Hi all,

First time here, and to tiling in general so please go easy!

I have been researching for the last few days, but still have a couple of questions.

I am planning to refurn the bathroom (very small) with new suite and lay travertine all over (floors and walls). I fully understand the importance of having a solid surface which is why I am confused!

House is roughly 1870, floorboards are uneven, different sizes and are starting to crack.

My plan is replace the old floorboards with 22mm WBP, with possibly 6mm of thermal boarding on top (UFH is going down too).

The floor space is roughtly 1.6m by 2.0m (with the bath taking up roughly half the space).

With this in mind, what size sheet of ply would be best suited to replacing the floorboards with? Should I go with 2 sheets of ply, leave a gap around the perimeter, then butt the 2 sheets together in the centre?

If I only use 2 sheets, do I need to stagger the sheets?

General advice is very welcomed!

Many thanks - Dean

cut the sheet of ply into 4 equal bits(easier to work with.make sure you put extra noggings in the floor joists for support every 450mm between the joists,leave a 2mm gap between boards for expansion and contraction,screw every 200mm in a grid type pattern.You might also want to look at a decoupling membrane such as kerdi or ditra or schluter,as the travertine can be soft and break easy depending on which type you use(honed and filled or not)

Hi Brian,

That is very informative - thanks

I was planning on using either a floor levelling compound on the underfloor heating mats, or simply laying a bed of flexi adhesive. You mention the decoupling membrane, would you still use this with the above?

Travertine is honed and filled for reference.

Cheers - Dean

Yes I would, lay the ufh, self leveling over ufh then lay decoupling membrane, then tile

If you can lay the ply in 2 bits then do....the less joints the better......

If using travertine then an un-coupling membrane would be a good idea...this will prevent any lateral stress from cracking the travertine....make sure you put support noggins evry 300mm before you re-skin the floor in the 22mm ply...

As for floor leveller over the UFH...then mapei fibre plan is great for levelling over UFh on timber...

Not all latex levellers are suitable for use on timber/ply.......so always check first....

Also it is a good idea toleave a small perimter gap in the ply then fill with silicone to allow expansion and also stop any SLC falling through the gap and into the ceiling void and possibly downstairs...

Let us know how you get on and how about a few pics of the finished job....


Good luck..

Thanks Dave/whitebeam - very informative posts.

I am currently struggling to find a supplier of Mapei near Stroud (one that isn't trade only anyway) so have looked at Bal Multibase for levelling on ply - although the datasheet doesn't state its suitable for ply (actually, not many do!) Any more suggestions on suitable products chaps?

I will definately get some pictures up once the project starts

Bal isn't suitable for ply and ufh.......

this is your nearest CTD>>>>
Ceramic Tile Distributors
20-22 Melchett Road
Kings Norton Business Centre
Kings Norton
Birmingham
B30 3HS

T:01214 338 787
F:01214 338 788


but i'm sure one of the members will know some where closer to get it..

hi i got a job next week.... and am layin on to ply... im goin to prime the ply with sbr.... can you prime it the night before.....and do you just roll it on with a roller.?? one coat??

Originally Posted by JC tiling

hi i got a job next week.... and am layin on to ply... im goin to prime the ply with sbr.... can you prime it the night before.....and do you just roll it on with a roller.?? one coat??

Which bit you putting the SBR onto, the back and sides or tiling surface? You need to check with you chosen adhesive manufacturer as to procedures for sealing/priming ply!

I picked up some Ball Fast Flex 700 self levelling compound today LINKY - very much like the Mapei fibre plan.

I also brought the recommended primer for the ply.

Now I have read that you shouldn't use more than 100w underfloor heating on ply, and instead to use an insulating board. I really don't want to have to add another 6mm of depth to the ply, plus I am not sure if the F-Ball Fast Flex compound will go over the thermal board OK.

Any comments? I am very confused now

You don't have to use insulation boards....but if you did...you can slc over them if you want..no probs..