include cementitious-based sheathing, calcium silicate boards, and masonry.

Gypsum sheathing usually consists of a gypsum core and a water-repellent paper surface. The

standard U.S. practice is to secure the gypsum board to light gauge steel stud framing. Either adhesive

or mechanical attachment can fix the insulation to the gypsum board. Because of the board's laminated

paper surface, moisture represents a threat to board integrity. In the presence of moisture, the paper facing

of the board can loosen from the gypsum core, jeopardizing adhesive attachment. Weakened adhesive

attachment may not sufficiently resist positive and negative wind loads acting upon the building facade.

Over time, the continued presence of moisture together with the pressures of wind loads can cause EIFS

failure.

Recommendations differ on the type of attachment suitable for use on gypsum substrate. Most EIFS

manufacturers approve adhesive attachment. However, concerns about delamination have led certain U.S.

gypsum board manufacturers to endorse only the mechanical attachment of any exterior wall system,

20
including EIFS, to their paper-faced gypsum sheathing. For any proposed use of EIFS over gypsum

sheathing, the manufacturer's most current installation procedure/details as well as Corps of Engi'iers

Guide Specification requirements must be strictly followed. (The December 1988 CEGS-072402 requires

the system to be mechanically attached when used over gypsum sheathing boards)3.

A gypsum board composed of a fiberglass surface over a gypsum core is available. This product

is specifically designed to address concerns about the delamination of paper-faced gypsum boards.

Fiberglass surfaced gypsum costs from 40 to 50 cents more per square foot than paper-faced gypsum.

Currently, paper-faced gypsum is approximately 80 cents per square foot.

Sealant Joints

Materials

EIFS sealant joints typically use polyurethane sealant, an elastomeric material capable of maintaining

a good seal when completely cured. A multicomponent sealant consisting of a base compound, a curing

agent and an optional coloring compound is generally specified. Multicomponent sealants are mixed at

the site just prior to application. Careful attention must be given to the complete dispersion of curing and

coloring agents in the base compound.

Back-up rods, correctly specified and installed, are critical to good sealant joints. Joint depth on

EIFS should not exceed joint width, with a maximum depth of 1/2 inch stipulated. To control the depth

of joints deeper than this, joint back-up rods are used. Importantly, back-up rods vary in their material

composition. Open-cell rods retain moisture which can cause deterioration of sealant joints from the inside

out. Closed-cell polyethylene rods, with their smoother surface, are less likely to hold moisture; hence,

only closed-cell rods should be used.

Since rod shape determines the cross-sectional contour of the installed sealant, only round rods

should be used. Correctly installed, round back-up rods allow the sealant to bond only at the joint

interfaces, creating an hourglass shaped cross section for the sealant bead. This shape reduces cohesive

strain within the sealant material and increases contact at the bonding surfaces.

Some manufacturers offer a line of accessories to ensure the proper installation of their EIFS. The

basic accessories include comer aids, stop beads for termination, starter tracks and joints, all made of

plastic and/or metal. In the U.S. today, accessories are primarily specified for Class PM systems, with

only minor use in Class PB systems.

Design and Application

Careful attention must be given to sealant design and application at all EIFS building

terminations-places where EIFS begin, end, or join other portions of the building construction. Joints are

needed at two basic conditions: where EIFS meet EIFS; and where EIFS meet dissimilar materials.

2 CEGS-07240, Exterior Insulation and Finish System (Headquarters, U.S. Army Corps of Engineers [HQUSACEJ, December

1988).

R.G. Lampo, J.C. Trovillion, Exterio " Insulation and Finish Systems (EIFS) on U.S. Army Facilities Lessons Learned, Technical

Report M-91/02/ADA228572 (U.S. Army Construction Engineering Research Laboratory [USACERL, October 1990), p 16.

21
EIFS-to-EIFS conditions require horizontal or vertical expansion and control joints at changes in

substrate; major changes in wall or plane direction; and at any change in height, configuration, or system.

Expansion joints control composite and/or widespread building movement and provide relief for the entire

wall system, while control joints control localized movement and penetrate only the EIFS cladding. Conditions in which EIFS meet dissimilar materials include places where EIFS meet other building materials

such as masonry; where EIFS meet building penetrations such as windows, doors, pipes, railings, or fixtures; and where EIFS meet the roof or ground.

Sealant joints should be neatly tooled to compact the sealant and eliminate air pockets or voids.

Tooling also provides a smooth finished appearance to sealant joints. Poorly tooled joints or those lacking

tooling altogether can precipitate sealant joint failure. This underscores the importance of tooling as well

as quality workmanship in achieving a proper adhesion between the sealant and the sealant substrate.

Sealant Joint Failure

Most systems rely on the finish coat as the sealant substrate. Since certain noncementitious finish

coats tend to soften with exposure to moisture, there is concern that the finish coat may not be the best

substrate for sealant. Sealing to the base coat or sealing to accessories are alternative approaches

recommended by some manufacturers.

Concerns about sealant joint failure have led some manufacturers to recommend double seals on

sealant joints. The installation specifications of these manufacturers vary, but typically one seal is placed

in the wall cavity construction, separate from the EIFS cladding; the other is detailed to the EIFS finish

coat. Another approach consists of a primary seal detailed to the base coat and backed up by a secondary

seal placed either in the EIFS component layers or in the wal cavity construction. Of course, the actual

detailing of any double seal requires a thorough assessment of specific project conditions and construction

allowances.

22
4 COMPARISON OF EIFS TYPES

Overview

As reported earlier, EIFS are classified by EIMA according to typical system components. The

EIMA classification is considered a standard reference terminology for EIFS. In the U.S. today, the

product lines of many EIFS manufacturers encompass both Class PB and Class PM systems. Differences

in materials, application, and attributes characterize each system. The unique as well as shared features

of each system type, its advantages, disadvantages, and recommended usage situations, are discussed

below.

Class PB Systems

Class PB systems, with their polymer-based finish coats, are sometimes called "thin coat," "soft

coat" or "flexible" systems. Class PB systems dominate the industry, with Class PM systems second in

usage. Proprietary Class PB systems generally share the same basic components, as discussed in Chapter

3. Despite this, the actual material composition and application techniques of individual Class PB systems

vary from manufacturer to manufacturer. The most common Class PB system configuration includes a

polymer-based finish coat, a base coat composed of portland cement and polymer, and external fiberglass

mesh reinforcement embedded in the base coat. A diagram of Class PB system components is shown in

Figure 1. The following summarizes the distinguishing features of Class PB systems:

" Most Class PB systems use a noncementitious finish coat.

" All Class PB systems specify a thin base coat, roughly 1/16 to 1/4 inch.

" All Class PB systems use external reinforcement in the form of fiberglass mesh and applied in

one or two layers. Some Class PB base coats contain internal fiber reinforcement in conjunction with

external reinforcement.

