Repairing old DPC

jonjack · Post by **jonjack** » Sun Apr 05, 2020 11:12 am

I'm looking for some suggestions for repairing the DPC on my home.

I have lived in this property for 10 years and never had any damp issues, and do Not have any at this time.
I have removed the decking that was here when I arrived 10 years ago since it was becoming dangerously rotten.
It was elevated above the DPC.

After removing the decking, I have discovered that some brick courses could do with re-pointing but the DPC is damaged in places and so I'm concerned about re-pointing and bridging the DPC.
Also, there was a damaged airbrick that was allowing mice to get in and I have removed that but unfortunately the DPC, just under it, just disintegrated even though I tried to take as much care as possible.

The DPC seems to be a bitumen type material given how it just crumbles - the house was built in the 1930s.

My intention was to try and repair the chipped areas of DPC and patch under the airbrick with another bitumen-based DPC that I could paint on in layers, but it seems, after doing some searching, that the products on the market are only intended for DPM under floors and the like and that DPC is generally always a plastic roll. Not sure I will be able to get the required overlap under the airbrick if I use a length of DPC roll since if I chase out the mortar either side of the base of the airbrick then I'm sure the DPC will continue to just crumble away.

Any advice on materials or techniques much appreciated.

Rorschach · Post by **Rorschach** » Sun Apr 05, 2020 11:32 am

Given the way your current DPC has become damaged I would say you do have a bitumen based DPC, you should be able to repair it quite easily with some new bitumen sheet and a blow torch/heat gun.

jonjack · Post by **jonjack** » Sun Apr 05, 2020 11:36 am

Thanks for your comment Rorschach.

The blowtorch would be used to get the sheet to adhere to the existing DPC at the edges right?

For the small areas that are chipped, I'm assuming I would just try and use small patches of bitumen sheet and melt them onto the existing- seems a bit fiddly but I guess I don't have much choice.

Argyll · Post by **Argyll** » Sun Apr 05, 2020 1:02 pm

You might be best using dryrods but I'm not sure if you can just buy a couple of sticks.

Edit: You can buy ten here. You probably would only need two.

https://www.ebay.co.uk/itm/123415006251

wes56 · Post by **wes56** » Sun Apr 05, 2020 8:28 pm

Dont worry about pointing just go ahead and do it.
There's no need to repair the DPC - thats an outside wall in a cavity wall, plus there's no signs of rising damp.
you can just replace the air brick.
If you must then apply some liquid bitumen or similar - but dont sweat it
although the air brick only seems to be ventilating the cavity, and there's no need to ventilate cavities unless there's cavity condensation.
air bricks at low level are to ventilate below any suspended floor.

Whats maybe a concern is what looks like a wood plate embedded in the inside wall just above the inside DPC - it looks fine but probe it and see if its in good condition?

jonjack · Post by **jonjack** » Thu Apr 09, 2020 2:36 pm

Thanks for your comments Wes. Ye Im trying not to be too concerned about it given that I've never had any moisture issues.

The wall is actually 2 brick thick with no cavity - fk knows why, maybe it was acceptable back in the 30's.
That wooden plate is actually the top of the sleeper wall supporting the floor joists.

I was thinking of just using a couple of coats of this beneath the airbricks - https://www.ebay.co.uk/itm/Bitumen-Emul ... 3256740726