The program of research on building materials and structures, carried on by the

National Bureau of Standards, was undertaken with the assistance of the Central Housing Committee, an informal organization of Government agencies concerned with

housing construction and finance, which is cooperating in the investigations through a subcommittee of principal technical assistants.

CENTRAL HOUSING COMMITTEE

SUBCOMMITTEE ON TECHNICAL RESEARCH

Walter Junge, Chairman. Aethur C. Shire, Vice Chairman.

Federal Housing Administration. United States Housing Authority.

Sterling R. March, Secretary.

Albert G. Bear,

Veterans' Administration.

Pierre Blouke,

Federal Home Loan Bank Board.

Carroll W. Chamberlain,

Procurement Division (Treasury).

Joseph M. DallaValle,

Public Health Service (Federal Security

Agency).

John Donovan,

Farm Security Administration (Agriculture).

George E. Knox,

Yards and Docks (Navy).

Vincent B. Phelan,

National Bureau of Standards (Commerce).

Edward A. Poynton,

OflSce of Indian Affairs (Interior).

George W. Trayer,

Forest Service (Agriculture).

Elsmere J. Walters,

Construction Division (War).

Chairmen of Sections

Specifications Materials Maintenance

Carroll W. Chamberlain Elsmere J. Walters John H. Schaeper

Mechanical Equipment Methods and Practices

Robert K. Thulman

NATIONAL BUREAU OF STANDARDS

STAFF COMMITTEE ON ADMINISTRATION AND COORDINATION

Hugh L. Dryden, Chairman.

Mechanics and Sound

Phaon H. Bates, Gustav E. F. Lundell,

Clay and Silicate Products. Chemistry.

HoBART C. Dickinson, Addams S. McAllister,

Heat and Power. Codes and Specifications.

Warren E. Emley, Henry S. Rawdon,

Organic and Fibrous Materials. Metallurgy.

The Forest Products Laboratory of the United States Department of Agriculture is cooperating with both committees on investigations of wood constructions.

[For list of BMS publications and how to purchase, see cover page III.]
UNITED STATES DEPARTMENT OF COMMERCE • Harry L. Hopkins, Secretary

NATIONAL BUREAU OF STANDARDS • Lyman J. Briggs, Director

BUILDING MATERIALS

and STRUCTURES

REPORT BMS29

Survey of Roofing Materials in the

Northeastern States

by

HUBERT R. SNOKE

and LEO J. WALDRON

ISSUED OCTOBER II, 1939

The National Bureau of Standards is a tact-finding organization;

it does not "approve" any particular material or method ot construction. The technical findings in this series ot reports are to be construed accordmgiy.

UNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON • 1939

KOR SALE BY THE S U P E R I Nl E N D E N T OF DOCUMENTS, WASHINGTON, D. C. • PRICE lO CENTS
Foreword

This report is the second of a series issued by the National Bureau of Standards on

the results of surveys of the weathering qualities and extent of use of roofing materials in

sections of the country representing different climatic conditions.

The results of the first survey have been published as report BMS6, Survey of

Roofing Matei'ials in the Southeastern States. The present paper describes the results of a similar survey in 11 Northeastern States. Frequent reference is made to the first survey for the purpose of comparing conditions in the two sections of the country.

Included is a tabulation, by States, of the kinds of roofing materials used on more

than 10,000 rural and small-town dwellings along approximately 1,600 miles of highway

in the Northeastern States, and a summation of the kinds of roofing on more than

20,000 dwellings along more than 4,000 miles of highway in the 20 States included in the

two surveys. More than 500 photographs, showing types of weathering of roofing

materials, and features of design and construction of roofs, were taken in the course of

this survey. Of these, 48 have been selected for publication.

Lyman J. Briggs, Director.

[11]
Survey of Roofing Materials in the Northeastern States

by HUBERT K. SNOKE dud ].eO [. WALDRON

C O N T

Page

Foreword ii

I. Introduction 3 n. Method of making the survey 3 HI. Extent of use, and apperance, of the

various roofing materials in rural

districts and small towns in the Northeastern States 4

1. Factors which affect the choice

of roofing materials in rural dis- tricts and small towns 4

2. Distribution of roofing materials in rural sections and small towns

in the Northeastern States 4

(a) Villages and small towns 4

(b) Rural sections 4

3. Territory covered and routes fol- lowed in making the survey 5

4. Extent of use of particular materials in rural sections 5 IV. Weathering qualities of roofing materials

in the Northeastern States 6

1. General discussion 6

2. Discussion of particular materials _ 7

(a) Asphalt shingles and roll roof- ing 7

(b) Wood shingles 8

(c) Cement-asbestos shingles 9

(d) Slate 10

(e) Built-up roofing 20

(f) Tile - 20

(g) Metal 20

3. Flashings, valleys, gutters, and

downspouts 21

(a) Flashings 21

(b) Valleys 21

(c) Gutters and downspouts 21

NTS

Page

V. Extent of use of the various roofing materials in urban centers in the Northeastern States 22

1. Factors which affect the choice of roofing materials generally 22

2. Distribution of roofing materials in the cities included in this sur- vey 22

(a) Asphalt shingles and roll roofing 22

(b) Wood shingles 22

(c) Cement-asbestos shingles 23

(d) Slate 23

(e) Tile 23

(f) Metal 23

(g) Built-up roofing 23

VI. Damage to roofs by the hurricane of September 21, 1938 23

VII. Costs of roofing materials, including cost

of application, in vu-ban centers in the Northeastern States 24

VIII. Summary 25

1. Distribution 25

2. Weathering 25 IX. Selected references 26

1. Asphalt shingles and roll roofing 26

2. Wood shingles 26

3. Cement-asbestos shingles 26

4. Slate 26

5. Tile 27

6. Metal 27

7. General, including built-up roofing. 27

[1]
Figure 1.

Northeastern States covered by survey.

[2]
ABSTRACT

A survey of the weathering qualities and extent of

use of the various roofing materials on dwellings in the Northeastern States is described, with numerous comparative references to a similar survey in the Southeastern States. Detailed studies of roofing materials in Wilmington,

Del; Philadelphia, Pa.; New Haven, Conn.; Boston,

Mass.; Manchester, N. H.; Portland, Maine; Rutland,

Vt.; and Albany and Syracuse, N. Y., are reported.

A tabulation, by States, of the kinds of roofing materials used on more than 10,000 rural and small-town

dwellings, along approximately 1,600 miles of highway

between the cities listed above, is included; also a summary of the kinds of roofing materials used on almost

21,000 rural and small-town dwellings along 4,000

miles of highway in 20 Eastern States. Forty-eight photographs, illustrating types of weathering of roofing materials and features of design and

construction of roofs, are shown.

I. INTRODUCTION

The general research program of the National Bureau of Standards on building materials and structures includes, as part of the

work on roofs and roofing materials, a comprehensive survey of the various types of roofing

materials used in locations typical of widely

differing climatic conditions in the country.

The first of these surveys, which was made in

April 1938, included the following states: Virginia, North and South Carolina, Georgia,

Florida, Alabama, Tennessee, Kentucky, and

West Virginia. Results of this survey have

been published as Building Materials and

Structures Report BMS6, Survey of Roofing

Materials in the Southeastern States.'' The present paper describes a similar survey

in the following cities: Wilmington, Del. ; Philadelphia, Pa.; New Haven, Conn.; Boston,

Mass.; Manchester, N. H.; Portland, Maine;

Rutland, Vt. ; and Albany and Syracuse, N. Y.

It includes also a report on the extent of use of

the different roofing materials, classified roughly

from the standpoint of appearance, on rural

dwellings along the highways between the cities that were visited. This survey was made from

September 12 to October 12, 1938, and in- cluded approximately 2,500 miles of travel.

' Price 1.5 cents. See cover page III.

This report, while made ii]) primarily of

observations on tlie wcatheiiiig characteristics

of roofing materials which apply only to the

territory covered by this survey, also makes

frequent reference to the previous survey in the

Southeastern States. In this report the "Survey in the Southeastern States" is referred to as "the previous survey", for convenience.

The authors were in New Haven, Conn., at the time of the hurricane, September 21, 1938,

and had an opportunity to observe the eft'ect of

winds of unsual velocity on many types of roofs. Space is not available in this report to deal

at length with the history, methods of production, composition, etc., of the various kinds of roofing materials. A list of selected references

is given at the end of the report for those who

wish to make a more detailed study of roofing

materials. Numerals in brackets throughout

the text refer to publications in this list.

II. METHOD OF MAKING THE

SURVEY

The methods used in making this survey were

essentially the same as those followed in the

previous survey.