* Most Class PB systems use base coats which incorporate cementitious materials. However, a few

manufacturers of Class PB systems specify a noncementitious or "all polymer" base coat.

* Virtually all Class PB systems specify MEPS insulation, although depending on the Class PB

system, other types of insulation can be used.

* All Class PB systems can accommodate adhesive attachment; some Class PB systems use a

combination of adhesive and mechanical attachment. As discussed in Chapter 3, optional mechanical

fasteners are now offered by most manufacturers.

* Exterior grade gypsum board is the most frequently used EIFS substrate, but there are other

recommended substrates. Reliance on gypsum sheathing reflects an independent preference in the

construction industry. Most Class PB systems can be used with other substrates, including masonry,

concrete, and cementitious board.

23
A number of advantages explain the wide use of Class PB systems in the United States today. One

principal advantage is that Class PB systems are typically less expensive than Class PM systems and

represent cost savings over other types of exterior wall treatment. The lower cost of Class PB systems

is related in part to material composition: the MEPS insulation is less expensive than the XEPS used in

Class PM systems.

Another advantage of Class PB systems is a high polymer content, which requires fewer control

joints to resist cracking that can occur in more cementitious systems. A proportionally greater reliance

on polymers together with a thinner application results in a more flexible, less rigid exterior wall.

However, like all EIFS, Class PB systems require joints when abutting dissimilar materials. As noted

earlier, this typically occurs at large and small penetrations (window or door openings and pipes, railings,

fixtures, etc.) and at major changes in plane or wall direction.

Class PB systems are the most lightweight of all EIFS. Exterior walls clad with Class PB systems

are significantly lighter than those using traditional exterior materials. While EIFS claddings generally

place less structural load on buildings than traditional materials, Class PB systems, with their high polymer

content and fiberglass reinforcing mesh, place the least load.

Theoretically, Class PB systems should have better impact resistance because of their inherent

flexibility. To some degree, this is true. Specifically, when Class PB systems are struck with a blunt

object, they may simply dent, not crack. However, insufficient base coat thickness will lessen impact

resistance. While Class PB coatings are more flexible, their thin application provides less protection when

compared to the thicker Class PM systems.

Class PB systems possess certain disadvantages. First, they are prone to puncture damage from

sharp objects. Since both the base and finish coats are thinner, the overall protective !ayer is also thinner.

For this reason, virtually all Class PB systems offer a heavier mesh to reinforce these wall areas which

are anticipated to have high contact.

Second, Class PB systems usually incorporate MEPS insulation, a material which is less dense than

the XEPS boards used in Class PM systems. MEPS consists of molded polystyrene beads fused together

to create insulation board. This fused-bead construction results in a more "breathable" insulation material

than the closed-cell construction of XEPS. The capacity of MEPS to allow water in its gaseous (vapor)

state to pass through the insulation layer has some benefit; however, with respect to insulating properties,

this capacity contributes to the lower thermal resistance of MEPS.

Third, the finish coats of Class PB systems rely on polymers in emulsion to provide moisture and

weather protection. These polymers tend to soften when continuously exposed to moisture. As previously

noted, constant water exposure can cause the finish coats of some Class PB systems to lose cohesion and

delaminate, causing sealant joint failure. While no EIFS system can tolerate moisture intrusion, Class PB

systems which are adhesively attached are particularly susceptible to the adverse effects of moisture

penetration.

Class PM Systems

Class PM systems are sometimes called "thick coat," "hard coat," or "rigid" systems. This type of

EIFS usually contains higher proportions of portland cement in the base coat compound. The higher

24
cementitious content of Class PM system coatings results in a thicker, more rigid system than Class PB

systems.

Like Class PB systems, Class PM systems vary widely with respect to material composition and

application techniques. The most common Class PM configurations include the following: (1) a

cementitious finish coat with polymer modification, a base coat of polymer and portland cement,

mechanically attached external fiberglass mesh or metal lath reinforcement, and XEPS insulation, and (2)

a cementitious finish coat with polymer modification, a base coat with chopped glass fiber reinforcement

(internal), mechanically attached fiberglass mesh (external), and XEPS insulation. Figure 2 illustrates

typical Class PM system components. The following summarizes the distinguishing features of Class PM

systems:

* Most Class PM systems use a polymer-modified cementitious finish coat, although a noncementitious finish coat can also be used.

* All Class PM systems specify a "thick" base coat, ranging between a nominal 1/4 to 3/8 inch.

Finish coat 

Base rovode-,-.' coatan 

.....•.• .

Reinforcing .'.''..

mesh

M etal studzA4

Sheathing..

00 o.o.? • .,

00 . Zo 

X E P S i n s u la t io n w ith 400..' " " ..;

tongue and groove edge 'o OW '° :

[ ~~l " ......... :. .

Mechanical fastenerii ..;: ,"" .,.,'. .,

Figure 2. Typical Class PM System.

25
" For Class PM systems, a metal lath or fiberglass mesh reinforcement is commonly used.

" All Class PM systems use mechanical as opposed to adhesive attachment. This method of

attachment is used because of the weight of Class PM cementitious materials. In addition, the smooth

surface of XEPS cannot provide an adequate surface for lamina adherence.

* Class PM systems usually use XEPS insulation, which is always mechanically attached to the

substrate.

* Exterior grade gypsum sheathing is the most frequently used substrate material. Others substrates

include cementitious-based sheathing, calcium silicate boards, and masonry.

Class PM systems offer several advantages. Because of their cementitious content, they are more

resistant to puncture from sharp objects. The thicker base and finish coats provide a greater total

protective layer than Class PB systems. Under heavy use, Class PM systems tend to hold up better than

Class PB systems with standard reinforcement. If frequent contact or high impact is anticipated because

of intended building use or proposed occupancy, Class PM systems may provide the best protection

against damage to the exterior wall.

The insulating value of Class PM systems is typically better than that of Class PB systei.,s because

the closed-cell construction and material properties of XEPS insulation provide better thermal resistar,.. -

At the same time, because XEPS insulation is less vapor permeable, condensed vapor may collect within

Class PM systems, causing deterioration from the inside out. Accurate vapor transmission analysis is

critical for overall system performance.

Mechanical attachment is a distinct advantage of Class PM systems. It allows for the inclusion of

a weather barrier membrane such as building paper to protect the insulation and/or substrate from

deterioration should water penetrate the system. Compared to adhesively attached Class PB systems, mechanically attached Class PM systems are less sensitive to substrate conditions. The mechanical

attachment of Class PM systems makes this type of EIFS a potentially better choice for retrofit projects

with questionable substrates.

Finally, Class PM systems can incorporate natural stone aggregates of a larger size because of their

thicker finish coats. While both types of EIFS offer aggregate finishes of quartz, granite, or other stone,

Class PM systems can provide finishes that are aesthetically closer to nonsynthetic materials.

