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Loft conversion ensuite flooring, need some advice
We are renovating the upstairs shower room and under the tiles is a chipboard floor. The tiles will be coming up (floor wasn’t prepped properly so they are all cracked) but I was wondering if you could advise how I should prep the chipboard floor before putting the shower tray down? (Plan will be for shower tray to go down first then flooring up to the shower tray rather than how the previous owners did it which was to tile under the shower tray)
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5 Replies
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I’m not completely sure why but when I had my bathroom done, my builder used marine cement board under the shower and all walls where tiling would be.
Chipboard has no place in a bathroom, any slightly leak and everything has to come up, plus it does tend to move
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I’d probably do the lot on marine cement board or any waterproof tile backer board then tank it (tanking kit from screwfix etc) just to be sure you don’t want anything coming through your ceilings in the future
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Agree with the cement board, we had this down in both bathroom and ensuite and there’s not a mm of movement in the tiles several years on, no gaps in grout or anything.
Id also look at baker board.
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Waterproof tile backer board.
You don’t want any leaks coming out of a loft conversion into the floors below.
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For a shower tray going onto chipboard, the main priority is making the floor solid, level and moisture-resistant before anything goes on top of it. Chipboard on its own is never ideal under a tray, so the prep matters more than the order of installation.
First check the chipboard for movement. If there is any bounce or flex, screw it down firmly into the joists using plenty of wood screws. Any movement under the tray will eventually cause leaks. If the chipboard is damaged, swollen, or crumbly from moisture, replace that section rather than trying to patch it.
Once it is solid, the usual next step is to overboard the chipboard with something stable and waterproof. Most fitters use either 6mm cement backer board or 18mm plywood. Cement board is better in wet rooms because it does not swell. Screw it down tight, making sure the surface is flat.
After that, seal the joints with waterproof tape or a suitable sealant, then apply a tanking slurry or primer around the shower area. This gives you a moisture barrier and protects the floor if any water escapes.
Once the base is flat, rigid and sealed, you can bed the shower tray on either a full bed of flexible adhesive or a sand and cement mix, depending on the tray manufacturer’s instructions.
A full, even bed is essential so the tray is fully supported with no hollow spots.
Your plan to install the tray first and then run the flooring up to it is the standard way of doing it and much better than tiling underneath the tray.
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