Screed or Backerboard?

[dontbelieveawordofit]

op. however the problem with jamieh’s suggestion is that the 3 boards he suggested you remove in the corner land on a joist.
meaning when you cut them off there will be a void in the corner. nothing for his suggested 22mm ply to sit on as the next joist along is the other side of the wall, good luck nogging that.

 

[JaimieH]

Looking closer at your floor it looks like the existing ply runs under the tiles on the other side of the door. If you're happy the existing floor is sound with no movement it would probably be better not to disturb it, otherwise you might have issues with the other tiles. If you're happy the floor is solid and deflection free then prime with an acrylic primer, overboard with 6mm No More Ply or Hardibacker, laid with the C2-S1 or S2 adhesive and prime again before tiling. Overboard in the opposite direction to the existing join in the plywood and follow manufacturers instructions regarding the joins. Do not tile onto plywood, the quality about these days is not great and it is affected too much by moisture and the environment. It expands when hot, contracts when cold, swells when wet and can even de-laminate. It's not worth taking the risk when there are far better alternatives about.

 

[JaimieH]

.....also, don't forget to screw down the No More Ply or Hardibacker in addition to the adhesive, just follow their instructions. Good luck.

 

[Harburt]

Morning

That was an interesting back and forth. Thanks for all the advice. The existing ply does indeed run under the exisiting tiles on the other side of the threshold so would be tricky to remove. I will stick a few more screws into it to secure it and make sure it's not moving.

Is the acrylic primer to provide a layer of waterproofing to the wood?

Thanks

 

[JaimieH]

Partly, and also to provide a stable surface for the tile adhesive to adhere to. Don't ever use PVA when priming for tiling, it's water soluble and will deteriorate when wet.

 

[Harburt]

That's great, thank you

 

[Nige F]

It's not regarded as good practice to tile over any wooden substrates anymore. Good luck.

Thankyou for your post .Very informative. Unfortunately bobasd has a habit of arguing with certain posters ad. nauseam .