As Victorian Registered Commercial and Domestic Builder (Unlimited) and Manager/Director of a Melbourne based waterproofing company (Findlay-Evans Waterproofing) that provides remediation works, I have witnessed the compounding effects that tiling and waterproofing have on the success (or otherwise) for a watertight construction.

Waterproofing, tiles, and tile adhesives are interconnected.

Also as President of the Australian Institute of Waterproofing (AIW), I am aware of the large number of complaints the Institute receives about the combination of waterproofing failures and substandard tiling.

The AIW receives inquiries not only concerning waterproofing issues but tiling problems as well.  These issues range across the building industry and include projects currently under construction, recently completed new construction, commercial, residential, industrial and existing buildings.

One problem is a lack of communication between waterproofers and tilers. This is a common challenge among many construction trades as the industry relies heavily on subcontractors and sole contractors who operate independently.

For waterproofing and tiling, the skills, products and materials used by both these tradespeople directly affect each other and together are responsible for a successful outcome.

For example, it is important that the waterproofing membrane system which is installed is compatible with chosen tile adhesive and that both products are fit for purpose. Doing this involves simple cross-checking and can avoid waters leaks. Yet this cross-check is often not neglected.

Another issue can occur where tilers offer to provide both trades and to apply waterproofing membrane as well as tiling. For builders, this can be beneficial as having using one trade for two skillsets saves on organisation, time and money.

This must only happen, however, where the tilers in question have waterproofing training. Vice versa if waterproofers provide tiling work. Should this not be the case, homeowners can be left with either water leaks or an unprofessional tiling job.

A third challenge involves determining who and what is responsible where leaks occur. Is it building design? The membrane selected? The quality of waterproof application? A poor tiling job? Use of incompatible products? Or is it a combination of some these?

Complex and conflicting questions arise: the waterproofer is confident they installed a good membrane; the builder is confident there was no damage inflicted to the membrane prior to tiling, the tiler is confident of the tile laying process. All attest to using appropriate products/materials for the project. Who is responsible and who is going to fix it?

Often, I have witnessed site meetings within a bathroom, surveying water leaks and the resulting damage. The conversation goes around in circles without anyone wanting to take responsibility. Indeed, the question of fault is often not clear. The source of water leaks either may not be obvious or may involve multiple variables across several trades and/or various products. Added to this is, all involved are aware water ingress rectification costs are far greater than costs of the original installation.

Eventually a resolution of sorts involves a compromise to spread the responsibility; the builder pulls apart the defect; the waterproofer re-waterproofs and the tiler re-lays tiles.

So laborious and costly remediation works begin. Tiles are pulled up which in turn destroys the membrane, as they are bonded together (or should be).  Evidence shows the tell tail signs of water ingress: rotting and/or water-stained timbers in the near vicinity under, behind or nearby. However, this does not confirm the exact cause.  Tiling or Waterproofing? Building design? Drainage?

What can go wrong?

Here are some examples:

  • Humping. This can occur where tiles have insufficient expansion joints or expansions joints which are too small (too narrow). This results in tiles being “blown off” walls or “humping’ in the case of floor tiles as tiles expand or grow. Often, this destroys otherwise effective waterproofing systems as most membranes will not stretch enough to withstand the resultant pulling.
  • Excessive expansion of cheaper tiles, which can occur with high temperatures and without adequate expansion joists as these tiles tend to expand more than others. These tiles will pop up/out – causing membrane failure.
  • Having insufficient expansion joints as clients or architects sometimes desire a harmonious design without ‘visible joists’ for aesthetic reasons. Unfortunately, some contractors comply to these designs despite knowing this does not comply with Australian Standards. This can potentially lead to water ingress down the track.
  • Laying of tiles over a polyurethane membrane. This can be fraught with danger as bonding to polyurethane is at best problematic. However, this topic is too big to go into here.
  • Re-emulsification of tile adhesives on new projects. This is often mistaken as effervescence. Re-emulsification comes to the surface of tiled areas via the grout lines, particularly on balconies. It is a milky substance and when dries can look like effervescence (salt residual that normally comes from the sand in under tile cement screeds or grouts). Sometimes re-emulsification can be caused by inadequate falls. Water travels under the tiles (but over the membrane) taking a long time to get to the drain point/s and can cause adhesives to re-emulsify. Re-emulsification also may cause the tile/s to de-bond (come loose). Fortunately, this may not damage the waterproof membrane as the adhesive becomes soft and mush. I personally like adhesives that are designed for swimming pools for this reason.
  • Tiles being affixed without a proper notched trowel. Another problem is tiles affixed without a proper notched trowel, where application is merely by blobs of adhesive on the back of tile and then pushed down into the surface. This creates voids behind the tiles and causes a “drummy” or hollow sound when tapped. As a result, tiles are left without support at the back and thus may be subject to breaking.

Both tiling and waterproofing require thought, knowledge and experience. Both trades require collaboration, correct application, suitable products and effective supervision from building contractors.

Many factors can contribute to poor water management.

For one, long term successful waterproofing can be compromised by poor general building design and construction. To name a few, problems in this area can include insufficient falls built into the floor, large gaps, poor supervision for wet area wall lining installation or incorrect joint preparation on plasterboard or cement sheet. Poor joint preparation is particularly difficult to determine as the evidence is hidden underneath the membrane.

Waterproofing membranes may also be poor quality and/or not correctly installed in accordance with manufacturers’ specifications. i.e., too thin, surface area incorrectly prepared. At project completion, all this is covered by tiles and difficult to detect.

Sadly, waterproofing planning prior to construction is often minimal and inadequate. Indeed, construction drawings often fail even to nominate waterproofing items and processes. Even where nominated, many waterproofing specifications are of the “cut & paste” variety.  The generic “refer to manufacturers’ specifications” provides the out clause for many architects and building designers. Rarely do waterproofing specifications direct to use the product/s “best” for specific projects: internal, external, rooftop, balcony, below ground etc. Manufacturers’ specifications are accepted as is. Invariably, these include very general statements about their products. However, failure is laid at the installers, tilers and waterproofers.  Manufacturers can be reluctant to take responsibility for their products. Thorough training for product knowledge, methodology and skills is imperative, however sadly lacking.

Waterproofing is critical for all involved. Water leaks can cause serious damage – both structurally and aesthetically. This leads to lengthy legal battles, expensive remediation work and emotional turmoil for owners.

Leaking buildings are unacceptable.

The Australian Institute of Waterproofing (AIW) is a voluntary group of contractors and manufacturers offering their own time to be a voice for waterproofers and better the industry in general across Australia.

As always, the AIW is here to help.  We have a strong team of qualified and dedicated members who care about the industry. AIW welcomes tilers to become members and help our two trades work together. The AIW has representation in most states and members across Australia.

Contact AIW at or check our website: