Advice required please. I am to have a new kitchen fitted, the old damaged chipboard flooring has been removed, will it be possible to use 18mm marine ply directly onto wooden joists then UFH tile adhesive for 600mm x 600mm quartz tiles? i am concerned about the height increase incured if i use any more layers as my tiles will be 12mm thick. All comments/advice will be greatly recieved along with advice on which UFH to use.

It is possible to do your floor as you have described. Whilst you have got the old floor removed add some extra noggins to the joists for extra strength. I would also consider using a 6mm insulation board on top of the ply to assist with the running costs and warm up time of the heated floor, this will increase your floor height by 6mm but, will save you lots of money in the long run. What is the area of your floor? Welcome along to the forum.

Are you fixing quartz tiles or granite

Thanks for the reply Bri, the floor area is 16m squared but the UFH area is approx. 9 m2. Forgive my ignorance but do you use adhesive for the insulation board or screws?
I am fixing Quartz tiles with mirror flex in, which are expensive hence making sure i know what i am getting myself in too!!!

Check with your tile supplier about the quartz with ufh..

also if you're having granite tops make sure you have extra support under the feet as the extra weight concentrating on the ply between the joists could cause the floor to bow

Conglomerate quartz tiles are mainly not suitable for under tile heating , check with tile manufacture as some retailers are saying they are ok when infact they are not.

The heating can cause the tiles to dish and quite a few have had this happen after bad/wrong advice , especially from a certain online seller


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Please also ask yourself what you want from your underfloor heating system.

On top of the already laid screed or insulation boards as Construction Boards etc, you can use Elektra MD160/MD200 underfloor heating Mat or same output in loose cable. 160w/m2 or 200w/m2 output underfloor system will be a heating system.

On top of the already load bearing timber base, you can only use Elektra MD100 underfloor heating Mat or same output in loose cable. This Elektra underfloor heating system may or may not be a total heating solution, depending upon the heat loss & how well insulated the dwelling is.

When using a 6mm insulation board with u/f heating the overall extra thickness needed is 8mm: 6mm board with 2mm powder flexible tile adhesive under to fix the boards.

All good advice above. Are you going to be tiling the floor yourself or getting a pro to do the work? It will probably be a good idea to do a search on here and have a read through similar threads to get a better idea of the correct process.