If waterproofing is to be applied, it must of course be done before subsequent backfilling. Various methods are used, depending largely on local conditions. When applying a coating to a wall, it is good to place it on the outside.
This prevents water from entering the wall, and the pressure of the water tends to force the coating into contact with greater force. If waterproofing 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 1/2-inch bed of Portland cement mortar (mixed at the ratio of 1 bag 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 instruments and a wire brush and then dampened before applying mortar.
It is better to cover the surface with a bituminous layer if there are worse conditions than mere damp. This may consist of a single layer of coal tar pitch or asphalt, or it may be a built-up layer of alternating layers of 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 a coat of plaster is not required. However, if the walls are rough, such as brick, stone, or cinder block, they usually require a coat of plaster before waterproofing.
When applying cold bituminous coatings, first apply a primer coat of the same bitumen thinned with gasoline or kerosene to paint consistency. This mixture is applied cold with a mop or large brush and is designed to penetrate the pores and provide a good bond for the top coat.
Ordinary bituminous coatings are generally hot applied and rubbed in with a roofing mop to a thickness of at least one eighth of an inch. Multiple coats can be applied if necessary, and dull spots, indicating absorption, should be touched up until a uniform gloss 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 onto the surface in much the same way as it is used in spraying paint.
Bituminous coatings or membranes are similar to ordinary bituminous linings, except that they are much thicker and consist of alternating layers of bituminous material and tar paper. Membranes should be used in extremely humid conditions or where there is water pressure against the walls from a spring or other source. The number of layers to apply depends on the conditions to be overcome.
More coatings may be needed to protect the walls of a steam room and steam sauna, but for a dry (or infrared) sauna you really won’t need much.
