DPM over DPC

[wyk126]

Hi
My builder already put the DPC strip in the brickwork and block work, and already built the cavity wall and brickwork wall, they haven’t but will start doing the floor/ concret etc and told me that the DPM will just go over the DPC level, is that fine? I saw some builder they insert the DPM inside the DPC before putting up the wall, but I also saw a video on youtube seems like what my builder gonna do.

Will there be any damp, is this methods fine?

thanks

 

[Swwils]

What is the detail for the floor?

 

[noseall]

Hi
My builder already put the DPC strip in the brickwork and block work, and already built the cavity wall and brickwork wall, they haven’t but will start doing the floor/ concret etc and told me that the DPM will just go over the DPC level, is that fine? I saw some builder they insert the DPM inside the DPC before putting up the wall, but I also saw a video on youtube seems like what my builder gonna do.

Will there be any damp, is this methods fine?

thanks

The DPM should lap onto the DPC prior to building upwards. If the floor is to be done retrospectively, i.e. after the walls are built, then the builder should build in tails of DPM left protruding say 600mm or so from the walls.

 

[Notch7]

Hi
My builder already put the DPC strip in the brickwork and block work, and already built the cavity wall and brickwork wall, they haven’t but will start doing the floor/ concret etc and told me that the DPM will just go over the DPC level, is that fine? I saw some builder they insert the DPM inside the DPC before putting up the wall, but I also saw a video on youtube seems like what my builder gonna do.

Will there be any damp, is this methods fine?

thanks

It’s fine if the DPM wraps up the inner wall enough so it can be cut to top of screed level.

pone important thing is to make sure the DPM doesn’t get punctuated in the corners anywhere - esp at door reveals

 

[noseall]

It’s fine if the DPM wraps up the inner wall enough so it can be cut to top of screed level.

Not especially no. It's fine as long as say the screed finishes slightly above the DPC. However, that method would rely upon the diligence of the skirting bumper or the plasterboard fixer, having the nous to leave the DPM vertical longer, in case the screed happens to fall a touch lower than the DPC.

Not good practice at all.

 

[Swwils]

Should also add perimeter insulation to the screed, not just the barrier foam tape.

Something that achieves at least 0.75m2K/W would be good.

 

[^woody^]

It’s fine if the DPM wraps up the inner wall enough so it can be cut to top of screed level.

Not at all fine. The DPM should be a continuous barrier, not cut.

 

[wyk126]

Thanks all for your reply, is this different requirement based the BC inspector? I'm checking with my BC to see if that is fine, what could be done then?
I've attached the floor details from BR and SE drawing.

 

[^woody^]

Shiite design

Passage of ground water .....

 

[wyk126]

Shiite design

Passage of ground water .....

View attachment 265647

Thanks Woody, I believe the builder is gonna do like this, is this called apron DPM? would this suffice?

 

[^woody^]

Thanks Woody, I believe the builder is gonna do like this, is this called apron DPM? would this suffice?

If the DPM laps the DPC in the wall, and if the builder is laying the floor afterwards, any DPM skirts hung out of the wall are lapped and taped to the DPM that goes under the slab, then yes it's OK.

But why is that DPC so high in the first place. That's nonsense

 

[wyk126]

If the DPM laps the DPC in the wall, and if the builder is laying the floor afterwards, any DPM skirts hung out of the wall are lapped and taped to the DPM that goes under the slab, then yes it's OK.

But why is that DPC so high in the first place. That's nonsense

When you say "lap" do you mean just go over the DPC level, not "inserted" to the wall right? As my wall is already built with the DPC strip in...
This is the party wall section from structural engineering drawing so it might just be demonstrating, not as per dimension etc.

 

[^woody^]

The DPM should lap the DPC by being in the wall and the wall above laid over both DPC and DPM.

This is standard knowledge for any competent builder, not something that needs to be explained to them.

That detail is still crap whether its a party wall or not. Drawings are not for demonstrating, but for building from without guessing what the designer actually meant. It's a mad world when the builder says, "I built what the drawing said" and the plan drawer says "Well it was just for demonstrating, not to be built like that"

 

[Swwils]

Make sure they specify what insulation strip at the screed perimeter should be used. Also ideally insulation in the cavity will be carried down at least 150mm from the top of the floor insulation.

Why aren't your drawings detailed enough to build from? They should not be guesswork.