Damp on internal party wall

[SJRSJR]

Hi. I'm wondering how I can solve my damp problem in the living room.

It's about 12 inches above floor level along an internal party wall of a terraced house built in 1895. There's no staining, mould or effluorescence just a darker area of paint.

It's two rooms knocked into one with two chimney breasts front and back. The damp meter readings reduce towards the centre of the room so I'm thinking it's to do with them. One is open with a DFE gas fire and the other has been blocked and plastered over with no air vent. I know it should have one but it's been like that for the 20+ years I've had it and it's only in the past year I've noticed the problem. Also the front of that breast is less affected, it's far more obvious on the side and front of the chimney breast where the fire is.

I had someone out last year who said I needed my chimneys capping, which I did, but nothing has changed.

It's a large well ventilated room, no damp clothes drying out and no leaking pipes. I'm changing the skirting and the nails and screws coming out are rusty and the brick dust is damp. I've got a laminate floor down so can't get underneath but it seems well ventilated as I can feel the draught at the edges.

My neighbours say they don't have a problem (their chimney breasts have been removed).

Any suggestions? Thanks

 

[JohnD]

Wet ground. Take up the floor and have a look. Don't grumble about having to take up the laminate.

What makes you think there is no leaking pipe? I bet there is.

Have you got a water meter? Has your neighbour?

 

[SJRSJR]

Thanks for the reply. The other walls are okay so wouldn't it affect all of them? From memory there's a decent sized void below, would that make a difference? I've had my nose to where the draughts are coming from and it's not musty.

I've got a water meter and it didn't move when I was away for six weeks. I did wonder if it was down to the heating being off but it's been back on for ages now. I'll ask my neighbour about her meter but both our mains pipes come in on the opposite side to where the damp is. Neither of us have radiators against that wall either (and I've never had any loss of pressure in my boiler).

The laminate is decent quality and glued so I'd only want to pull it up once I've eliminated everything else. I've used the damp meter where I can get to the chipboard subfloor edges and they seem ok.

So you don't think it could be condensation in the chimneys breasts?

 

[vinn]

There's no need to lift any laminate.
Where the flooring below the laminate contacts the wall is it damaged?
Its possible that the soil infill below the hearth is the source of your moisture. So i would very closely examine the other side of the chimney breast and party wall.
Your floor joists might run into that wall & will be trimmed around the hearth.
The trimming and the joist ends seated in the wall might be at risk of rotting so its best that you go below the floor and examine the situation around the hearth and chimney breast. Probe all the woodwork. You might have an access hatch under the stairs.
A posted photo of the full fire place and chimney breast might help.

Does the flue have through ventilation from behind the deco fire through the stack terminal?
When was the flue last swept?
You have a Restrictor Elbow and an old style gas isolator on the gas supply pipe: only the Restrictor is usually needed.

The other, blocked, chimney breast and flue should be opened at some convenient time and swept & vented top and bottom.

 

[SJRSJR]

I got to the edges of the boards under the laminate, they seem fine. They've haven't rotted and the only bit that is giving a higher damp reading is where it was in contact with the wall, there's a small gap elsewhere.

I've been into my neighbour's with the damp meter and their side is sound and dry, although they did say the gutter had been dripping into their garden, which might account for the damp to the right of the plain chimney breast. It's worse in the alcove than the chimney breast itself.

There's no hatch to get to the underfloor. I have an understairs cupboard on the other side of the room where I could create one but I don't think the void would be deep enough to crawl through.

When you ask about flue ventilation behind the fire, do you mean between the void and the chimney pot? If so I don't know. I had a ventilated cap put on the chimney pot in November because a roofer told me the damp was caused by rainwater bit it made no difference. It was last September 20 years ago before the gas fire was installed. How often should it be done?

If it is the soil infill below the hearth what can I do about it if I can't get under the floor?

I've got a damp firm coming out next week. Any thoughts on what I should be wary of agreeing to? Thanks.

 

[vinn]

You should be wary of everything, and count your fingers after shaking hands with a Damp and Timber salesman. Listen to what they have to say or report, and then come back on here with it.
Your neighbour's could have removed their hearth infill along with their chimney breasts.
Lift a board under the stairs and see what space you have. Going under and examining things is good practice. At least you will have a better understanding of how things are.
There should be ventilation above the deco fire - shine a torch up the flue.
The other chimney breast should be opened and swept.
A photo showing the outside wall where the leaking gutter has been dripping might help. I suppose you are getting the gutter fixed?

You would have nothing to lose by going into the loft and examining the loft chimney breast for damp or stains.

 

[SJRSJR]

Sorry for asking a dumb question but when you say 'ventilation above the fire' what do you mean? It's wide open and goes straight up the chimney.

