Wet under floor heating

[mayurw]

this might be the wrong forum to post this so mods please move if required.

so I'm thinking about installing wet under floor heating on the ground floor in my 1920's semi detached house. The original floor is suspended but the new rear extension is solid. So I'm thinking I will just remove the screed from the ext down to the insulation and lay the pipes on that but how do I lay the pipes on the suspended floor? I think the floor joists are 4x2" with around a foot below and I don't really want to go down the root of filling that up and making it a solid floor. I'm hoping to lay tiles on this once complete.

any suggestions?

 

[Agile]

So why was the new extension not built with the UFH ?

 

[dilalio]

With 4x2"s you aren't really going to get a good depth for insulation and screed in between. You'll also need to check load bearing capacity of existing timbers. There are proprietary ufh panels you can get but these can affect finished floor levels or involve lots of joist notching which may not meet regs. With only a foot below, I'd be considering concrete and screed!

 

[mayurw]

So why was the new extension not built with the UFH ?

didn't have the money at the time, to be fair I say new extension but it was done on 2009

 

[mayurw]

With 4x2"s you aren't really going to get a good depth for insulation and screed in between. You'll also need to check load bearing capacity of existing timbers. There are proprietary ufh panels you can get but these can affect finished floor levels or involve lots of joist notching which may not meet regs. With only a foot below, I'd be considering concrete and screed!

so if I was to go down the fill a screed route, would I need to re-route all the wiring or could I simply put them into some sort of conduit?

 

[Agile]

Conduit.

 

[mayurw]

So if I somehow get the all the mains wiring into conduits then I'm ok? do they do such conduits with splits? that way I don't need to remove the cables.

would I need to remove the joists?

 

[dilalio]

So if I somehow get the all the mains wiring into conduits then I'm ok? do they do such conduits with splits? that way I don't need to remove the cables.

would I need to remove the joists?

Not my area of expertise. I'd suggest you put this to the electrical and building forums, but do post back here as I'd be interested to hear your findings!

I am thinking though, that if you're trying to avoid disturbing anything but the floor, then you'd be looking to form some kind of cable tray directly in the screed, away from the ufh runs (i.e. Tight to the wall) with flexconduit branching off of this 'service duct' to various points!?

 

[bernardgreen]

You could use clip front trunking, examples here... http://www.screwfix.com/c/electrical-lighting/trunking/cat1910006 many other sources.

You will need to ensure that the derating of the cable due to the new thermal insulation is acceptable. ( cable in ducting and / or thermal insulation has a lower maximum current rating due to the risk of it overheating )

 

[mayurw]

what if the cables can be placed under the screed? say below the insulation in a conduit

 

[bernardgreen]

There is a lot more to electrical installations then just "throwing a cable on the wall"

Puller might learn something if he looks at cable calculations and how the installation method has to be considered. https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html is a good starting point written in simple terms. Click on "application" to see the choices of installation method for cables/.

More detailed info at http://www.cse-distributors.co.uk/cable/technical-tables-useful-info/table-4e1a/

 

[dilalio]

And the upshot of this @bernardgreen is... NOT for DIY!!!
Call in a farkin electrician

 

[Underfloor Guy]

Have you thought about insulation between the joists and then spreader plates on top of the joists in direct connection with the underside of the floor boards?
Not as efficient as pipes in screed but a possible solution, I would also recommend a different blending/pumpo assembly for each construction type as the temp on spreader plates will need to be higher than screed.

 

[mayurw]

Could I keep the existing wood joists and use them as the guide for the floor level? Just thinking instead of removing them, leave them insitu and work around them.

 

[mayurw]

Coming back to this thread, I've seen "Overlay" systems on the market, are these any good?