Class PM systems are not used as often as Class PB systems. Major reasons for this appear to be

cost and a limited number of manufacturers. As previously noted, one factor in the higher cost of Class

PM systems is XEPS insulation, which is about twice the cost of MEPS board. Often, cost appears to be

the decisive factor in EIFS selection. The greater initial expense entailed in a Class PM system leads

many building specifiers to choose a less costly Class PB system. However, when appropriate, the

selection of a Class PM system can minimize maintenance and repair costs once the system has been

installed.

Class PM systems are thicker by design and typically rely on polymer-modified cementitious

material, resulting in a more rigid, less flexible cladding. Class PM systems require more control and

expansion joints than do Class PB systems. Careful adherence to square footage and proportion requirements is necessary in order to minimize cracking. The attendant placement and detailing of joints is also important in order to avoid cracking due to movement.

26
Typically, Class PM panels should not exceed 150 square feet or be longer than 20 feet in any

dimension. The application of Class PM materials must be contained within control joints that are in a

proportion of no more than 2.5 to 1.0. This requirement avoids long panel applications and eliminates

cold joints, meaning the juncture of wet finishes with set material. Of course, adherence to the

manufacturer's recommendations for climatic conditions and mixing is necessary for a successful

installation.

27
5 EIFS SELECTION

The great majority of EIFS use to date by the U.S. Army Corps of Engineers has been for retrofit

projects. It appears that this trend will hold for the near future. To achieve a retrofit project's full

potential, careful consideration must be given to existing conditions and project goals. The decision to

use EIFS should be made within the context of a project's program of requirements.

Economic factors should be considered along with less tangible concerns such as the existing

building context and the desired architectural expression for the finished retrofit. Depending on project

needs, quantifiable and nonquantifiable criteria assume varying degrees of importance. For instance, there

may be a need to bring design unity to a group of military buildings which possess different exterior wall

treatments. In this case, nonquantifiable factors may have precedence over other concerns. The relative

weight of these factors can only be determined by project particulars.

The possibilities presented by the combination of rigid insulation and synthetic coatings are many.

However, an understanding of the limitations as well as possibilities of EIFS is necessary for successful

use. EIFS limitations relate largely to the unique material properties and behavior of these claddings.

When correctly specified, installed and maintained, EIFS can be a thermally efficient, moisture-protective

and cost-effective cladding for buildings.

Once it is established that EIFS will be used on a project, the type of EIFS to be specified-Class

PB or Class PM-must be determined. This determination is influenced by building use, substrate type,

proposed occupancy, site, climate, and exposure, among other factors. When choosing a system type, one

important principle which should guide selection is that while Class PB systems are inherently more

flexible, Class PM systems offer greater puncture resistance. For example, a Class PB system with

standard reinforcement may be well-suited to an office building that is anticipa.ed to have ordinary impact

exposure. However, for barracks or retail stores that may be exposed to repeated impact, either a Class

PB system with heavy-weight mesh or a Class PM system may be best.

Based on the authors' survey of nearly 50 EIFS-clad facilities at seven Army and Air Force

installations, the U.S. Army Corps of Engineers has generally specified these systems appropriately. In

most cases, the type of EIFS specified-Class PB or Class PM-is suitable to building use and occupancy.

The EIFS buildings surveyed were relatively new installations in good to excellent condition at the time.

Nonetheless, circumscribed signs of failure were found, including varying degrees of cracking, impact

damage, and inadequate closure. These are discussed in Chapter 6. While it is difficult to single out any

one cause, application deficiencies as opposed to improper specification and maintenance appear to

account for the most problems. Tighter monitoring of application procedures during installation would

undoubtedly diminish application inadequacies.

Even though a couple of major problems were noted in the field survey, overall the Army's and Air

Force's use of the systems is still considered successful. This succe3ss is largely because the predominant

application has been retrofit use on existing low-rise masonry structures. This use is consistent with the

original intent of these systems. In many respects, this type of application carries a diminished risk of

failure. Not only has the original construction had ample time to settle, thereby providing a stable

substrate, but also most of the military buildings surveyed had masonry or concrete substrates. These are

highly durable substrates that carry a low risk of deterioration even if moisture penetrates the system.

Related to this, the low height of the buildings is advantageous because exposure to positive and negative

wind pressures is minimized.

28
As the Army continues to upgrade and replace aging facilities, EIFS use will no doubt expand.

Successful use on a wide range of project types is possible, given knowledgeable EIFS specification,

design, and installation, along with careful attention to the particular needs of a given project.

29
6 TYPICAL EIFS FAILURE MODES

Overview

Because Class PB systems are the most frequently installed type of EIFS in the United States today,

the failure modes discussed in this report generally relate to Class PB systems. However, certain failures

are especially common in Class PM systems; these are also discussed. Table 1 is an overview of failure

modes, the areas of origin, and contributing factors. The following text discusses these factors in detail.

Table 1

Failur- Modes

Failure Mode Area of Origin Contributing Factors

Cracking Insulation boards Failure to abut boards

Varying quality insulation board

Adhesive beyond board edges

Incorrect backwrapping

Omission of insulation slivers

Failure to interlock comers

Omission of running bond pattern

System articulations Configuration

Improper installation

- uneven base coat

-failure to embed mesh

Incorrect backwrapping

Improper alignment with windows

Articulation corresponds to board joints

Window and door comers Omission of diagonal mesh

Improper board installation at

windows

Control joints Omission of Class PM control joints

Poor joint design

Poor control joint installation

Premature joint termination

Accessories failure

Expansion joints Failure to provide as needed

- height

- substrate

- plane/wall

- system

- configuration

Poor joint installation

30
Table 1 (Cont'd)

Failure Mode Area of Origin Contributing Factors

Spalling/Cracking EIFS lamina Excessively thick/thin application

Improper mixing of coatings

Materials deterioration

Inappropriate substrate

Impact Damage External influences Thin, poorly applied lamina

Improper mesh embedment

Mesh deterioration

EIFS unsuitable for building

Lack of provision for penetrations

Inadequate Closure Through-wall openings Inadequate seal

- windows

- fixtures

- doors

Inadequate maintenance/repair

EIFS terminations Poor detailing at roof line

- parapets

- downspouts

- gutters

Improper backwrapping

Poor detailing at ground

- granular drainage

- raised EIFS line

Sealant joints Improper joint design

Improper installation

Cohesive EIFS lamina failure

Cohesive sealant failure

Adhesive sealant failure

System Detachment Insulation/substrate Adhesive attachment

- incorrect material

- incorrect application

- ribbon-and-dab method

Mechanical attachment - incorrect application

Unsound substrate

Surface Degradation Finish coat Fading

Staining

Mildew

Iron spots

31
CRACKING

INSULATION BOARDS

Contributing Factors

Failure to abut boards - Insulation boards must be tightly butted to avoid gaps between boards. Poor

abutment can be attributed to a number of factors, among them varying quality board and incorrect

application practices. Gaps represent breaks in the insulation surface. This surface serves to support the

overlying lamina. Gaps cause cracking of the lamina along board lines (Figure 3); this in turn allows

moisture to intrude. Unwanted moisture inside the system can pass through board gaps and cause further

deterioration of system components. Aside from cracking, the outline of board gaps can be detected

through the finish coat at the system's surface, a condition which detracts from building appearance

(Figure 4).

