Hello all I've just found this new forum. Looks great.

Now for my question: My builder has told to me to prime my bathroom and kitchen walls in pva to make them waterproof.

Before I plan to start I'd like a second opinion. What do you think?

Sorry to say but you need a new builder, he is talking from the lower end of his overalls.
Never ever use PVA when tiling and pve will break down in water, you can tile direct onto plastered walls once they are cured over 4 weeks.

If you need to waterproof your walls for lets say a shower area then you need a tanking system.

Adhesive and grout products are water resistant not waterproof.

Hope this helps you.

Pro

do not, never ever, pva walls prior to tiling. tank the shower area and use a proper primer on the rest of the room . particularly new plaster. pva is a poor substitute for using the correct stuff. you only want to do it once, and right dont you.? go to trades direct on the web. you can get a tanking kit ,which will fully waterproof your shower area ( its very simple to apply), and bal apd for the rest of the walls delivered to your door. p.s. i am in no way connected to t d s.! LOL

As earlier posts, you should not use pva. If using a cement based (bagged) adhesive on plaster, you must first prime with a primer such as BAL APD as plaster and cement are incompatible. Some dispersion adhesives (ready mixed) are self priming so you wouldn't need to prime first. Check what the packaging says and follow the manufacturers instructions.

from my experience it would be wise to sand off the polished surface of modern plasters,otherwise you will be tiling onto what is basically compressed dust.Use very course aluminuim oxide type paper as it doesnt clog. Brush down and prime with whatever primer (not PVA) is compatible with your adhesive. Tiles fixed in this manner are damned hard to remove once adhesive has cured.

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young again

I think most of us tilers are agreed on not using PVA in conjunction with tiling. But have you ever had to argue with a customer or his 'know it all' next door neighbour over it? I know I sure have because they or their friend did their job with PVA and there was never any problems.

Probably the worst was a retired lady telling me I didn't know my job when I said that PVA over an asphalt covering prior to tiling was not a good thing. Apparently she'd read it in womans own or something like that.

Cheers,

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Dave M. Carr
TilerSpace.com - Tiling News - Tiler Nottingham