In over 10000 building inspections, by far the most common building problem that we encounter is leaking shower recesses. In certain types of building the likelihood of a shower recess leaking approaches 50% of all buildings inspected. Brick veneer buildings with timber floors are the most likely to show leaking shower recesses. There are a number of reasons but perhaps the best way to explain why they leak is to examine the construction of a typical brick veneer cottage with timber flooring.  These buildings are built with brick perimeter walls, and the middle of the building is supported off brick piers. Often, the bathroom, laundry and WC rooms in these buildings have suspended concrete floors supported on brick walls. The perimeter walls of the bathrooms are framed up in timber, but part of the wall structure is supported off the concrete slab floor of the bathroom and other parts are supported off bearers and joists from the perimeter walls and internal piers.

 The timber framed walls of a brick veneer building are lined with plasterboard and these walls become very stiff truss like structures. Over the years the moisture levels under and around the building will stabilise and normally the moisture levels around the perimeter are higher that the moisture levels in the middle of the building. As a result, the timber floor joists and bearers will shrink more in the middle of the building than they will around the perimeter. For the purposes of illustration the classic 4 by 3 (100mm x 75mm) hardwood bearer can shrink as much as 5.0mm, and the joists can also shrink by the same  margin. If the shrinkage is uniform there will be no stress on the bathroom sealing. If however the shrinkage is greater in one section of the building than it is in another, some stress may develop in the junction between the floor and walls of the bathroom and the sealing may deteriorate.

 Once a shower recess starts to leak the surrounding timber becomes saturated and wood decay fungus can establish itself in the damp timber. Wood decay causes the rapid loss of compressive strength in the timber and in extreme cases can result in the compression of the affected timbers.

 Regular under floor inspection of a building is essential so that leaking can be detected and appropriate remedial action can be taken before severe structural damage occurs. One additional problem in leaking shower recesses is that the increased moisture levels under a building can be attractive to pests of timber such as termites.

 The ideal way to build a shower recess is to incorporate a copper tray under the shower. The copper tray should be installed over the concrete slab, before the walls are lined with plasterboard (water resistant grade), or fibre cement sheet. Waterproofing membranes need to be installed at the corners of the walls and at the wall / floor junction before the tiles can be installed.

 The advantage of using a copper tray is that the detail is a self flashing junction at the wall joint and water that does get behind the tiles can be caught. There are a number of other tricks in the waterproofer's trade, but the most important one is to insist on the installation of "two level floor wastes". These function as a normal floor waste, but have slots in the upstand that allow water that has penetrated into the cement bedding to be drained away. 

Most modern buildings do not use copper trays in shower recesses, but use fibreglass reinforced membranes. In sound structures these membranes can be successful, but where there is any significant movement in the walls and floor structures due to timber drying out , they will almost certainly fail. The other difficulty with painted on membranes is that the success or failure of the systems relies on the workmanship of the applicator.

 Another successful method used by premium waterproofing companies is to use a highly elastic membrane that is capable of surviving very large elongation in very small areas. If a floor / wall junction is to move say 3.0mm, the elongation of a rigid membrane over the stress area can be over 300%. This level of elongation will destroy any fibreglass based membrane and severely stress even a ductile copper tray if it is rigidly fixed. Highly elastic membranes like EPDM and PIB synthetic rubbers and some other similar materials can survive in these environments.


The appropriate method will depend on the severity of the damage.

 If the leak is newly discovered and the damage to the structure of the building is negligible, the most appropriate repair methodology may be to strip and re-grout the tiles. Companies like Mega Sealed Bathrooms and Dr Stop leak remove the grout between the tiles on the floor of the shower recess and often the first course of the wall tiles and replace the grout with an epoxy compound. The cost starts at around $500.00 and the shower recess can be back in service in around 24 hours.

 If the shower has been leaking for some time and there is visible damage to walls and floor structure, the shower recess may need to be stripped and waterproofed before re-tiling.  There are many specialist shower renovation companies out there and the average cost is around $2,500.

 Severely damaged shower recesses can require extensive  structural repairs to the surrounding wall and floor structure. The worst shower recess we have seen cost over $12,000 to fix.


There are other places where a shower recess can leak and some of these can only be detected by specialist methods. The three most common points where showers leak apart from tiling and corners are.

 1.             Around the tap bodies

         This a leak site that is sometimes overlooked. Water splashing off one's body can run down the walls and get in behind the tap bodies and then track down behind the tiles. The secret here is to seal the hole in the tiles where the tap body emerges with bathroom sealant.

 2.             Around the outlet

         If the shower fitting is not well secured to the pipe  nipple, water can escape down behind the tiles.

 3.             In the concealed piping inside the walls

         Plumbers use a pressure test to check whether the connections and pipe junctions are pressure tight.

 Each of these types of leak has a characteristic plume of damage to the adjacent walls. The height and distribution of the damage to the adjacent  walls can provide clues to the source of the leaks.

 Modern tilers use special adhesives that are applied to the rear of the tiles. There are often water paths in the incomplete bonding that occurs when the tiles are applied with dabs of glue. The water can track a considerable distance from the point of entry and often the only solution is to remove all of the wall tiles and seal the whole wall before re-tiling.

 One other cause of water leaks in shower recesses is over enthusiastic cleaning. Some of the more aggressive bathroom cleaning products have been shown to attack the resins used in fibreglass bathroom waterproofing products. What happens is that the cleaning products are applied too liberally and then allowed to stay in the shower recess for too long. The acids in the cleaning products etch out sections of the cement grouting between the tiles and produce a concentrated point of attack on acrylic materials in the waterproofing membranes.

 We suggest that aggressive cleaning products be used sparingly, and thoroughly rinsed off immediately.





Advanced Building Inspections Pty Ltd