Varying quality insulation board - Depending on the manufacturer's production methods and quality

control procedures, insulation boards can vary in their dimensions: length, width, thickness, squareness,

and planar flatness. Varying quality boards are difficult if not impossible to abut. Boards which are out

of square or those which vary in thickness are especially likely to cause lamina cracks. Differences in

board thickness create step-in board faces and variations in lamina thickness. The lamina at such locations

inevitably cracks. The insertion of insuiation slivers to fill gaps and the rasping of board edges to level

variations in thickness are recommended installation practices.

Adhesive beyond board edges - If applied improperly, excess adhesive can overrun the perimeter of

insulation boards. Adhesive between boards obstructs tight abutment (Figure 5). Manufacturers

recommend that board edges be wiped clean of excess adhesive prior to installing adjacent boards.

Incorrect backwrapping - Backwrapping is typically required at all exposed edges of the insulation

board. This recommended procedure is sometimes misconstrued by applicators as meaning backwrap all

insulation board edges (Figure 6). This practice thwarts tight abutment and creates gaps.

Omission of insulation slivers - Where gaps between insulation boards exist, slivers of insulation should

be inserted. The omission of insulation slivers is one of the most common reasons for lamina cracking.

Failure to interlock corners - MEPS boards should be interlocked at comer terminations. The use of

an interlocking board pattern results in a staggered joint configuration. The stacking of board courses

without interlocking comers creates continuous joints. This incorrect method of installation results in

cracks along the comers of Class PB claddings (Figure 7).

Omission of running bond pattern - Insulation boards should be applied in a running bond pattern with

staggered vertical joints. Gaps left between boards caused the cracking (Figure 8). Boards should not be

installed in a stacked pattern such that the vertical edges of boards are in line with one another. This

creates continuous vertical joints which can run the entire height of the building and precipitate lamina

cracking along joint lines.

32
Figure 3. Crack in EIFS lamina due to a failure to abut the insulation boards.

Figure 4a. Cracking which follows the outline of the insulation boards is a sign of failure

to abut boards.

33
Figure 4b. Closeup of cracking in Figure 4a.

-W~x r

Figure S. Adhesive between EPS boards - improper.

34
Figure 6. Incorrect backwrap between EPS boards.

Figure 7. EPS outside corner - interlock omitted.

35
Figure 8. Vertical and horizontal crack intersection shows the omission of a running bond patte.

36
SYSTEM ARTICULATIONS

Contributing Factors

Configuration - System articulations include aesthetic joints which serve to enhance building design and

character. Unlike joints which accommodate movement, aesthetic joints are surface details. The

configuration of these details weakens the structure of EIFS cladding. Specifically, the removal of

insulation board to create aesthetic joints diminishes system integrity. In addition, mesh in recessed

grooves changes plane which reduces tensile strength. During joint installation, tools such as trowels can

cut the mesh in system articulations. This interrupts the continuity of system reinforcement and results

in cracking of the lamina (Figure 9).

Improper installation - System articulations require that EIFS lamina be applied on either a protruded

or recessed (U- and V-groove) insulation surface. Careful workmanship is required to properly install

these details. The risk of uneven base coat application and partially embedded mesh is heightened because

of the limited working space available at system articulations. A base coat that is too thick or too thin

is prone to cracking. Likewise, mesh which is not fully embedded weakens the lamina composite and

increases the chance of cracking (Figure 10).

Incorrect backwrapping - Backwrapping is typically required at all exposed edges of insulation board.

System articulations do not require backwrapping; they are continuations as opposed to terminations, of

the cladding. Where board joints are incorrectly aligned with grooves, and where insulation boards are

unnecessarily backwrapped, system cracking is extremely likely.

Improper alignment with windows - The alignment of system articulations with window heads, jambs,

or sills can cause cracking (Figures 11 and 12). Proper design should isolate these articulations from other

system details.

Articulation corresponds to board joints - The alignment of system articulations with underlying insulation joints is an incorrect installation practice. Cracking typically occurs at these alignments. Planning

and foresight on the part of the applicator ensures that system articulations do not correspond to

underlying board joints.

37
-4 fV

-41 ;Iv -ON-,

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Figure 10 ~ xoe ~ms t ; n"" roeatiuain

OY -%, X38
, ; j'FU

vm

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0

Fiue1.Cakn n'I"gov riuain

YA~

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39-. ~
WINDOW AND DOOR CORNERS

Contributing Factors

Omission of diagonal mesh - Doors and windows are the most common kind of building opening. Other

system penetrations include openings for building equipment such as air conditioning units and fixtures.

Because the comers of openings are points of concentrated stress, additional reinforcement is necessary.

Diagonal mesh is required at the comers of all EIFS openings. The omission of diagonal mesh at comers

leads to cracking (Figures 13 and 14).

Improper board installation at windows - An incorrect practice is to install insulation boards against

door and window openings so that board joints align with window heads, sills, and jambs. When board

joints coincide with comers, horizontal and vertical cracking typically occur (Figure 15). L- or saddleshaped boards should be installed around all openings to diminish the number of board joints at comers

(Figure 16).

Figure 13. Crack at window head; diagonal mesh omitted.

40
M4zt rV 2 ~~:&. '-R

OMI Ov

~~t*l t a-" 

w*2 -'

'CV.,

Figure 14. Diagonal crack at window sill.

-A4

Figure~~~~~~~~~~~~~j Vetclcaka 15 ino-edsoigimrprainetofislto'or

join wido at' had

41"
WRONG

COAIPECT

I ffCA7IO 5A1 KAIW MJ04 TAAT gOAM M DO'TALroN WMl CMM OFPMUTIAONd

Figure 16. Dryvit: Wall Penetration Details. (Source: Dryvit Systems, Inc.

Used with permission.)

42
CONTROL JOINTS

Contributing Factors

Omission of control joints- Control joints accommodate movement by limiting EIFS application to areas

of specific proportions. Unlike expansion joints, control joints do not traverse the building structure;

rather, they are detailed to the EIFS substrate. Class PM systems with their typically higher cementitious

content require a greater number of control joints. The omission of control joints on EIFS installations

can cause horizontal, vertical, or diagonal cracking (Figures 17 and 18).

Poor joint design - For Class PM systems, control joints should be placed between areas which are in

a length to width ratio no greater than 2.5 to 1.0. Class PM joint placement which does not adhere to this

ratio reflects inadequate joint design. In addition, structural needs should guide design decisions regarding

joint placement. A joint which is consistent with building design and detailing but does not successfully

accommodate movement can crack, thereby undermining both the integrity and appearance of the cladding.

