dpm under screed

[wakey77]

Hi fellas just a quick 1
I'm screeding the floor In my extension
Where should I put the membrane
Above the insulation or below
Or does it not matter
Thanks in advance

 

[^woody^]

Below the concrete floor

 

[wakey77]

I put 1 in under the concrete floor I now have 150mm to make up to ffl
75mm insulation 75mm of screed
I'm of the understanding I still need a secondary dmp
But am unsure of the positioning

 

[kazuya]

if you put one under the concrete why would you need another one?

 

[noseall]

It is good practice to either fit another DPM or tape the insulation joints, when adding a screed on top of inso'. The idea is that you are to prevent any screed material from falling down any joints and coming into contact with the cold slab.

 

[wakey77]

Ahhhhh ok thanks for the reply guys
So a secondary dpm isn't needed
I was taping the joints anyway with foil back tape just wasn't sure whether the screed would attach the insulation in any way

 

[jeds]

If you screed over insulation you should fit a separation layer between the screed and insulation. This also doubles as a vapour layer. It needn't be 1200g, the minimum is usually 500g.

 

[kanester]

Hello guys. Im in the same boat as the op only I have started laying my underfloor heating pipes, i have only done one bed room. I have layed dpm under the kingspan and taped all the joints, we are using flow screed. Im going to put some 500dpm everywhere else, do you think it would be ok to leave the one room without the top 500dpm? If not its a case of removing the pipes?

Thanks in advance.

 

[jeds]

Not likely to cause any major issue. BC may not allow it though, if it's being inspected.