Ground Floor Slab & Underfloor detail

corkonian0110

Am just up to deadwork level on a self build and my groundwork guy ( who is building at the mo with underfloor as well) is suggesting laying the pipework on the insulation just over the hardcore base. I thought i would be putting in a slab with insulation under, then more isulation with the pipework fixed, then screeded..? Was wondering what the rest of self builders are up 2?

Ewan

theres a few different way to construct....but prob. the best is to lay your insulation on the ground floor slab, install the uf pipes/loops and pour the screed. The foil backed insulation is important to "bounce" heat up into the screed. Theres very little point in putting insulation in below the ground floor slab if your insulating between slab and screed. Just as important to install your perimeter insulation to the slab....get your hands on the "homebond" House Builders Manual, loaded with details and drawings....

corkonian0110

corkonian0110 wrote:

suggesting laying the pipework on the insulation just over the hardcore base. ?

Yes that's exactly how I did my floor,

first I laid hardcore blinded and compacted, then laid radon barrier followed by insulation sheets then steel mesh and tied UFH pipes to this before pouring concrete.

Perimeter insulation was not an issue as I am using an ICF wall system.

Salem

Check out the Kingspan website ...

www.insulation.kingspan.com/uk/pdf/tf70.pdf

corkonian0110

Useful info there, thanks all

Vertical

I have insulation (100mm), ground floor slab (100mm) and will be laying foil-backed high density insulation and ufh screed on top of this.

Make sure you have factored in the extra height of the floor if you are doing this...

sunnysoutheast

to me the layman there's two different methods:

* "standard" slab, insulation on top of this (floor and edge), pipes on top then floor screed
OR
* insulation on subfloor, then pipes, then slab, then finished floor screed

AFAIK which to use depends on the expected usage patterns as the latter method should take longer to heat up but should stay warm longer as there is higher thermal mass

we're using the first method with 100mm Extratherm, 60 mm edge insulation and 100mm floor screed

I think the two methods are outlined in the little Kingspan booklet you can get from builder's providers

SSE

Ewan

the biggest problem with insulation below the ground floor slab is that the majority of heat from your ufh dissipates into the 150mm slab before it hits the insulation and bounces back....why heat your subslab?
I am looking for information regarding the installation of uf heating coils/loops i.e. all the bits and bobs accociated with it.....any ideas where to get some info?

You could always try any of the UFH company websites, eg
http://www.keeheating.co.uk/ http://www.nu-heat.co.uk http://www.invisibleheating.co.uk

Plus many others, most sites have technical information and different solutions to various floor types.