Correct plywood preparation

[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.