Waterproof a bathroom by using a water based polyurethane membrane
All "roughing in" of plumbing and electrical work must be completed before waterproofing commences. Floor panels must be installed so that there are joints in the shower recess area. The area around the floor wastes should be rebated so that safe-way trays fit flush to floor not above floor level. This assists water to flow to the floor wastes. The room must be cleaned of all dirt dust and laitance.
At all floor and wall junctions a fillet must be installed using polyurethane joint sealant. The fillet allows for movement in a wood framed room and also stops water from ponding at the floor and wall junctions. All joints in the floor sheets and screw heads should be sealed with polyurethane joint sealant. A bond breaker, using polyurethane joint sealant, should be installed in all vertical angles that will be waterproofed. If installing a frameless shower screen for the shower recess a water bar should be installed. The water bar should be 3mm thick aluminum and set on the floor so that the shower screen sits immediately over it. The water should be equal to the height of the tile bed. The room is now ready for waterproofing.
Usually a water based primer is sufficient but water based epoxy primers can also be used and are applied by brush and roller. The primer must be applied to the shower walls, as splash back over vanities and to the floor area turned up against other walls to a height of 100mm above the proposed tile bed height. Follow product information regarding drying time before applying the membrane.
A minimum of two coats of membrane should be applied over the previously primed areas. Follow product information regarding the time between coats and achieving the recommended dry film thickness. It is also good practice to install membrane over the tile bed before the tiles are installed. The tile must be left to dry out and then using the same primer and membrane seal over the tile bed.
The benefits of doing this are:
Water will also fall to the drains and will never pond in the tile bed.
The membrane will prevent efflorescence, which is salt leeching from the tile bed that will stain the tiles.
It will also seal the under side of porous tiles so that they do not absorb dirt and soap fats.