346 WATERPROOFING 



cations, will be found excellent for placing a coal-tar pitch 

 and felt roof over concrete. These specifications also 

 describe how the work should be carried out. 



"There shall be used five thicknesses of approved felt 

 weighing not less than 14 Ib. per 100 sq. ft., single thickness, 

 not less than 200 Ib. of approved pitch, and not less than 

 400 Ib. of gravel or 300 Ib. of slag from J to f in. in size, free 

 from dirt, per 100 sq. ft. of completed roof. 



FIG. 17 



"The material shall be applied as follows: (1) Coat the 

 concrete a (see accompanying figure), with hot pitch b 

 mopped on uniformly. (2) Lay two full thicknesses of 

 tarred felt c, lapping each sheet 17 in. over the preceding one, 



