Salty/fluffy damp - how do I identify the source?

timefortea

Hi forumites,

I’d love some advice on my damp issue. I’ve read a lot about damp in old houses and it’s made me very nervous to get a professional in. 

My house is a late victorian terrace, built in 1899. I have damp just on the corner of one internal ground floor wall. It doesn’t feel damp to the touch and I never see condensation in this room. It’s a back porch/utility, no one’s in it for any length of time and I don’t dry washing in it but it is colder than the rest of the house (though there is a radiator). 

I don’t know whether this is relevant but there’s a radiator on the other side of that wall (in the kitchen). I’ve included the floor plan with the damp spot and the position of the radiator marked. I’ve also included a picture showing the other side of the wall from under the floorboard level (there are original built in cupboards and the space under the bottom drawer is just open). The darker bit of wood maybe looks like water has travelled up it at some point, could that cupboard be conducting water up the wall? There’s a radiator in between that and the visible damp though. 

The bottom of the affected wall feels cold but not damp. 

My house generally is cold. It’s usually heated to 13-15 degrees in winter, maybe 16 if I’m feeling flush. 

I bought the house 4 years ago and the problem has just got worse since then. I don’t know whether the previous owners ever did anything with it. 

Can anyone suggest where I should go with this? I’ve read that there’ll be a slate barrier at the bottom of the wall and I should check whether that’s been breached, but I don’t know how I’d get to that without doing more damage than I can put right myself. I think it’s odd that the other side of the wall isn’t affected, is the problem that the radiator on the other side is causing a difference in temperature? 

There’s no man of the house, it’s just me and my DIY skills are very basic  

twopenny

The under cupboard bit looks a darker colour near the wall and there seems to be water marks on the wood divide.

I had something similar on a wall with the paint blistering and found that the gutter had a dripping overflow into it and somehow the block at the end had worn away allowing the brick to get damp enough to make the paint blister in one room. It also got into the back of the stair well and upstairs loo and damaged the skirting.

All for a drip!

It's possible that the cold air coming from the hole in the side where the copper pipe comes in would draw cold air. The pipe may also create condensation and keep it cold.

The radiator on would drive any moisture out of the bricks to that side.

If it were me I'd sand down the damaged part, clean and leave to dry out throughly during the whole of the hot summer we're going to get ........I hope. Then you can repair.

Also get a torch and look through the hole where the pipe goes to see if it's damp in there. Cotton wool on the end of a cane if you aren't sure. Leave for a few days and see what it's like when you remove it. When not damp then seal that hole properly so the cold is not drawn in. I had to do this to my old house.

One thing I notice is that beautiful edging around the floor and skirting is preventing any air cirulation by sealing it. So it's probably just sealed in any damp or condensation.

Like you, just me and some diy skills. I managed to deal with it though it took a couple of goes, trades didn't want to know, but I got it looking just dandy - while grumbling/worrying all the time.

RedFraggle

Looking at the plan I'd say your downstairs WC and cupboard used to be an outside loo and coal shed and it wasn't intended as an internal wall so won't have been built as such. Is that back end single skin? 

timefortea

twopenny said:

If it were me I'd sand down the damaged part, clean and leave to dry out throughly during the whole of the hot summer we're going to get ........I hope. Then you can repair.

Also get a torch and look through the hole where the pipe goes to see if it's damp in there. Cotton wool on the end of a cane if you aren't sure. Leave for a few days and see what it's like when you remove it. When not damp then seal that hole properly so the cold is not drawn in. I had to do this to my old house.

Thank you for your really thoughtful reply - it's encouraging you managed to get your own problem sorted. When you sealed what did you use, was it the usual sealant or something that would allow a bit of moisture to pass through if needed, just not cold draughts? Because of everything I've read about old houses needing to breathe I'm nervous about blocking air flow. That pipe comes out into the utility room/boiler cupboard on the other side of the wall, and it's sealed on that side, though I don't know what's happening in the gap between that wood and the wall - I know mice can get in, hence the foil. 

RedFraggle said:

Looking at the plan I'd say your downstairs WC and cupboard used to be an outside loo and coal shed and it wasn't intended as an internal wall so won't have been built as such. Is that back end single skin? 

That would make sense. The external walls in that WC and cupboard area are thin, much thinner than the wall with the damp problem. Do you think that the wall being built as an external wall then changing function to an internal wall would cause this kind of damp somehow?

twopenny

Well you may laugh but it was cardboard and tape. That's because it was supposed to be a trial but it worked so I left it

This was two understairs cupboards with an outside wall and pipes between them.

I've done the same with my new place where the cold pipe/stopcock is under the sink and a larger hole cut through the kitchen cupboard floor and a freezing draught through.

The card won't work against mice. You need a very fine wire mesh like they used to use on meat safes.

But I'm thinking this has happened a while ago, maybe when it's been unheated  because it takes some time to get into the wall like that......we've had exceptional heat and cold in 6mts

Yes if the wall was made internal recently.

Could be you keeping the house warm has triggered it?

flashg67

I've had/having  similar issues in an old house and have found that scraping the paint back to the plaster in the affected area and using a breathable paint such as lime wash, this has cured the vast majority of the problems I've had, which are in cold spots and areas hidden behind furniture etc. Moden emulsions seem to have latex added and retain the moisture allowing mould to grow