We often hear homeowners asking why go to all the time & expense of waterproofing behind the tile when creating a full tiled shower or tub surround … “My buddy sealed the grout and put silicon along the bottom of his shower so isn’t it waterproof?”
In a word, nope! There is a common misconception that tile sealer is for waterproofing of porous tile (eg. slate & marble) & grout. The purpose of tile sealer is actually to help prevent the grout or porous tile from being stained by dirt, soap scum, etc as well as to bring out the natural tones and add some sheen with products such as slate. Whether sealed or not, water can and will still penetrate grout. You may not imagine this to be very significant, but if you consider the number of gallons of water being used in a typical shower per day over a couple of years then this often will lead to significant problems behind the tile … the damage you cannot see until too late.
Given the expense of creating a full tiled shower or tub surround this is something most homeowners would like to see last at least 10 years, so it is well worth ensuring that your contractor uses products and techniques intended to prolong the life of the finished product. We always tell clients that they should only expect to redo one of our showers when they want to change the look/style and not because it is falling apart.
Water will penetrate behind the tile … this we can guarantee. What then happens to it and where it goes depends on whether short-cuts were taken during the install or not. In the worse case, you may find regular drywall behind the tile … this is a mould party waiting to happen. Even if a concrete board has been used, this is still a porous material and needs to be water-proofed.
We mostly use the Schluter Kerdi system as a waterproofing layer behind the tile for shower stalls … this is an orange waterproof & vapour proof fabric which is thinset to the backer-board (such as a concrete board or Denshield) & then the tile is set on to this. It has fibres running through it which allow for a tight bond to the thinset mortar. There are also liquid membranes such as RedGuard [seen in the picture on left] and Mapei Mapelastic HPG which are applied with a roller or brush and turn to a layer of rubber after a couple of coats. Whichever system your contractor uses, the result should be so as to direct any water so that it does not get behind the wall or under the shower tray.
So next time you are thinking of doing a bathroom renovation and you get a few quotes … check them over to see which system your contractor intends to use and make sure they understand the correct technique for the install. Done right you will have a bathroom which will last many years with minimal maintenance.