Poor control joint installation- Numerous application factors contribute to poor joint installation. One

of the most significant is the failure to remove coating material from inside control joint profiles. This

inside space should be cleaned of all coating material. If allowed to remain, this material can limit the

joint's capacity to accommodate movement, resulting in cracking (Figure 19).

Premature joint termination- Horizontal anl vertical control joints that are terminated prematurely lead

to cracking at the ends of joints (Figures 20 through 23). Control joints should extend the full width and

height of the detailed area. For instance, vertical joints should run the full height of the building from

roof line to ground. Vertical and horizontal joints which intersect should permit the vertical member to

continue through the intersection (Figure 24). If terminated at the intersection, the joint is prone to

horizontal, vertical, and diagonal cracking.

Accessories failure - Class PM systems typically use accessories at joints. Successful installation

depends on the material composition of accessories as well as proper installation. Vinyl accessories are

more likely to result in failed or broken joints than metal accessories (Figures 25 and 26).

43
;g~" wwg.

go

Figure 17. Crack due to control joint omission.

Figure 18. Control joint omission at substrate change.

44
- -2

.......

Figure 19. Impingement at control joint - crack.

45'5
F 2 r e r i M

Figure 21. Premature control joint termination.

Figure 22. Premature control joint termination at sill.

46
Figure 23. Premature control joint termination.

II

Figure 24. Improper control joint termination.

47
Figure 25. Vinyl control joint failure.

Figure 26. Vinyl control joint failure.

48
EXPANSION JOINTS

Contributing Factors

Failure to provide as needed - Expansion joints accommodate movement between building segments.

They cross through EIFS components to the underlying building structure. Expansion joints are typically

required at places where EIFS meets building components of dissimilar material or configuration (Figure

27). They are also required at major changes in building height, plane, or wall. The omission or

inadequate provision of necessary expansion joints on EIFS installations can cause cracking (Figures 28

and 29).

Poor joint installation - Among the numerous application factors that contribute to poor joint installation,

and thus cracking, are improper joint dimensions, incorrect use of materials, and incorrect finishing.

Expansion joints typically incorporate sealant material. The proper application and tooling of sealant

material are important aspects of successful joint installation (Figure 30).

L1

LOCATIOWS OF CXPANS@O

cxpaw'n JOan Tyrpu

I. U,, h w~ .W~iq 4in Idai.

. .i . U sIh ddg I 

1. me W" ashW4. sua"b. L Lmn 6AV q.q W"NW 

Figure 27. Dryvit: Expansion joint location drawing. (Source: Dryvit Systems, Inc.

Used with permission.)

49
Figure 28. Expansion joint omission at corner.

gm -.

- W-----lalvl I 

Figure 29. Omission of expansion joint between buildings.

50
Figure 30. Successful expansion joint at building base.

51
SPALLING/CRACKING

EIFS LAMINA

Contributing Factors

Excessively thick/thin application - EIFS lamina is intended to function as a composite layer of

integrated materials. The installation and detailing of the finish and base coats are critical for lamina

integrity. Coatings must be applied to the manufacturer's specified thickness. For instance, base coat

material that is applied too thick is likely to crack and spall (Figure 31). Alternatively, a thin base coat

provides inadequate protection for system components and is subject to deterioration, crackini,, and failure.

During application, the reinforcing mesh must be completely encapsulated by the base coat. A visible

mesh pattern in the base is a sign that the EIFS lamina has been applied too thin (Figures 32 and 33).

Improper mixing of coatings- Because base coats are typically mixed on site, adherence to the manufacturer's recommended ratio of components is essential. If the amount of cement in the base mix is

increased, or the polymer decreased, the resulting material will be stiff and prone to spalling and cracking.

Materials deterioration - Poor preparation of MEPS insulation board can result in the deterioration of

insulation and lead to spalling and cracking. Site dirt, UV degradation (Figure 34) and unevenness should

be corrected by rasping MEPS board surfaces prior to base coat application. Correct board preparation

ensures a good bond between the lamina and insulation board.

Inappropriate substrate - The application of lamina on substrates other than those recommended represents noncompliance with manufacturer's guidelines; for instance, applying lamina directly to plywood

or gypsum board is rot an approved practice. Some products that have the appearance of EIFS allow for

the direct application of coatings over concrete, masonry, and stucco. Additionally, manufacturers offer

polymer paints which also resemble EIFS. However, the application of EIFS lamina on inappropriate

substrates results in failure (Figures 35 and 36).

52
Figure 31. Spalling of base coat due to improper application.

Figure 32. Insufficient mesh embedment.

53
Figure 33. Insufficient mesh embedment.

Figure 34. Ultraviolet EPS board damage.

54
12d

Tren~

tjG

~ -~ .g c

U -

55
IMPACT DAMAGE

EXTERNAL INFLUENCES

Contributing Factors

Thin, poorly applied lamina - The lamina provides a durable cladding surface and is intended to resist

impact from external forces. Coating thicknesses are specified by the manufacturer to achieve optimal

durability as well as lamina integrity. Thinly applied coatings or those varying in thickness lack

durability. Aside from the risk of spalling and cracking, a thin or inconsistent lamina is less likely to

sustain impact without damage.

Improper mesh embedment - Fiberglass mesh must be fully embedded in the base coat during

application. Partially embedded mesh weakens the impact resistance of EIFS systems (Figure 37).

EIFS unsuitable for building - EIFS claddings are not appropriate for all buildings or building areas.

The selection of EIFS cladding should take into account the intended building use and proposed

occupancy. Areas such as loading docks (Figure 38) or ground floors (Figure 39) are typically subjected

to frequent and repeated impact. These areas may require a wall cladding other than EIFS or additional

reinforcement. Cladding selection should be guided by individual project conditions.

Lack of provision for penetrations - Building penetrations (doors or windows) and fixtures (door

hardware or HVAC equipment) should be detailed and installed in a manner consistent with use (Figure

40). For example, an incorrectly positioned doorstop can subject the cladding to repeated impact from

the door knob and puncture the lamina (Figure 41). Design professionals and EIFS applicators must work

together to ensure adequate provision for such details.

Lack of provision for maintenance equipment - Lawn mowers and other lawn maintenance equipment

can cause impact damage to EIFS (Figure 42). This type of impact damage can be prevented by changing

the EIFS base detail (Figure 43) or by adding a gravel boarder around the base of the building (Figure

44).

56
Figure 37. Inadequate material application.

Figure 38. Impact damage at loading area.

57
A IA

Figure 39. Impact damage at service area.

A~ 4:

Figure 40. Doorstop prevents impact damage.

58
7-

Figure 41. Impact damage due to door hardware.

Figure 42. Impact damage due to lawn maintenance.

59
- 4 N. 2AjnQ.. tY

Figure 43. Base detail to accommodate lawn equipment.

Figure 4. Gravel border around building perimeter.

