Damp spots on walls - Cold bridging? Condensation? Other?

[tui85]

Hello,

I'm in the process of purchasing this flat. It's a 1930s detached house. Ground floor flat.
The property is riddled with damp spots on the walls. Predominantly but not exclusively on the external walls.

We've had our survey done and the damp metre readings are very high around the areas with the damp spots.

The property has been unoccupied for over 8 months. It's double glazed and some of the smaller windows in the flat have been left open.
I believe it's cavity walls (insulated, I don't know ), rendered on the outside (not certain of material but will post picture) and plastered on the inside. Some walls plastered directly onto brickwork, some with batten and plasterboard (according to builder).
The property had a damp proof treatment several years ago, but the company that carried out these works are no longer in business.

I'm really hopeful that somebody/bodies on here might be able to help me ascertain what is causing these damp spots. It's really holding me back from completing on the property. Especially given that I don't have a huge amount of money to invest in repairs.....

Please help if you can, I'd be extremely grateful. I've researched online and spoken with builders, but it's not becoming any clearer and I'm at my wits end trying to get to the bottom of it.

I'd very happy to try to answer any questions you have about the property in case anything needs clarifying...

Many thanks

 

[JohnD]

I believe it's cavity walls

why do you believe that?

the property had a damp proof treatment several years ago, but the company that carried out these works are no longer in business.

if you mean silicone injections, it makes no difference.

is the floor concrete?

 

[tui85]

why do you believe that?



if you mean silicone injections, it makes no difference.

is the floor concrete?

Hi John,

Thanks for your message.

From the structural report....

"The general construction appears to be external cavity block/brickwork walls rendered externally......."

and

"The property has solid and suspended floors at ground floor level with a suspended timber floor at first floor level...."

As for the damp proofing, we have a document confirming that damp proofing was carried out, but no indication as to what that was. As the company responsible no longer exists, we're unable to find out!

 

[JohnD]

To me, the damp spots resembles damp I have seen in a wet house after a severe burst pipe. You say it is on internal walls as well as external walls, so probably not caused by gutter spills or render cracks.

I was thinking that if there is a wet concrete floor, common if there is a leaking pipe buried in it, water could be soaking into the walls, and water vapour evaporating off the floor would give high humidity and condensation on the walls.

Spots would occur if the plasterboard was dot and dab to a damp brick wall. In this case wet spots would have a fairly regular pattern.

If you lift the carpet or other floor covering you will be able go see if the floor is concrete, and if it is damp.

If it is floorboards, take one up. Look and sniff for damp below.

Has the building had a burst pipe?

 

[Harry Bloomfield]

The property had a damp proof treatment several years ago, but the company that carried out these works are no longer in business.

Can you see any signs of a series of hole horizontally and at a low level around the property, probably filled in with a matching compound? That will be the injection points for the silicone treatment.

 

[tui85]

To me, the damp spots resembles damp I have seen in a wet house after a severe burst pipe. You say it is on internal walls as well as external walls, so probably not caused by gutter spills or render cracks.

I was thinking that if there is a wet concrete floor, common if there is a leaking pipe buried in it, water could be soaking into the walls, and water vapour evaporating off the floor would give high humidity and condensation on the walls.

Spots would occur if the plasterboard was dot and dab to a damp brick wall. In this case wet spots would have a fairly regular pattern.

If you lift the carpet or other floor covering you will be able go see if the floor is concrete, and if it is damp.

If it is floorboards, take one up. Look and sniff for damp below.

Has the building had a burst pipe?

Thanks John. When I say that the damp spots are predominantly on the external walls I mean probably around 90%. So I've always considered that it could be gutter spills or render cracks. There is a blocked gutter on one side of the house, but that obviously would only account for that specific location. The render itself seems in pretty good condition. There is some repointing that needs doing on the outside window sills (I imagine there's a more technical term for those...). Of course none of that would explain the few damp spots on the internal walls.

I'm unaware if the building has had a burst pipe. This isn't something that I've considered..... I will investigate this. Thank you.

Unfortunately we've gotten to the stage now where I'm not sure that the estate agent will let us in to have another look. We've been in a few times and they're now really beginning to pressure us to complete..

The structural surveyor suggested that the walls are batten and plasterboard, apart from one which is plaster directly onto the walls. Damp spots are there either way. Is there any possibility that the batten could be bridging moisture/cold in the same way that dot and dab does? I suppose it would be a more uniform pattern if that was the cause though....? It could be that this is dot and dab and that the surveyor got that wrong....?

