Depth Raised By Underfloor Heating & Screed

I’m Andy Parkin Managing Director of the Multi-Award Winning Speed Screed. Thank you very much for your question, Jack.

Your question is:

“have you got a rough measurement of how much the floor will be raised with the underfloor heating and screed?”

Watch Andy’s video to find out his answer:

I would take it from your question that you are looking to retrofit the system, and so will
make that assumption rather than you are building a house and you are going to
design it into the bill.

I think you come in from the perspective of retrofitting. Typically, you can do really one of two things when you are retrofitting. You can forget about insulation or you can put some insulation in.

I think that is going to be the first choice. Are you happy that you will be heating the floor and there is enough insulation currently installed?

You want the project to be resistant to heat loss. So is there enough insulation already there or not? Or do you need to put some in?

If you don’t need insulation and go for the thinnest possible solution, I would say, typically, a low profile system is around 20mm. That includes the screed and the pipe. Typically on a tray system, the screed will gain its strength through the tray and through the structural substrate. So 20mm all-inclusive.

There are no issues with screed cracking.

The minimum you are looking at is 20mm, but that is not allowing for any insulation.

The options are probably two-fold. You could go with a routed insulation board with the pipes fitted into the routed element of the board. Once installed, cover with screed.

If covering with screed, it is just the same rules for insulation. The minimum you can get
over the top of the insulation is 35 mm.

If using traditional sand and cement, you would be looking at 65mm for a domestic application.

With a polymer-modified sand and cement screed, it can be 35mm.

With liquid screed, it is typically 35mm for domestic 40mm for commercial.

If clipping the pipes to the top of the insulation, the minimum is 20mm liquid screed coverage over the pipes (specialist liquid screed).

If the pipes are 16mm, you are looking at a 36mm minimum and then add this to the insulation depth.
I hope that gives you an idea of the build-up.

20mm minimum without insulation
36mm for pipes clips to screed (plus the depth of the insulation used)

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