Tanking and Plasters

[Canyondust]

Good evening.
I am enquiring about the use of tanking systems (such as those used with wet room shower kits) and plaster.
If an area has any new plaster can the tanking system be placed over once dry, or after some prolonged time ? Does it need sealing, PVA or similar?
Does the type of plaster affect the tanking (e.g. browning, hardcoat, finish) ?

The question comes from time planning a shower installation. The majority of the walls surface is currently old plaster, some will need minor repairs and levelling.

All the very best
James

 

[Dan]

Don't seal with PVA it has no place in tiling.

 

[Old Mod]

Plaster should be finish, any other form of plaster is not recommended, and shouldn't be tiled to.
Yes you can apply tanking kits to dried plaster.
Prime according to tanking kits installation instructions.
As been said above. This will not be pva.
Do ensure ANY old and loose plaster is removed.
A plastered wall only has the weight carrying capacity of 20kgs m2. Which by today's standards, is not very much. Don't forget 4.-5 to 5kgs m2 for adhesive and grout.
And no, the weight limits of plaster after tanking, are not diminished/increased.

 

[Canyondust]

Thanks for lots of fast information.
So - assuming tiles are approximately 10mm thick and ceramic, that gives area weights in the order of (25kg + 5kg) / m2 which would suggest some form of tile backing board?

The primer with the kit is an acrylic type - BAL APD

With respect.

 

[Old Mod]

They're heavy ceramics, that's more in line with porcelain.
However, if they're the weight you mention, then yes, a backer board fixed either direct to wall with adhesive and mechanical fixings, or direct to studwork would be in order.
If you lined the area with boards similar to wedi, then you would only need to tank the board joints and transitions and over the mechanical fixings.
You'd then have a watertight & tile friendly area to tile.
Cement boards are NOT waterproof
(hardie, Aquapanel)

 

[Canyondust]

Thank you for your helpful advice.

Regards
James