ASPHALT ROOFING 257 



tions are essentially the same as for a gravel roof. For detailed specifi- 

 cations for laying slag roofing see description of the Locomotive Erect- 

 ing and Machine Shop, Philadelphia & Reading R. R., given in Part 

 IV. 



Asphalt Roofing. Asphalt roofing is laid like tar and gravel roof- 

 ing except that asphalt is used in the place of tar or cement. For dis- 

 cussion of the composition and properties of asphalt see Baker's Roads 

 and Pavements, Chapter XIII. The following specifications will give 

 a good roof: 



Five (5) Ply Wool Felt, Trinidad Asphalt and Gravel Roof. First 

 cover the sheathing boards with one ( I ) thickness of dry felt, and over 

 this put four (4) thicknesses of No. I wool roofing felt, weighing not 

 less than fifteen (15) pounds (single thickness) to the square of one 

 hundred (100) square feet. The felt to be smoothly and evening laid, 

 and well cemented together the full width of the lap, rot less than nine 

 (9) inches between each layer, with Trinidad asphalt roofing cement, 

 using not less than one hundred (100) pounds of asphalt to one square 

 of one hundred (100) square feet. All joinings along the wall and 

 around openings to be carefully made. The roof is then to be cov- 

 ered with a coating of asphalt and screened gravel, not less than one 

 (i) cubic yard of gravel to six hundred (600) square feet of roof, 

 gravel to be screened through a ^g-inch mesh and to be free from 

 loam. All walls to be flashed with old style tin or galvanized iron, or 

 a 2 x 4 is to be built into the walls to make roof connections to. 



Five (5) Ply Combined Flax and Wool Felt, Trinidad Asphalt and 

 Gravel Roof. First cover the sheathing boards with one thickness of 

 dry felt, over this put one (i) thickness of flax felt and three (3) thick- 

 nesses of No. i wool roofing felt, weighing not less than fifteen (15) 

 pounds (single thickness) to the square of one hundred (100) square 

 feet. The felt to be smoothly and evenly laid, and well cemented to- 

 gether the full width of the lap, not less than eleven (n) inches be- 

 tween each layer, with Trinidad asphalt roofing cement, using not less 

 than one hundred (100) pounds of asphalt to the square of one hun- 

 dred (100) square feet. All joinings along the walls and around open- 

 ings to be carefully made. The roof is then to be covered with a coat- 

 ing of Trinidad asphalt roofing cement and screened gravel, not less 

 than one (i) cubic yard of gravel to six hundred (600) square feet 



