TECHNICAL INFORMATION ON BUILDING MATERIALS

TIBM - 42

FOR USE IN THE DESIGN OF LOW-COST HOUSING

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THE NATIONAL BUREAU OF STANDARDS

UNITED STATES DEPARTMENT OF COMMERCE

WASHINGTON, D. C,

December 29, 1 Ho

T riage11 and galvanized sheets for rss in house construction

Steel and. iron for house construction are used chiefly in sheet or strip form and, to some extent, in the form of metal lath and concrete

reinforcing "bars. Bare strio steel is used for light structural framing

and panels for prefabricated houses. In the more convent i oral type of

house, bare sheet steel is not used extensively, preference usually being

given to steel coated with zinc, or tin-lead alloys. Galvanized sheets

are used for steel panels in certain prefabricated, houses and in houses

of the conventional type for gutters, leaders, heating and ventilating

ducts, furnace casings, steel window frames, and occasionally, for roofs.

However, the greater number of metal roofs are made of so-called roofing

tin" or terneplate—a steel cr iron sheet coated with an alloy containing lead as the major constituent. (See TIBM .» 4"1 "Roofing Tin (Terneplate) for House Construction" ) .^

Sheet steel or iron is usually known only by a trade name or brand.

More specific information such as commercial grade, size, gage, surface

finish, weight, and type of zinc or other coating, and physical qualities,

like tensile strength cr bending properties, is generally lacking. This

release presents briefly information of this kind and refers to a Federal

Specification giving mere details.

Black Sheets ; Plain sheet steel, as supplied to the trade, for

builders’ use, usually has a light coating of oxide produced during a hot-rolling manufacturing operation. Such sheets are called "Black"

sheets. If easily worked sheet material is desired, it may be secured

by specifying "Black Sheets, One Pass Cold-Relied Eox Annealed" or "Black Sheets, Hot-Rolled, Box Annealed". pcr practically all uses in

house construction flat rather than corrugated sheets are required. Hie

Hiay be

Washington,

obtained

D. C.

'ree of the National Bureau of Standards

012 - 1 - 23 7-

J

ratal used for making the sheets may he ulain carhon steel, "copperhearing1

' steel fSee TI3M - 10 "Atmospheric Corrosion of Ferrous Metals" )1 or open-hearth iron. Stainless iron or steel, is occasionally used "out at present is too costly for extended application.

Prime or first-grade "black sheets should he free from laminations,

blisters, slivers, onen seams, nits from rolled- in scale, ragged edges

or other defects affecting the appearance. Table I on uage H of this

digest gives useful data regarding black sheets*

Galvanized Sheets ; Galvanized sheets are made by passing black

sheets, after thorough cleaning by pickling in acid, through a bath of

molten zinc. By this treatment, the sheet is covered on each side with

an adherent layer of zinc, the thickness of which may be varied to meet

different service requirements. The unique properties of a zinc coating

for protecting steel against corrosion are referred, to in TIEM - 17 "The

Atmospheric Corrosion of Galvanized Ferrous Sheet Metals"©-*- For a high

degree of protection, a thick coating (2 oz» of zinc per sq 0 ft, of

sheet, i<,e 0 , 1 oz, per sq, ft, cn each side) is desirable, but if very

severe bending or forming oeeraiioiis are necessary a thinner zinc coating

is better.

The American Society for Testing Materials in its specification for

Zinc-Coated (Galvanized) Iron or Steel Sheets (Designated as A93-2 7)

classifies galvanized, sheets as:

Class A - Extra heavily coated sheets that are not intended to be

primed other than by corrugating.

Class B - Heavily coated sheets that are not intended to be primed

other than by corrugating and curbing to large radii.

Class C - Moderately heavily coated sheets for moderate bending.

Class D - Ordinary coated sheets for general utility. These coatings auproximate those of Class C except in medium gages in which coatings

of Class D are appreciably lighter. Class D represents material generally

available in warehouse stocks which is not intended for use where relatively long life, represented by Classes A, B, and C or severe forming, represented by Class E, is required.

