Prepping for tiling

Best will be 12mm comment boards and dotted matting on top Make sure u use s1 mix with liquid to glue the dittra If u do all this I’m sure it will stay there over 20 years

I would Remove the old floorboards and inspect the floor joists for movement. In most if not all cases in older properties a row or two of new noggins in between the joists to brace it all together will be needed. From here you have a couple of choices. You could install 22mm moisture resistant caberdec t&g floorboards, staggered joints and glued to the joists with d4 PU adhesive glueing all the joints too. Then screwed every 300mm being careful of any pipes or cables below. Then lay 6mm cement board such as nmp using their proprietary pu glue following the manufacturer’s instructions and then screwed down every 200mm. It’s then ready to prime, tile or if needed self level and tile. Or Glue and screw directly to the joists 22mm no more ply t&g cement boards with their mega strength adhesive gluing the joints as you go. Then it’s ready to tile or self level and tile if required. Flexible self levelling and tile adhesive always. Absolutely no need for decoupling mat. Decoupling mat is for lateral movement and will give no additional support for deflection (bounce) in a timber floor. Both of the methods I’ve outlined above are tried and tested and recognised in the industry as the standard. Done properly your floor will be bomb proof.

If the existing floorboards are sound and there is no significant movement, I would normally recommend first securing all loose floorboards properly to the joists. Then I would use a suitable tile backer board, fixed in accordance with the manufacturer’s instructions using flexible adhesive and the correct screws. An uncoupling membrane can also be used where additional movement protection is required. The most important thing is to make sure the timber floor is rigid enough before tiling, as movement is what normally causes cracked tiles or grout. I would inspect the floor and joist spacing first before deciding the final build-up, as this also affects the finished floor height. Happy to have a look at the floor and advise on the most suitable preparation before giving you a quotation.