60
INADEQUATE CLOSURE

THROUGH-WALL OPENINGS

Contributing Factors

Inadequate seal - In light of the overriding need for moisture tightness, all through-wall openings must

be properly sealed. Improperly sealed through-wall penetrations such as windows (Figures 45 through 48),

fixtures (Figures 49 through 55), and doors facilitate moisture intrusion beyond the EIFS barrier. The

correct design and installation of sealant joints at penetrations is essential to a successful EIFS barrier wall.

Figure 56 shows a door jamb which was properly and successfully sealed.

Inadequate maintenance/repair: Correct repair and timely maintenance ensure the long life of EIFS

buildings. Maintenance and repair methods provided by EIFS manufacturers should be followed.

Although damaged lamina can be patched by methods other than those recommended, the results can be

disappointing. Short-sighted or haphazard methods may result in more costly repairs at a later time.

Under certain lighting conditions (light source parallel to building face), most patches will be somewhat

visible due to changes in surface texture. However, patches on light colored finish coat material are less

noticeable if guidelines are followed. In comparison, it is more difficult to achieve undetectable patches

on dark colored facades.

Figure 45. Inadequate closure - EIFS/metal sill.

61
MB

.. . , R RI 5L=

Figure 46. Inadequate closure at metal sill.

Figure 47. Inadequate closure at metal sill.

62
Figure 48. Inadequate closure at window sill.

Figure 49. Inadequate closure at pipe.

63
Figure 50. Inadequate closure at pipe.

Figure 51. Inadequate closure at pipe.

64
Figure 52. Inadequate closure at pipe.

Figure 53. Improper covering of pipe.

65
t.Y r~q pw

vl-.14 me~

Mal

Of -64

2Z

Figure 54. Inadequate closure at hose bib.

Figure 55. Inadequate closure at through-wall cable.

66
Figure 56. Good termination at door jamb.

67
EIFS TERMINATIONS

Contributing Factors

Poor detailing at roof line: Careful attention to the design, installation, and maintenance of roof line

details is important. Parapets should be sealed at joints, and adequate provisions for water drainage should

be made. Figure 57 illustrates insufficient slope at a parapet detail which allows moisture to collect on

the EIFS. Finish coat softening and moisture penetration usually result. Gutters and downspouts carry

water from the roof to the ground. These elements should be properly detailed and maintained. Figure

58 shows a gutter which was not properly sealed. Incorrect placement, faulty installation, or insufficient

maintenance of these details can result in roof water falling directly on the cladding. This can cause finish

coat softening, staining, and overall EIFS deterioration (Figure 59).

Poor detailing at ground: Standard measures for drainage of water at ground level are required. An

unsealed cladding in contact with ground moisture can carry water up the wall and into the system (Figure

60). Granular drainage beds of stone or aggregate around the perimeter of buildings allow water to seep

into the ground rather than collect at the building's base. Ideally, EIFS claddings should terminate above

ground to avoid contact with moist conditions. An expansion joint above grade on buildings with masonry

or cement foundations prevents moisture migration.

Improper backwrapping: Backwrapping is typically required at all exposed edges of EIFS. Boards at

the roof and ground require backwrapping. Figure 61 shows backwrapping which was improperly

installed. This can subject insulation boards to moisture and chemicals. In addition, the continuity of

system reinforcement is interrupted, making unwrapped areas more vulnerable to impact damage.

-~.4

Figure 57. Poor parapet termination - insufficient slope.

68
Figure 58. Poor EIFS termination behind gutter.

-- &-SS%.7, R

Figure 59. Poor EIFS termination at downspout.

69
Figure 60. Poor EIFS termination at grade.

Figure 61. Good EIFS termination - incorrect backwrap.

70
SEALANT JOINTS

Contributing Factors

Improper joint design - Proper joint dimensions are critical to successful joint design. Joint depth on

EIFS should not exceed joint width, with a maximum of 1/2 inch stipulated. Poorly designed sealant

joints are a common cause of EIFS failure. Narrow as well as excessively wide joints may fail to

accommodate building movement. Cracking will occur at improperly designed joints.

Improper installation - Sealant joint installation requires informed and skilled workmanship. Field

applicators must verify that sealant substrates are clean, dry, and sound. Only specified materials should

be used. Back-up rods, for example, should have a closed-cell construction; opened-cell rods retain

moisture which damages the system. Improperly mixed sealant or poorly tooled joints (Figure 62)

facilitate moisture intrusion. Moisture tightness is the prime goal of sealant installation, and any condition

or practice counter to this goal should be avoided.

Cohesive EIFS lamina failure - Cohesive EIFS lamina failure at sealant joints in Class PB systems is

common. A major cause is the tendency of certain Class PB finish coats to soften with extended exposure

to moisture. Softening in combination with the standard practice of sealing to the finish coat leads to this

type of failure (Figures 63). Sealing to the base coat or sealing to accessories are alternative approaches

to sealant installation which avoid failure due to finish coat softening.

Cohesive sealant failure - Cohesive sealant failures, those within the sealant material itself, are usually

caused by incorrect application procedures (Figure 64). EIFS and sealant manufacturers recommend joint

preparation procedures, specify joint materials such as bond-breaker tape and back-up rods, and provide

directions for sealant mixing and installation. Noncompliance with these recommendations is a common

reason for cohesive failure. Improper tooling is another. Techniques standard for all sealant joint

installation as well as those particular to EIFS should be followed.

Adhesive sealant failure - Adhesive sealant failure occurs between the sealant material and sealant joint

substrate. Improper sealant preparation, omission of primer or back-up rods, the j:csence of exposed mesh

(Figure 65), and improper backwrapping are factors which contribute to adhesive failure.

71
Figure 62. Improper tooling.

z

Figure 63. EIFS/sealant - cohesive EIFS lamina failure.

72
-~ ' k

'j.~

Figure 64. Cohesive and adhesive sealant failure.

Figure 65. EIFS/sealant - adhesive failure.

73
SYSTEM DETACHMENT

INSULATION/SUBSTRATE

Contributing Factors

Adhesive attachment - System detachment is often related to improper installation procedures or the

deterioration of insulation/substrate materials (Figures 66 and 67). In the case of adhesive use, permanent

system attachment is unlikely if improperly prepared or nonapproved substrates are used; for example,

questionably painted substrates or those contaminated with foreign substances result in bond failure (Figure

68). One of two methods of adhesive application are typically used: ribbon-and-dab or notched trowel.

Some manufacturers and users approve only the latter method because the ribbon-and-dab approach is

perceivLd to carry the risk of ;uconsistent application, which results in inadequate protective coverage if

moisture penetrates the system.

Mechanical attachment - In the case of mechanical attachment, fasteners improperly placed or spaced

can result in system detachment (Figure 69). Fasteners should generally not be placed on board

perimeters. Spacing should be in accordance with manufacturer directions. In Class PB systems, fasteners

are sometimes countersunk and covered with plugs of insulation board. Figure 70 shows a protruding,

exposed fastener. The spot application of base coat to cover fasteners is not an accepted practice (Figure

71).