Class E - Sheets having lighter, more tightly adherent coatings to

reduce liability of flaking in severe forming. The sheet-maker should be

made acquainted with the requirements of fabrication.

ay be obtained free of charge from the National Bureau of Standards,

Washington, D. C,

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Some variation in the thickness of coating on different parts of a galvanized sheet is -unavoidable,, Galvanized sheets should be free

from defects already described under black sheets, and also from bare

or imperfectly coated snots, serious abrasions, drops of zinc, except

on ends, sal ammoniac (flux') spots or similar defects affecting apnearance or serviceability,, Gagas, weights per square foot, and thicknesses

of zinc coated sheets, are shown in Tables II and III on page 5«

There is often considerable variation in the "spangle" or crystal

structure of the zinc coatings on sheets produced by different manufacturers. This variation, however, has little effect on corrosion re- sistance. Occasionally galvanized sheets take on a white film as a result of being stored in damp places, or from other causes. This is

essentially an oxidation oroduct of zinc and has but little effect on the corrosion resistance of the sheets, unless the attack is exceptionally severe.

Further details regarding bl ciC 311 d galvanized sheets are given:

in Federal Specification Q,Q,—

— 696 (March 6, 193-0 for "Iron and Steel;

Sheet Black and Zinc-Coated (Galvanized)".^- See also Simplified Fracp ticc Recommendation R23 "Sheet Steel", promulgated by the Rational

Bureau of Standards, and Circular of the Rational Bureau of Standards

C391 "Standard Thicknesses, Weights, and Tolerances of Sheet Metal

(Customary Fractice)"*-^

^-Obtainable from the Superintendent of Documents, Washington, D. C.

(Price 5 cents).

^Obtainable from the Superintendent of Documents, Washington, D. C.

(Price 10 cents).

^Out of print but may be consulted in Government Depository Libraries..

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heights of Black Sheets (United States Standard Gage)

- Black Sheets

Gage Ann r ox. Approx. Ann r ox s Approx.

Wt* per Ft , per Thick- Thick—

So* Ft*,* Sq « Ft . , ness ness

Lbs. Cz* Decimal Fractions

Avoir- Avoir- parts of of an duocis dupoi

an Inch Inch

16 2.500 40 .0613 l/l6

13 2 * 000 72 • .0490 l/20

20 1,500 24 0 03 63 3/80

22 1*250 20 O o306 1/32

24 lc 000 16 .0245 i/4o

26 0,750 12 *0134 3/160

27 .637 11 .0169 n/64o

23 cb2p 10 .0153 1/6U

29 .562 9 .0133 9/640

30 .500 3 .0123 1/30

For single sheets there is a permissible plus or minus weight variation of 10 percent; for sheet packages a permissible ulus or minus weight

variation of 4 to 7 percent
TABLE ?T

Desired or Ordered Weight of Zinc Coating. Cz/Sq.Et. of Sheet

: Classes

Galvanized ‘. Sheet Gage : A B C . : Dl I E

2

16 : 2 o 75 2 c 50 2.00 : IS : 2 c 7 o 2,. 50 1„75 : 20 ! 2,75 2,50 1 0 75 • ° 22 : 2*75 2.50 lo 75 : 24 2,-,50 1 0 9O 5 26 ; 2.25 lo25 ;

1 ; 28 1-75 1,25. 2 29 1.50 1,25 . : 30 : 1.25 lo25 :

No coatings specified. See 3 age 2 paragraph 7 * "No coatings specified;, See page 2 paragraph 8,

TABLE III

Weight of Galvanised Sheets, All Classes

Gage Ampr ox. Wt» per

Sq. Et.,

Bos.

Avcirdapois

Approx.

Wt. per

Sq.. Et.,

Oz®

Avoirdupois

16 2.656 42 „ 5

IS 2.156 3^.5

20 1 0 65 6 26.5

22 I0H06 22.5

24 1.15b IS.

26 0.506 14,5

27 0.844 13 0 5

23 0,751 12.5

29 0.719 11.5

30 O.656 10.5

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