Backer Board or Membrane

[Smudger]

Just reading a post about expansion joints and it got me thinking so I was reading Schluter's info on "Uncoupling Theory"; which raised a couple of questions:
1) How much would a typical tiled floor expand and contract throughout a year
2) When tiling over a timber floor, would backer board or membrane be more reliable if there is likely to be thermal movement.
(Joining this site has made me realise how little I really know :yikes

 

[doug boardley]

ah! I was reading and just about to reply to your post but it cut short (kilty's thread)

1) How much would a typical tiled floor expand and contract throughout a year
depends on the substrate
2) When tiling over a timber floor, would backer board or membrane be more reliable if there is likely to be thermal movement.
depends if ufh is used (and what type, wet/electric?) imo, personally I prefer backer board over timber

 

[Smudger]

Yeah, sorry Doug. Thought it was a bit rude to hijack Kitty's thread.

 

[Smudger]

I never really imagined that the tiles themselves would expand/ contract much,and always thought it was just the substrate that would move. I also prefer backer board, but it got me thinking that if the backer board is fixed to the timbers and the timbers move, will that not run the risk of cracking the boards and therefore tiles, as the whole thing is bonded together? WHereas a membrane would allow the boards to mve independently.

 

[doug boardley]

timber floors (imo) are more prone to deflection rather than lateral expansion/contraction Smudger, this is why we always stress that timber floors should be deflection free before tiling, the backer boards don't add to the rigidity or make the timber deflection free in any way, but do provide a good surface to tile onto.