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Identifying Damp Proof Course Along Party Wall

Postby Lazynovice » Mon Jun 27, 2022 10:03 pm

I'm looking for a little advice regarding damp issues along a party wall in a 1910s terrace.

There was minor discolouration along the top of the skirting when I moved in 2 years ago. This has gotten progressively worse since, to the point where the wallpaper was beginning to crumble. I've had a damp survey carried out and that confirmed that the problem does appear to be ground water rising up.

The surveyor recommended that I either have a dpc barrier installed by removing a few bricks at a time, or have a chemical injection course

Since the survey I've hacked off the plaster along the affected wall and you can see there's a fair bit of brick spawling now. I've also been running a dehumidifier next to it for a little over 3 weeks continuously and keeping an eye on moisture levels. They shoot up immediately after any rainfall, causing excessive humidity and condensation throughout the entire house. Mold control is a neverending struggle.

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I'm having issues progressing further as I'm struggling to identify whether there is in fact a damp course in the wall itself. I can see what looks like a plastic membrane running underneath the concrete floor that laps up to the edge of the wall and then down, but I'm not sure if if actually goes into the wall further down or just loops back on itself. Its only visible in a few places, most of it is completely hidden under a layer of concrete that goes to the brickwork.

Further to this, that wall is single brick in places (chimney breast and alcoves on the other side, converted to a student HMO shortly after I bought this one - yay for fire doors in edwardian terraces :-\ ) so would I be right in assuming that the damage would also be extensive on the other side? They filled the alcoves in when they converted, potentially covering the proble, so I don't think a surveyoyr will be able to spot anything without poking holes in things.

If I've missed any details that might be relevant, please let me know and I'll try to update as soon as I can.

Many thanks
Lazynovice
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Postby stoneyboy » Fri Jul 01, 2022 9:48 pm

Hi lazynovice,
There is probably a slate DPC in the wall located below finished floor level. The floor was probably a suspended one, fully ventilated underneath (have a look for old vents outside).
The plastic DPM has probably created a bridge across the DPC and a chemical DPC may be the easiest solution.
Regards S
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Postby Lazynovice » Sun Jul 17, 2022 5:42 pm

The surveyor came back last week. She seems to think there is no dpc at all, that the plastic sheeting I'm seeing is for the floor (I'm sorry, I can't remember exactly what she said it was for, but she said it definitely wasn't a damp membrane).

This response has me confused though. She is adamant that it's the case, but if there was no dpc at all, wouldn't everything from the walls to the floors be wet?

There is a vent outside, but it is far higher than the level of the floor. Outside ground level is less than 10cm below the level of the internal floors (both front and back). The garden boundary wall outside is the only thing that makes contact above floor level.

I removed skirting in the back room expecting to find hidden damage, but there doesn't appear to be any...certainly no wet brickwork like there was from the front door to the stairs.
Lazynovice
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Postby stoneyboy » Sun Jul 17, 2022 8:48 pm

Hi lazynovice,
Thanks for the update.
The plastic sheet you can see will be a DPM for the concrete floor. As I said earlier your house probably had ventilated suspended floors and these have been replaced with concrete. You best option will be to have a chemical DPC formed in the problem wall.
Regards S
stoneyboy
Rank: Project Manager
Posts: 5514
Joined: Wed Dec 10, 2008 6:44 pm


Postby Lazynovice » Mon Jul 18, 2022 3:02 pm

Thanks Stoneyboy,

Since the most recent visit I've received a new (far more expensive) quote telling me I also need an extractor fan to deal with the high moisture in the backroom.

I am as far from an expert as possible, but I am not convinced this has been diagnosed properly. I keep a close eye on relative humidity throughout the whole house. The stretch of wall being blamed on condensation reads 70-75 continuously hours after any moisture causing appliances have been turned off when the rest of the house is around the 50 mark. That doesn't make sense to me, and the wall is not hidden behind any obstructions.

It feels as if this particular company is more interested in making a sale, regardless of how effective it would be, than actually solving the problem properly.
Lazynovice
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Posts: 3
Joined: Mon Jun 27, 2022 8:47 pm


Postby stoneyboy » Mon Jul 18, 2022 9:30 pm

Hi lazynovice,
If you have an openable window in your back room put this on nightvent permanently, if no nightvent fit a window restrictor.
Try a different damp proofing company and see what they suggest but beware of the same company trading under different names.
Regards S
stoneyboy
Rank: Project Manager
Posts: 5514
Joined: Wed Dec 10, 2008 6:44 pm



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