Damp. :( self help required.

[Hanlonsamazer]

This is an internal wall, brick and flint (was external about 150 years ago). New roof and nothing unusual above the wall. Have had the dehumidifier running for about a week and zero change. Lived here 15 years and it’s not happened before! it was behind a sideboard which has now been moved.

I absolutely cannot afford to do anything to the house until the new year, until I can get someone to look at it, what should I be doing.

If it suddenly appears on an internal wall coming up from the base I would guess a pipe leak.

Four types of pipes. Radiator pipes. Cold water, hot water, foul water drain.

Leaks from pipes under pressure probably appear more quickly and are more likely to happen.

If you have pressurised CH has there been a pressure drop recently ? This could indicate loss of radiator coolant ?

Where are the nearest pipes to that wall ? Are there any pipes internal to it or under the floor next to it ?

sorry radiator water not coolant.

I think it's a leak too - we had the same and it turned out to be a pipe from the radiator

That looks like a leak to me too , to have appeared that fast it’s got to be either a pipe leak from the roof somehow running down . What’s on the other side of the wall ?

When was your floor laid?

Definitely check for leaks, but it been a very wet summer so lots of us in old houses that haven't been kept properly breathable as a result of past use of 'modern' impermeable materials, are experiencing more moisture in the walls than usual.

Thank you so much. These are the nearest pipes, nothing goes through the wall or is on the other side. You can just see the left margin of the damp on the right of the picture.

No loss of pressure, bathroom and kitchen plumbing is all on the other side of the house.

Could it be an underground spring? When we moved in there was a mouldy carpet hidden under some more hideous carpet in the room on the other side of the wall (which is like the under stairs area where the dogs live).

The stairs and where the dogs live! No pipes or radiators.

If there was moisture coming up under the carpet, and then you've put tiles on top to seal it, it looks like it's instead coming out through the walls. I'm guessing the walls are gypsum plaster and emulsion paint?

Floor was laid in 2009.

Mouldy carpet was in the next room but we’ve put quarry tiles in there now, I now know slate isn’t breathable (didn’t know we had damp when we did the floors, just thought the bloke was grotty!).

No idea what the wall is plastered with, if we re-did it with lime plaster, might that help?

Why has it taken 14 years to show!?

Do I just keep dehumidifying until I can get someone in?

Replacing with lime would definitely help.

I need to do that with my house, been here 13+ years and this year is the first with substantial moisture coming through.

Dehumidifiers can contribute to drawing out more moisture from the walls, more passive ventilation, from windows and through drafts, can be more useful in old houses.

The FB group 'your old house UK - repair and conservation' is worth joining.

Is piglet John still on Mumsnet?

Thank you. I did think this about the dehumidifier! Will move onto passive ventilation. Upstairs windows are always open and kitchen when we cook, I’ll get these ones open and give the dehumidifier a break. No doubt we will light the stove soon!

That seems weird.

Can you access the other side of the wall which I assume is the space under the stairs ? is that wet too ?

I have seen a problem before where water drips from above, down the cavity in the wall and pools at the bottom. The water then leaks into the wall and moves up it by capillary action. But you say it is a solid wall, so hard to see how that would happen.

Is there anything underneath the wall other than the concrete floor ? A cellar maybe ?

It's really not weird at all @GasPanic, it's a completely inevitable result of decades of poor understanding of old solid walled buildings and the use of inappropriate materials. It's very very common for many of us who become custodians of such homes.

The other side isn’t at all damp but it’s also not plastered and we don’t paint it. I can’t access it at the moment to take a pic bcse there’s a wardrobe in the way that I can’t fit up the bloody stairs. (Wardrobe blocking the door, not against the wall).

I wish there was a cellar but I don’t think there are even foundations.

Im hoping it’s the wrong plaster and a wet year… that might not break the bank in 6 months or so.

Now we’ve learnt, we are trying to use traditional methods and materials but it’s such a slow process, very expensive, and almost impossible to find reliable tradespeople.

It really is. I made mistakes when I first moved to mine (1830s rubblestone), mainly for urgency/safety but I'd do it differently now if I had my time over. Now I know, I'm resigned to living with it until it can be done properly.

I understand that if the floor was permeable before then moisture could escape from it. If it is then sealed with tiles, moisture could then build up beneath over time and eventually get to the wall, which it climbs up via capillary action.

What I don't get is the relative speed of the process.

If the above was happening, I would expect it to be a slow event. Over time the water would build up, and soak up the wall slowly.

But the OP implies it has appeared rapidly (?).

If the leak comes from a reservoir of water under the floor and has climbed up the wall rapidly, that implies that that reservoir of water under the floor has increased significantly recently ?

Where do your waste water drains go, do they run under the floors?

And yes, I think @pigletjohn is still here sometimes. I'm always very impressed with their advice.

It's been a strange year and this doesn't appear to be that uncommon this year!

And OP did say it was behind a wardrobe IIRC so maybe not that sudden.

Would there not be black mould growth if it had been there a while?

Ah so it is weird then :) !

Maybe a two pronged strategy would be to check the drainage outside the house and make sure the roof run off/foul water drains are working effectively and possibly a drain inspection. Also if there is any water pooling outside the house.

I kind of see where you are going with the lime plaster. Effectively you are trying to create a "humidity radiator" as large as possible and engaging the walls to replace the floor radiator which has been sealed. The larger the surface area the more humidity it can "radiate". But it still strikes me very much as a sticking plaster re the real issue, excessive moisture beneath the house.

I am not convinced about drafts vs de humidifiers either. At the end of the day to remove the moisture you need a humidity gradient. The higher that gradient the more moisture you will pull out. That gradient can either be generated by dehumidifiers or ventilation (depending on the humidity of the ventilated air coming in), it's the same thing.

There is maybe a question on whether it is a good idea to draw moisture through the internal pathway though. For example, drawing moisture in and out through the internal wall ensures that pathway remains saturated, whereas there might be an external pathway that is more effective in pulling the water out. I think it's unlikely that that pathway probably will be established in damp winter conditions though.

It's an interesting problem to speculate about. Sorry OP :)