All travel in connection with this survey was by automobile. An actual count was made of

the lands of roofing materials used on the rural

dwellings along the liighways traveled. The

record was kept on special forms, each covering

50 miles of highway, forms being changed at State lines to permit tabulation by States. Local representatives of the Home Owners'

Loan Corporation assisted in collecting data on

roofs of different kinds and known history.

Acknowledgment is made to them for their

wholehearted cooperation in this work.

A short time was spent in each city in dis- cussing the details of the investigation with

representatives of the Home Owners' Loan Corporation, and then, with them, in discussing

roofing practices with local roofing contractors. Actual inspections were then made of as many

roofs as time would permit, followed by a general tour of the city, including long-established and new communities, to determine

roughly the extent of use of the various roofing

[3]
materials. It was also a regular practice to re- quest permission to examine any roofs that

looked particularly interesting.

III. EXTENT OF USE, AND APPEARANCE, OF THE VARIOUS ROOFING

MATERIALS IN RURAL DISTRICTS

AND SMALL TOWNS IN THE NORTHEASTERN STATES

1. Factors Which Affect the Choice of

Roofing Materials in Rural Districts

AND Small Towns

Initial cost, relative availability of particular materials, and appearance are factors wliich

affect the choice of roofurg materials in rural

districts. These factors, plus that of cost of mamtenance, probably govern the choice of roofing materials in most sections. Strikmg

evidence that the ready availability of a material is a strong factor in determining the extent of use was obtained in the slate-producing areas of Pemisylvania and Vermont, where

slate roofing is used on all classes of structures. In the riu'al sections of the New England

States, where the house and barn are frequently

connected through several intermediate buildings, it is not mnisual to see three or four types

of roofing materials on different sections of the

structure. Occasionally two kmds of roofings

of the same type are used on different sections

of the same structure. Apparently failure bad

occurred in various sections of the roof at differ- ent times.

2. Distribution of Roofing Materials in

Ritral Sections and Small Towns in the

Northeastern States

(o) Villages and Small Towns

The villages and small towns in the Northeastern States, in general, show a greater variation in the kinds of roofing materials that are used than do those in the Southeastern States. Also, the northern villages are more congested,

so that any observations on the extent of use

of the various roofing materials in them had to be most general. Slate is used exclusively int towns and villages adjacent to slate-producing

areas; asphalt shingles have relatively wide use

in most other areas, excepting Delaware, where,"

wood shingles predominate. At present, me-^

tallic roofings have limited use. Old dwellings

in some small towns in eastern Pennsylvania,

have mainly tin and slate roofs in about equab

proportions. Cement-asbestos shingles have'

been used less widely than other materials.!

Wood shingles have had extensive use in the

past and are apparently being used to a con-j

siderable extent at present.

{h) Rural Sections

The various kinds of nu-al roofs were divided'

roughly into two classes, "Good" and "Poor."

This classification, of necessity, was based en-'

tirely on appearance and, in most cases, was made from a hasty observation of one side of aj roof. For this reason, and also because it is not possible to set down the exact criteria by

which a roof was judged to be good or poor, and because the various kinds of roofs have

different criteria of appearance, it is realized

that this classification is open to considerable

criticism. It should be emphasized also that

the data do not indicate the age of the roofs

reported. However, it is felt that the classi- fication as made is better than a simple census

of the kinds of roofing materials that are \ised.

The subdivision of roofs classed as "Poor''

into "Poor" and "Damaged," representing nor- mal weathering and damage by storm in areas

affected by the hurricane, excepting Connecticut, does not differentiate between roofs that were damaged badly and those that were dam- j aged but slightly. The relative proportions of

the different kinds of roofing materials must also l; be considered when studying storm damage to

roofs. For example, only one tile roof is re- [ ported as being damaged by the hurricane, but

only three tile roofs were observed in the whole ! rural area affected b}^ the storm. Obviously,

with such meager data, one could draw no defi- nite conclusions.
,3. Territory Covered and Routes

; Followed in Making the Survey

A map of the territory covered by the survey

' is shown in figure 1

Table 1 Hsts the cities in which studies were made and the routes from city to city in the

order they were traveled.

4. Extent of Use of Particular Materials

IN Rural Sections

Table 2 is a tabulation, by States, of the

kinds of roofing materials used on dwellings in

Table 2. —Tabulation, by states, of the kinds of roofing materials used on rural dwellings

Asphalt shingles Wood Slate Sheet metal

State Good Poor Damaged

Total Good Poor Damaged Total Good Poor Damaged Total Good Poor Damaged Total

Maryland -.. 138 56 194 97 133 230 25 2 27 140 68 208 Delaware. . 33 20 63 166 199 365 1 5 6 17 18 35 Pennsylvania 506 266 772 127 95 222 700 44 744 283 28 311 New Jersey. . 147 113 260 83 83 166 69 114 183 15 2 17 New York .

_

. 433 264 697 397 204 601 267 9 276 127 65 192 Connecticut. _ 100 130 (») 102

230 266 95 361 2 1 3 3 3 Rhode Island 46 11 159 5 6 9 20 2 2 Massachusetts 107 44^ 81 232 13 13 1 27 3 4 7 Maine 316 194 45

89

564 190 139 12 341 6 6 59 33 92 New Hampshire 385 266 740 154 185 6 344 18 7 1 26 66 35 2 103 Vftrmnnt 48 52 100 54 48 102 263 15 268 29 14 43

Total 2,258 1,416 317 3, 991 1, 552 1,200 27 2, 779 1, 344 197 5 1, 546 739 263 4 1,006

Roll roofing Cement-asbestos Metal shingles Tile Thatched

State Good Poor Damaged Total Good Poor Damaged Total Good Poor Damaged Total Good Poor Damaged Total Good Poor Damaged Total

Maryland . 2 18 20 14 10 24 40 6 46 1 1 Delaware.. 1 10 11 5 2 7 1 1 Pennsylvania New Jersey.

14 60 74 110 3 113 16 8 24 8 8

3 10 1396

39 12 51 1 1 4 4 New York... 20 76 42 9 51 35 11 46 8 8 1 1 Connecticut. 7 15 22 3 4 7 1 1 1 1 Rhode Island 1 2 2 6 Massachusetts... 1 1 2 4 1 1 2 2 Maine 25 37 62 9 9 2 2 New Hampshire.

Vermont... ...

12 58 5 75 12 8 20 1 1 4 13 17 1 1 10 2 12

Total 90 300 9 399 235 49 284 103 31 134 22 1 23 2 2

« Roofs damaged by storm were not tabulated in Connecticut

[5j

the na-al sections along the routes hsted in table 1. Table 1.

Routes traveled in making this survey

Cities

Washington, D. C, to Wilmington, Del. Wilmington, Del., to Philadelphia, Pa... Philadelphia, Pa., to New Haven, Conn New Haven, Conn., to Boston, Mass.

Boston, Mass., to Manchester, N. H

Manchester, N. H., to Portland, Maine

Portland, Maine, tci Rutland. Vt . Rutland, Vt., to Albany, N. Y

Albany, N. Y., to Syracuse, N. Y . Syracuse, N. Y., to Washington, D. C .

Routes 1

50, (404), (18), (14), 13. 13.

1, 206 , 202, (.59), 9, Merritt Parkway, I

I, (84), (3)", 1. (28). (101), 1. (207), 4, 302, 3, (25), (2.5a), 4. 4. (286), (22), 67).

20, (92).

II, 309, (45), ((M6), (702), (512), (H5\ 222, 422, 15, 40.

1 State routes in parentheses, all others arc U. S. routes.
The results of the counts of rural roofs in

both the Southeastern and Northeastern States

are summarized in table 3.

Table 3.

Summary of rural counts

[Miles traveled: Southeast, 2,447; Northeast, 1,591. Total, 4,038]

Type of roof

Sheet metal Asphalt shingle Eoll roofing. Wood shingle Metal shingle Cement-asbestos shingle

Slate Tile Thatched

Total

Southeast

3, 722

2, 558

1, 982

1,757

366

10. 677

Northeast

1,006

3, 991 399

2. 779

134

284

1, 546

23

2

10, 164

Total

4,728

fi. 549

2, 381

4. 536 500

468

1. 610

67

20, 841

Assuming that the roofs along- the routes traveled were representative of the rural areas included in the surveys, this summary shows

that asphalt shingles, wood shingles, and sheet

metal account for approximately 76 percent

of the rural roofs in the Eastern States. It is believed that in these counts the normal proportions have been somewhat upset by the

fact that a considerable part of the travel was

in some areas where roofing slate is locally

availnble, and in other areas where prepared

roll roofings are used almost exclusively.