Unsound substrate - An initially sound substrate can deteriorate when exposed to moisture. Paper-faced

gypsum sheathing serves as a good example. In the presence of moisture, the paper facing of gypsum

board debonds and causes system detachment (Figures 72). Substrates in marginal or poor condition can

lead to system detachment if adhesive alone is used. In such cases, a mechanically attached metal lath

with a bond breaker placed over the substrate is an attachment alternative.

Figure 66. Insufficient adhesive attachment.

74
Figure 67. Insufficient adhesive attachment.

Figure 68. Catastrophic system detachment.

75
Figure 69. Improper mechanical fastener spacing.

FRO'

Figure 70. Improper mechanical fastener application.

76
Figure 71. Improper mechanical fastener coating.

Figure 72. Water intrusion - deteriorated exterior gypsum.

77
SURFACE DEGRADATION

FINISH COAT

Contributing Factors

Fading - Finish coat fading due to sun or moisture exposure can occur over time. Moisture-induced

fading is often seen in conjunction with finish coat cracking. Micro-cracks allow water to settle in the

finish coat, causing the color to fade. Dark colors are more likely to fade than light colors (Figure 73).

Staining - Staining of the finish coat can occur at the location of gutters, sills, or other elements if these

details are not properly installed or maintained (Figures 74 through 76).

Mildew - The continuous exposure of EIFS finish coats to moisture can facilitate the growth of mildew

microorganisms on EIFS facades (Figures 77 through 79). Sources of moisture such as shrubs and

planting should not be placed close to the building.

Iron spots - Impurities contained in the finish coat can oxidize and appear as rust colored spots on the

cladding surface (Figure 80). Until the impurity is removed, iron spots tend to redevelop even when

covered with remedial coatings.

_vA

Figure 73. Faded finish coat.

78
R-0,2 LH,-" "

50

Figue Sain 7. du toleas i guter

xi2 M.- -'.

4n

Figure 7. Stains due to lasndr gomeutt.

79
Figure 76. Stains due to leaks in gutter.

Figure 77. Mildew at grade.

80
Figure 78. Mildew at mid-wall section.

Figure Mide 79 at grade. .

81
Figure 80. Stains due to finish coat impurities.

82
7 SUMMARY AND RECOMMENDATIONS

EIFS is a relatively new type of exterior wall cladding. These nonloadbearing systems are

composed of several materials. A single, integrated cladding is achieved by the systematic application of

the following individual components:

1. An insulation board

2. An adhesive and/or mechanical attachment of the insulation board to the substrate

3. An integrally reinforced base coat on the face of the insulation board

4. A textured protective finish.

The possibilities presented by a combination of rigid insulation and synthetic coatings as in Class

PB and Class PM systems are many. However, an understanding of cladding limitat 'rns as well as

possibilities is necessary for successful use. EIFS limitations relate to the unique material composition,

properties, and behavior of these claddings. When these are taken into consideration, EIFS can provide.

a thermally-efficient, moisture-protective cladding for building exteriors.

Based on the survey of nearly 50 EIFS-clad facilities on seven Army and Air Force installations,

the U.S. Army Corps of Engineers has generally specified these systems appropriately. In most cases, the

type of system specified-Class PB or Class PM-is suitable to building use and occupancy. (It is noted

that the EIFS buildings surveyed were relatively new installations in good to excellent condition at the

time.)

The survey did, however, find circumscribed signs of failure including varying degrees of cracking,

impact damage, and inadequate closure. While it is difficult to single out any one cause, application

deficiencies as opposed to improper specification and maintenance appear to account for most of these

problems. Tighter monitoring of application procedures during installation would undoubtedly diminish

application inadequacies.

Even though a couple of major problem areas were noted in the field survey, overall the Army's

and Air Force's use of the systems is still considered successful. This success is due to the fact that the

predominant application has been retrofit use on existing low-rise masonry structures-a use consistent with

the original intent of these systems. In many respects, this type of application carries a diminished risk

of failure. Not only has the original construction had ample time to settle, but also most military buildings

surveyed had masonry or concrete substrates which are highly durable. Since the buildings surveyed were

for low-rise structures, EIFS exposure to positive and negative wind loads is also minimized.

Recommendations

As the Army continues to upgrade and replace aging facilities, EIFS use will no doubt increase.

Greater emphasis is likely to be placed on EIFS for new construction projects. The Corps must attend

to the special conditions that new construction brings. For example, the climate and intended occupancy

of the project assume heightened importance because-unlike with retrofit use-these factors have not been

tested by time.

Successful EIFS installation on a wide range of project types is possible, given knowledgeable EIFS

specification, design, and installation, along with careful attention to the particulars of a given project.

83
To assist in this regard, it is recommended that information on the design, application, and repair/

maintenance of EIFS be formally developed for use by Corps' personnel.*

* Development of an EIFS Application and Inspection Manual and an EIFS Maintenance and Repair manual are

under development at USACERL. These manuals should be available by early FY 93. Development of an EIFS

Design Manual is planned pending finalfunding approval. This proposed Design Manual will include such topics

as EIFS selection criteria relative to potential energy savings and life-cycle costs and HVAC system

considerations when using EIFS in retrofit applications.

