How to fix a damp interior wall and exterior bricks?

Blackvault

Blackvault

Blackvault

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Northern Ireland
I'm seeking advice on the cause of dampness and how best to fix it.

The house is a 1970s bungalow, with a cavity wall around the exterior garage wall, and the garage space has been converted by the previous owner.

As can be seen from the photographs, two or three bricks above a slate-covered ditch show visible dampness, and then the interior wall is moist. A plastic membrane sits under the slate followed by earth/clay in which a plastic drainage pipe from the downspout sits.

Given there has been torrential rain in Northern Ireland, particularly all winter, has the ground under the slate got so wet that it crept up the wall, filled the cavity and eventually seeped through the plaster?

Is the solution to dig up the pipe, lower it below the bricks and recover it?
What's the best method of drying the interior wall?

Thanks in advance.
 
I would be looking at the drains to check they aren't leaking as the wall doesn't look that wet (no green/moss/growth etc.) and I'd also be looking at that white downpipe as I reckon that is splashing water around the place as it stops short of the drain for some reason. I also can't see your DPC, but I suspect the ground level might be too high. Is there insulation in the cavity?

For drying - that wood burner would do the trick ;) - or a dehumidifier and fan will sort that out. But no point until you've found the source of the damp.
 
SeatIbiza said:
I would be looking at the drains to check they aren't leaking as the wall doesn't look that wet (no green/moss/growth etc.) and I'd also be looking at that white downpipe as I reckon that is splashing water around the place as it stops short of the drain for some reason. I also can't see your DPC, but I suspect the ground level might be too high. Is there insulation in the cavity?

For drying - that wood burner would do the trick ;) - or a dehumidifier and fan will sort that out. But no point until you've found the source of the damp.
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Thanks for the advice. We, my partner and I spent yesterday looking at the drains. The downspout at the front turns right and along the length of the house then turns left and goes under the patio at the back of the house. Unfortunately, the downspout drain runs away from the pipework around the house, and does collect in the pipe, but is free following, with nothing clogging it based on yesterday's tests. We do indeed need to put an angled end on the bottom of the downspout, I've one ready to go, I just need the time to fit it.

I'm not sure if the house has a DPC. If the ground is too high, is that where my suggestion of a fix would come in? There isn't any insulation in the cavity, yet. However, we plan to get that job done later this year, but wanted to fix the dampness first before filling the cavity with insulation.

Wood burner it is then. Yes, I agree, there is little point in drying inside unto the source of the dampness is found.
 
What are the drains made of, do you know? There could be a crack that is allowing water to come out that you can't see. Do they drain to a main drain or soakaway? Has this just appeared?

If it is a 1970s house (with a more modern garage conversion) then it will (should!) defo have a DPC. Do you know if it was done DIY? I've had another look at the pictures but I cannot see a DPC in there, so it might be well buried and it looks like the wall is painted too. On your third image you can see the tarmac is covering most of that corner brick and I suspect your DPC might be under there and the tarmac has bridged it and, therefore, it won't work. FYI there should be 150mm below the DPC to ground level. I would dig out some of that slate to see if you can locate one. If you do, then I think you'll have found your issue!

What are those panels internally in your last image behind the burner? Some sort of fire boarding?
 
SeatIbiza said:
What are the drains made of, do you know? There could be a crack that is allowing water to come out that you can't see. Do they drain to a main drain or soakaway? Has this just appeared?

If it is a 1970s house (with a more modern garage conversion) then it will (should!) defo have a DPC. Do you know if it was done DIY? I've had another look at the pictures but I cannot see a DPC in there, so it might be well buried and it looks like the wall is painted too. On your third image you can see the tarmac is covering most of that corner brick and I suspect your DPC might be under there and the tarmac has bridged it and, therefore, it won't work. FYI there should be 150mm below the DPC to ground level. I would dig out some of that slate to see if you can locate one. If you do, then I think you'll have found your issue!

What are those panels internally in your last image behind the burner? Some sort of fire boarding?
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The drains look like standard PVC plastic. I believe the drain water goes to a septic tank and then to a soak away. Checking the Home Buyers report there is wish-washy language, if it can't be seen, it can't be confirmed. No, it has started really this winter, with all the rain we've been having and I've only gotten around to investigating it, as the room isn't currently used.

Reference the DPC, again the Home Buyers report, couldn't find evidence due to the outside render. Would lifting a bit of the tarmac in the third picture help? Typically rain rainwater does collect in front of the now-defunct garage door, although it does go under it. If I dig a bit of the slate, what am I looking for to identify if there is a DPC?

To answer your question on the conversion of the garage, it does seem very DIY or should I say Heath Robinson. Yes, it does look like the fire boarding is screwed directly into the plasterboard of the internal wall. I believe there is nothing actually behind the plasterboard and the garage door either!
 
