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Question:

How do I waterproof Plasterboard (or gyproc)?

I have recently put up some plasterboard (or gyproc) in my kitchen and need to seal it (as it's behind a sink and a cooker). I have bought a tub of PVA, but there are no instructions on the back for what ratio to mix it to apply to the gyproc to waterproof it... Any ideas?

Answer:

It really all depends on the level of waterproofing that you require. PVA is a good bonding improver but is not recommended as a waterproofer although it is often used as such. PVA will re-emulsify when it becomes damp, leading to possible delamination problems. SBR is a very similar looking product to PVA, but is more expensive and better for waterproofing applications as it will not re-emulsify once it is fully cured. Alternatively you can go for a full under tile tanking system such as Aquaproof. These systems are designed to be used behind tiles is showers, bathrooms, kitchens in apartment blocks. It may however be a bit over the top for a splash back!
May 11, 2017
You can buy waterproof boards for putting in showers. But for usual plasterboards.. are you plastering on the boards of tiling straight on top? If you are tiling, you probably dont need to seal it. Though a weak mix of pva may be good to put on. 50/50 or a bit less. If its undiluted it will set too thick and shiny for tile adhesive or plaster to stick to.
May 11, 2017

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