DPM

[Callismichael]

I've had various pipes installed in concrete. I need to join to existing DPM but the problem i have is the DPM has been damaged flush with channelling.

I know you should have 150mm overlap but the issue i have is that will mean bashing the concrete above DPM back 150mm which will be pretty hard work as it's solid. What implication could this cause if i lap by only say 80mm and tape up?

 

[r896neo]

Use double sided self amalgataing tape and it should be fine.

 

[Callismichael]

Cheers and one other question I'm having skirting up to the door I've laid a trough of dpm in my cavity. Because I've pinched the folds to make the trough square I'm now left with thick folds of dpm up the pladterboarded cavity wall.

Does this part need to lap the wall or can I trim it back flush with the concrete slab?

 

[r896neo]

It shouldnt be an issue to trim it back because your floor internally should now be above your wall dpc level? if not you have bigger problems than a lump of folded dpm.

 

[Callismichael]

Floor internal is about 4 inches above dpc. So, so long as it's trimmed above dpc there's no issue? Also have a void below dpc how is best to deal with that or is it a case of relying on the dpm to bridge?

 

[Callismichael]

 

[Callismichael]

Also slight gap here but dpc going right round do I need to lap these pieces? Sorry for questions

 

[r896neo]

What are you filling this with? Screed or concrete? How see are the holes? The trough could be filled with kingspan and screeded over. Trying to fold your dpc into that trough will make a mess. Do the trough separately.

 

[Callismichael]

The second pic is where a gas pipe was removed from the floor so is about an inch thick.
There's a slight gap between dpc and dpm so wasn't sure if needed to lap another piece or just fill as is. The trough by the door threshold is going to go 2 course down and filled to ffl. When closing vertical cavities does the insulation end above or below dpc?

 

[r896neo]

If the dpm around the gas pipe area is not damaged just fill it with screed.

When closing a vertical cavity you need a strip of dpc against the outer leaf and then insulation behind it sandwiched in. The insulation and dpc should both extend below the horizontal wall dpc. You don't need to go on for ever but at least a couple of inches past it.

 

[Callismichael]

Very helpful thanks for your help much appreciated