1st floor over posijoists in ICF build

[Renegade105]

Hi guys, 

 

we planning an ICF build with posijoists on first floor. Want to incorporate UFH over the joists but there are lots of options!

 

I don’t want a creaking floor and can’t afford a concrete deck, also will probably be looking at having tiling done upstairs too.

 

please can someone guide me on the type of system or combo that works best please?

 

thanks All!

[Nickfromwales]

Hi. 
Alu spreader plates will work A-OK, used them a load of times in clients houses. Just make sure you have the joist detail done at 400mm centres not 600mm!!!

Using an electric or air staple gun is my preferred method of installing the plates, and it’s important to make sure the butt up to each other and do not overlap. That will allow you to get them fixed down snug and be squeak free.

If possible, you are best off keeping the underside of the finished floor exposed so you can go underneath and staple the plates up tight against the 22mm deck boards. Staple either side of each of the pipe “omega” channels so 4 runs of staples per joist void. That’s to make sure that the spreader plates are in very good contact with the deck board as it’s that which is then the emitter.

If you cannot get underneath, you’ll need runs of 11mm osb set down between joists to make a cradle / support for the plates. You part fill those cradles with rock wool to make the plates distended, so the plates are then forced down under compression when you lay the deck boards. It’s very important that the plates are in good contact with the deck boards or results could suffer significantly. 

You’ll also need 2 manifolds, one upper and one ground floor, if it’s screed / slab ground and plates above, as you’ll need 2 different flow temps, ideally.

[Renegade105]

Thank you @Nickfromwales that makes perfect sense having looked it up. I guess this also avoids the need of any sort of screed on the 1st floor too, and we can lay any tiles onto the OSB prepared floor.

longterm though, with expansion and contraction, would this lead to creaks etc in the future?

[Nickfromwales]

17 hours ago, Renegade105 said:

Thank you @Nickfromwales that makes perfect sense having looked it up. I guess this also avoids the need of any sort of screed on the 1st floor too, and we can lay any tiles onto the OSB prepared floor.

longterm though, with expansion and contraction, would this lead to creaks etc in the future?

Nope. It's either done right at the outset or not, simple as. You really need to instill this into the installers as sloppy work will fail in any instance. For reference, I did one like this over 8-9 years ago, pozi-joists, spreader plates stapled up underneath, stapled down atop, 22mm P5 deck board, 6mm plywood atop the P5 ( PVA glued and screwed down at 120mm centres religiously ) and then tiled with large format porcelain tiles using Ultra flexible adhesive. Still solid and crack free when I went there about 3 years ago to service the swimming pool heating setup ?

[Renegade105]

Awesome advice Nick. Thanks for sharing and for giving me the details I need! I will ensure it is exactly done this way.

 

 

[Canski]

On 13/12/2021 at 09:37, Nickfromwales said:

Hi. 
Alu spreader plates will work A-OK, used them a load of times in clients houses. Just make sure you have the joist detail done at 400mm centres not 600mm!!!

 

I'm looking into this at the moment. Any suggestions for 600 mm posi joist centres ?

[Nickfromwales]

30 minutes ago, Canski said:

I'm looking into this at the moment. Any suggestions for 600 mm posi joist centres ?

Yes, but it’ll need some woodworking skills!!

[Canski]

On 06/10/2022 at 21:30, Nickfromwales said:

Yes, but it’ll need some woodworking skills!!

Ahh I have some of them. My plumber mate reckons that UFH to the first floor would work out cheaper than rads. I’d also prefer  UFH to the first floor and after being talked out of beam and block to the first floor I am considering alternatives. 

[Nickfromwales]

1 hour ago, Canski said:

Ahh I have some of them. My plumber mate reckons that UFH to the first floor would work out cheaper than rads. I’d also prefer  UFH to the first floor and after being talked out of beam and block to the first floor I am considering alternatives. 

Rads with TRV’s vs UFH in plates, pipe, manifold, pump, blending valve, actuators, individual rooms stats and wiring…..

Doubt it, but DIY can reduce this a fair bit. 

Edited October 8, 2022 by Nickfromwales

[Canski]

How about 50 mm celotex on 9 mm osb between joists with pug mix around the UFH pipes then 22mm caber deck on top ?  Plenty of DIY