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Thanks to a leaky underfloor central heating pipe, we now have a hole in our concrete floor slab and the damp proof membrane. I’ve got some new membrane but do I need to seal it to the existing membrane somehow? And how - there’s not much room in there and not much membrane left to actually stick anything to? There’s also a vertical membrane as the vertical wall adjacent is actually below ground level at this point so adds an extra complexity I guess.
Is the CH pipe copper? If it is it'll need room to expand. Consider a waterproof cement that isn't acidic to maintain the waterproofness (that might not be a word) and won't corrode the pipe
If it is underfloor heating laid over insulation it migh5 not be a DPM it a vapour check barrier.
I’d be tempted to use a liquid dpm for the whole job (no new membrane) like blackjack.
Just traditional CH pipes buried below the slab.
Hmm, liquid membrane does sound the answer…
Liquid membrane vote from me, mainly because that's what I've used when patching a concrete floor with UFH in the past and it was specified for the job by Sika.
I've used a liquid membrane before on a job that spanned old and new build, with some flipping awkward bits. It worked well. We sold house 16 years ago and know the current owners - no problems at all.
