Five Bathroom Waterproofing Mistakes That Cost Thousands Down The Track

Waterproofing is the least glamorous part of a bathroom renovation and the one that causes the most expensive problems later. Nobody takes photos of a membrane on Instagram. But when a shower starts leaking into the room below eighteen months after handover, the repair bill lands somewhere between eight and twenty thousand dollars, and it usually involves tearing out tile you paid good money for. We've stripped out enough failed bathrooms to know exactly where the shortcuts get taken. Mistake number one is skipping the primer. Membrane will not bond properly to a dusty cement sheet, and installers who are in a hurry roll straight over the top. Number two is using liquid membrane in a shower floor without reinforcement — you need a bonded fleece or bandage across every junction, corner and waste collar, or the movement in the floor will open a pinhole crack within a year. Number three is not letting the membrane cure for the full seventy-two hours before tiling. Tilers hate waiting. The membrane does not care. Mistake number four is the one we see most often in older Perth homes: no fall in the shower floor. If water pools in the corner and sits there, the membrane is being asked to hold a permanent puddle, and eventually it loses. We cut every floor with a level and check the drainage with a bucket of water before tiling anything. If it doesn't run to the waste within a couple of seconds, it isn't finished. Mistake number five is paperwork, or rather the lack of it. A waterproofing certificate isn't a piece of paper you file away for fun — it's the thing that makes an insurance claim possible three years down the track, and it's what a building inspector will ask for if you ever sell. Get it in writing, from the installer who actually did the work, on the day it passes. That single document is worth more than any tile choice you'll make.

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About the author

Every post on this blog is written by the same people who run the jobs — carpenters, tilers, and a builder who has spent the last decade tearing out other people's work.

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