It's a three storey house and the four chimney breasts in the rooms above are all sound. The loft ones are okay too. I asked the roofer to check when the chimneys were capped in case there was a problem with the flashing.

I can't get a photo of the area where the gutter has been dripping right now because it goes into my neighbour's garden.

Will come back with the damp report. Should I be wary if they want to inject chemicals - won't that just send the problem somewhere else?

Thanks

 

[SJRSJR]

Well I had my damp inspection, which was diagnosed within 30 seconds and he was gone within 5 minutes. He slid his damp meter up the wall and said 'rising damp' caused by a broken DPM. Said that it was particularly bad around the chimney breasts because when these houses were built (late 1800s) no one paid much attention to the DPM around fireplaces because they expected an open fire would always sort it.

I tried to offer up condensation in the chimney breasts - no because there'd be black mould. Leaking guttering - no because it would be present half way up the wall, not from the bottom up. I didn't even get to soil infill in the hearth or a leaking water pipe because he was heading for the door with a promise to email the quote to hack off the plaster up to a metre, inject silicone cream, apply sand and cement render and a plaster skim.

Is that a tried and tested solution or just putting a plaster on a broken arm? Thanks.

 

[SJRSJR]

Hi, I posted this a few weeks ago and I've since become paralysed with indecision. I'm hoping someone can kickstart me.

For the alcove of the plain chimney breast I'm getting the guttering looked at on the rear of the house in the hope that it is the cause of the damp. That leaves the chimney breast with the fireplace.

Even though the room doesn't feel damp I went with a friend's offer to borrow a de-humidifier. I set it to Auto however it kept turning itself off and wasn't collecting any moisture. I had a call from the 'damp specialists' which only made me even more certain that I don't want to use them. I then decided to commission an independent damp survey from Property Care Association but I read here http://www.heritage-house.org/ that their members have a vested interest in perpetuating the rising damp 'myth'.

So before I get the floor up I have a couple of questions:

What is a failed DPC? My damp is on an internal party wall in a terraced house built in the late 19th century. I assume that it will be some sort of slate layer. How might it have failed if it's been quietly standing there, no renovations, no movement, no exposure to weather etc. And even if it has failed, how will getting the floor up make it any easier to fix, won't I just have to go down the chemical injection path?
The darker area of paint that alerted me to the dampness isn't stained, blistered or flaking. It doesn't change shape whether the heating is on or off. I read elsewhere on here that damp at the base of a wall is just normal and if it's not stained or flaking it's not a big deal.
If the damp is caused by soil infill in the hearth, why would it have changed recently?

I have going round in circles reading conflicting opinion about damp. Even my local builder said he doesn't trust damp companies and doesn't know what to do!

 

[vinn]

What happened with the damp report and quote?
Damp is not "just normal" - damp anywhere should be dealt with.
Read up on here all about damp and flues and hearths.
Dont confuse chimney breasts with flues.

The simplest approach for you would be to sweep your chimney breasts and vent the blocked opening.
Hack off all stained/damp plaster for 1m ht. and render in a 3:1 sand & lime mix.

 

[SJRSJR]

The report said the damp was caused by the lack of an effective damp proof course and that to remedy it they recommend 'that a new chemical
damp-proof course be installed in accordance with our technical specification and the walls replastered using our waterproof rendering system and skimmed with plaster to provide a smooth finish. ' It will be done to 1m height and cost £1200.

I will read up on hearths and flues, thanks.

 

[vinn]

If you felt like it you could DIY inject DPC chemical cream cartridges using an ordinary applicator gun and 6mm or 10mm drill bits. Thats FWIW.
Are your walls solid or cavity?
I still dont understand if your chimney pots are ventilating the flues or blocking them.
The only venting needed in a flue is air/vent from the bottom and some kind of vent/opening at the very top.

 

[SJRSJR]

The external walls are cavity, does that suggest the party wall is too?

The chimney pot caps don't seem to have had any impact at all. I had all 6 done only after the damp appeared. They're C Caps which allow ventilation although the roofer told me there was a a different one on the living room one because it has a DFE fire.

I had the living room plaster skimmed about 12 years ago and I have a feeling there may already be some kind of cement render underneath. The rest of the house has a rock hard surface - there's no knocking a picture hook in, it has to be drilled.

 

[vinn]

The odds are that its not a cavity wall but I'm constantly surprised so:
Measure the thickness of the party wall on the exterior brickwork of the nearest outside wall - you will need the neighbour's interior measurement and your own, then find the centre of the brickwork panel between your outside window reveal and your neighbour's. Work back from the centre line.

You have damp, take the plaster off.

 

[SJRSJR]

Thanks for your advice, I feel better about tackling it. I found this too. http://www.diydoctor.org.uk/projects/damp-chimney-breast.htm