Minimum requirements for plywood under tiling

A

ali

Registered User
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Is it necessary to use 18mm WBP plywood under wall tiles or is 12mm sufficient in any / all cases?



Thanks,

A.
 
It all depends on what the ply is being attached too. 12mm will bend a little over an uneven surface, and this will make the tiling more difficult. 18mm will give a more solid base if you're attaching it to a stud frame.
Leo
 
hi. I have used 12mm extensively for tiling in showers etc. and it is fine and is the same thichness as the plaster board which is ideal. !8 mm is a bit over the top
 
nediaaa said:
hi. I have used 12mm extensively for tiling in showers etc. and it is fine and is the same thichness as the plaster board which is ideal. !8 mm is a bit over the top
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This is my issue. In tying in with existing plasterboard which is 12mm the 12mm ply works better. I'm interested to know what the building requirement is though.

A.
 
12mm properly bonded and screwed to sound plasterboard should be more than adequate.
 
Leo said:
12mm properly bonded and screwed to sound plasterboard should be more than adequate.
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Thanks Leo.

Actually the plywood is going onto a stud but will replace 12mm plasterboard which was in situ and will then line up with untiled plasterboard at the side which is just painted. I am totally confident of it being sound but an engineer on the job suggested 18mm was required for wall tiles. Not my experience or my very experienced tiler's.

A.
 
Ali,

It will have a lot to do with the soundness of the stud-work you are fixing the plywood to. 12mm should be perfectly adequate if fixed at 12" centres with screws to the strudwork.

If you experience any give in the plywood you should move up to the 18mm, as the tiles could simply pop off the wall if anyone leans against it.

If the give is in the stud-work (check before fixing the 12mm ply) pack out the studs or add additional noggins to brace the timbers to prevent movement.

A lot has to do with the substrate you are fixing to.
 

Appreciate that input thanks,

A.
 
Your engineer is correct, plywood will shrink over time due to moisture evaporation a plasterslab will not. 12mm plywood more so than 18mm.
 
I would never use ply on stud for wall tiles. Any timber movement moves ply, which leads to tiles cracking.

Use double green 1/2" plasterboard with joints overlaped.
 
aulita said:
I would never use ply on stud for wall tiles. Any timber movement moves ply, which leads to tiles cracking.

Use double green 1/2" plasterboard with joints overlaped.
Click to expand...

This is a 12mm plasterboard wall. Are you suggesting double slabbing?

ONQ.
 
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