IV. WEATHERING QUALITIES OF ROOFING MATERIALS IN THE NORTHEASTERN STATES

1. General Discussion

The previous report (BMS6) states that "Any

discussion of the weathering qualities of roofing

materials in a particular section must, of necessity, be couched in the most general

terms," and then cites some of the factors which

must be considered in such studies. This

section of the previous report is repeated here

to avoid possible misunderstandings. No two

conditions of exposure are ever identical.

Thus, two dwellings may be built side by side, of the same materials and design; one may

remain dry throughout the building operations,

whereas the wood sheathing on the other may

be thoroughly soaked by several days of rain;

one may be shaded by trees which protect it from the effect of sunlight but subject it to damage from falling branches, whereas the

other may receive the full effect of sunlight.

These roofs, in all probability, will show diff- erent weathering characteristics. The same^

materials on roofs of different pitch will behave

differently, a fact that can be observed fre- quently where the same material is used for the,, steeply pitched main-roof sections and thej

porch roofs of lower pitch. The weathering of I a roof is invariably less severe on the north,

than on the south. , Faulty workmanship probably causes more

premature roof failures than faulty materials, l A roof well laid with inferior materials will give^

good service as long as the material will withstand the effects of weathering, but a roof; improperly laid with good materials will prob-.

ably give poor service from the beginning.

When the materials used for roofing are considered, the problem becomes even more

complicated. Materials available include: as- phalt shingles in a wide variety of shapes,

colors, and weights; slate in a variety of sizes,

weights, and colors; and sheet metal, including

"Roofing tin,"^ galvanized steel, copper, and

zinc, in either roll or shingle form. This

multiplicity applies equally to other kinds of roofing materials.

Another factor which precludes definite and

positive statements concerning the "life" of any particular roofing material is the difficulty

of determining just when a roof has failed and

exactly what constitutes a failure in a roofing

material. Theoretically, a roof that does not

admit water might be considered serviceable,

yet roofs may be serviceable and still not be

satisfactory. Appearance is a factor that is becoming increasingly important in choosing

roofing materials, but it is a variable factor that

cannot be weighted generally.

It can be readily understood, therefore, that no positive statement can be made concerning

the probable service that a given, general type

of roofing material will render in a particular

' Made by coating steel sheets with an alloy containing about 80 percent

of lead and 20 percent of tin.

[6]
locality. However, some of the materials, as

classes, do show different weathering characteristics in different locations.

Essentially the same roofing materials are used in the Northeastern States as in the Southeastern States, but the difference in climate

between the two sections is reflected in differ- ences in roofing practices. Low-pitched roofs on dwellings characterize the South, whereas

I in the North, roofs are usually steeply pitched,

largely to prevent the accumulation of snow. Snow on a roof would not be objectionable, in

fact, it would be desirable from the standpoint

of preventing the loss of heat from a dwelling,

if it would remain in the state it falls. It is the

subsequent melting and freezing that is responsible for most of the damage to roofs by snow,

particularly those laid by the shingle method.

Heat from the interior of a structure and from

the sun will melt some of the snow during the

daytime. At night, when the temperature outside is lower and when the interior of the building is cooler, some of this melted snow will freeze

to form ice dams which cause water to back up

underneath the shingles and, if the shingles are

laid without sufficient head lap, will cause the

roof to leak. This process may result in severe breakage in roofs constructed with rigid roofing

materials, such as slate and cement-asbestos

shingles, if they are fastened too tightly. This

form of weathering is most severe on the projecting eaves of shingle-type roofs, which are usually weathered more than other sections of

the roof. It is noticeable, particularly, on wood

and asphalt-shingle roofs. This effect is obviated frequently by placing a wide strip of metal

or, occasionally, asphalt-prepared roll roofing

at the eaves. Metal strips are usually of tin or galvanized iron, though copper is used occasionally. Figure 2 shows the methods of installing a metal eaves strip.

Snow guards are of value mainly in preventing snow from sliding from a roof in large quantities and damaging gutters, porch roofs, or shrubbery that may be placed below. In this respect they serve a very useful purpose, but,

obviously, by retaining snow on a roof, they

increase the possibility of damage of the type

previously described. In subsequent sections an attempt has been

made to discuss and illustrate by means of

photographs certain of the weathering characteristics of the roofing materials used in the

Northeastern States. No attempt has been

made in this discussion to differentiate between

brands of roofing materials.

2. Discussion or PyVETicuLAR Materials

(a) Asphalt Shingles and Roll Roofing

In the previous survey it was determined that

asphalt-prepared roofings weathered more rapidly the farther south they were exposed.

Similarly, in the present survey it was apparent

from many observations that normal weathering of these materials on steeply pitched roofs

proceeded much less rapidly than in the southern area. Weathering proceeded more rapidly on low-pitched roofs than on steeper roofs,

partly because of the tendency of snow to remain for long periods on these roofs ac- companied by subsequent freezing and thawing.

The same types of weathering were observed

in the Northeastern States as in the Southeastern States: namely, color changes, blistering, pitting, loss of granules, cracking, and

warping. However, with the possible exception

of changes in color, which are extremely difficult to evaluate, each of these types of weathering

can be said to be less severe in the North than

in the South when exposed for the same period

The greater color changes that were observed were in certain natural green granules which

after exposure became a light tan. Blistering of asphalt shingles, observed occasionally, was negligible when compared to that

observed in the Southeastern States. The

longer service life of these shingles in the Northeastern States is probably due, in a large measure, to their relatively slight tendency to

blister. Blisters are preliminary to pits and,

in forming pits, cause loss of granules and

158868°—39 2 [7]
asphalt coating, thus permittmg water to enter

the felts more readily.

Considerable so-called "alligatoring" of as- phalt coating was observed, most noticeable on shingles with thick coatings. Figure 3 shows this condition on heavyweight asphalt

shingles after 12 years of exposure in Wilmington, Del. Figure 4 is a close-up of a section of one of these shingles.

The practice of laying aspbalt shingles di- rectly over weathered wood shhigles is not so prevalent in the North as in the South. Also,

it is not a common practice to reroof with

asphalt shingles over weathered asphalt shingles.

This is, no doubt, due in part to the fact that

asphalt shingles have been in general use for a period that approximates their maximum life. Direct evidence that asphalt shingles weather

less rapidly in the North than in the South is shown in figures 5 to 10, inclusive. Figure 5 shows individual shingles after 7 years' exposure

in Greensboro, N. C. These shingles were laid

by the hexagonal method, over wood shingles.

Figure 6 shows shingles of the same type after 15 years' exposure in Manchester, N.H. Those

in figure 7 had been exposed 10 years in Albany,

N. Y. These roofs were of approximately the same pitch and the exposures were the same.

Figure 8 represents the soutbern exposure of a

roof of individual shingles, laid by the American method, after 1.3 years in Savannah, Ga.

Figure 9 shows shingles of the same type on

the southern exposiire of a roof 22 years old in

Syracuse, N. Y. Those in figure 10 were also individual shingles exposed 21 years in Portland, Maine. Figure 11 shows an asphaltshingle roof in excellent condition after 18

years of exposure in Boston, Mass. As observed in the previous survey, the oldest

asphalt-shingle roofs were invariably of individual shingles laid by the American method.

Mineral-siu'faced, asphalt-prepared roll roofing is used but very little on dwellings in the

Northeastern States, and smooth-surfaced roll roofing is scarcely used at all. Wliere mineralsurfaced roll roofing has been used, it has been

laid mainly over weathered wood-shingle roofs.

No attempt will be made to estimate the

probable useful life of asphalt shingles and roll roofings in the Northeastern States. Shingles

are marketed in so many different weights and

shapes and are subject to so m.any other variables that any estimate would be meaningless. \ However, it is apparent from evidence obtained J in this survey that asphalt shingles or roll roofings exposed in the Northeastern States may

be expected to give from 50 to 100 percent

longer service than the same materials exposed ij similarly in the Southeastern States. In any case, it is reasonable to expect that

asphalt shingles that are produced at present

will render longer service than those produced

20 years ago. Methods of manufacture have

been improved greatly and are controlled more

carefully than formerly, research has produced

better felts and asphalt coatings, and the

development of ceramic granules has made

possible a wide variety of permanent colors and

color combinations. Advancements along these

lines, however, have been nullified somewhat

by the constant tendency to produce shingles

that require less and less material per unit area

of roof. The average home owner is confused

by the multiplicity of designs that are available

in asphalt shingles.