Have you just bought the house or do you have another winter's experience with it? It would be interesting to know if it's a seasonal occurance because that, I think, would point to a construction error. Do you have any building regs sign off for it? It is usually a requirement to declare this on sale and your solicitors should have checked all was above board (well certainly is over here!).

DPC spotting - it's usually plastic membrane but maybe in the 70s it would have been other materials (the conversion is most likely to be something like: THIS).

They used bitumen, slate, engineering bricks, lead all sorts for DPCs- have a look here: https://www.designingbuildings.co.uk/wiki/Types_of_damp-proof_courses

Lifting the tarmac wouldn't do any harm, the only benefit I can see is that it is angled away from the property and that is minimal and it looks like water would get down between it and the bricks as it is. On that third picture, by your plant pot/box, I can maybe see something there right by the ground, bit it's very hard to see from that image - can you grab a better image at all?

I've noted some newer looking concrete around the drain, has work been done here?

You can get fire rated boards that give 30 min fire protection (and in this scenario you're only really talking about heat), it seems strange they've done it like that but, as you say, a bit Heath! Personally, I'd be taking those boards off to have a look to see if you can spot a water source. They only look like they're held on by a few screws! And, being what looks very wet, they're compromised anyway.
 
Could it be that rain is running off your tarmac drive into the slate chips, and then water is pooling underneath them? The water is then being drawn up your internal walls. Inside it does look rising damp. It might just be that you don't have effective drainage for the run-off water from your driveway.
 
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radderfire said:
Could it be that rain is running off your tarmac drive into the slate chips, and then water is pooling underneath them? The water is then being drawn up your internal walls. Inside it does look rising damp. It might just be that you don't have effective drainage for the run-off water from your driveway.
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The water drains off the drive from the road and sits in front of the arch of the house, although that is a fair bit away from the downspout. But regardless the amount of rain pooling isn't helping matters. Cheers!
 
Are there vents anywhere on the outside? It is odd to have that many pics of a wall and not see vents. Can you Google Street View from a previous/older version?

My friend moved into a place recently and they had rendered over the airbricks and DPC....
 
dlockers said:
Are there vents anywhere on the outside? It is odd to have that many pics of a wall and not see vents. Can you Google Street View from a previous/older version?

My friend moved into a place recently and they had rendered over the airbricks and DPC....
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I can't see any in the house, never mind the old garage. Unfortunately not, it is set off the road surrounded by 20-foot confirs, and therefore can't see the house.
 
Hard to tell from the pics where the internal wall is based.

The first pic though, seems to be green mildew on the stone render? the tarmac is up to the brick which seems uneven

Also the render on the first pic looks smooth so maybe replaced recently?
 
The air bricks are a good point, but it doesn't look like there are any along that gable and only damp in this spot. That's not to say they should not be investigated and added as appropriate but they might well be buried!
 
Kill_Phil said:
Hard to tell from the pics where the internal wall is based.

The first pic though, seems to be green mildew on the stone render? the tarmac is up to the brick which seems uneven

Also the render on the first pic looks smooth so maybe replaced recently?
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The internal wall is along the long-sided wall in the first picture.
Where do you see the smooth render in the first picture?
 
Blackvault said:
The internal wall is along the long-sided wall in the first picture.
Where do you see the smooth render in the first picture?
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Is it pic 3 behind the planter and painted brown? I thinkit's a leap to say that's new...but does ask the question of why it isn't pebble dashed like the rest of the walls...
 
SeatIbiza said:
Is it pic 3 behind the planter and painted brown? I thinkit's a leap to say that's new...but does ask the question of why it isn't pebble dashed like the rest of the walls...
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Yes, it is. Sorry, I guess I know the layout and expected everyone else to! :p I haven't a clue why that bit isn't pebble-dashed. Around the front porch is the same.
 
I've done a bit of investigating and I think I can see the DPC. Is it the tiny bit of black plastic in between the red lines? If so, then that is well below the slate, and soil.
Image
 
Hard to see from that pic. It would be worth digging that out further for a proper inspection.

If that is your DPC, then you likely have found the source of the problem. Is that the same spot as the damp on the internal side.If heavy downpours cause water to run or pool against the wall above the DPC, the bricks will wick the water through, probably enough to cross the cavity.

I had similar with my garage where the neighbours had built up their back lawn against my garage wall. They raised it just enough to go above the DPC. I couldn’t believe how much water bricks could wick through after a heavy shower.
 
Blackvault said:
I've done a bit of investigating and I think I can see the DPC. Is it the tiny bit of black plastic in between the red lines? If so, then that is well below the slate, and soil.
Image
Click to expand...
As per Scuzi, if that is the DPC, I think we've likely found the issue. I do wonder if the air bricks might be under there too? They are placed below/at DPC level.
 
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