Damp patch at base of wall

Joined
11 May 2023
Messages
11
Reaction score
0
Country
United Kingdom
Hi Guys,

The property in the photo illustrates a plaster-rendered wall with damp appearing to be rising up it. It was plastered about a year or two ago.
Initially, I thought it was possibly just the plaster drying out but quite recently it has now started to show some salts in one place, which is concerning.

It is an original brick wall behind the plaster (cavity with a dpc), and on the right-hand side of the vertical silicone line, it has a new extension (cavity wall with blocks and dpc) and it is even rising up the new wall as well., although not quite as high.

1. What is the likely cause of this and
2. How should I go about fixing it?

Thanks
 

Attachments

  • wall.jpg
    wall.jpg
    299.6 KB · Views: 111
Sponsored Links
Need a aco drain along wall to stop rain splash and water rising up. Don't think that render should go right to the ground. Check drain is clear with no overspill of water.

Brick Dpm covered with render so water rises over?
 
Stand back and take some wider pics, inside and out

Walk round the house looking for the original dpc. It is pretty sure to be at the same height all round the house. It may be visible under or beside a doorstep.

The pattern of damp suggests you have a severe and long term leak, probably from that gulley and the underground pipe it joins to. The chippings and render may have been an attempt to hide it until the house was sold. Scrape away those chippings and see what you expose.

The leak may possibly be in the floor inside.

Repairing the leak is the most important action.
 
Thanks for the suggestions so far guys.

The gulley drain is clear and the water gets away no problem, it was only fitted when the extension was put on about 2 years ago and should be fine. An aco drain could be a good idea to help stop splashback but I'm not sure if that will fully solve the issue.

I'm not completely ruling out the possibility of a leak but there's nowhere really for a leak to come from apart from the tap and it was fitted by a reliable plumber when the extension was done, so I'd be confident it's not that. The guy who fitted the gulley was also a professional. I guess there is a possibility it wasn't fitted right but I'd be doubtful of that. The floor inside is newly put in with the extension and no damp showing inside and I'm pretty sure there isn't a leak inside either.

The render was put on because one-half of the wall is brick and the new extension is block, so it would look weird having half the wall plastered and the other not, hence why it was all plastered to tie in the look better.
I do think that as the brick dpm is plastered over, it may be allowing water to rise up over the dpm which should be stopping it. That to me sounds like the most logical cause. I've been reading about fitting a bellmouth drip, or belcast bead and these sound like a good idea also but I'm not sure if they can be retrofitted easily?

Has anyone had any experience with retro fitting a belmouth drip/Belcast bead, or know how to do it?
Might that be a good way to go, as well as installing an aco drain?

For completeness, I've attached a photo of the dpm level and also the level where the dpc was injected on the brick just above it.
 

Attachments

  • wall2.jpg
    wall2.jpg
    506.6 KB · Views: 96
Sponsored Links
For completeness, I've attached a photo of the dpm level and also the level where the dpc was injected on the brick just above it.

If you have a dpc, why is there an injection?

Please scrape away some of those chippings and see what is benesth

Please stand back and take wider pics of the wall, all the way up to the roof and gutter, inside and out.

There is a lot of water.
 
If you have a dpc, why is there an injection?

Please scrape away some of those chippings and see what is benesth

Please stand back and take wider pics of the wall, all the way up to the roof and gutter, inside and out.

There is a lot of water.
Thanks for your assistance with this John.

There was damp in some of the walls internally that is now resolved, however the injection was done more as insurance in case the property was sold, so that there would be a certificate, to allow it to be mortgageable.

Underneath the chippings, there is just clay. I shovelled the chippings in myself and there's about 8 inches or so depth of chippings (much more depth around the gulley). I wouldn't rule out the possibility of a leak related to the gulley but the gulley was fitted by a long-established professional installer who does them everyday, so although it's certainly possible there could still be a leak in it, I feel it should be quite unlikely.

