Example of waterproofing structure in rock with brick wall laid in mastic. The necessity or otherwise of using the waterproofing is, of course, governed entirely by the local subsurface conditions, the plans provide for what may reasonably be expected, based on the results of the borings, but the judgment of the field engineers is relied on largely to modify this to conform to actual conditions developed as the work progresses. In that section of Lexington Ave. Burlap coated with an asphalt compound is generally used for the fabric, but where there is water, as in the bottom under the floor or in depressed bays, etc., one layer of felt is used first. When the floor is to be waterproofed, a 6-in.
Loose rock is packed behind the hollow tile as it is built up.
In many cases the protection wall of 4-in. The steel columns then act as braces for the rough board forms necessary to support this latter until the mastic hardens. These boards are usually painted with a good thick coat of cement grout to prevent their sticking to the mastic, the grout sticks to the mastic and the boards are easily removed. This site is not affiliated with any transit agency or provider.