underfloor heating

[Anonymous]

Does anyone have experience of installing underfloor heating under an old delabole slate floor? The flagstones are between 1 1/4 and 2 inches thick. Would the heat be efficient through such thick slate? The floor is in a 250 year old cottage with lime plaster walls. We were intending to use storage heaters, but our builder says that the wall directly behind the heaters will expand and contract causing a damp patch. Can anyone recommend a good builder in North Cornwall who we can contact for a second opinion please?

 

[Anonymous]

No personal experience but I have seen underfloor heating work well, below Caithness slab of similar thickness. In that instance it was a new-build property and had a lot of insulation below the heating pipes, I would imagine you would need to dig a lot of floor out to be able to do the same.

 

[Anonymous]

Hi the thickness is no problem and the material is ideal for UFH. (Especially Wet i.e. With Water filled pipes).

Your real issue is disturbing the fabric of the building to lay UFH.

You will need to dig down quite a bit and if your foundations are shallow that might cause a problem. Also if you have a listed building that will need approval etc...

We have UFH and if I could live with the disturbance (I can't) and the cost (I can't) I would have it in all the ground floor rooms. Absolutely fab walking on stonefloors that are warm under foot.

Pity we never really picked up this after the Romans left.

MJ

 

[Anonymous]

I think it was a case of the slaves not wanting to do the work any more ....
And you'd have to dig very deep to build a hypercaust.

 

[Anonymous]

We have underfloor heating under thickish slate tile with no problems. I'm not sure what the hot water system option costs to run, but we have (inherited) the electric cable type and switched it off once we'd seen the bill - be warned!

 

[Anonymous]

The thickness of the slab is not a problem, all that will happen is the thicker and denser the floor covering the longer the system takes to heat up but then conversley it will take longer to cool down - a bit like a mini storage heater.

Typically you will need to dig out 50mm for insulation and anywhere between 45-75mm for the screed - dependent upon the type used.

You really need to get designs, prices and specifications done by at least 3 specialist underfloor heating companies, I'm afraid I don't know any down your way but a search on the internet is a good place to start.

 

[Anonymous]

UFH heating under slate works well. I've recently spec'd a job using UFH (water) with slate and it works fine.

You should give some thought to if the exg slate can be successfully lifted without damage. Slate incl delabole may be wet and laminated underneath as its only onto earth and as you lift they can break.

Secondly, you need to consider just how much excavation will be required. You will need to take into account the slate, 68mm above the water pipes, then insulation, over 100mm oversite which ideally should be over hardcore. All this adds up and on the barn that we recently completed we had to underpin, which is not cheap. It may be worth some investigation to wall depth before you go too far.

You will require LBC so worth talking to NDDC about the principle of the work as a first step.

As far as specialists are concerned, any good builder can install. You could try talking to JDC over the Tamar. I've seen their work to historic buildings and happy to report good experiences.

 

[Anonymous]

Thank you all for advice on this subject. Given us a lot to think about....this web site is so useful!

 

[Katy Middlewood]

Thank you all for advice on this subject. Given us a lot to think about....this web site is so useful!

Hiya, similar query for a cottage near Bodmin Moor, did you ever go ahead with it? I think lifting the tiles without damage will be the hardest part.