There was a brand new roof and guttering fitted too, all done and passed by building control and they're not leaking either, so all signs seem to suggest water is rising up the wall, hence the tide mark (likely via the bricks in the ground and I'm guessing the plaster is bridging over the dpc, allowing the water to rise slightly higher than the dpc level). It's a hard one for me to figure out and I appreciate you trying to help me.
 
I think the render could do with chopping back to the DPC layer, (which looks like bitumen to me), being and old form of DPC this can deteriorate and allow damp through it, the render can also be sucking up the moisture
 
OP,
The cause could be capillary action behind the render due to render/ground contact - & maybe historical splash from the eaves/gutters?
You dont need ACO drains, and it doesn't appear to be from a drainage leak.

On the gable, strike a level line one brick/course above the height of the visible DPC (bitumen?) bed.
Hack off back to brick from the level line to ground, and see what you expose - presumably you will expose the gable DPC line.
You can install a plastic Bell Cast along the gable line just above the DPC - you must not bridge the DPC.
The Bell Cast can be plugged & screwed to the brickwork, & later rendered over.
After the above allow the upper render to dry over the summer & then make good if all stains are clear.

FWIW: The manhole/IC cover is higher than the gulley - it should be level or lower.
DPC's rarely fail.
Certain injection fluids can dissolve bitumen.
The vertical stop bead was unnecessary - the render on both sides should have been blended in over a strip of metal lath.
It would be worth your while to remove a few bricks to examine the cavity for bridging/blockage.
A pic of any interior decorated surface water stains might help?
 
Last edited:
What are the chances of a waterpipe under the floor or in the ground nearby?
 
OP,
The cause could be capillary action behind the render due to render/ground contact - & maybe historical splash from the eaves/gutters?
You dont need ACO drains, and it doesn't appear to be from a drainage leak.

On the gable, strike a level line one brick/course above the height of the visible DPC (bitumen?) bed.
Hack off back to brick from the level line to ground, and see what you expose - presumably you will expose the gable DPC line.
You can install a plastic Bell Cast along the gable line just above the DPC - you must not bridge the DPC.
The Bell Cast can be plugged & screwed to the brickwork, & later rendered over.
After the above allow the upper render to dry over the summer & then make good if all stains are clear.

FWIW: The manhole/IC cover is higher than the gulley - it should be level or lower.
DPC's rarely fail.
Certain injection fluids can dissolve bitumen.
The vertical stop bead was unnecessary - the render on both sides should have been blended in over a strip of metal lath.
It would be worth your while to remove a few bricks to examine the cavity for bridging/blockage.
A pic of any interior decorated surface water stains might help?
Thank you for your informative post.

After the Bell Cast is applied when you mention make good if all stains are clear, do you mean re-render where the plaster was removed?
Also how likely will it be that there'll be a visible line where the new render joins the old? If it was painted perhaps might it hide it?

If I'm having to replaster the lower part of the wall anyhow, might I be as well (and probably not far off the same price) to remove the plaster up to just above the top point of the tide mark and replaster it too?

Once all sorted, I assume the lower part of the wall plaster below the Bell Cast will remain damp looking right up to the bottom of the Bell Cast?
Is there any way to stop it from looking damp?

Thanks
 
What are the chances of a waterpipe under the floor or in the ground nearby?
Externally there is nil chance of a waterpipe in the ground, as I've seen what's there. There is a drainage below the ground for the gulley but it should be fine and even if it was leaking a bit, it shouldn't really extend across the whole wall. Internally there is a newly fitted water pipe under the internal floor going to a sink but it was fitted by a reliable plumber and wasn't leaking before the new floor went in, so I'd be extremely doubtful if it would have a leak in it.

I think at this stage, capillary action rising up the old bricks to the dpc level sounds like the most likely cause and then the plaster bridges the dpc, which allows it to rise on up a bit further past it. I'm not sure but I think it sounds like the most plausible reason.
 
John, it's buried in. Essentially sitting within the insulation between concrete subfloor and screed layers. Obviously there might be a very, very, small chance it has a leak but I'd say that chance is absolutely miniscule... I saw every stage of the floor going in and internally all is fine.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top