Multiple Sub Base with UFH

[coreypower]

Hi All. This is my first post. I've tried to find similar posts but not found anything that mirrors my current project. I'm hoping you have some good advice.

I've bought an old house that used to have two separate rooms converted to one very big kitchen. Both sides of the room have a different sub floor. One concrete and one is joist and floorboards. As it happened the floorboards and joists are rotten so need to be replaced. I will be replacing these with the same large dimension joists to maintain the current floor height with plenty of noggins and supports but will be replacing the floorboards with 22mm moisture resistant Weyroc. The concrete side is largely level but might need one corner raising an inch or so with some self levelling compound and finally a chemical dpc.

I want to install under floor heating and been researching suitable floor coverings. What I have come up with is bascially levelling the concrete and making sure it is at the same level and the weyroc flooring. Over the top of this I was planning to install 10mm marmox boards over the whole floor fixed as per manufacturers recomendations. Over the top of this will be the ufh cable and finally a 12mm travertine tile fixed wth Bal rapidset flexible white adhesive.

I had considered using a decoupling membrane, such as ditras or genesis gmat, but thought it a little unneccessary. I had also though of using 25mm wbp ply instead of weyroc. The whole task if replacing the wooden side of the kitchen was unexpected work so money is tight so thought it best to leave both of these options. Is what I have planned suitable to give proper support, adhesion and protect against movement? Can Marmox boards function as a sort of decoupling layer or at least serve a similar function? Is my adhesive choice suitable? Is 10mm Marmox enough? Is there anything else I should consider? I do realise I can make it a lot better but I want to keep costs down.

Any help anyone can prvide would be greatly appreciated.
Regards,Corey

[doug boardley]

I'd go with wbp rather than weyroc, have an expansion joint between the two substrates, then level the concrete, then fix your insulation boards, then use 2 sets of ufh (one for each zone), then use a flexible slc over the cables, then use a ditra uncoupling membrane, and then finally fix your trav.

[Sir Ramic]

Same as Doug
Depending on the sizes of the kitchen UFH you can run 2 mats or cable systems from the same thermostat. I believe you can not exceed 3000 watts on most systems..

[coreypower]

Thanks for the replies. I realise I can make the whole job a lot better but I am really tight for cash. Changing the weyroc for ply, adding ditra (or similar), adding the slc, having two runs of ufh cable and the extra adhesive required would add way over £500 to the job. If I compromised by replacing the weyroc with ply but kept everything else the same would you think it would be satisfactory?