A number of oddly placed damp patches

[EddieK19]

Hi all,

We have recently bought and moved into a Victorian house. The surveyor said he measured a small amount of damp but couldnt see any. Once we moved in we found 4 patches significant patches.

I have searched the internet and asked all my friends and these damp patches seem to be different to the typical damp problems. These are the traits.

1. They are in the kitchen, on two separate walls (3 on each) and are half way up and seem random.
2. They are not that near to windows.
3. They get A LOT worse when it gets super humid e.g. drying clothes on radiator
4. I went outside, took 12 bricks out, cleaned out all the mortar (some of it had patches of black which could indicate some moisture). Put in an air brick - and no change what so ever. We couldnt take all bricks around the patch on one wall due to stretcher bricks - but thought we would see a difference.
5. Got persuaded (i.e. conned) to replaced the damp rods on the bottom around the kitchen and then told to get an industrial dehumdifer, leave it on for the weekend and then should be OK. I hired a dehumidifer for a week, left it on for a lot of it. The patches virtually disappeared - not completely but almost all gone. But when we switched it off - it came back within a day.
6. The patches only get bigger when there is humidity caused from cooking or drying clothes on a radiator...at least most obviously
7. The plaster is pretty much solid i.e. not rotting or caving in if it is softer, it is not obvious!

The only theory I can think of is:

• It is likely to be carlite plaster or has salts in these areas
• traps moisture

But in short, I do not know. I am guessing I would have to knock the plaster off and replaster using a different plaster?!

Any help or advice would be greatly appreciated.
I would attached a picture but cannot see a image attachment to this.

Thanks :)

I have uploaded some photos:

drive.google.com/file/d/1HPGd-4oayZ7_Sdkln5I2JqrobZY20CcO/view?usp=sharing

drive.google.com/file/d/120fz7OUmEWJk1OhqFm4jjj9lGS1e4Ya6/view?usp=sharing

I know nothing, but sympathise Eddie.
I live in a Victorian house too and have a couple of damp patches on a chimney breast which also look much worse when cooking, particularly when boiling pans etc.

They have been there for a while but this week they look particularly bad.
My theory is, condensation on cold spots on the wall.
I've tried all sorts to improve things, running dehumidifier etc etc.
I read something on the internet, written by a plasterer, responding to someone's query on a similar issue.
He spoke about "neutralising the hygroscopic salts" on the wall, which attract more moisture.
He made his own neutralising solution of 1 part water to 1 part vinegar and a couple of drops of washing up liquid.
Well, yesterday I tried this thinking I had nothing to lose - next step would be hack off plaster and renew.
I am AMAZED at the effect. Seriously.
The patch seems to have gone completely.
I have also used the cooker this evening and no sign of damp at all.
Clearly,I don't know if this would help your situation but, for the price of a bottle of vinegar it must be worth a shot.
Good luck.

Sounds like the damp course has been bridged in small areas. Don't get a builder/damp proof specialist in - they have a product/service to sell and of course they will give you a quote for repair. Instead pay for a chartered surveyor who will give you a detailed report and tell you the cause and how to remedy it and more importantly how much you should be expecting to pay for the repair. They don't do the work and have no product to sell. I guarantee it will save you money and offer a permanent solution rather than a patch up.

Also adding that damp proof specialist said we needed a new damp proof course. And he needed to knock all plaster off around the whole room. Inject chemical into brickwork and replaster. Cost £2.4k

Surveyor however, said damp was caused by rain water splashing down from roof, landing on concrete path and splashing up onto brickwork and penetrated through to inside because the cavity wall was full of rubble.

Remedy - new guttering to catch water. No new damp course required because we already had one. Rubble needed removing. Yes, plaster needed hacking off (but only in affected area) and replacing but chemical injections were totally inapropriate - a simple membrane was all that was required. He suggested cost no more than £1k.

Injecting wall with chemicals may have kept the damp at bay for a while but without treating the cause of damp it would have come back again in a few years.

Thanks all for the responses.

It isn't guttering or weather related simply as though they are external walls, they are very well sheltered and this happens even during dry weather.

It always gets worse when there is condensation e.g. when my wife cooks and puts wet clothes on the radiator near by (even though I have told her 1000s of times that makes it worse); The patches almost "leak" when there is a lot of condensation around - so they do not rise and not related the weather or guttering.

I guess the most viable thing is the salts....however, I tried making around 1/3 cup of water, vinegar and bit of washing up liquid and kinda seems to have worked on the more shallower patches but don't know how to administer it?! So any help on that would be great!

Thanks again

The patches don't go to the floor and are too high to be a DPC failure. Is it a chimney breast?

Please take some pics of the outside of the wall, including one that shows the guttering above.

Tape a piece of clear plastic tightly to the wall over the patches. If water forms on the room side, it's condensation.

If it forms on the wall side, the wall is wet.

Either stop draping wet washing around, or open the windows.

@EddieK19: My damp patch has stayed away even after making a huge cauldron of soup and having 2 ovens on the go this weekend.

I emptied out a bathroom cleaner spray bottle, rinsed it out and made up approx 400mls of neutralising solution - 200ml cold water and 200ml white vinegar with 2 drops of washing up liquid.
I then sprayed this all over to soak the damp patch area and beyond and rubbed it in with a microfibre cloth. My patch didn't need to use all 400ml but just give it a good soak.
Then I just left it to dry out naturally ie. no heat or anything.
I opened the window a bit to help and to get rid of the vinegar smell.

I had planned to wash down with cold water after and re-paint, but, in all honesty, the wall looks so good, I'm not touching it!

Mine was definitely condensation and also used to glisten on the wall when any cooking was in progress.

I do hope it works as well for you as it has for me as damp in your home is depressing and you can drive yourself insane trying to get to the bottom of it.
Good luck!