hello all,
I have been looking for information regarding tiling on floor grade chipboard, moisture resistant.I intend to tile a bathroom using limestone tiles, matt on the floor, area 5sq metres and polished on walls.I intend to use ardex P51 primer and ardex flexi 7001 on the floor, the floor is heated and the chipboard has been screwed down using turbogold screws @ 250 mm spaces.The walls are both plastered and skimmed and studwork boarded and skimmed.I know that tiling onto plaster is not recomended in wet areas unless moisture resistant board is used,which i intend to use for the shower enclosure on two sides, the third side is a block wall plastered and skimmed.What i would like to know is if i prime the walls is there any way to waterproof the walls before tiling and which adhesive for walls would be suitable and sealant for tiles would you recomend.Tried to phone ardex technical but they had problemes with their phones, so will send them an e-mail or try phone again.In the mean time I thought I'd give you guys something to get your teeth into.The tiles I intend to use are 465x305 x12mm.I am aware there is likely to an issue regarding weight per sq metre.the adhesive will be white.advice regarding grout joint width would be appreciated.looking forward to replies. by the way I'm a diyer.

Hi Dal, you may want to reconsider your options a little. Ardex 7001 is brilliant stuff but if you are laying limestone tiles I would strongly recommend laying a decoupling mat on top of your UFH. This will isolate your expensive stone from the thermal changes that will occur with the heating. If you go down this path then I would also recommend using thermal underlay board first and skim over the top of the heating mat/cable with leveling compound. This will make the ardex 7001 un-necessary and you can use a different flexible adhesive on top of the decoupling membrane. Flexible grout as well.

thanks grumpy,
the heating is wet and is installed under the chipboard.The construction of the floor is: 7 inch joists infilled with 9mm ply laid on battens fixed to the side of the joists,on the ply sits insulation 50mm on which are laid heat deflection plates which carry the heating pipes.There is advice on this site regarding tiling on chipboard hence my choice of ardex.It will be interesting to find out if anybody has a similar system installed and managed to tile on to it successfully. There are many schools of thought regarding tiling on to chipboard.My problem is avoiding a step between bathroom and hall floor.

Hi Dal, i have tiled straight onto chipboard a few times with Ardex-flex 7001 and I ma this forums great advocate of this adhesive. The issue you have is the fact that you have a heated floor. I assumed it was an electric matting system so my previous comments are no longer valid. The main issues are is ithe floor is 1, solid and 2, isolating from lateral movement of the floor becuase of thermal changes.

As i now know you have wet heating, I would suggest, subject to no. 1 above that you layditra/durabase matting onto your chipboard and then tile on the top of that. I have not used 7001 onto ditra but I am pretty sure it will be ok, the stuff seems to stick to anything! Ardex would be able to confirm that.