If waterproofing is to be applied, it should, of course, be done before back filling. There are various methods used, depending largely upon local conditions. While applying a coating to a wall, it is well to put it on the outside.
Water is thus prevented from entering the wall, and water pressure tends to force the coating into tighter contact. If the water proofing is required for a bathroom, perhaps around a bathtub or other bathroom fixture, the technique is a bit more complex.
This may consist of a half-inch coating of Portland cement mortar (mixed in the proportion of 1 sack of Portland cement to 2 cubic feet of clean, well-graded sand, plus finely divided materials, such as hydrated lime or diatomaceous silica), or a plastic cement applied to the interior surface of the wall with a trowel.
For bathroom remodeling, the walls surrounding the steam shower or steam room should be thoroughly scraped and cleaned with sharp edged instruments and a wire brush and then dampened before the mortar is applied.
It is best to cover the surface with a bituminous coating if worse conditions than mere dampness exist. This may consist of a simple coating of coal-tar pitch or asphalt, or may be a built-up covering of alternate layers of the bituminous material and tar paper.
These coatings are often used alone on new walls or in cases where the walls are in such good condition that they do not require the plaster coat. If walls are rough, however, like brick, stone, or concrete block, they usually require a plaster coat before being waterproofed.
In applying cold bituminous coatings, first apply a priming coat of the same bitumen thinned with gasoline or with kerosene to the consistency of paint. This mixture is applied cold with a mop or large brush and is intended to soak into the pores and provide a good bond for the top coating.
The ordinary bituminous coatings are usually applied hot and swabbed on with a roofing mop to a thickness of at least one-eighth inch. Several coats may be applied if necessary, and dull spots, which indicate absorption, should be touched up until a uniform shiny appearance is produced.
There have been recent developments in the application of such materials, one of which is the use of compressed air to “shoot” the material upon the surface in much the same manner as that employed in paint spraying.
Bituminous layers, or membranes, are similar to ordinary bituminous coatings, except that they are much thicker and consist of alternate layers of bituminous material and tar paper. The membranes should be used in extremely wet conditions or where there is water pressure against the walls from a spring or other source. The number of layers to be applied depends on the conditions to be overcome.
More coatings may be needed to protect the walls of a steam room and a steam sauna, but for a dry sauna (or infrared) you really won’t need much at all.