84
INDEX

Accessories 21, 43

Adhesive sealant failure 71

Aesthetic joints 37

Attachment 12

adhesive 12, 18-20, 23, 24, 74, 83

mechanical 12, 18-20, 26, 74

Back-up rod 14, 21, 71

Backwrapping 15, 32, 37, 68, 71

Barrier wall 10, 61

Base coat 12-19, 22-24, 83

application defects 37, 52, 56, 74

Bond breaker 20, 74

Class PB system 12, 15, 16, 18, 20, 21, 23, 24, 26, 28, 30, 32, 71, 74, 83

Class PM system 12, 15, 16, 18-21, 23, 24, 26-28, 30, 43, 83

Cohesive EIFS lamina failure 14, 71

Cohesive sealant failure 71

Color 10, 12-15, 21, 61, 78

Control joints 22, 24, 27, 43

Cracking 12, 17, 18, 24, 26, 28, 56, 71, 78, 83

control joints 43

EIFS lamina 52

expansion joints 49

insulation board 32

system articulations 37

window and door comers 40

Detailing 11, 16, 22, 26, 43, 52

roof and ground level 68

Efflorescence 17

EIFS

classification 12, 23

components 12, 14-22

conclusions/recommendations 83

failure modes 30, 32, 37, 40, 43, 49, 52, 56, 61, 68, 71, 74, 78

history 9, 10

selection 28

system types 23, 24, 26, 27

EIMA 10-12, 23

Elastomeric 14, 21

Expansion joints 22, 26, 43, 49, 68

Exterior Insulation and. Finish Systems, see EIFS

Extruded expanded polystyrene insulation, see XEPS

85
Finish coat 12-17, 20, 22-24, 26

degradation 32, 61, 68, 71, 78

Impact

damage 28, 56, 83

resistance 15, 24, 26, 28, 56

Insulation board 12, 15, 17, 19, 20, 24, 83

and cracking 32, 37, 40, 52

and system detachment 74

Iron spots 14

Joints, see specific type of joint

Lamina 12, 14, 15, 26, 32, 37, 52, 61

Mechanical fasteners 12, 19, 20, 23

MEPS 12, 18, 23, 24, 26, 32, 52

Mesh, see reinforcement

Metal lath 12, 15, 16, 20, 25, 74

Mildew 14, 78

Molded expanded polystyrene insulation, see MEPS

Notched trowel application 19, 74

Portland cement 13, 15-17, 23, 24

Rasping 18, 32, 52

Reinforcement 12, 15, 16, 19, 23, 25, 26, 28, 37, 40, 56, 68

Retrofit 10, 14, 20, 26, 28, 83

Ribbon-and-dab method 19, 74

Sealant joint 14, 21, 22, 24, 61, 71

Spalling/cracking 52

Staining 68

Substrate 11, 12, 16, 17, 19, 20, 22, 23, 26, 28, 43, 83

gypsum sheathing 12, 20, 23, 26, 52, 74

Synthetic stucco, see EIFS

System articulations 37

System detachment 74

XEPS insulation 12, 18, 24-26

86
DISTRIBUTION

ChiefofEninmect USA Japan (USARI) WESTCOM

ATTN: CEIHEC-IM-LII (2) ATTN: DCSEN 96343 Fort Shaftr 96858

ATTN: CEHEC-IM.LP (2) ATTN. HONSHU 96343 ATTN: DEH

ATTN: CERD-L ATTN: DEH.Oksuwa 96376 ATTN: APEN-A

ATTN: CECC-P

ATTN: CECW Area Engineer. AEDC-Area Olfice SHAPE 09705

ATTN: CECW.O Arnold Air Force Station, TN 37389 ATfN: Infreatrcture Branch, LANDA

ATrN: CECW.P

ATTN: CECW.RR 416th Engwe Comnmand 60623 HQ USEUCOM 09128

ATTN: CEMP ATTN: Fsaiies Engineer ATTN: ECI 417-LO

ATTN' CEMP-M

ATTN: CEMP-O US Military Aca&my 10996 Fort Belvoir, VA 22060

ATTN: CEMP.R ATTN: Facilities Engineer ATTN: Australian Liaison Offner

ATIN: CEMP-C ATIN. Dept of Geography & ATTN: Water Resource Center

ATTN: CEMP-E Envkionmental Enmgrg ATTN: Engr Strategic Stud s Car

ATTN: CERD ATTN: MAEN.A ATTN: Topographic Engr Center

ATIN: CERD*C ATTN: CECC-R

ATTN: CERD-M AMC - Dir., Iut.. & Svcs.

ATTN: CERM ATTN: DEH (23) CECER, ATTN: Libray 61826

ATIN: DAEN-ZCE

ATTN: DAEN-ZCI DLA ATIN: DLA-WI 22304 CECRL, ATiN: Libray 03755

AIN: DAEN-ZCM

AMN: DAEN-ZCZ DNA ATIN: NADS 20305 CEWES, ATTN: Library 39180

CE ISC FORSCOM (28) HQ, XVIII Airbomo Corps and

ATrN: CEHSC-ZC 22060 FORSCOMEnginer. ATiN: Spa Dot. 15071 Pt. Bragg 28307

ATrN: DET III 79906 ATIN" Facilities Engineer ATTN: AFZA-DEHEE

ATTN: CTJISC-F 22W.

ATIN: CEIiSC-T.F 22060 HSC Chuite AFB. IL 61868

F. Sam Houston AMC 78234 3345 CES/DE, Stop 27 US Army Engincer Districts ATTN: HSLO-F

ATN: Library (41) Fitzimor AMC 80045 AMMRC 02172

Alaska 99506 ATrN: HSHG-DEH ATIN: DRXiIMR-AF

ATN: NAPEN-PL Walter Reed AMC 20307 ATIN: DRXMR-WE

ATITN Facilities Engineer

US Army Engr Diviions Norton AFB. CA 92409

AIN: Library (13) INSCOM - Ch. urd. Div. ATTN: APRCE-MX/DE

Pt Belvoir VA 22D60

US Army Europe ATTN: Engr & Hig Div Tyndll APB, FL 32403

ODCS/Engineer 09014 Vilt Hill Farms Station 22186 AFFSCIEogineering & Service Lab

ATrN: AEAEN.FE ATTN: 1AV-DEH

ATTIN: AEAEN-ODCS NAVFAC

V Corps USA AMCCOM 61299 ATTN: DivIsionOflicas (11)

AMN: DEH (II) ATIN: Library ATTN: FulitiesEngr eCod (9)

VII Co" ATTN: AMSMC-RI ATIN: Naval Pubi Works Center (9)

ATIN: DElI (15) ATIN: Naval Crvi En Lab 93043 (3)

21st Support Command US Avry Engr Activity. CA ATTN: Naval Conm Batalion Or 93043

ATTN: DElI (12) ATTN: DEH

USA Berlin Cameron Station (3) 22314 Engineering Societies Library

ATIN: DElI (9) Fort Lerey I. McNar 20319 New York. NY 10017

Allied Command Europe (ACE) Fort Meyer 22211

AM-N ACSGEB 09703 National Guard Bureau 20310

ATTM: SIllllB/Engineer 09705 MdiiryTrafficMgzt Conana Installation Division

USASETAP Falls Clurch 20315

ATTN: AESE-EN.D 09613 O lla, Army Base 94626 US Onurmnect PlintingOffice 20401

ATTN. ACSEN 09029 Baotnre 07032 RecervioaDepouitry Section (2)

AMTN: AESSE-VE 09029 Sunny Point MOT 28461

US Army Env. Hygiene Agency

8th USA, Korea NARADCOM, ATTN: DRDNA.F 01760 ATTN: HSHIB.ME 21010

ATTN. DEH (19)

TARCOM. For. Div. 48090 Aericar Publk Works Association 60637 ROK/US Combined Forces Comand 96205

ATTN. EUSA-IHIC-CFCdEngr TRADOC (19) Nat'l Insitue of Statirdt. & Tech 20899

IQ. TRADOC. ATN. AIEN.DEH 23651

Ft. Leonard Wood. MO 65473 ATfN: DElI Defense Technical Inc. Center 22304

ATTN: AT7A-TE-SW ATrN: DTIC.FA8 (2)

ATTN: Canadian Liaison Officer TSARCOM. ATTN: STSAS.F 63120

ATTN: German Liaison Staff

ATTN: Britih Liaison Officer USAIS 326

ATTN: All Li.son Office Fort Huadoica 85613 11/91

ATTN: French Liaison Officer AT7N: Facilitcs Engineer (3)

Fort Ritchie 21719