Tiling over wet underfloor heating

[clawless]

I have just installed wet underfloor heating in our new kitchen in a ground floor extension. The extension was part of the house when we bought it. The floor constructions was a timber suspended floor (400mm spaced joists) with void below. I screwed batons to the under side of the joists, which are 100mm deep, and laid 80mm celetox flooring insulation. Above this I marked out where all the kitchen units/oven/fridge etc was going to be and laid down the pipes using lengths of spreader plates as appropriate so as not to go under any unit.

I have now fitted 22mm chipboard moisture resistant floor boards on top, as per recommendations. I now have two questions, the floor takes a good while to heat up and not as much heat as I expected is coming through so should I have used thinner flooring? maybe 18mm?

My other question is can I prime and tile straight onto the chipboard flooring? Using the appropriate wood tiling primers and adhesive?

The size of the kitchen is 2.75m by 4m.

Thanks in advance for any help.

Craig

[haveagohero]

Can't comment on heat of UFH but it is not advisable to tile on floorboards especially with UFH. The floor needs to be made deflection free (noggins would have helped with this), to check how much deflection there is fill a glass of water, place it on the floor and walk around it. If there is minimal deflection i would over lay the floor with 6mm cement boards then an uncoupling membrane then a rapid setting flexible adhesive (BAL, Mapei and Weber are good brands) then tile. If there is deflection over lay with 18mm WBP ply (this may need to be primed, check with the tech department of your chosen adhesive manufacturer, do this BEFORE you lay the ply as some manufacturers advise priming the back and sides of the ply) then 6mm cement boards then uncoupling membrane, adhesive and tiles. What tiles are you laying? it is advisable to back skim the tiles before laying into adhesive on the floor to aid bond between tile and adhesive. Make sure you don't lay the tiles and turn the UFH right up, turn it up slowly over a couple of weeks. We repair more floors that involve UFH and or chipboard floors than any other type of repair. Do it right first time or you will have to do it again properly when the floor fails