(b) Wood Shingles

Work on wood shiugles in this investigation

is limited to such observations as are necessary

for a comparison of them with other roofing

materials.^ Few wood shingles are employed

in the congested sections of the cities visited,

because of regulations forbidding their use

within fire zones. In some places these regulations have not been enforced strictly because of recent economic conditions. Wood shingles

have been used to a considerable extent in recent suburban developments of a number of

cities, notably Wilmington, Del., Philadelphia,

Pa., New Haven, Conn., and Syracuse, N. Y.

Their use has not been confined to dwellings

in the low-cost groups.

' Inquiries for technical information covering wood shingles should be

directed to the Forest Products Laboratory, United States Department

of Agriculture. Madison, Wis.

[8]
Wood shingles are applied on spaced sheathing (shingle lath) or on tight sheathing. This

latter practice is quite common in some sections, no doubt, due to the fact that snow may filter through a wood-shingle roof laid on shingle lath. Wood sliingles absorb a considerable amount of moisture in long-continued rains, and when

laid on tight sheathing, have less opportunity to dry thoroughly than those laid on open decks.

Figure 12 shows a roof of wood shingles laid on

tight sheathing after 15 years' exposure in

Manchester, N. H. These shingles had been

stained originally. Figure 13 illustrates the

extreme weathering of untreated wood shingles

that had been exposed more than 40 years near

Hillsboro, N. H. These shingles were laid on

sliingle lath. A larger section of this roof is shown in figure 14. The shingles directly beneath the chimney show less curling and general

weathering than those in other sections of the

roof. This condition is characteristic of hundreds of wood-shingle roofs observed. Many

cases were observed where sections of asphalt

and galvanized-iron roofs beneath chimneys

were weathered more severely than others.

See figures 15 and 16. Menhaden oil, colloquially Pogy oil, was used

formerly in certain sections of Maine for pre- serving wood shingles. Figure 17 shows a roof so treated after 20 years of exposure in

Portland, Maine. Except for slight curling and

cracking of a few shingles, this roof showed

practically no weathering. The oil treatments

had made these shingles quite dark in color. Shingles on this roof were laid on 6-in. sheathing

spaced 2 to 3 in. Wliether or not wood shingles should be

treated and the preservative value of various

treatments are subjects about which there are

differences of opinion among shingle experts.

Results of weathermg tests on treated and untreated wood shingles are given in a report of

the Pennsylvania State College, School of Agriculture and Experiment Station [2 (a)].^ A complete study of the weathering of wood

shingles in the Northeastern States would re- quire much more time than was spent in this

' Numerals in brackets refer to the list of selected references at the end

of the report.

entire survey. An investigation of this kind

should include studies of the various kinds of woods that are used, methods of laying, and

exposures in dift'erent locations. It should

also include a comparison of edge and flat-grain

shingles of different thicknesses, with and without sapwood, both treated and untreated.

Opinions vary concerning the life of wood

shingles and are usually prejudiced One may

claim that they will last from 10 to 15 years and

another that the average life is about 40 years. Actually, first-grade shingles of the weatherresistant woods, applied properly on roofs of

sufficient pitch, will usually give excellent

service. Wood-single roofs 40 and more years

old are not unusual, though these roofs have

probably required some patching during that

time. It is also not unusual to find woodshmgle roofs that have to be replaced or re- covered in less than half that time, either be- cause the shingles were of poor quality or improperly applied. The adoption of proper

grading rules by the bulk of the industiy makes

it possible for the individual home owner to buy wood shingles with much greater confidence

than formerly.

(c) Cement-Asbestos Shingles

In general, cement-asbestos shingles have

been used less in the Northeastern States than

in the Southeastern States. They are reported

to have given excellent service in that they

resist normal weathering for long periods.

They are quite brittle and are subject to damage

by being walked upon or by heavy objects

falling upon them. In industrial locations

they may present a dingy appearance after

long exposures, due to their tendency to collect dust and dirt. Figure 18 shows a roof after

18 years of exposure m Portland, Maine, illus- trating this tendency. That not all of these

roofs become dirty is illustrated by figure 19,

showing cement-asbestos shingles more than 20

years old in Boston, Mass. More cementasbestos shingle roofs were observed in Albany,

N. Y., than in any other city visited. They are

also used quite extensively in Syracuse, N. Y.

Most of the older cement-asbestos roofs are

[9]
laid as those shown in figures 18 and 19. Many of those applied recently use shingles in attractive colors laid by the American method.

Cement-asbestos shingles show the same type

of weathering in the North as in the South.

After long exposure the surface is roughened

somewhat, and the asbestos fibers become

plainly visible. It was not possible to establish differences in the degree of weathering of cement-asbestos shingles of the same type

exposed in difi'erent localities.

(d) Slate Two areas which produce large quantities of slate for roofing purposes were visited in the course of this survey, namely, the Vermont and

east Pennsylvania regions. In addition, some

observations on Peach Bottom slate, made on a

previous visit to Delta, Pa., and Cardiff, Md.,

are included.

Most of the colored slates used for roofing

purposes during the past 75 years have been

produced in western Vermont and eastern New

York. Those from Vermont include purple;

green, both fading and unfading; and the

so-called variegated slates, which are mottled

purple and green. The belt that produces these

slates extends into eastern New York and is the

only source from which appreciable quantities

of red slates have been produced for roofing

purposes. Quarries have been operated in this region for about 85 years, and the slates pro- duced have an excellent record of durability.

Figures 20 and 21, representing roofs in and

near Fair Haven, Vt., need no explanation as regards the age of the roofs shown. In each

instance the main body of the roof is of purple

slate with the numerals outlined in unfading

green. The coloi' of these slates is almost

identical with that of similar slates produced

today.

The fading green (sea-green) Vermont slates are also extremely durable, as evidenced by the

roof shown in figure 22, reported to be more

than 75 years old. These have weathered to a

light brown and some have begun to dis- integrate by scaling. This roof is failing principall}' tlu'ough failure of the nails used to

fasten the slates. The unfading and fading

green slates are quarried within relatively short

distances of each other and are practically

mdistinguishable to the layman when taken

from the quarry. The fadmg green slate splits

into tlun sections more readily than the unfading variety. Experts are able to idei^tifj^

the fading green slates by their somewhat

imctuous feel when freshly quarried. They I usually show color changes within 1 or 2 years. Prolonged exposure changes them to a dark | tan or light brown.

The red slates produced in eastern New York

are unique in that their color becomes more

'

intense on prolonged exposure. They are also extremely durable. Figure 23 shows a red

slate roof in Rutland, Vt., more than 50 years old. Frequently slates of different colors and

thicknesses are mixed intentionally to produce

a blend of colors and a pleasing architectural

eft'ect. In these cases, the larger, thicker

slates are laid near the eaves to give the

proper perspective.

Areas in Maine where roofing slate has been

produced were not visited. In Portland, however, a number of roofs were inspected which

were said to be of Maine slate. These slates were of a very dark color, almost black, and

woidd certainly be classed as unfading. Figure

24 shows a section of one of these roofs after 38 to 40 years of exposure. Similar slates were

used as a siding material on this dwelling with

excellent workmanship throughout. See figure

25.Slate for roofing purposes has been produced

m Pennsylvania for about 200 years. The

earliest operations were in York County, on

the Maryland border, where the well-known

Peach Bottom slates are still produced. This

bed extends across the Susquehanna River into

Lancaster County, Pennsylvania, and south

into Maryland. These slates are extremely , din-able, figure 26 showing a roof laid recently

with slates that are reported to have served

previously on another roof for more than 100

years. They are dark bluish gray when quarried and retain their color on long exposure.

Some that are reputed to have been in service

[10]
Figures 2 to 7.

Asphalt shingles

Figure 2, wide metal eaves strip and dormer flashing, 3 and 4, severe alligatoring, heavyweight asphalt shingles exposed 12 years in wnmington,

Del.; 6, 6, and 7, re-cover asphalt shingles; 5, exposed 7 years in Greensboro, N. C; 6, exposed 15 years in Manchester, N. H.; 7, exposed 10 years in Albany, N". Y.

[11]
Figures 8 to 13.

Asphalt and wood shingles

Figures 8, 9, and 10, individual asphalt shingles, southern exposures; 8, after 13 years in Savannah, Ga.; 9, after 22 years in Syracuse, N. Y.; 10, after

21 years in Portland, Maine; 11, asphalt shingles exposed 18 years near Boston, Mass.; 12, wood shingles on tight sheathing exposed 15 years in Manchester, N. H.; 13, wood shingles more than 40 years old near HUlsboro, N. H.

[12]
Fxa.H.s 14 to 19.-irood. as^kaU, and cement-asbestos sMn.les; ,aMm.ed skeet metal FlGtJBESl4to y. .

