Correct plywood preparation

[Brad]

Hi all....

Now I know that plywood is not the best substrate to tile onto, especially walls. Problem is that most builders still use the stuff so you just have to make do. Could I get a few comments from those who have been in the trade for some time about preferred methods of substrate preparation prior to tiling onto plywood.

About a year ago I tiled a wall, 600x600 porcelain tiles onto a solid plywood backing. I primed the ply surface with PRIMER-G. Then used MAPEI keraflex. A short while later I had to replace a tile through no fault of my own. Getting the original tile/adhesive off in preparation for the new was quite a task! So my method seemed a good one. What of the tilers out there that warn against priming plywood or maintain that it is not necessary.....

I welcome any comments........

 

[White Room]

Hardie backer or a Marmox type board wold be my preference....

 

[Brad]

That's ok if you have control of the job from the start.....What if the wall has already been ply'd out? i.e. you have no choice but to tile onto ply??

 

[beanz]

You're better off speaking directly to adhesive manufacturers about this. I was under the impression that you should never prime the surface of the Ply, but should prime sides and back. I only ever tile onto Ply floors, but i'm slowly going off that idea, and avoid where possible. I assume you're working for other builders when doing these jobs? Are you working under their Public Liability Insurance, or your own?
If i had to tile a Ply wall, i'd be looking at a 2 part addy, but would definitely speak to manufactureres first.

 

[White Room]

Me personally as my patience wears thin nowadays, change it or I don't bother and reason I say that I tiled onto ply many years ago and the resins leaked into the white grout and and turned it brown.

Your choice at the end of the day though.

 

[Brad]

So the worst that happened was the grout turning colour? No tile failure or anything like that? Did you prep the ply in any way?

 

[White Room]

I did'nt but was informed a coat of pva had been applied to the ply after the event, not good.

 

[beanz]

I've never had any bleeding. What worries me more, is the shrinkage. I've had a couple of tiles pop now, for no apparent reason, so can only put it down to the ply shrinking. Re-layed them, and so far they've stayed down.

 

[DHTiling]

I am not a lover of tiling to ply but it can be done no probs..

 

[charlie1]

Plywood would have more reaction to water ingress. I tile on plywood floors but not walls. Suppose it comes down to price.

 

[SJPurdy]

I don't have a copy to hand but from memory the last edition of BS5385 (2009) advises that ply should only be used for small areas (less than 1 sheet), box construction etc. If larger areas then joints in the boarding should not be tiled over (put in movement joints). This rather makes me think there have been problems with ply walls.

 

[tfs]

I have seen problems where joints have caused cra cks in floor tiles after being down for a few years. membranes can help where ply cant be avoided.

I too have no confidence in tiling direct to ply these days. It can be a hit and a miss, especially with all the crap ply being brought into the country nowadays. I have seen ply veneer shredding when spreading adhesive in some cases. Despite my concerns I am yet to have a call back due to ply.

Recently my own bathroom floor tiles have risen by a few mm in the area near the bath due movement in ply as a result of water and moisture reaching the sub floor. I will now have to re grout My kids cant have a bath without turning the floor into a swimming pool so next time I will be waterproofing everything before tiling.

Avoid if possible every time or prep over the ply with membrane, cement board etc

 

[DHTiling]

I am a big believer in over kill and where it is applicable then i will do it

 

[Peter]

Tiled on ply quite a bit before I was able to source backer boards at a good price, and still do tile it from time to time. Malaysian ply, braced to the hilt with taped joints and solid bed fixing. Never really had any problems with it, some adhesive manufacturers say to prime all sides and edges some say just to prime the rear. Main problems I have seen with ply have been cracking along untaped joints, and 18mm ply straight to joists failing due to ordinary flexible rapidset being used, needs to be rubber crumb at the very least.