 

[tui85]

Can you see any signs of a series of hole horizontally and at a low level around the property, probably filled in with a matching compound? That will be the injection points for the silicone treatment.

Hi. Thanks for your response. I looked for these as I assumed that this was the damp proofing work that was carried out. Couldn't find any though!

 

[tui85]

Also, did you notice that in the first image, the damp takes a different form....? They are streaks running down the wall.... Dry to the touch, but at some point moisture has travelled down the wall.... That only seems to be in the one spot..

 

[Harry Bloomfield]

Also, did you notice that in the first image, the damp takes a different form....? They are streaks running down the wall.... Dry to the touch, but at some point moisture has travelled down the wall.... That only seems to be in the one spot..

That would suggest a pipe burst to me. 8 months unoccupied, partly in winter, with no heating, perhaps a pipe froze and burst? Damp from the burst would condense on the other walls. Quiz the seller.

 

[JohnD]

Unfortunately we've gotten to the stage now where I'm not sure that the estate agent will let us in to have another look. We've been in a few times and they're now really beginning to pressure us to complete..

Do you mean "complete?"

If you have exchanged contracts, you are obliged to complete.

If there are signs that water has run down the walls, it is either a leak from above, or severe condensation as might result from a wet floor due to a leaking buried pipe.

A leak from above is likely to mark or damage the ceilings and light switches.

Perhaps you should look for another home.

 

[tui85]

My mistake, I meant "exchange".....

If it was a burst pipe that is causing this damp, what would you suggest is the prognosis? How serious would that be? What would be the potential fixes?

A friend of mine that is part time builder/handyman has suggested that there may be water ingress via the "lip" between ground and first floor? We'd have to get a ladder to take a look if there are many cracks in the render there, but does this seems feasible? He's also suggested that the ground around the house is too high and that lowering this in order to help take water away from the house may help solve the problem.... Is that just wishful thinking?

 

[JohnD]

The wall with the chimney is wet. Probably spilling gutter.

 

[mrrusty]

I have seen this in my own house, particularly a few months after we D&Dabbed plasterboard straight onto internal walls. In our case the bricks on the affected walls had been exposed to coal fire fumes for 100 years and are hence fairly loaded with the salts that are created when combustion products react with lime https://www.heritage-house.org/damp...-have-i-got/salt-damage-in-old-buildings.html . What I found was that the water in the dab adhesive drew salts out of the brick which migrated through the PB and skim. These salts are very hygroscopic and showed up as dark patches on the skim coat exactly corresponding to the dabs. (mid wall -not near the bottom) Left to their own devices they grew a very slight crystallized surface. 100% not leakage, rising or penetrating damp.

Heating cured 95% of it, but still found a small amount of "roughness" on the paint coat corresponding to the dabs after a few months - the salts suck water vapour out of the air and grow. I have 99.9% cured this by patch painting damp resistant paint where the problem areas were https://www.amazon.co.uk/Ronseal-OC...ocphy=9046534&hvtargid=pla-420369330702&psc=1 and then re-emulsioning over the top. The damp proof paint seems to stop room air getting to the salts and the slight problem has been eliminated.

IMHO condensation and cold external walls with or without any salt poisoning is responsible for a huge % of so-called "damp" issues.

 

[Mr Chibs]

Tap the effected areas, if it’s solid in sound but hollow around the stain, this could corroborate the advice above.

Seems plausible to me.

 

[tui85]

Hello, thanks for your responses.

Yes mrrusty, hygroscopic damp is another thing that has come up in my reading around this. I've also spoken with an independent damp specialist today, and having seen the images, has also suggested that this is quite possibly hygroscopic damp. Thanks for explaining what you did to solve the problem.
My issue here is that according to our structural report, the walls are batten and plasterboarded. So in that case, the dot and dab hypothesis doesn't quite work out..... I am open however to the idea that the structural surveyor may have mistaken dot and dab for batten and plasterboard.

I like the idea of tapping around the stains Mr Chibs and if we're able to access the property again before exchange, this is the first thing I'll check.

JohnD, the wall with the chimneys is clearly wet and covered in algae. Could this be a symptom of anything in particular is this just par for the course for an old and not particularly well cared for rendered house?