. 15 and 16 deterioration Of asphalt Shingles and galvanized

..,re U, .ood Shinies preserved «chi.ne. J-^^-- in SuaS; ce.ent-ashestos shingles exposed :S .ears

sheet metal below chimney; 17 treated f

n les e^^^^^^^^^

in Portland, Maine; 19, cement -asbebtos shmgles exposea >

[13]

Figures 26 to ZX.^Slaie.

Bottom slate n Pen Argyl,

[15 ]
Figures 32 to 37.

Slate and sheet metal.

igure 32, ribbon slates, exposed 20 years in Washington, D. C; 33, Vermont slate laid with alternate courses of saturated felt after exposure of less than

1 year in Searsdale, N. Y.; 34, standing-seam tin roof more than 80 years old in Reading, Pa.; 35, old standing-seam tin roof in Portland, Maine,

showing lack of proper maintenance in recent years; 36, galvanized sheet -metal roof 8 to 9 years old, near Thurmont, Md.; 37, copper roof on Christ Church, Philadelphia, Pa., applied in 1749.

[16]
[17]
Figures 44 to 49.

Hurricane damage to roofs. a, old asphalt-shingle roof; 45, damage to small section of comparatively new asphalt-shingle roof laid over wood shineles; 46, old wood-shingle

roof; 47, old metal roof; 48, slate blown from hips; 49, damage to tile roof.

[18]
on a number of buildings over a period of about 200 years show slight evidence of rust on

the surface. Figure 27 shows a very old slate roof of heavy Peach Bottom slate. The slate that has been produced in the Peach Bottom

district represents but a small proportion of the

total slate production in this country.

By far the greatest quantity of slate that

has been used for roofing purposes in this country has been produced in Lehigh and

Northampton Counties, Pennsylvania. Quarries have been operated in these counties for about 100 years, with the principal operations

at Slatington, Slatedale, Bangor, Pen Argyl,

Wind Gap, Belfast, and Chapman. In this region, operations generally are on a much

larger scale than elsewhere and utilize the most

modern equipment, including wire saws, electric hoists, etc. Quarries 600 ft deep are not uncommon. A thorough comparative study of the slates produced in this region was not attempted.

Probably as much has been written about slate as about any roofing material, and in the bibliography at the conclusion of this report are

listed a number of references to excellent treatises on slate. Reference 4 (d), "Slate in

Pennsylvania," by Charles H. Behre, Jr., published by the Pennsylvania Geological Survey

in 1933, is a book of 400 pages, mainly about

slate from this particular region.

Many dwellings in the towns listed have

slate roofs more than 50 years old. The slates from this area are classed generally as fading

{4 (b)], the kind and amount varying considerably in slates produced from different quaiiies

or, in some cases, from different parts of the same quarry. One of the most common forms

of fading is shown m figure 28, where the sides

and bottom of the exposed portion of the slate change to a light gray which on long exposure

will spread over the entire exposed surface.

The roof illustrated m figure 28 is 35 years old

and is said to have never given any trouble.

After prolonged exposure many of these

slates develop a tan color. The roof in figm-e

29, reported to be more than 60 years old, antl patched in many places, showed this change.

Figure 30 shows a roof 37 years old witli but

little fading; figure 31, one 25 years old with

practically no fading. The slates in tlus latter roof were 12 by 24 in. in size, and were laid on

slats. All of the illustrations mentioned show roofs

25 or more years old and all are in good condition except the one in figure 29. Roofs of slate from this section may require considerable re- pair or even replacement in less than 25 years. Figure 32 illustrates a roof that was replaced

after 20 years of exposure, and which had re- quired extensive repairs for a number of years. These were ribbon slates,^ though most of them

would be described by producers as "No. 1 Ribbon," smce the ribbons were mainly in the

unexposed portions of the slates. "No. 2 Ribbon" slates are those with ribbons in the

section that is exposed to the weather, and

"clear" slates are those without ribbons. A

number of roofs of ribbon slate have been observed where the ribbons in the unexposed

portions show disintegration as great if not

greater than those in the exposed section. The

authors are convinced that much of the sofi- vein ribbon slate should not be used for roofing

piu'poses.

Ribbons in slates are not necessarily undesirable (see footnote 5). Some of the ribbons

in hard-vem slates weather to a light-colored

band. These are rough-splitting slates which

are used frequently for textural effects. It is often very difficult to distinguish, without tests, between slates of good and poor

weathering characteristics, and many persons

have been disappointed because a roof that was expected to last as long as the structure required frequent repairs and, in some cases, replacement in a comparatively short time.

Frequently fading slates, or mixtiu'es of fading

' "Bands of different color, texture, and composition in slate are com- monly called ribbons. The most common ribbons are darker in color than the main part of the slate and vary in width from a fraction of an

inch up to several inches." D. W. Kessler and W. H. Sligh, BS J. Research 9, 381 (1932) RP477. "When exposed to the weather the ribbons in the 'soft-vein' slate o' Pennsylvania decompose more readily than the clear stock. In side- walks, made of ribboned slate, deep grooves have commonly resulted from the weathering of the ribbons. The ribbons in the 'hard-vein' slate

of Pennsylvania resist weathering." Oliver Bowles, Bulletin 218, Bureau of Mines, United States Department of the Interior, p. 11 (1922).

[19]
and unfading slates, have been sold as unfading

slates. A number of modifications of the usual

methods of laying slate roofs have been pro- posed. Usually these provide for less slate per

unit area of the roof by substituting asphaltsaturated felt or asphalt-prepared roofing for a part of the slate. This is accomplished by

introducing a strip of felt or prepared roofing

between each course of slate. Because these

roofs require fewer slates and, consequently, a lighter supporting structure, they may be applied more cheaply than by usual methods.

One group of dwellings roofed with Vermont

slate, with alternate strips of saturated felt, was examined in the course of this survey.

Tliese dwellings are located in a region where

there is considerable snowfall in winter, with

alternate thawing and freezing. It was re- ported that it was necessary to replace a number of broken slates on these roofs after each

winter. Figure 33 shows a section of a roof

which had been completed during the previous

winter. Note the exposed felt where the

slates have been broken.

(e) Bvilt-U'p Roofing

No detailed study was made in this survey

of the weathering qualities of built-up roofs. These roofs are more commonly used on large

structures, such as apartment houses, office and industrial buildings, and to a considerable extent on low-pitched, row-house roofs in cities in the Northeastern States. This use has been

twofold—as a replacement for the old standing- seam tin roofs and on new construction.

It is expected that a later publication will discuss the weathering qualities of built-up

roofings. Material for this report is being obtained from inspections of roofs of Governmentowned buildings throughout the country by

competent engineers.

(J) Tile

Very little tile roofing was observed in the

territory covered by this survey. Where used,

it was usually on the more expensive dwellings.

Ceramic-shingle tiles are being used on some new dwellings, but to a very limited extent compared to the whole volume of roofing materials. A few cement-tile roofs were also observed, but not nearly as many as were seen

in the Southeastern States. The severity of

the winters in the northern sections limits the use of porous roofing materials of any type.

{g) Metal

It was found difficult to obtain accurate information concerning the durability of various

metallic roofing materials. Ferrous sheet materials, unless adequately protected, suffer deterioration through corrosion, the severity of

which is determined largely by the conditions

of exposure.

Roofing tin when properly protected by

painting gives long service. Many of these

roofs are still in good condition after 40 or more years of exposure. The oldest roof of

this kind of loiown history that was observed was more than 80 years old and had been

painted regularly for more than 60 years by

the same person (see fig. 34). Another standing-seam tin roof that was in good condition

after 73 years of exposure was observed. The

underside of the metal was unpainted and

showed no rust or other evidence of corrosion.

Much shorter life results if roofs of this type

are not adequately maintained. Roofs covered

with roofing tin are usually either good or poor ; they are either well maintained and present a good appearance, even though they may have

considerable age (fig. 34), or are in a poor

condition due to improper maintenance (fig. 35).

A somewhat similar condition obtains in the

case of galvanized sheet steel, though the life of this material may be shorter than that of

roofing tin. Two conditions contribute to

this: First, the zinc coating on any galvanized

sheet exposed to the weather has limited life which depends on the weight of coating,

character of the prevailing atmosphere, roof

drainage, etc. ; second, too much dependence

if often placed on the coating, and galvanized

roofs in many instances are never painted.

[20]
I Even when painted, if proper pi'eeautions are

; not observed, difRculties are encountered with

respect to proper adherence of the coating

of paint to the metaUic surface, witli the

result that cracking and peeling of the coating

occur. In such cases, the durability of galvanized roofing depends almost entirely upon

the protection oft'eretl by the zinc coatnig.

The need for painting galvanized roofing

should be strongly emphasized. Methods for pretreating the surface of galvanized-steel

sheets before painting, which improve greatly

the paint adherence, have been developed

recently but are not in wide use as yet.

