Damp / Water Ingress Problem?

[newforestcottage]

I have a damp / water ingress issue, which I'd like to understand better, and solve.

We live in an early c.1900 red brick cottage, with uninsulated cavity walls. This is the only room suffering from this problem, on all three external walls.

As you can see in the photo below, there are some obvious water marks around the window, and on random areas along the wall. Not all these patches reach the ground, so whilst I'm sure there is a [slate] DPC breach somewhere on the internal leaf, they don't all appear to come from below. Saying that, they appear no higher than 5/6ft. I suspect it's mostly down to the cavity wall being breached by debris (?) but this seems very high for that too. They are not wet to touch (which I presume rules out condensation). There is some very very minor peeling of paint around the window.

I'm able to run a dehumidifier overnight, in the meantime, which keeps it at bay, but they never fully disappear. This is it, at it's worst.

I am unable to see into the cavity, for obvious reasons, but do intend to extend our hallway (left) with a front porch at "some point in the future", which would allow me to look down there and investigate with more certainty. But until then, I can't.

The floor is a raised timber floor, if that's in any way helpful?

Ultimately, what is the correct thing to do here? Happy to provide more info and/or share more photos. I'd like to better understand potential causes, and how to fix it (obviously there are more costly solutions, and more budget friendly ones, so I'd just like to understand options, and what the journey is to get from "this" to solved).

Needless to say, it is worse at this time of year, and not a problem at all during the summer.

investigate more

 

[Wayners]

I you sure its a cavity wall? Unlikely with that age of property.

 

[newforestcottage]

Yes, certain. We’ve done structural work on other parts of the house, and it’s cavity wall. Early cavity wall.

 

[newforestcottage]

I’m not adverse to getting into that cavity, if required. I’m wondering if removing the window might help (not that I’ve done that before) as it’ll be a very central location from which to remove any rubble?

 

[23vc]

What’s the outside wall(s) like in terms of how well protected/pointed, any leaking gutters/downpipes etc. Photos will help

 

[newforestcottage]

Gutters are fine. No downpipes. I’ll add some photos of the external wall …

 

[newforestcottage]

You can see some of the pointing has been affected by metal planting ties, which the previous owner put in. I’ll remove these and fill the holes, but even then, that shouldn’t be enough to breach the cavity to this extent, should it?

 

[noseall]

You can see some of the pointing has been affected by metal planting ties, which the previous owner put in. I’ll remove these and fill the holes, but even then, that shouldn’t be enough to breach the cavity to this extent, should it?

The brickwork looks in good nick for the age and seems to be well maintained. I'm wondering if it could be a tie iron issue? Or perhaps a hygroscopic issue? I hate damp problems because they are rarely obvious. Is it a rainy day thing? Is it a low temperature outside thing? Year round thing?

 

[newforestcottage]

Yes, it’s mostly about low temperature, I’ve found.

Whilst it does happen after it rains, I find dry but cold mornings produce more/stronger stains compared to mornings after overnight rain. So perhaps the rain is irrelevant?

If it’s due to the cold, what’s the cause, and possible solutions?

Only ever at this time of year. Summer produces no problems at all and the dehumidifier disappears into the loft.

 

[ToolboxTalks]

Since the patches are not wet to touch, it might still be a moisture issue from poor ventilation and cold walls, not just water ingress. You are running a dehumidifier, but maybe look at adding an extractor fan to this room. I'd definitely check the exterior of the house first for bad seals, cracked pointing, or blocked gutters, because those are often the cheapest fixes.

 

[mrrusty]

Needless to say, it is worse at this time of year, and not a problem at all during the summer.

I also live in a 1902 house with an early cavity. When we acquired the house, the main back room had had a coal fire every day for about 120 years (the house was built by wifes great grandfather and we know the history). The lime plaster walls of this room were sodden with condensation from wifes uncle, who was born in the house, living basically in one room. Once stripped to brick and left, they dried out - not "rising" damp!!

We have completely refurbed the house, and since doing that we have found that the walls of this room are incredibly salt poisoned through the combinations of condensation, combustion gases and lime. We have found walls directly exposed to wet trades, particularly wet dabs, allow salt migration and random "damp" patches through surface salts which show up, sometimes high on an internal wall. We have also found that those walls where we have used plasterboard but fixed with foam adhesive have no salt migration.

The problem seems to be that when wet trades are applied to salt poisoned bricks, as the water in the dab evaporates to the surface, it draws hygroscopic salts which then are very prone to drawing condensation/water vapour from the air which show up as damp patches. We have had limited success, painting these areas with damp-seal paint before re-emulsioning (limiting room humidity getting to teh salts), but the 100% remedy has been stripping back to brick again, isolating with SBR slurrey, and re-plasterboarding using foam adhesive. Problem eliminated.

I certainly wouldn't contemplate filling a ventilated cavity because IMHO this is essential to dry the cavity should any insterstitial condensation or penetration occur.

This may not be anything to do with your property, it is just one of the challenges we have had converting an edwardian house in to an insulated modern home (with incidentally now an EPC C rating) and a commentary on the observations and remedies we have seen and tried. However, if your room was ever a main occupation room where it is likely a coal fire/range was used routinely, it might be worth thinking about salt poisoning and all the "damp" just coming from the water vapour in the room. The fact that it happens when the room is cold points to condensation as a source of liquid water - the dew point of 20 degree 60% humidity ambient room air is just 12 degrees, and somewhere within the temperature gradient in that wall between the warm inside and the cold outside will be the dew point of the room air.

The salts are formed because sulphurous, carbon and nitrogen combustion gases combine with water to form sulphuric and other acids which then react with lime to create sulphate, nitrate and carbonate salts, which are hygroscopic, drawing moisture and growing crystals.

Here are a couple of dab "damp patches" caused by salts on a single skin internal wall which has had PB dot and dabbed and which divides the room described above. These are approx 2m above the ground level under the floor, with that wall, with a slate DPC, standing on corbelled brick footings over clay approx 800mm below internal floor level. The only place the damp can conceivably come from is out of the room air.