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In No. 3 the side wall waterproofing, as shown, has been completed and plastered with a coat of Cement Mortar about one inch thick to protect the waterproofing from fracture while the main concrete wall of the building which is to be built up against it is being constructed.

When the waterproofing of the floor surface is completed it will be covered with a heavy concrete mass of weight and strength sufficient to resist any pressure." The waterproofing is thus shown to be a continuous seal or lining covering the entire floor and extending up in the walls lo a point above the water line.

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IN general, the use of Coal Tar Pitch and Tarred Felt underground is applied to some form of masonry or concrete; if rough stone, the surface to be waterproofed must be plastered fairly smooth to receive the waterproofing, which consists simply of, first, a coat of Pitch, applied hot with a mop, then a layer of Tarred Felt with alternating layers of Pitch and Tarred Felt, until the requisite number is solidly and securely in place. The number of courses varies with the character of the work, from ten plies in a water pressure operation,

 to 2 or 3 where only the ordinary dampness of the earth is to be excluded. In large cities the application of this character of work is a trade in itself, requiring workmen of great skill under the direction of experienced contractors, who make a specialty of waterproofing the cellars and foundations of the most modern buildings. The method of applying alternating layers of Pitch and Felt to masonry is shown in a

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