It is frequently observed, with galvajiized

roofs, that some sheets are rusted severely,

whereas others show little or no rust, a condition indicating a lack of uniformity in the

sheets. Figure 36 illustrates this condition.

Information obtained from other sources indi- cates that this behavior prevails in other

sections of the country.

The oldest metal roof (fig. 37) that was

observed was the copper roof on Christ Church

in Philadelphia, Pa., which dates from 1749.

3. Flashings, Valleys, Gutters, and

Downspouts

It was practically impossible to secure definite

information concerning the din-al)ility of these

vital roofing accessories. Consequently, only

general observations could be made.

It was qiute evident that considerable

attention is given to the correct instahation

of chimney flashings, valleys, and eave strips

in the majority of cases that were observed.

This is pronounced in the Northeast owing,

perhaps, to the fact that all roofs in the

northern sections of this country are subjected

to loads of snow and ice which may remain in contact with the roofing material for long

periods. Alternate thawing and freezing may

intensify this condition. Consequently, to withstand these climatic conditions, adequate

provision must be made so that all roof intersections and contacts with chimneys, vents,

etc., are watertight.

(a) /''/a.s7/,/"nr/.sCopper, galvanized iron, roofing tin, zinc,

and lead are widely used for ciiinuiey iuid vent

flashings. Figures 39 and 40 represent some

typical histallations of flasliings.

Copper, zinc, and lead are used principally

in those sections along the seacoast where salt atmospheres exert a deleterious effect on ferrous

materials. It was found that the use of particidar metals for these purposes was confined

locally to given sections and was due to a combination of satisfactory service and local roofing

practices. Rarely, and only on the cheapest

types of construction, was roll roofiTig utilized as flashing material for asphalt-shingle and

roll-roofing i-oofs.

(b) Valleys

Roll roofing, copper, galvanized iron, and

roofing tin are used most frequently for valley

flashings. The use of wide valleys, as illus- trated in figure 41, is rather prevalent. Mineral-surfaced roll roofing, tin, galvanized iron,

and copper are used with asphalt shingles.

The practice of interlacing the butts of asphalt

shingles to form continuous valleys is used to a limited extent. Figure 41 shows a valley, part

of which is made by interlacing the butts of asphalt shingles with a wide metal strip forming

the lower section. Copper, galvanized iron,

and tin are used largely with wood shingles.

Galvanized metal is used exclusively with

galvanized sheet-metal roofs.

(c) Gutters and Downs-pouts

The use of these accessories on houses in the

northeastern section is almost universal. Most

gutters and downspouts are constructed of

either copper or galvanized iron, the former

material being used on houses in the higherpriced brackets, whereas the latter is used on

lower-priced houses. A few of the old-type

biult-in gutters can be found throughout this particular territory. In some sections, wood

gutters are reported to give many years of

service.

[21]
V. EXTENT OF USE OF THE VARIOUS

ROOFING MATERIALS IN URBAN

CENTERS IN THE NORTHEASTERN

STATES

1. Factors Which Affect the Choice op

Roofing Materials Generally

Initial cost, cost of maintenance, fire re- sistance, and appearance are factors which

influence the choice of roofing materials generally. Nearness to sources of supply and cost

of application are strong factors in determining

the initial cost. Maintenance costs must be

considered as important as is the initial cost, for some roofing materials will last indefinitely

if maintained regularly, while others have a more or less definite period of usefulness with

little or no cost for mamtenance. City regulations and fire insurance rates are factors which

govern the use of the more inflammable materials. Appearance is becomuig mcreasingiy more important as a factor in the choice of

roofing materials. The manufacturer of asphalt

shingles and the producer of colored-slate

roofings emphasize the possibilities of pleashig

color effects that can be obtained with their

materials. Architects strive for roofs that are

individualistic and that do not repeat the same

[)attem on the whole surface of the roof. Wood shingles are frequently stained to give

the appearance of great age. Ribbon slates are used for decorative effect. The producers

of copper roofing mateiials emphasize the

beautiful patina that will develop on copper

after long exposure. There is no question but

that it is possible and proper to enhance the

appearance of a dwelling by choosing a pleasing

roofing material, although the primary purpose

of a roof should not be forgotten in the choice

of the materials or the design.

2. Distribution of Roofing Materials in

the Cities Included in This Survey

(a) Asphalt Shingles and Roll Roofing

Asphalt shingles have had comparatively

wide use duiing the past 20 years in all cities

that were visited in the Northeastern States,

both for reroofing purposes over old wood

shingles and on new construction. Apparently,

however, they have been employed less generally than in the cities of the Southeastern

States. They give much longer service in the

North than in the South, so that, with the

relatively short period that these shingles have

been on the market, the practice of reroofing over weathered asphalt shingles with new

shingles has not become a general one. Many

more roofs of mdividual asphalt shingles, laid

by the American method, are found in the

North than in the South. These were the first asphalt shingles that were produced, and many

of them remain after more than 20 years of exposure. The cheaper types of individual

asphalt shingles laid by the Dutch-lap or hexagonal methods, used principally for reroofing purposes, have had much less use in the

North than in the South.

One would judge, from the large number of comparatively new asphalt-shingle roofs that were seen, particularly those of the so-called

"thick-butt" strip shingles, that the use of asphalt shingles is increasing in the territory

covered by this survey.

The use of asphalt-prepared roll roofing,

either smooth or mineral-surfaced, on dwellings

in the Northeastern States is so slight that it may be considered negligible.

(6) Wood Shingles

Wood shingles are being used to a considerable extent on all classes of construction in the

outlying districts of Northeastern cities. Western red cedar shingles, unstained, are used most

widely, with some white cedar shingles being

used occasionally. In Wilmhigton, Del., Philadelphia, Pa., and New Haven, Conn., recent suburban developments were observed in which

wood shingles were used exclusively.

More wood-shingle roofs were found in the

congested sections of cities in the Northeastern

States than in the Southeastern States. Most

of these were old roofs, since wood shingles are not permitted now, generally, because of fire regulations.

[22]
(c) Cement-Asbestos Shingles

Cement-asbestos shingles have not had very

ij wide use in the past, through it is apparent

that the use of these shingles is increasing.

More cement-asbestos shingle roofs were observed in Albany and Syracuse, N. Y., than in

any of the other cities.

(d) Slate

Slate has been employed for roofing purposes

' to a much greater extent in the cities of the

Northeastern States than in the Southeastern

States. The extent to which availability of a particular material influences its use is best

illustrated by the use of slate roofing on all types of structures in the rural and urban

sections near slate-producing areas. The

amount of slate for roofing purposes now produced is much less than it was 35 to 40 years

ago. The year of greatest production was 1902,

since which time competition of cheaper materials and rising labor costs have tended to decrease production. The absence of proper

specifications and a unified merchandising plan

have more or less crippled the roofing-slate

industry. Recently specifications which should

be of considerable help to purchasers and

producers of roofing slate have been adopted.

[4 (e, f)].

(e) Tile

Very few tile roofs of any type were observed

in the cities covered by this survey. Some

ceramic-shingle tiles are being used on new

dwellings in the higher-priced classes. Unglazed, porous tiles are not suitable for use in areas where extremes of temperature prevail.

(J) Metal

Metal roofing materials, as a class, are used

to a lesser extent at present than formerly. In

every city visited were found many row houses

with comparatively low-pitched roofs which

were covered originally with standing-seam tin. Figure 38 illustrates representative installations. Galvanized-iron roofing is used but

little on urban dwellings; in locations near the

seacoast, practically not at all.

A few roofs of 10-oz and 3-oz sheet copper

and some of crimped-copper shingles were

observed in Connecticut near the cities where

these materials are rruiiuifactured.

ig) Built- Up Roofing

Asphalt and coal-tar-pitch built-up roofs

have largely superseded the standing-seam tin roofs in most cities. They are cheaper to install and give good service with but little mainte- nance for periods of 10 to 20 or more years, depending on the number of layers of felt and

moppings of bitumen.

VI. DAMAGE TO ROOFS BY THE HURRICANE OF SEPTEMBER 21, 1938

Observations on the effects of the destructive

hurricane that swept thi'ough New England on September 21, 1938, were made in New Haven,

Coim., Boston, Mass., and Manchester, N. H.

