DPM for dug out wet UFH

[JamesDRG]

Hello folks,

 

We are retrofitting UFH in our late 1980s house and I have a question on the DPM.

 

So far we have dug out the existing concrete floors, compacted hard-core and laid a 5cm sand blinding. The next step is a DPM, followed by 200mm Celotex, visqueen sheet and finally a 100mm cement screed encasing the ufh pipes.

 

We have left about 30cm of the original floor around the perimeter of the room - so in effect we have dug a pit in the middle.

 

The existing DPM under the undug floor is now 10cm above where our new DPM will be. How should we lay the new DPM to ensure there is no moisture transfer?

 

The old dpm is only petruding about 5cm (we had to cut it to dig out). 

 

Any help greatly appreciated.

 

Thanks

James

[Dave Jones]

so your new floor is 10cm lower than the old one ?

 

They need to be linked really, you can allways use a paint on blackjack type dpm direct onto block or brick (not plaster) to link the two.

[Chanmenie]

Can you lap the new DPM up the sides to meet the old one and tape it with double sided DPM tape 

[JamesDRG]

1 hour ago, Dave Jones said:

so your new floor is 10cm lower than the old one ?

 

They need to be linked really, you can allways use a paint on blackjack type dpm direct onto block or brick (not plaster) to link the two.

Thanks Dave. The finished floor level will be the same, but the level of the DPM in the new part is 10cm below the original one.

 

Ah I see, so you can paint a DPM. Thanks!  

[JamesDRG]

1 hour ago, Chanmenie said:

Can you lap the new DPM up the sides to meet the old one and tape it with double sided DPM tape 

Hi yes that's a good idea. The tape would create a good seal.

[Chanmenie]

On 04/08/2024 at 11:27, JamesDRG said:

Hi yes that's a good idea. The tape would create a good seal.

Yes it’s very sticky