May the roof above us never fall in
And may we good companions beneath it never fall out.

~Irish blessing

Monday, January 23, 2012

Waterproofing the bath/shower area

You may remember me writing about the shocking state of the subfloor and joists when we started demolishing our bedroom ensuite last year. It was pretty bad, not just mouldy bad, which you might expect under old tiles, but earthworms living in soggy chipboard bad. The bathroom wasn't that old either - only early 90s - but from what we could make of the remnants, no waterproofing of the shower area had ever been properly done, just chipboard with villaboard over the top and then tiles laid straight on. 

Now I'm no expert, but something I've learned is that while villaboard is a water resistant product, it's not waterproof and if it's used in shower or bath areas it needs to have a waterproof membrane applied to it up to 1800mm high. Some people use 'blue board' in their showers as it has a water resistant coating, but blue board is actually an exterior product for eaves and has really poor tile adhesion, so villaboard or wet area plasterboard with a membrane over the top is the way to go.  The membrane comes in a tub and you brush or roller it on like a thick paint. You also need to use a bond breaker (either a 'bond breaker bandage' or a neutral cure silicone - see video) on any joins, cover over any fixings with a waterproof polyurethane product (we used marine sikaflex) and use reinforcement bandage around any gaps such as taps etc.

If you want to tile your own bathroom, but feel a bit nervous about doing the waterproofing there are tradesman that will come in and do just the membrane for you. The video below though should give you an idea of what's involved.

There are membrane kits available from the major hardware stores that come with membrane, bandage etc. Dunlop do one and Crommelin is also readily available. We used Crommelin because a friend had half a tub leftover after doing his own bathroom. Even with two generous coats, it was more than enough to do the shower area in the ensuite #1 and the bath area is ensuite#2 with plenty left over. It's a bit smelly, but not too bad, and only takes a couple of hours to dry between coats so it's easily all done in a day.

You can use masking tape between the wet area to be tiled and the area to be painted, but it's probably not necessary if you have a steady hand. The tiles will overlap a bit over anyway.

And we extended the membrane over the whole floor as it's to be a children's bathroom and splashing is bound to happen.

I've been a bit slack and these photos are actually from last week and don't show all of Tom's late night painting work. Our weekend was packed full of childbirth education classes and similarly themed excursions, but tiling will hopefully commence over this coming Australia Day weekend. Don't worry though, time out is scheduled to catch up with a few friends for some drinks and an inaugural pavlova. Hope everyone has a great long weekend.


  1. I can't believe what you are managing to achieve yourselves. Very very clever. A question, know anything about rising damp/rot in the bricks? Me thinks we have a serious problem and I shudder to think about the state of our joists (big sigh)

  2. Thanks Alison. As far as the bricks go, I don't know much at all I'm afraid. We have just the one brick wall on the boundary which thankfully was ok because despite the constant water seeping into the floor, there was still quite a bit of ventilation underneath keeping the bricks aerated. Probably the only thing of comfort I can say is that replacing joists was not very expensive or difficult. The upheaval of everything else to access and fix them was the real hurdle.