Damage to rural roofs in this area is reported

in section III, 4, page 5. Elsewhere in this report considerable space is devoted to a discussion of the necessity for limiting descriptions of the normal weathering

qualities of roofing materials to the most general

terms. It might appear, at first glance, that

with but a single causative factor, such as the

strong winds of a hurricane, it would be possible

to discuss the rtuitive damage to roofs of the

various types more specifically; that it might

even be possible to list the different kinds in

the order of the damage they received. Such,

however, is not the case. Roofing materials

are designed and roofs are constructed to withstand winds of usual velocity. With winds of intensity sufficient to completely demolish

thousands of dwellings, it was natural that numerous roofs of all types should be destroyed.

To determine definitely which types were

affected most under such conditions woidd

require a census of a great many roofs with a complete history of each one. The age of any

roof, regardless of the roofing material, is of great importance in studying wind damage;

wood and asphalt shingles that have been ex- posed a number of years may be slightly curled

[23]
at the butts; old asphalt shingles are more

brittle than new ones; wood shingles may be

weakened greatly by erosion; and all types of roofs may be rendered less resistant to high

winds by the disintegration of the nails used to fasten them. Faulty application, particularly

improper nailing of shingle-type roofs, is re- sponsible for the failure of many roofs under

wind conditions that are not unusual ; and under

winds of hurricane intensity, roofs that are not

fastened properly have little chance.

The first reaction from the observations of roofs after the hurricane was one of surprise,

not that the damage was so great, but that so many roofs of all types had escaped with little or no damage. The action of the wind can be

described best as freakish because many in- stances of adjacent identical roofs were observed where one would be damaged badly and

the other but little, if at all. Figures 42 to 49, inchisive, illustrate damage

to roofs by the hurricane. They have been

selected, not to show the maximum damage to any type of roof or the relative amoimt of damage to various kmds of roofs, but rather to show damage that was typical, with several

examples of damage due to improper application of the roofing material. The age of these

damaged roofs was not determined; but, generally, the oldest roofs were damaged most,

except where some structural weakness was at

fault or where the roofing was applied

improperly.

The roof shown in figure 42 was photographed

during the height of the storm. The only

shingles that are affected in this roof are those

in the course next to the ridge. Apparently

these shingles were nailed very high in order

that the ridge roll would cover the nail heads,

as indicated by the shingle on the extreme

right. Another roof that illustrates the improper application of asphalt shingles is shown

in figure 43. These were square-tab strip

shingles that were each fastened with three

nails, one at the center and one at each end,

about 1 in. from the top.

Figure 44 shows damage that was typical of

badly weathered asphalt shingles. Figure 45

shows typical damage to a small section of a comparatively new asphalt-shingle roof laid over wood shingles. Numerous asphalt-shingle

roofs in the immediate vicinity of that shown

in figure 11 were badly damaged.

Figure 46 shows damage to a rather old

wood-shingle roof. While only a few shingles were blown from one section of the roof, an- other whole section was blown off entirely.

Very little damage was done to roofs of wood

shingles that were not curled and weathered.

The metal roof in figure 47 is probably not

typical of damage to roofs of this type, because

generally, when these roofs were damaged, a section of the roof or the entire roof would be, rolled up and blown clear of the structure. The roofs shown in figures 48 and 49 illustrate damage that may occur to slate and tile roofs.

It was characteristic that damage to slate roofs was usually confined to small sections of the

roof. Note that the felt underlay in figure 49

has not been disturbed. Very few tile roofs were observed in the hurricane area.

VII. COSTS OF KOOFING MATERIALS,

INCLUDING COST OF APPLICATION,

IN URBAN CENTERS IN THE NORTHEASTERN STATES

The current price, including cost of application, per square (100 sq ft of roof surface) for each of the materials listed in table 4 was fur- nished by representatives of the Home Owners'

Loan Corporation in Wilmington, Del., Philadelphia, Pa., New Haven, Conn., Boston,

Mass., Manchester, N. H., Portland, Maine,

and Rutland, Vt. The range in costs is shown

iji the columns marked "minimum" and "maximimi." The minimum and maximum costs were distributed among the difi'erent cities and

were not confined to any particular one. The

average cost shown is the average for all of the

cities.

[24 1
Table 4.

Costs of roofing materials, including application, per square, on a simple pitched roof with no valleys, hut including chimney flashings

[Data obtaineii from the Home Owners' Loan Corporation]

Materials

16 Asphalt shingles: Giant individual, 12 by

American method

Standaril individual, 9 by 12% in., American method

Four-tab scjuare butt strip, 12^

by 30 in Three-tab square butt strip, 12 by

3fi in. overlay Two-tab hexagonal strip, by

36 in Individual re-cover. Dutch lap Individual re-cover, hexagonal

Asphalt roll roofing: Mineral-surfaced Smooth-surfaced

Cement-asbestos shingles {gray color only): American method..

Hexagonal method

Dutch-lap method

Slate Wood shingles... Metal roofing: Shingles (galvanized) Five V-crimp sheets (galvanized) Standing-seam "tin," 26 lb, unpainted

Flat lock and soldered "tin," 25

lb, unpainted

Ceramic-shingle tile Bnilt-up roofing: Five-ply coal-tar-pitch, surfaced with slag or gravel Five-ply asphalt, surfaced with

slag or gravel

Weight

per square

325

255

167 126 to 140

125 to 110

Cost per square

MinimuiTi Maxi- mum

Average

.$12. 85 $20. 00 $16. 50

10. 50 16.50 13. 7(1

10. 30 ,16. 00 13.36

9. 50 14. 00 11. 55

f. 50

7. 50

V2. 00

12. on

12. 00

o! 70

4. 50

4. 25

7. 26

6. 60

6. 20

5.30

21 00

16' 00

15. 00

13.00

10. 00

2l'. 80

24. 50

28. 00

18. 00

23 95

is! 05

19. 60 21.00

14. on

9. 75

7. 25

25. 00

22. 00

16.80 U. .50

13. 60 25. 00 19. 25

13. 26

35. no

30. 00

60. on

20.60

47. 50

7. 25 13. 00 10. 10

8. 00 12. 00 9. 90

VIII. SUMMARY

1. Distribution

Initial and maintenance costs, availability,

and appearaDce largely govern the choice of roofing materials.

Asphalt shingles, wood shingles, and sheet

metal (galvanized) are found on approximately

76 percent of the rural dwellings along the

routes traveled in the two surveys. Sheetmetal roofs are used most frequently on lowcost rural roofs in the Southeastern States; asphalt shingles on roofs of the same class in

the Northeastern States. The villages and small towns in the Northeastern States show a greater variation, generally

,

in the kinds of roofing materials that are used,

than those in the Southeastern States. Slate roofs are used almost exclusively in rural sections, towns, and villages near slate- producing areas.

Few old wood-shingle roofs remain in con- gested areas of the Northeastern cities, but

they are being used to a consideriible extent in new suburban developments near some cities,

notably Wilmington, Del., Pliiliidclpliia, Pa.,

and New Haven, Conn.

Standing-seam tin was used formerly on many

low-pitched roofs in the congested areas of most

cities in the Northeastern States. A number of these old roofs remain but many have been

superseded by bituminous built-up roofs. Slieet metal and metal shingles are not in wide use on dwellings in the Northeastern

States. Asphalt-prepared roll roofing has comparatively little use on dwellings in the Northeastern

States. Fewer single-coverage asphalt-shingle roofs

are seen in the Northeastern States than in the

Southeastern States. Roofs in the Northeastern States are generally more steeply pitched than in the Southeastern

States because of snow and ice conditions.

Wide metal eaves strips are installed frequently

to pi'event leaks and to reduce damage by snow

and ice to shingle-type roofs.

2. Weathering

Asphalt shingles and roll roofings in the

Northeastern States exhibit the same types of weathering as in the Southeastern States, but

weathering proceeds more slowly in the Northeastern States. In general, these roofs may be

expected to render from 50 to 100 percent

longer service in the Northeastern States than

in the Southeastern States. The oldest asphaltshingle roof that was examined was 22 years

old, of individual shingles, which showed severe weathering on the southern exposure.

Many asphalt-shingle roofs that had been

exposed for a number of years sutt'ered damage from the hurricane. Many comparatively

new asphalt-shingle roofs showed no damage,

or only slight damage to small areas. Several wood-shingle roofs were found to be

in good condition after more than 20 years of exposure, also some that were in poor condition

after 10 or 12 years. Some very old roofs of

[25]
wood shingles (more than 40 years old) were

also observed, but invariably these had been

patched and showed severe weathering. Ecigegrain shingles of weather-resisting woods, of proper thickness and without knots or cracks,

may be expected to render long service. Old

wood-shingle roofs suffered damage from the

hurricane ; roofs of wood shingles that had been

exposed only a few years showed but little damage. In many instances, entire sections were blown off with no damage to the individual

shingles.

