Help with damp in new purchase

[craigr1]

Hi all,

I’m hoping someone might be able to help me with some advice.

I’ve just bought a new home, a 1890s terrace. I have a few damp issues, one on an external wall (kitchen) and one on an internal wall (between hall and living room)

I have attached some photos, the external wall appears damp on the outside and inside, it has an air brick above the dpc. My surveyor belived the floor to be solid concrete floor, it looks to be a blue visqueen covered by a black bitumen?

Also there is some airbricks at the front, brick sized and below the dpc which look be to original.

The house also appears to have had dpc injection throughout, internal and external walls.

Any advice on how to deal with the damp?

Many thanks

 

[stuart45]

To start with, I'd check how well the water from the downpipe drains away. It looks like there has been a lot of standing water around there along the wall. It looks like you have cavity walls. There could be debris in the cavity.

 

[craigr1]

Thanks! The downpipe is the boiler condensate pipe, so I would assume it isn’t that.

I can remove the airbrick and check for debris.

Really not sure on the internal wall? Could it be whatever the damp proofing they’ve put down on the floor causing it to track along and up the wall?

 

[stuart45]

The DPM should lap into the DPC to be done properly, so this could be a weak spot. Back in the 70's it was common practice on new builds to cut off the DPM flush between the slab and the wall to make it easier to lay the DPC and the inner skin. They realized after a while that this was causing a few damp issues, so made it a rule to lap them.

 

[craigr1]

Ahh ok thanks.

So check DPM is lapped into DPC on internal wall and check for debris in cavity on external wall? Should I really have a French drain on that external wall? Or not needed as the ground level is quite low?

 

[a twig]

How is the guttering above? Often green growth like that can be a sign of poorly functioning rainwater goods causing drips / overflows which the splash back up onto the wall.

Personally I’m always leery of concrete patios or paths going right up to a wall, so would be tempted to cut back at least 6” and use gravel, but if you’re sure that the ground levels are ok then probably wouldn’t make much odds

 

[a twig]

If there are airbricks it would suggest that the house used to have a suspended floor and has had a concrete one retrofitted - that can create/exacerbate issues as well so might be worth investigating that, I’ve seen concrete floors where the “DPM” underneath was newspaper painted with black jack

 

[craigr1]

Ok thanks. The airbricks at the front look original. I’m not quite sure on the one in the photo? It’s been added later but not sure why? It doesn’t go all the way through, just for the cavity?

 

[stuart45]

Years ago air bricks were often used to vent the cavity, but they realized that it caused a cold spot on the inner wall.

 

[craigr1]

Thanks Stuart, would it be wise to remove and brick back up?

 

[stuart45]

If it's sole purpose was to vent the cavity, then it's probably better to remove it. If you ever have any doubts about removing an air brick, it can always be blocked up on a temporary basis to see the effects.

 

[MatthewC]

Can you please tell us the relative heights of the ground outside, the floor inside and the dpc? What are the floors made of? As has been said, there's been a lot of water outside that wall - have you checked the rainwater goods above? Do they overflow when it rains heavily? Are there any signs of water down the wall anywhere? Where does the water drain to? There's also been a lot of pretty poor pointing done since it was built which might be indicative of poor work elsewhere. Dampness has to come from somewhere, so trace the source.

A lot of questions, but in my defence I think that a couple of your photos are pretty difficult to comprehend!

 

[craigr1]

Thanks, I’m not sure on the floor, it looks like it has been concreted at some point in the past, it then looks to have a blue visqueen layer and then some sort of black bitumen?

I’ve attached a few more photos to hopefully help. I don’t think the boiler conndesate pipe actually goes to a drain, it appears to be some sort of soak away?

 

[craigr1]

Ok, further investigation looks like this pipe just goes into a hole full of gravel, not a drain.

Also I can’t see any sign of original damp course so not sure it had one?



Internal floor height is about 250mm from external floor height. Floor looks to be filled with concrete, then visqueen and topped with asphalt.

I believe my damp in the kitchen will be solved once I put the boiler condensate pipe to a proper drain. But I’m still clueless to the damp on my the internal walls, it’s on two separate walls I’ve found so far, on the first row of bricks (they’ve had injected dpc at some point in the past)

 

[MatthewC]

Is it possible that the boiler condensate pipe is leaking INSIDE the wall? What is it made of? Otherwise, no ideas come to mind.