262 ROOF COVERINGS 



6 inches pitch per foot; they are very satisfactory where slate is too 

 expensive. For flat roofs a tar and gravel composition is preferred and 

 will last 12 to 1 8, and even 20 years. Slag or broken stone of the 

 size of peas is sometimes used in the place of gravel. In such roofs, 

 much depends upon the paper used, the pitch, and the thoroughness of 

 the work ; 3-ply is too light, 4-ply is good, but 5-ply is better. Asphalt 

 pitch is sometimes preferred to coal-tar, but the latter is sufficiently dur- 

 able. An asphalt-gravel roof must slope not more than J/ inch to the 

 foot, on account of the liability to run in hot weather; but tar-gravel 

 roofs may have a pitch of I inch per foot. With such very flat roofs 

 as are required for asphalt, any settlement will form hollows that will 

 hold water. 



"Sheet metal roofs, corrugated or flat are not durable. Steel is less 

 durable than iron and will last only about one year, where exposed to 

 engine gases. Tin shingles of good quality give good results. Painted 

 shingles have a short life unless frequently painted. 



"Of patented roof coverings, Sparham is pulverized talcose lime 

 rock, mixed with coal-tar pitch and applied hot to the roof with a 

 trowel. This may be used for a flat roof or for a roof with a pitch of 

 3 or 4 inches per foot. Ruberoid is a wool felt saturated with a parafine 

 preparation. Perfected Granite Roofing is 2-ply tarred paper with sea 

 grit on one side. Both of these last may be used on any roof with a 

 pitch of not less than 2 inches per foot. Cheap roofs made from roofing 

 papers require mopping with tar, and if thus treated every two years 

 (before the paper is bare) will last almost indefinitely. In railway 

 work, however, roofs are generally left without attention until leaks 

 are reported, when it is too late for mopping to do any good. 



"Roofs requiring treatment every two years can hardly be consid- 

 ered as permanent. Slate for pitched roofs and tar and gravel for flat 

 roofs are as nearly permanent as can be obtained for railway buildings. 



"The cost per square of 100 square feet for roofs of different kinds 

 in New England is as follows : 



Slate $ 9.00 to $12.00 Tar and gravel $4.00 to $5.00 



Tile 30.00 to 33.00 Sparham 5.00 to 5.50 



Shingles Ruberoid 2.75 to 3.75 



Sawed cedar. . . 4.50 to 5.00 Prefected Granite.. 2.75 to 3.25 



Tinned 5.00 to 6.50 Paroid t . 3.00 to 3.50 



Sheet tin, standing 2-ply double... 2.00 to 2.25 



seam 6.50 to 8.00 3-ply single .. 1.50 to 2.00" 



