Punctured holes in DPM; How much of a problem

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apple1

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Folks,
At subfloor level of a new build currently & laying rigid insulation. With the recent inclement weather conditions, there was a significant volume of water sitting on the subfloor. My plumber in his wisdom, decided to drill a number of holes in the subfloor (& presumably through the DPM) to allow the water escape. Assuming he did, how much of a problem might this be in the future & is there any way to remedy it now (plumber already given a major bollocking)? Thanks, apple1
 
Does your DPM also function as a radon barrier? If this is the case you got two problems- the membrane is now punctured and this will allow gas and water vapour to migrate through the slab. The only solution is to (carefully) break up the slab in the locations of the holes and repair the membrane using a special (butyl I think) repair tape (such as Monobond) and make good with concrete on completion. The plumber should have used a sump pump to pump off the water, the cost of repairs should be chargeable to him. A pretty stupid thing for him to have done I think.
 
apple, i assuming the subfloor has no insulation under it??? and you will be installing the plumbing in the screed??

If so what i would do is incorporate another DPM sheet over the subfloor and install the insulation and plumbing over this...and then pour your screed. A second DPM layer is no harm to the construction.
Carpenters suggestion is ok but is very labour intensive, more expensive, awkward and may not guarantee the result you want.
 
sydthebeat said:
If so what i would do is incorporate another DPM sheet over the subfloor and install the insulation and plumbing over this...and then pour your screed. A second DPM layer is no harm to the construction.
Carpenters suggestion is ok but is very labour intensive, more expensive, awkward and may not guarantee the result you want.
Click to expand...

Good idea, but you may need to rethink the DPM and DPC junctions and detailing at the perimeter walls.
 
Syd/Carpenter, thanks both for the tips. He drilled numerous holes in various rooms so I think breaking up the slab & repairing will be an arduos task. Thankfully, radon levels in the area we're building are supposedly very low (granted the last radon map isn't exactly very current), so my primary concern is moisture. I didn't see the radon barrier being fitted, so who's to say it is perfectly sealed in any event.

Syd...you are correct, the insulation is now laid above the subfloor and UFH pipes to be laid on top of it. Remaining plumbing pipework to be routed through studwork.

Carpenter...assuming I follow Syd's suggestion, what exactly do I need to look out for in terms of detailing at the perimeter? Not sure of the relevance to this problem, but it is a TF build.

Thanks again....apple1
 
will your plumber be willing to uproot the UFH in order to lay a secondary DPM???
The main issue you need to remember about the DPC at the external walls is to have an upstand on the inner leaf and slope down to the other leaf.
 
sydthebeat said:
The main issue you need to remember about the DPC at the external walls is to have an upstand on the inner leaf and slope down to the other leaf.
Click to expand...

That about sums it up, but if your DPM is also serving as a radon barrier (even in a low risk area) the DPM should lap across the cavity (with a downstand) to seal the cavity from radon.
 
Syd/Carpenter...thanks again for the responses.

Syd...the UFH pipes are not laid yet, so I'll fit the secondary dpm over the insulation. Given that its very unlikely to be completely rain-free while laying this DPM, then laying the UFH and finally screeding, how much of an issue is it if rain-water gets underneath the secondary DPM? Thanks in advance, apple1
 
apple1 said:
Syd/Carpenter...thanks again for the responses.

Syd...the UFH pipes are not laid yet, so I'll fit the secondary dpm over the insulation. Given that its very unlikely to be completely rain-free while laying this DPM, then laying the UFH and finally screeding, how much of an issue is it if rain-water gets underneath the secondary DPM? Thanks in advance, apple1
Click to expand...

I'm afraid this won't work, as the UFH pipes will be clipped to the insulation, puncturing the DPM again.
 
QWERTY is correct... you should removed the insulation and lay the dpm over the concrete slab... now is the time to do it.

assuming the first dpm is punctured like you say, then any water underneath the secondary dpm will drain away into the hardcore...
 
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