Under floor heating and suspended floors

[Ben R]

Hi all

I've just bought a 1950's bungalow and would like to install a wet underfloor heating system. The floor construction is suspended floorboards. Under these there is a void approx 50cm deep. The total area of floor is about 90sq metres.

I understand that fitting underfloor heating to a suspended floor can be problematic in terms of installation and efficiency.

As a relative newcomer to DIY I wondered if it would be best just ripping up the existing floorboards and removing the joists then filling the void and making a solid floor? If so, a few questions:

1. What would I fill the void with?
2. Would there be a consequence of the weight of the material I use as infill?
3. How much is this likely to cost?

or does anyone have any other ideas?

I look forward to hearing from anyone with any advice whatsoever.

Cheers

Ben

[Owain]

Insulation, then concrete (probably with rebar in), then the UFH pipes laid in screed.

Yes. Depends on the foundations. If the foundations aren't up to the weight, things may start sinking/cracking. I would advise a structural engineer's input.

Concrete's quite cheap, provided you can tip it straight out of the lorry into the hole. If you need to pump or barrow it about the site costs increase.

You can get suspended concrete beam and block floors but I don't think they'd be much help.

Owain

[Christian McArdle]

It is fine, although maximum output is limited compared to a solid installation. This is only a problem if the wall insulation isn't up to scratch, or it is a conservatory.

It is a possibility, although it probably a more expensive and messier option.

Concrete, damp proof membrane, insulation, screed and plastic pipe.

Possibly. You need to have someone look at it with regards to the foundations, although it is unlikely that there will be issues.

A reasonable amount.

Just underfloor heat the existing floor.

Christian.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Ben R" saying something like:

You can get a type of ally channel with two grooves in for running the ufh pipe. Under the channels is a layer of approx 4~5" of rockwool. The channels are simply nailed to the joists and the pipes laid in the grooves then floored over.

This system works well and doesn't have a large thermal inertia. Made in Germany, iirc, but not too cheap. Having said that 60sqm cost me ~1500Euros in materials some 4 years ago, including manifolds, pump, etc.

[The Natural Philosopher]

Have a look at

They do underfloor insulated trays for pipes. It ISN'T cheap, but its quick. If you have the time, make up your own. All its about is stopping heat going downwards.