Mystery patches on internal wall - please help :)

[Yazoop]

Hi there,

I've not posted on Property / DIY before, and I'm not great with this stuff - wondered if you wonderful people could help :)

Today I noticed two long stripe-type patches on my internal living room wall. They look like big smudges. I think they have just appeared (it is certainly the first time I've noticed them!)

I live in a Victorian first floor maisonette (so it isn't rising damp or anything like that). The patches are nearly a third of the way up the wall from the floor, on either side of a small dining table. It doesn't look like a leak and they don't feel noticeably damp/wet. The wall is shared with our neighbours. Pictures attached (they are more noticeable in the pics than in real life).

We don't have any big damp issues, other than a bit of damp/mould we had in our bedroom at the other end of the house (which has two external facing walls and is the coldest room in the house). To combat this, we have a dehumidifier in that room and make sure we open windows when cooking / showering etc. This basically solved that issue.

However, I have a hunch this is related to condensation due to the severely cold weather we've had this week (we've kept the place warm - so maybe cold meets warm air?). What do you think? Any other suggestions?

is there a bathroom or kitchen on the other side of that wall? Are the marks at about the same height as a bath or sink?

There may be water pipes in the wall. Have a look at the position of visible taps or pipes to see if that fits.

Tape some clear plastic or clingfilm tightly to the wall over the marks and see if water forms on the wall side or the room side of the plastic.

Have you been draping wet washing indoors?

Thanks, PigletJohn.

As far as I know, the other side of the wall is also a living room. This type of maisonette has a set layout, and it wouldn't make sense to change that front room to a bathroom or kitchen, so I don't think there is a sink or bath on the other side.

I'm guilty of drying wet washing in our spare room (which is next to the living room but not connected to the particular wall in question) in the winter. We don't have a tumble dryer currently. I try to leave the window open to ventilate while I'm drying but it has been too cold to do this over the past couple of weeks - so I guess this could have something to do with the patches?

I'll try the clingfilm test - thanks for that tip!

if you have a extractor fan, that works, in the bathroom, you can leave it running while draping wet washing in there, with the door and window shut. It will at least suck the water vapour out and prevent it drifting round your home.

I had marks like this on the bedroom wall. It was because an old fireplace had been removed and a vent hadn't been put in place. Got one now and the problem has gone. Fairly easy to remedy if yours is the same.

Ah yes - that's a good idea. Our extractor fan is not the best (I'm looking to replace it), but better than nothing. I guess a small dehumidifier would also help?

Thanks @Littlewhistle - this might be the case, we have our fireplace but it is blocked up. Will look into it!

Do you use candles? I've heard of some certain candles burning and the soot gets attracted to cold patches of walls (normally along the lines within breeze blocks etc). Could they be soot??

Don't use candles @knockknockknock (or at least I haven't for a long while). But do agree it kind of looks like it could be soot.

Do you use candles? I've heard of some certain candles burning and the soot gets attracted to cold patches of walls (normally along the lines within breeze blocks etc). Could they be soot??

Google thermal tracking

Don't know why it posted twice. Do you have a fire then??

I have an old fireplace, but it isn't functioning. Don't think any of the neighbours use their fireplaces either, so I actually don't think it can be soot. It just looks a bit smudge-y.

We live in a semi detached cottage built in 1897 and the internal walls between the cottages on our side had similar mysterious patches which we never got to the bottom of .Couldn't understand why they showed halfway up like yours. Had walls damp proofed twice and next door did the same to no avail and in the end we dry lined so we didn't have to look at it any more. I sometimes wonder what's going on between the internal wall and the dry lining but try not to dwell on it.

It's weird they are exactly the same height as the table - does the mark continue behind the table or is it just either side?

@Celticdawn5 how interesting. It is hard not to worry but maybe it is just a ventilation issue due to the age of the property?

@seeline - I know - it is weird! it trails off behind the table, and then gets worse again once the table ends. This makes me think it isn't a leak and is condensation related (as the table traps in the heat somehow??)

It's not something like the back of chairs rubbing against the wall or something, or people leaning against the wall whilst sat at the table?
Does the wall feel cold/damp?

@Seeline. It doesn't really feel very damp, a little cold maybe.

We don't sit leaning against the wall but beside it - so we could rub the occasional arm on the wall but are not constantly up against it.

It is one of those tables that extends at either end. As there is only me and DP, we only have one side extended out and at meal-times the two of us sit on opposite sides of the extended bit, parallel to the wall, if you know what I mean?

Yes,ventilation is very important.Sometimes you just have to accept that older properties will have some damp.furniture such as wardrobes are not pushed right up to the wall.We are very careful not to drape damp clothing about and bathroom door kept closed etc However until today I was not aware of anyone else who had the mysterious damp patches such as ours.The so called experts who came and looked had no idea.

Yazoop We always found these patches appeared in cold weather - never in the summer. All ours needed was a hole gouged out, a vent inserted and the hole plastered up.

We were worried it was some sort of damp issue, but happily not!

We have the same thing - going across the middle of an internal (shared with neighbour) wall. It’s a Victorian semi and we’ve had all sorts of people to look at it and no one has a clue, so we are about to have it dry lined like Celticdawn!
Ours is above and next to the radiator but even the heat from that doesn’t ever properly dry it. It is bizarre.

Thanks, everyone - seems a more common thing than I thought! I'll try using my dehumidifier in the front room and hanging washing in the bathroom with vent fan on and see if that makes a difference. I do think it is to do with the sudden cold spell - as never happened before.

More often it's temperature or damp related, but I have sometimes seen odd marks where the texture under the paint changes, for example where a dado rail has been taken off and the gouge replastered or filled with a different material; or where there is gloss paint that has been covered over. It might be to do with different absorbency.

This (and other queries regarding untraceable 'damp') could in fact be the result of hygroscopic salts present in the brick and plasterwork. These are typically found on or adjacent to chimney breasts in old houses. They could be on walls which back onto chimney breasts. They are formed as a result of years of burning coal in unlined stacks.

The 'damp' is actually caused by the salts in the plaster constantly wicking moisture from the air. Many houses have erroneously been treated for rising damp as this problem is less commonly understood.
Rentokil's treatment (expensive) is not scientific but works. They chip off all affected plaster and that surrounding to provide a good margin. They paint bitumen based paint on the brick (Black Jack or similar) and then re-plaster with some form of moisture repellent plaster - all to stop the moisture in your room from meeting the salts which stay trapped in the bricks. If the two cannot meet your 'damp' problem will go away.

Did you ever get to the bottom of this OP!? I have come across two patches like this in my kitchen on the wall next to my fridge. They’re similar to yours but vertical! X

Not really, but ruled out leaks or dampness! And it didn’t change or spread. We think it was simply marks where we had previously had a sofa against the wall rather than anything more serious! So could be from the fridge being close against it, the fridge door opening on to it, or people bumping up against it? Sorry that might not be of much help!

Thank you