Visqueen/Gas Membrane

[Mark Boland]

Evening Folks, looking for some advice. 
 

Been building a 4 bedroom detached since March 2020. 
 

On the pre-planning conditions it stated we use a gas membrane compliant with CS2. I have used this all round the perimeter and above the engineering brick. However, I have used 1200 gage visqueen above & below the insulation and pinned the underfloor heating to it and lapped this onto the perimeter/gas membrane.  I have found out this evening that I must get a Geologist to do a site survey in order comply with the pre-planning conditions (basically to check the gas membrane is correct)…. And pay £500 for the pleasure. 
 

I have a concrete pour happening Tuesday at 8am and the chance of me getting someone out is slim and if they do come I’m presuming it’s going to fail? I’ll also have to take back Up the underfloor heating and start the process again using gas membrane which doesn’t come cheap!
 

please note - The gas trace was very very minimal. 
 

On the planning, we initially said 75mm scread for floor level but since I have changed to 100mm finished/polished confrere floor, does anyone know if this has any benefit to me given the above? 
 

any help/advice would be massively appreciated! 
 

thanks 

[SuperJohnG]

15 minutes ago, Mark Boland said:

have found out this evening that I must get a Geologist to do a site survey in order comply with the pre-planning conditions (basically to check the gas membrane is correct)…. And pay £500 for the pleasure.

Who told you this? 

 

Is it a radon membrane? They are not really massively more expensive than a 1200 gauge visqueen. 

[Mark Boland]

I already had rolls of 1200 visqueen, that’s the only reason I used it…
 

regards the membrane, i can’t think of the name and it’s at site. I’ll check in the morning but I believe it’s circa £300 a roll. 

[Jenki]

For my build in Scotland, the Radon report comes back as 3, IIRC. So need radon minimal Radon protection. I.e Radon barrier and top hats and tape for pipe penetrations. Extra cost over std visqueen for my 98m2 is about £200.

Edit: just read that cs2 is non vented protection. 

 

If you've used STD visqueen and not a Radon gas membrane then it's not going to pass. The thickness of concrete will have no effect.

 

It's an obvious question but why use it on the perimeter but not over the main area?. 

 In my view the thought of long term exposure to Radon gas and resultant poisoning isn't worth the £200 budget worry.

At least you've not poured the X cubic meters of concrete yet

 

If you were having a screed afterwards you might be able to use a radon barrier here, but not sure how this would be detailed to the outside of the building .n

Edited February 24, 2022 by Jenki
Detail added

[Jenki]

https://justthejobsupplies.co.uk/products/radon-barrier-yellow?variant=40474272825501

This is the thicker membrane. 

With regards to an expert, cs2 is a non vented solution, so membrane only. So you would only need to prove you've used the correct membrane, (not what you want to hear). building control would / should check they are satisfied with the install.