UFH floor preparation

bassmonster · Feb 15, 2016

Hi all,
I could really do with some help.

I'd like to know how the floor should be constructed for underfloor heating in my new rear kitchen extension. the builders have laid the concrete floor which is about 20sqm. The outer ground level is quite low, around 55cm.
The new internal concrete floor in the extension is about 20cm lower than the internal floors of the house.

I'd like to make the new floor level taking into account UFH. How would be the the best way to prepare the floor? joists? screed? kingspan insulation?
the floor is to be tiled.

The UFH kit will be something like this one:

20m2 Under Floor Heating Kit PE-RT AL PE-RT Pumped Single Room Kit

stevetheplumber · Feb 15, 2016

you should have had the concrete laid to the right height to suit your underfloor system ie insulation,pipe and recommended cover of screed 200mm down sounds to be too much you could allways screed over before the insulation to get the right depth or double up on insulation but that might be expensive

Chalked · Feb 15, 2016

200mm seems low!
Your build up should be around this for on top of base cement.
100mm kingspan or other make.
Vapour barrier. ( make sure you do install this, otherwise it will pull moistur up from the ground forever!)
50-60mm of liquid screed. Or 80mm of sand and cement screed.
Then tiles ( about 15mm)

Looks like you will need an extra layer of 25mm insulation to get your level.

kozak1968 · Feb 16, 2016

Don't forget the expansion joint around the edges. This usually comes in a roll about 100mm wide.

bassmonster · Feb 16, 2016

Thank you for all the replies. Much appreciated.

I wanted to have joists for all the electrical wiring and flow and return for 1 radiator. the floor is actually 18cm lower. I've seen that 12cm kingspan boards are available. Will it be ok if I use the board, run all my electrical wiring and flow and return for radiator inside conduits then screed with 5cand then tile over? Will the kingspan board and 5cm screed be ok or will it be too soft?