Underfloor heating and wooden subbase - will it work?

[ikeadyounot]

I'm having underfloor heating in my new extension.

However, the base UNDERNEATH the heating will be concrete in one part of the kitchen (new build) and wood in another part, which will be the utility (existing house).

The floor covering above this, in both cases, will be porcelain tile. I want to run it through the two rooms.

Will the underfloor heating installed in the wooden section still be effective and efficient?

Sorry, should have mentioned: this is wet underfloor, not dry.

yes, but I don't know how the tiles will react if laid over a wooden floor. The wood will shrink in winter as it dries (and swell back in summer). This might cause cracking of the grout. You can get cement-based backing boards for tiles now that might overcome this problem. Your tiler should know if he is an experienced specialist.

UFH is a minority interest in UK. Again you need someone practiced at it. I have seen them arguing over heat output depending on the makeup of the floor. A concrete floor, laid on a slab of insulation, is preferred.

When a tiled concrete floor butts up to a tiled wooden floor, it's not uncommon for a crack to occur at the joint. They move differently with heat expansion. You may benefit from some kind of expansion joint.

PigletJohn - that's amazingly helpful, thank you. I hadn't even thought about the different movement of the two floors - dammit, dammit, dammit. I want to lay the tiles with a minimal grout line too, which I guess makes this worse??

Would there still be a problem if I put UFH in ONLY the new build part (concrete subbase) and then used rads in the utility room/backdoor corridor? I guess the wood and concrete would still move differently, but would the lack of that (slightly) more intense heat from the UFH on the wood help?

One reason I'm having UFH is that one of the rooms I am building is especially high (13ft) and I am worried about all the heat from a radiator ending up at the ceiling! The price of it has come down a lot since a few years ago, but I guess it's still not common.

I'm sure a new, insulated and tiled concrete floor will be fine with UFH. I just don't know how well the tiled wooden floor will work. I don't know if it will make a difference if you take up the old floorboards and use a different board. If you find a UFH specialist they should know. The manufacturers of the system should also have some guidance.