What is this?

[Iwasjustasking]

My house is 106 years old and have recently moved in (around about a year) I have been noticing these round marks on my walls recently, I don’t think it’s a water leak and my partner seems to think it might be where they have dot and dabbed the plasterboard? This is a back external wall but also have similar on the ceiling in the living room, can anyone advise?

We have had this in our 1920s house, mainly in the living room around the chimney breast (external wall) and French doors. We had an independent damp assessment company out and apparently it’s mainly condensation. (Though some repointing needed on the chimney stack, which may be letting moisture in.)

The main reason for the condensation in this room is that a) the French doors have no way of opening just a window and we rarely use the doors and b) the previous owners added insulation plasterboards in the alcoves to keep the house warmer - but these are stopping the walls from ‘breathing’ and need to be taken off and lime plastered instead.

The assessor also discovered our bathroom extractor isn’t working, despite being louder than a jet engine. He just held a piece of toilet tissue up against it to test, and it didn’t move!

Thankyou for replying, I had a thought it might be condensation as we have had a problem upstairs on the floorboards which has been confirmed as condensation, do you know if there is anything we need to do, or just try and ventilate them room more? I thought of getting a humidifier but wasn’t sure if this would dry the bricks out to much in an old house?

It’s really hard to say what’s best to do, sorry. If budget allows, I would recommend getting in the experts for a damp survey. We used Alpine Surveys and it was just under £400 (about 18 months ago). They provided a really detailed report with their recommendations.

Don't dry clothes indoors on airers.
Make sure the bathroom fan works, or open the window.
Buy a dehumidifier - it'll be less than half the price of a survey.

Thankyou, unfortunately we can’t use a dehumidifier as the house is so old we have been told it will dry out the walls too much and cause problems.
i was going to get a damp survey but unfortunately this close to Christmas cannot afford it at this time, I think I am going to have to ventilate/heat and keep my eye on it at the moment.

@Iwasjustasking I have never ever heard of a house being too dry, who on earth told you that? 100 years really isn't that old.

Optimum for people is about 50% relative humidity.

@Daftasabroom two different builders have said it will dry the mortar out too much?? I haven’t got a clue whether this is right or not and don’t know who else to ask!! My house is extremely humid and I think that is what’s causing the condensation but I don’t know how to fix the problem without a dehumidifier? Can I use a dehumidifier?

You would need some kind of super powered industrial dehumidifier to suck the moisture out of the mortar ( through the plaster ). I think your builders are exaggerating a bit. A small 12l one will be fine.

It certainly looks like plasterboard that has been dabbed on. It could be damp striking through the drywall dabs but if its only recently appeared it could be due to the outside cold striking through to the warmer inside air.

A dehumidifier will dry out the walls of an old house too much? I assume you live in England and not in the Sahara. I don't think that will ever be a problem in an old house.

I also think that comes from outside. Try and get everything off that traps it there ( is it drylined?) and then ventilate and create dry air (extractor fan, dehumidifier, heating).

Our house is 98 years old. We run a dehumidifier all winter and have done for the last 20 years. It doesn't dry out the mortar, we've not suffered from any 'drying out' issues - but we can dry washing over night in the bathroom and don't suffer from mould in the bathroom.

If it was builders that told you not to run dehumidifiers, they were either thinking of the big industrial ones (which would be silly to consider running in a house full time) or were hoping to get some nice work from you when all the plaster falls off because it's got so damp!

Thankyou all, I am going to look into getting a dehumidifier and try and dry it out, we have had condensation in the bedroom too and we do really need to get it sorted. My last house was a new build so I just trusted what the builders said about the mortar, I have no clue!

Also just to answer above queries, we have lived here a year and a bit and it has only happened in the past few days, I don’t know if the wall is dry lined, I suspect the old owners did everything really cheaply so probably not. My house is render, concrete and brick but there are no cracks in the render near this bit, this is the kitchen and we don’t have an extractor fan, or any windows that let fresh air in (the window is attached to the side conservatory) so it could possibly be condensation/damp that has got into the dot and dab of the plaster and a dehumidifier would help with that? And also getting an extractor fan for over the oven? As you can tell I am prettt clueless!