Ufh solid floor build up

[Tommyt01]

Hi all. 
I’ve been searching the forum and the internet to see what the best solid floor build up would be for Ufh, from what I have found, I’m thinking of going with 

type 1 

sand binding 

dpm

150mm pir 

dpm

Ufh stapled

100mm fibre reinforced concrete 

 

I’ve suggested this to a couple of companies and they have advised against it and it’s not the correct way it’s done and needs a concrete under the pir and a screed above. 
 

is what I’m suggesting correct or is there a better way? If it is, what spec of concrete would be needed? 
 

Cheers 

[JohnMo]

What do you structural drawings say?

[Tommyt01]

I don’t have any drawings, this is to replace a uninsulated slab in the kitchen and wooden floors throughout downstairs 

[nod]

As above SE drawing should really dictate this 

Also Why only 150 insulation If your putting it into a slab without any restrictions 

 

[nod]

2 minutes ago, Tommyt01 said:

I don’t have any drawings, this is to replace a uninsulated slab in the kitchen and wooden floors throughout downstairs 

Then I would definitely update the insulation Even 50 mil can make a massive difference 

[Tommyt01]

I can put the 200mm in if it would make a difference.

 

i didn’t know if a se would make a set of drawings just for a floor build up? I will contact some locally to advise and purchase the drawings 

[Andehh]

How's the rest of the house? 150mm to 200mm is a big step, for disproportionate improvement.... Especially if rest of the house is lacking!

[Iceverge]

I assume you mean something like a light grade of polythene between the UFH pipes and the PIR rather than another DPM? Alternatively you could forgo this and just tape the joints in the boards. All it's doing is stopping the juice from the concrete going between the boards and floating them. 

 

 

Otherwise it looks fine to me. With insulation more is always better. It might be as cheap to get 200mm of Seconds&Co PIR as 150mm of new stuff. Beware you will need to do more digging however. 

 

 

 

Edited Thursday at 20:58 by Iceverge

[Iceverge]

On the pipes in 100mm of concrete. This will be obviously slower to heat up or cool down than a thinner screed.

 

Not an issue if you run your house at a constant temp 24/7 but it will require some extra heating if you have a very high heat loss building and only intermittently heat the house. 

 

If this is the case I would just use extra large rads. 

[Tommyt01]

All of the downstairs floor will be coming out, so it’s pretty flexible on what we can do as the new slab will run throughout downstairs with regards to depths 

 

If it doesn’t need to be as thick as a dpm, Ill use polythene to keep the concrete off the pir boards

[JamesP]

My floor build up has 100mm of concrete below the 150mm insulation. I set the UFH in 60mm screed. 

1 hour ago, Tommyt01 said:

I’ve suggested this to a couple of companies and they have advised against it and it’s not the correct way it’s done and needs a concrete under the pir and a screed above. 

 

[Roger440]

2 hours ago, Tommyt01 said:

I don’t have any drawings, this is to replace a uninsulated slab in the kitchen and wooden floors throughout downstairs 

 

I did foamed glass with concrete over. Total depth 240mm.

 

Didnt meet current regs, but light years better than what you have, and avoids any risks of excavating too deep next to existing foundations.