DPM under DPC - is there a trick to keeping it in place?

[Digmixfill]

I've got a 9 inch wall that i have to place a DPC on and a DPM that i need to trim and lap under the DPC.

My google fu has failed. Anyone have a handy hint on how to hold the DPM against the wall, and on top of the wall whilst i lay the DPC and blocks?

[Mr Punter]

Often the DPM is under concrete slab with the wall just built to DPC level.

[Digmixfill]

My DPM is under the concrete  base slab. The wall to DPC is 225mm higher that the top of the base slab. Insulation and UFH screen take things up to the DPC height from the top of the base slab.

 

 

[epsilonGreedy]

The procedure I have seen is:

1. Forget about the DPM until the masonry walls are up to gutter height and the roof is on.
2. The DPC is installed from a roll of extra wide material and this is left as a loose flap on the inside.
3. Pre screeding, you lay the DPM, install the insulation sheets and create vertical upstands of insulation block around the outside perimeter of the wall. DPC and DPM are lapped together at this stage.

This process is not 100% foolproof and so during screeding an extra pair of hands is useful to tuck the materials together until the weight of the screed holds everything in place.

 

 

[curlewhouse]

If I understand the correctly, why not just use DPC joining tape to connect the 2? Thats what we have done. It also means a fully waterproof join. The blue Visqueen stuff is really strong. I've found the black bitumastic type, though cheaper, harder to work with and if cold, not very "sticky" - in fact I've even had the rolls sitting in front of a fan heater on a low heat setting before to improve things before use.

 

Edited August 19, 2018 by curlewhouse

[Digmixfill]

2 hours ago, epsilonGreedy said:

The procedure I have seen is:

1. Forget about the DPM until the masonry walls are up to gutter height and the roof is on.
2. The DPC is installed from a roll of extra wide material and this is left as a loose flap on the inside.
3. Pre screeding, you lay the DPM, install the insulation sheets and create vertical upstands of insulation block around the outside perimeter of the wall. DPC and DPM are lapped together at this stage.

This process is not 100% foolproof and so during screeding an extra pair of hands is useful to tuck the materials together until the weight of the screed holds everything in place.

 

 

 

Our floor detail has been drawn up with the concrete, insulation and UFH + screed all above the DPM. This particular wall has to be completed before the other walls in this room can be dealt with, It's part of a height change in the room.

Thanks for the idea of downstanding the DPC into the rooms.  That might be useful for the main event.

 

 

 

1 hour ago, curlewhouse said:

If I understand the correctly, why not just use DPC joining tape to connect the 2? Thats what we have done. It also means a fully waterproof join. The blue Visqueen stuff is really strong. I've found the black bitumastic type, though cheaper, harder to work with and if cold, not very "sticky" - in fact I've even had the rolls sitting in front of a fan heater on a low heat setting before to improve things before use.

 

 

Did you tape over the overlap or butt joint with tape over?

 

 

[curlewhouse]

Taped the overlap - so the DPM comes up behind the DPC overhang with the blue Visqueen tape in between. I guess you could also then tape over the top of the join too if required but I didn't see a necessity and I found by doing it that way, when I forced in the insulation boards in tightly, as the overlap was "downwards" it did not then pull the joint apart.