How To Ensure Your Tiled Floors Are Waterproof

[Dave]

These versatile underlayments not only provide the perfect solution to uncouple floor tiles from problematic substrates, preventing them from cracking, splitting and debonding -- they have another very important use: waterproofing tiled surfaces.
Ian Knifton, Technical Manager for Schlüter-Systems -- world market leader in tiling solutions -- answers your questions on ensuring that tiled floors are waterproof.

Q I'm installing a tiled floor in a bathroom, and will be using impervious grout and water-resistant adhesive, so I don't need to worry about any other form of waterproofing, do I?
A Impervious grout and water-resistant adhesive don't necessarily stop water seeping through into the fabric of a building, especially where modern, high-performance power showers throw out a lot of water at high force. So, yes, you do need to ensure that the installation is fully waterproofed.
Q How can I do that?
A The British Standards Institution (BSI) recommends the use of impervious membranes such as the polyethylene Schlüter-DITRA. BSI also says that further advice should be sought from specialists in the waterproofing field. As the world market-leader in tiling accessories, Schlüter is regularly called upon by specifiers to advise about waterproofing on particular projects.
Generally, waterproofing is a matter of education -- first of all about the overall need for it, and secondly which type of membranes to use.
Q

In bathroom situations - make sure there is a waterproof joint between wall and floor

What sort of damage can occur if the installation isn't properly waterproofed?

A We were recently discussing a problem at a private house where water was dripping heavily from a first-floor shower cubicle into a garage below every time the power shower was used.
The sealant between the shower base and tiled wall was leaking, meaning water was finding its way to the room below. It's discoloured the plaster on the garage ceiling and wall -- no real problem in a garage -- but what if it had been a lounge? A correctly installed waterproofing membrane prevents this damage.

Schluter-DITRA is a polyethylene sheet with an anchoring fleece laminated to the underside.

Q Installing these protective membranes obviously helps flooring contractors make more profit, but from the customers' point of view it all adds to the cost of the job. How can we convince our customers that they are necessary?

A Anyone who's suffered water damage because of the lack of waterproofing would readily agree that prevention is better than the cure. How about including photographs of damage caused by water seepage in your portfolio. Then when you're discussing price with customers you can illustrate the waterproofing option.
Q How easy are these membranes to install?
A Schlüter-DITRA is a polyethylene sheet with an anchoring fleece laminated to the underside. After ensuring that the substrate is even and load-bearing, the bonding adhesive is applied with a 3mm x 3mm or 4mm x 4mm notched trowel. While the type of bonding adhesive depends on the type of substrate, for most substrates a dry-set tile adhesive is suitable.
The fleece on the underside of the membrane needs to be solidly embedded into the adhesive so that its entire surface is bonded
Work the membrane into the adhesive, in just one direction, using a float or screed trowel. The tiles can be laid on top immediately afterwards, by anchoring the adhesive into the square cavities.
Q Are there any alternatives to using impervious membranes?
A Other forms of waterproofing include brush-applied liquid. This, essentially, does the same job as the flexible membranes quoted in the BSI code, but will normally take longer, because each coat usually requires a drying time before tiling can start.