Joining new DPM to existing DPC

[Eng33]

Just laid a new concrete floor in a lounge, with the finish level being 10 - 20mm below existing DPC. I assume I should really chase a narrow groove out below the existing DPC and insert the edge of the DPM into it... how deep should this groove be, and what adhesive should I use to seal / hold it in place?

Thanks.

 

[Softus]

Just laid a new concrete floor in a lounge, with the finish level being 10 - 20mm below existing DPC.

Why have you done that?

 

[noseall]

don't bother.

you may unintentionally do more harm than good.

i take it the floor level matches the existing?

 

[Eng33]

I was hoping someone would say that... I've been putting it off for that reason! Yes, in fact original screed was higher than DPC, have laid new floor level lower as final floor finish will be 25mm battens + 18mm oak.

 

[noseall]

i should just trap the polythene at the back of the skirting.

 

[Softus]

i should just trap the polythene at the back of the skirting.

That's an excellent way of guiding any moisture that rises between the slab and the wall into the space behind the skirting.

 

[noseall]

there will be a 20mm section of wall remaining that will be unprotected apart from the polythene dpm abutting it.

you could leave the dpm pressed against the wall or stick it to the wall.

the detrimental effects of it being pressed as opposed to stuck will be negligible for the sake of 20mm.

i happen to think that trying to cut in the dpm at dpc may damage the dpc.

 

[theSouth]

I have this problem too as the builders forgot to slip in a length of DPM I'd cut for a floor that I'll be laying after the new extension walls have been built

I plan to just cut off the DPM at the level of the DPC, can't see much trouble with that. I can see much more trouble with trying to cut this in to the wall....