Think my architect forgot about the UFH downstairs.

SillyMonkey

Have just started the building of my house through direct labour. Last minute decided to go for geothermal with UFH. Asked architect to draw up new plans.

On new plans:
Ground floor make-up: 150mm Concrete floor slab on 100mm expanded polystyrene. He has forgotten (I think)to put in the screed for the UFH. BTW is this a normal thickness for the floor 150mm seems a lot.

First floor: 20mm Floor Finish, 70MM screed with floor heating piping on 50mm expanded polystyrene floor insulation (20Kg/M3) on 150mm hardscore precast concrete slab.

Won't get to talk to architect until Mon. But maybe 90mm (20+70) of the 150mm floor will be used for the UFH. Any suggestions?

BTW foundation and footings have been done for concrete floor upstairs so don't worry about that.

sinnerboy

Suggest

75 screed with UFH
500 gauge polythene
2 x 60 layers of kingspan or xtratherm ( or more if you €€€ it )
Ensure min 25mm kingspan or xtratherm to edge of screed
150 concete
Radon barrier
50 sand
150 well compacted hardcore ( leave 225 opes at 1350 c/c in rising wall at hardcore leve ) with min 2 sumps

not familiar with the precast floor slab you mentioned - clarify it does or does not require a STRUCTURAL screed over it

also - provide a services cavity below it for cables , vents / drains pipes etc -allow min 75 cavity - 100 / 150 even better - if you have the height . Otherwise you will need to "box out" to non wired services below the first floor

sprinkles

You need a minimum of 70mm UFH screed. Anything less will crack! 150mm structural slab is normal - wouldn't want to go less. You can get a fibre mesh (with Polypropylene fibres that will prevent cracking and eliminate the need for mesh - which can be awkward trying to get in the UFH screed, especially if it's thin. Most if not all concrete suppliers will provide this.

As sinner boy said - you need to check if the hollowcore needs a structural screed - it may not but it's crucial if it does. Good advice with the suspended ceiling - hollowcore doesn;t give a good finish so you'll be slabbing it anyway - drop it 75 - 150mm and it'll make life a lot easier.

ircoha

Have u considered the concept of wall mounted 'UFH'?

As noted elsewhere check the need for structural screed on a 6" h-core

Mellor

If you were wall mounting it, you would need to up the wall insulation, or stick to internal walls.

sprinkles

does that cause problems with wall finishes - wallpaper etc?