Practically all colored slates that are used for roofing purposes in this country are produced in the Vermont-New York area. They are very

durable, and the unfading varieties retain their

colors dining long periods of exposure. The

greatest quantities of slate for roofing purposes

are now, as in the past, produced in Lehigh and

Northampton Counties, Pa. Slates from this area are classified as fading slates [4 (b)]. The

best grades may last 60 or more years, the poorest grades may have to be replaced within 10

years. Peach Bottom slates produced in York

County, Pa. and Harford Count)^ Md. are nonfading and very durable, some that have been

exposed more than 100 years still being in

service. Some roofing slates are being produced

in this area at present but in relatively small

quantities.

Comparatively few slate roofs were observed

in the area afl'ected by the hurricane. Damage

to slate roofs was confined chiefly to small sections, usually along hips or ridges.

Cement-asbestos shingles have been on the

market only about 30 years, and numerous

roofs that have rendered satisfactory service

for more than 20 years have been examined.

These shingles tend to collect dust and dirt and

become unsightly after long exposure in industrial locations. Only a very few cementasbestos roofs were observed in the hurricane

area—none that showed any damage.

Tin and galvanized roofs render very long

service if they are painted at regular intervals

but may deteriorate rapidly if they are not

painted. Galvanized sheets exposed in rural

sections may remain 8 or 9 years without severe

rusting; in industrial atmospheres or close to the seacoast they deteriorate more rapidly.

Sheet-metal roofs, particularly old tin roofs

of standing- and soldered-seam construction,

when damaged by the hurricane, were usually

destroyed, many being blown free of the

structure.

IX. SELECTED REFERENCES*

[1] Asphalt Shingles and Roll Roofing:

(a) Herbert Abraham, Asphalts and Allied Substances, fourth edition, D. Van Nostrand Co.,

Inc., New York, N. Y. (1937).

(b) O. G. Strieter, A study of the weathering quality

of roofing felts made from various fibers, J. Research NBS 16, 511 (1936) RP888. Out of print.

(c) 0. G. Strieter, Weathering tests on filled coating

asphalts, J. Research NBS 20, 159 (1938)

RP1073. 10(4. (d) Hubert R. Snoke and Braxton E. Gallup, Accelerated weathering tests of mineral-surfaced

asphalt shingles, J. Research NBS 18, 669 (1937)

RP1002. 10^.

(e) Roofing and Shingles; Asphalt-Prepared, Min

eral-Svirfaced, Federal Specification SS-R-521

(1933). 5^

[2] Wood Shingles:

(a) J. A Ferguson, Comparative Durability of Shingles and Shingle Nails, Bulletin 353, Pennsylvania Agricultural Experiment Station, State

College, Pa. (1938).

(b) Wood Shingles (Red Cedar, Tidewater Red

Cypress, California Redwood), NBS Commercial Standard CS31-38 (1938). 5^.

(c) Red Cedar Shingle Bureau, Handbook of Red

Cedar Shingles, Seattle, Wash. (1938).

[3] Cement-Asbestos Shingles:

(a) Shingles; Roofing, Cement-Asbestos, Federal

Specification SS-S~291 (1935). 50.

[4J Slate:

(a) D. W. Kessler and W. H. Sligh, Physical properties and weathering characteristics of slate, BSJ. Research 9, 377 (1932) RP477. 100.

(b) T. Nelson Dale and Others, Slate in the United

States, Bulletin 586, United States Geological

Survey (1914). Out of print.

(c) Oliver Bowles, The Technology of Slate, Bulletin 218, Bureau of Mines, United States De- partment of the Interior (1922). 20(4.

« Many public, college, and university libraries throughout the country have the publications of the Bureau, and possibly also publications from

other branches of the Government. Where prices are given in this list, the publications may be purchased from the Superintendent of Documents, United States Government Printing Office, Washington, D. G.

Postage stamps should not be sent.

[26]
(d) Charles H. Behre, Jr., Slat« in Pennsylvania,

BuUetin M16, Topograjihic and Geologic Snrvey, Department of Internal Affairs, Harrisburg, Pa. (1933).

(e) Roofing slate, NBS Simplified Practice Recommendation R14-28 (1928). 5(i.

(f) Slate; Roofing, Federal Specification SS-S-451

(1932). 5y5.

[5] Tile:

(a) Walsey Garnet Worcester, The Manufacture

of roofing tiles, fourth series, Bulletin 11, Geological Survey of Ohio, Columbus, Ohio

(1910).

[6] Metal:

(a) National Association of Sheet Metal Contractors, Standard Methods of Sheet Metal

Practices, Pittsburgh, Pa. (1938).

(b) Burns and Schuh, Protective coatings for metals, American Chemical Society Monograph

Series No. 79, Reinhold Publishing Corp., New

York, N. Y. (1939).

(c) Terne-Plate (Roofing-Tin), Federal Specifica- tion QQ-T-201 (1930). 5(4. (d) Roofing Ternes, NBS Simplified Practice Rec- ommendation R30-37 (1937). 5^.

(e) Copper and Brass Research Association, Sheet Copper Handbook, New York, N. Y. (1937).

(f) American Zinc Institute, Inc., Zinc workers

manual, New York, N. Y. (1929).

[7] General, Including Built-Up Roofing:

(a) James McCawley, Roofing: Estimating-—Applying—Repairing (175 Fifth Avenue, New

York, N. Y. 1938).

(b) Ernest G. Blake, Roof Coverings, D. Van

Nostrand Co., Inc. a925).

(c) .loseph Ross, Waterproofing Engineering. ,Iolin Wiley and Sons, Inc., New York, N. Y. ('1919). (d) Hubert R. Snoke and Leo J. Waldron, Survey

of roofing materials in the So\itheasterii States, NBS Building Materials and Structures Report

BMS6(1938). 15^4. (e) A. D. Edgar and T. A. H. Miller, Roof Coverings for Farm Buildings and Their Repair, Farmers' Bulletin No. 1751, United States Department of Agriculture (1935). ^4-

(f) Roofing, Siding, and Sheet Metal \^'ork ; Dampproofing and Membrane Waterproofing, Navy

Department Specification No. 7Yg (1934).

(g) List of Inspected Fire Protection Appliances,

published annually by Underwriters' Laboratories, Inc., Chicago, 111. (h) Asphalt; (for) Built-Up Roofing, Waterproofing, and Dampproofing, Federal Specification

SS-A-666 (1933). 5fS.

(1) Pitch; Coal-Tar (for) Mineral-Surfaced Built- Up Roofing, Waterproofing, and Dampproofing,

Federal Specification R-P-381 (1933). 5?;.

(i) Felt; Asphalt-Saturated Felt (for) Flashings,

Roofing, and Waterproofing, Federal Specifica- tion HH-F-191 (1933). 5j5. (k) Felt; Coal-Tar-Saturated Felt (for) Roofing

and Waterproofing, Federal Specification HHF-201 (1933). 5^.

Washington, May 11, 1939.

[27]



BUILDING MATERIALS AND STRUCTURES REPORTS

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BMSl Research on Building Materials and Structures for Use in Low-Cost Housing 10?S BMS2 Methods of Determining the Structural Properties of Low-Cost House Constructions lOfS BMS3 Suitability of Fiber Insulating Lath as a Plaster Base lOjS BMS4 Building Materials and Structures Report—Accelerated Aging of Fiber Building Boards. lOjS BMS5 Structural Properties of Six Masonry Wall Constructions 15^ BMS6 Survey of Roofing Materials in the Southeastern States 15^ BMS7 Water Eermeability of Masonry Walls 10^ BMS8 Methods of Investigation of Surface Treatment for Corrosion Protection of Steel lOjS BMS9 Structural Properties of the Insulated Steel Construction Company's "Frameless-Steel" Constructions for Walls, Partitions, Floors, and Roofs lOji BMSlO Structural Properties of One of the "Keystone Beam Steel Floor" Constructions Sponsored by the H. H. Robertson Company lOfS BMSll Structural Properties of the Curren Fabrihome Corporation's "Fabrihome" Constructions for Walls and Partitions 10j5 BMS12 Structural Properties of "Steelox" Constructions for Walls, Partitions, Floors, and Roofs

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Connecticut Pre-Cast Buildings Corporation 10(5 BMS21 Structural Properties of a Concrete-Block-Cavity-Wall Construction Sponsored by the National Concrete Masonry Association 10^ BMS22 Structural Properties of "Dun-Ti-Stone" Wall Construction Sponsored by the W. E. Dunn Manufacturing Company 10^ BMS23 Structural Properties of a Brick-Cavity-Wall Construction Sponsored by the Brick

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Floors, and Roofs 15^5 BMS28 Backflow Prevention in Over-Rim Water Supplies 10(4 How To Purchase

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