Asphalt Roofing

Asphalt roofing for flat roofs is applied as follows: (1) One or two layers of felt paper; (2) a coating of asphalt roofing cement; (3) a layer of roofing felt; (4) a final coating of asphalt cement into which is rolled clean sand and fine gravel. For pitched or sloping roofs the layers of roofing felt already cemented together by the first coating of asphalt cement are sold in rolls about 36 ins. wide. This covering is laid in courses with the edges overlapping about 2 ins. and fastened with the nails and tin washers. When laid the roofing is covered with the final coating of asphalt cement and gravel. A canvas bottom layer may be used in place of the first layer of paper. This form of covering, with the top covering and gravel complete and ready for laying is sold for $3.50 per square of 10x10 ft.

The principal advantage of any kind of asphalt roof covering is that it is perfectly water-proof, and after being laid it does not crack or peel off like tar and does not run at any natural temperature. When graveled over it makes a practically fire-proof roofing. Finally, it is easily applied by unskilled workmen.

Slag And Gravel Roofing

Slag is preferable to gravel for these roofs because of its lighter weight. The construction of both slag roofing and gravel roofing is as follows: (1) Three layers of felt paper are fastened to the roof; (2) a coating of tar is applied to the top layer of felt; (3) two layers of felt paper are laid on the tar; (4) a covering of tar is applied to the top layer of the second course of felt using about eight gallons of tar per 10x10 ft. square, and the slag or gravel is rolled into the tar. This form of roof covering should last from 10 to 20 years. It is fire-proof, needs no paint and refracts the heat. It is noiseless and is not affected by gas, acids, etc. Finally, it is a comparatively cheap covering, costing 50% less than tin.

Corrugated Iron Roofing

Corrugated iron is made from sheet iron of standard gages by stamping, one corrugation being stamped at a time. As there are no sharp joints to be made there is no advantage in using sheet steel. The corrugated sheets are made in lengths increasing in dimensions by even feet from 5 ft. to 10 ft., inclusive, and of such width that they lay 2 ft. even on the roof. The sizes of corrugations made in the United States are 5 ins., 2 1/2 ins., 5/8 ins., 5/8-in., and 3-16-in. c. to c. of corrugations. The 2 1/2-in. corrugation is the size most commonly used. Table VII. gives the costs and weights of both black and galvanized iron for Birmingham Wire Gage and the new American Standard Gage adopted by Congress in 1893.

Table VII. Showing Cost and Weight per 10 x 10 ft. Square of Painted and Galvanized Corrugated Iron.

-----------Birmingham.-----------

-------------American.-------------

-Painted.-

-Galvanized.-\

- Painted. -

Galvanized.-

Gage.

Wt.lbs per sq.

. Price per sq.

Wt.lbs. persq.

Price per sq.

Wt.lbs. per sq.

Price per sq.

Wt.lbs. per sq.

Price per sq.

28___

* • • •

• • • •

87

• • • •

69

$2.90

86

$4.90

27....

72

$3.00

94

$5.40

77

3.10

93

$5.30

26...,

81

3.20

101

5.60

84

3.30

99

5.50

24....

98

3.80

114

5.80

111

4.15

127

6.40

22...,

123

4.60

141

6.80

138

4.90

154

7.40

20....

153

5.40

188

8.40

165

5.80

182

.. •.

18....

214

7.20

221

11.60

220

7.40

236

....

16....

283

9.60

287

15.20

•.. •

8.60

• • • •

....

The prices given in Table VII. are for small lots; for car load lots . the prices will be about 10% less. This table also refers to 5-in. 2 1/2 in., and 3-16-in. corrugations; for 1 1/4-in. and 5/8-in. corrugations, 5% should be added to the weights and prices given. If painted with asphalt or graphite instead of iron oxide, the cost will be 25 cts.more per 10x10 ft. square. Wire nails cost 10 cts. per square; galvanized nails cost 15 cts. per square and cleats and bolts cost 25 cts. per square. The price of curved sheets is 20% more than that of straight sheets. The sheets of corrugated iron should be laid with a lap of 4 ins., as shown by Fig. 23, when used for covering side walls, and with a lap of 6 ins., as shown by Fig. 24, when used for roof covering. When laid on wood sheathing corrugated iron covering is lined with water-proof paper and fastened with 6d. nails, using about 25 nails per sheet. When laid on iron purlins for boiler houses or anywhere that water is likely to collect on the underside of the corrugated sheets, a lining of the following composition may be employed: (1) Wire netting tightly stretched over the purlins; (2) asbestos paper; (3) tar paper; (4) asbestos paper; (5) tar paper; and (6) the corrugated iron roof covering. When corrugated iron is laid over iron purlins it may be fastened to them by clinch nails bent around the purlins, as shown by Fig. 25, or by cleats of 3/4-in. hoop iron 2 1/2 ins. long riveted or bolted to the sheets and to the purlins. Generally, however, cleats of this form are used especially with channel or Z-bar purlins. The clinch nails or cleats should be placed about 5 ins. or 6 ins. apart and care should be taken to connect them always to the tops of the corrugations, as shown by Fig. 25. The following table shows the size of clinch nails to be used with different sizes of angle purlins and also the number of nails to the pound in each instance:

Corrugated Iron Roofing Mill Building 22

Fig.23.

Corrugated Iron Roofing Mill Building 23

Fig.24.

Clinch Nail Fastening for Corrugated Iron Roofing.

Fig. 25. Clinch Nail Fastening for Corrugated Iron Roofing.

Purlin angle

2 x 2 ins.

2 1/2 x 3 ins.

3 1/2 x 3 1/2 ins.

4x4 1/2 ins.

Length of nail.....

4 ins.

5 ins.

6 ins.

7 ins.

No. of nails per lb..

48

38

33

27

Corrugated iron of No. 27 and No. 28 gage is too thin to support any weight above and must be laid over sheathing. For other gages the purlin spacing should be as follows:

Thickness, B. W. G.

Spacing c. to c.,

ft.

ins.

No. 26..........

2

0

" 24...........

2

6

" 22...........

3

0

Thickness,

Spacing c. to c,

B. W. G.

ft.

ins.

No. 20..........

4

0

" 18....

5

0

" 16..........

6

0

The advantage of galvanized over black corrugated iron is that it requires painting less frequently. Galvanized corrugated iron seldom needs to be painted within five or six years after erection. When painting becomes desirable, it is always necessary to remove the zinc by applying with a brush the following wash: Chloride of copper, one part; nitrate of copper, one part; and salammoniac, one part, dissolved in 64 parts of water, with one part hydrochloric acid added to the solution. This solution will burn the metal black ready to receive paint in about 24 hours. Black corrugated iron should be painted upon leaving the shop and about every two years thereafter.

Corrugated iron is not recommended for roofs having a slope of less than 3 ins. in 12 ins., and if it is used for flatter roofs -all the joints should be laid in elastic cement. Cement joints can be used to advantage for roofs of any pitch since they ensure a much tighter covering. When corrugated iron is used for siding where it is liable to receive shocks, a heavy gage should be employed. The siding should not touch the ground as contact with the earth hastens its corrosion.