HELP Tiling over timber floor

[pendleh]

Hi Guys

I recently posted about the need to use ditra matting when tiling over a timber joist and floorboards. So apologies but your answers talked about deflection I dont know what this means yet and need a definitive answer as well as giving you the full picture. I boarded 12mm over floorbaords and tiled porcelain. Customer has had a second opinion heres what they said

"Further to the above the tiles have been laid over a timber joist and floorboards at first floor level which will result in some movement of the structure. The timber floor will have some flexibility in it and as such a porcleain tile fo this nature should have been laid over a flexible substrate to accept movement without damage to the tile surface. This does not appear to have been done"

Any help appreciated!

Howard

[grumpygrouter]

Deflection is the vertical movement or "bounce" that can happen in timber floors. To reduce deflection as far as possible is important and is the reason BS say to over board with minimum 15mm ply to add strength to the floor. As 15mm is not available here in Britain you must go to the next size up which is 18mm. I think the "flexible substrate" they are referring to means the adhesive used. With only a 12mm ply over lay, it really should be a 2 part (latex) cement based adhesive along with a highly flexible grout.

Hope this helps.

[pjc]

By floor boards you dont mean chipboard ? :Pete

[pendleh]

Hi Pete

It was floorboards which I had to secure.

Howard

[AllurePTS]

as grumpy says - should have been 18mm ply, but you might "get away with it" if you used a good quality flexible adhesive and grout ???