UFH and screed on Ground(beam & Block) & 1st Floor (posijoists) - ICF

[Renegade105]

Hi all,

 

I am trying my best to sort through this mindfield.

 

Were planning an ICF house and want UFH in some of the bedroom and bathrooms on 1st floor (Wife wont budge!), and throughout the ground floor.

 

Porcelain tiles throughout.

 

I need to work out floor heights, so:

 

1) Ground floor, beam and block, what thickness Insulation is needed on the GF under a screed? or we could use something like WUNDA with their grooved foil boards and tile direct to it.

2) First Floor, Posi-Joists and Chipboard P5 22m. what insulation/boards do you use here? Also we want to use a Screed appx 50mm as want a solid floor feel upstairs.

 

 

Thanks guys, this will really help as I'm trying to spec the posi-joists.

 

 

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Edited July 12, 2022 by Renegade105

[Temp]

Ground floor I would recommend at least 120mm PIR ideally more. 

 

Posi-joist can be used with screed on top. See..Separating Floor Applications in here..about page 13..

url=https://www.nuneatonrooftruss.co.uk/wp-content/uploads/2019/04/The-World-of-Post-Technology.pdf

 

Be careful with liquid screeds as some form a "latience" on the top that has to be ground off or tile adhesive won't stick well. Google the issue.

[JohnMo]

I would look to get a U value on the ground floor of around 0.1.  To work out the u value you need the perimeter to area ratio. Screed thickness will determine how your UFH reacts to changing heat inputs.  Thin (50mm) is quite quick (hour or two), thick quite slow, but you can buffer the input into the floor and it slowly releases the heat over the rest of the day.  I would only use the grooved boards with direct tiling in bathrooms, if I used at all.

[Renegade105]

hi @johnmo and @ Temp

Thanks for the heads up

 

So decided now on a KORE insulated ground floor slab, so no problem there for the UFH

 

1st Floor is a different story

 

I am confused, I want to put screed on the first floor so it feels solid, but what about UFH, insulation etc

 

UFH companies say they only really want a few mm of screed above their pipes, but Screed companies say they want atleast 10mm (so 50 in total) of screed.

Plus, where does the insulation go? if directly onto the floorboards, we are talking a very thick floor.

If we use the special UFH routed insulation boards, we won't satisfy the Screed guys as they want around 50mm min thickness, so that would be around 25mm on top of the sinulation panel with UFH pipe within the grooves.

 

I am just very confused what is the right thing to do here.

 

Many thanks

[Conor]

For first floor a good option is 150mm concrete planks, 50mm insulation, UFH, 50mm liquid screed. And below the floor deck, a 100-150mm suspended ceiling. That would be standard over here on a masonary or ICF build. Floor slabs go down in a couple hours.

 

For the ground floor, pretty simple really, UFH pipes ties to the top mesh later then have the concrete power floated, ready for your final floor finishes. Plenty here have down that.

[Renegade105]

@Conor This is why I love this site, awesome reccomendation friend.

 

Only problem is I have already paid for structural engineer to do all of the calcs using posi-joists on the 1st floor with 50mm screed. If i go about changing it to this frankly excellent solution, then Im left with a big redesign fee all over again, and Iv'e had enough of that. I have already wasted money on the Groundbeam engineer, as after I got quotes back for the piled and groundbeam foundation, I had no choice but to explore the Insulated slab option which my engineer said wouldn't work. Luckily got in touch with Tanners who said the opposite and are working on it now as we speak.

 

So, I am left with trying to work out the best solution using UFH and Screed and Posi-Joists on the 1st floor.

 

any tips?

[Happy Valley]

We have posi-joists with UFH on part of our 1st floor ICF build. 

 

In the end we went with Wunda's insulated trays that sit between the joists and backed this up with further insulation (more for noise than heat) before plaster boarding the ceiling below. 22mm caber board on top before the LVT flooring went down. There is some noise transmission but is acceptable no where near as much as I thought.

 

The two slabs (one ground and one 1st floor) both have 70mm screed.