Waterproofing is an integral part of bathroom and wet area construction and provides protection for wall and floor components used as the lining under tiles and other finishes .
In this case the waterproofing has failed in the shower recess and moisture is seeping out onto the main floor . Because this has been happening over a substantial period of time , the timber floor boards have rotted out and now pose a safety risk . As can be seen the main floor tiles have been laid directly over the timber floor and with subsequent moisture and some movement , the tiles have become loose and lifted off .In this circumstance , especially in a wet area , it is recommended that a fibre cement sheet under lay be placed over the timber floor boards and secured with adhesive and nailed at recommended spacings . This then provides a stable base to lay the tiles , using a flexible rubber compound adhesive , and allowing gaps to the wall junction which will accommodate any future movement . The junctions should then be sealed with a suitable silicon sealant and not with grout . Grout should only be used in the main floor tile joints . In larger areas of floor tiles , it is advisable to install silicon expansion joints at regular intervals , which will prevent the tiles lifting in the case of movement or extreme temperature variations .
Silicon joints and grouting should be checked regularly to unsure that the grouting is intact and that the silicon is still adhering to the tiles correctly .The use of commercial cleaning products which often contain bleach as the main ingredient , can contribute to the breakdown of the silicon seal , thus allowing water to penetrate the tile junctions and thereby compromise the waterproof membrane . Over time and with some movement this can impact the wall and floor linings and eventually the shower base will have to be repaired or replaced .