Odd Damp Problem

[MisterFish]

I have a strange damp situation in a first floor bedroom. The damp is over a fireplace and in a sort of S shape. The S loops into the chimney from the floor below. Above the room is a pitched roof.

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• MisterFish
• 6 Aug 2014
• 1

The room was replastered about six years ago, (just before I bought the place), I have no knowledge about the quality of work other than what I can see. The room still has an open fire place hole, which I intend to close and vent.

The top and bottom of the damp patch, (as measured by a damp meter), are bounded by a pair of courses of engineering bricks on the outside of the building, (the bricks between are original porous Victorian bricks).

On the floor below is the kitchen and I guess that there used to be a coal fire or even a coal range down there but well before my time. I do not know if the chimney is vented on the ground floor as that wall is concealed behind the kitchen cupboards.

The chimney pots, (for there are three – not sure why), are each capped with a vented cap.

The outside pointing seems, on visual inspection, to be sound and about three years ago, whilst doing other work from scaffolding I had the opportunity to check the chimney stack and the pitched roof which both seemed to be in good order.

The room has been used for some years since we moved into the house as a store room so I am unable to say for how long this damp has been apparent.

It has been suggested to me that the residual soot inside the chimney combined with the engineering bricks, (forming two de facto DPCs) means that the whole system is hydroscopic and will never dry.

Can anyone give me any input on this problem and how to approach/fix it?

 

[ree]

Is this an old property? Is there a cellar?

The odds are that the kitchen fire opening is bricked up and not vented, and that none of the flues have been swept. No matter what you intend, the flues (all your flues) must be swept, and if, after sweeping, the fire opening's are bricked up then install vents.

All plaster on the c/breast in the pic must be hacked off and then rendered with a 4:1:1 mix of sand lime and cement & skimmed with board finish - do not use any gypsum plaster. Any doubtful plaster on the return wall or the c/breast cheek then do likewise.

Why not go into the loft and investigate for any signs of moisture penetration around the chimney stack?


The store room was probably plastered before sale to conceal the damage, perhaps the kitchen c/breast area was also plastered or covered with units?

Vents cab be installed thro the outside brickwork - flues can also be opened up from the exterior to sweep them.

If the flues are smoke tested you will be able to ID each chimney pot with its flue.

Pics of the exterior wall and stack would help?

 

[MisterFish]

Is this an old property?

Built 1901

Is there a cellar?

There is, it is tanked and it does not run under this section of the house.

The odds are that the kitchen fire opening is bricked up and not vented

Probably

and that none of the flues have been swept.

Don't know about this. The ones I have seen, (and looking up this one) have looked pretty clean.

No matter what you intend, the flues (all your flues) must be swept, and if, after sweeping, the fire opening's are bricked up then install vents.

I am not sure that ripping the kitchen out on the off chance that a chimney hasn't been swept is going to make me terribly popular, (or keep me terribly well fed).

All plaster on the c/breast in the pic must be hacked off and then rendered with a 4:1:1 mix of sand lime and cement & skimmed with board finish - do not use any gypsum plaster. Any doubtful plaster on the return wall or the c/breast cheek then do likewise.

Okay. Replacing the plaster makes sense. Can you please explain why the rest of that?

Why not go into the loft and investigate for any signs of moisture penetration around the chimney stack?

Because I can't get up there. There is a VERY small roofspace, no boarding, and a large covering of insulation. I have inspected from the access hatch and can't see anything obvious, though I am a fair few metres away. (Oh for the days when I could have sent a child up there )

The store room was probably plastered before sale to conceal the damage, perhaps the kitchen c/breast area was also plastered or covered with units?

Maybe, no way to know for sure.

Vents cab be installed thro the outside brickwork - flues can also be opened up from the exterior to sweep them.

That sounds like a huge job. Would a chimney sweep do that ofr do I need a team of builders in first?

If the flues are smoke tested you will be able to ID each chimney pot with its flue.

There are , as far as I know, two places where fireplaces or the like could have been, and there three chimney pots. There is a lean-to on the outside of the kitchen wall, so I suppose that there could have been a fire place on each side of that wall if there had been some other room there in the past. That of course would make going into the kitchen fireplace from the back much more difficult.

Pics of the exterior wall and stack would help?

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• MisterFish
• 7 Aug 2014
• 1

 

[TheVictorian]

The lean to would probably have been the scullery and there would have been a fireplace in there as well as the kitchen.

Personally I'd vent the unused stacks (even if it's externally) and might even pop a cowl on top of each stack. As well as reducing the rain that goes down the chimney it would also stop birds getting stuck, which would be a pain with no fireplace to remove them through! I removed 3 dead pidgeons from the fireplaces in my house when I first moved in..

 

[MisterFish]

Personally I'd vent the unused stacks (even if it's externally)

Okay, so assuming there was a scullery I could go in through the wall of the lean to to the fireplace on that side of the wall. Any thoughts on figuring out where on the wall the fireplace might have been? (I am assuming that it has been bricked up and not just plasterboarded over, so tapping for a change in sound might be a little difficult?).

The fireplace in the kitchen though would require ripping out the kitchen to vent ... and then probably covering the vent again with kitchen units. Which would surely defeat the object.

Any thoughts on a workaround?

and might even pop a cowl on top of each stack.

Difficult to tell from the picture but they are each capped with a vented cowl

 

[ree]

If some of your flues are bricked up its difficult to know how they could have been swept?

Where necessary, units are simply removed, they are not "ripped out".

You have possible access, at floor level, to two flues from the lean-to side of the main rear elevation wall, vents can be installed from there as well. Its a simple matter of removing a few bricks and later making good.

All suspicious plaster comes off now or you might be removing it in a few years time. Flue Sulfuric acid contamination can spread sideways.

Even with the high ceiling, your outrigger roof pitch is well adequate for crawling thro - as a DIY'er you've entered the building trades and you accept dirt and uncomfortableness - you dont give up at minor obstacles.

Edit: just noticed your latest post. Measure the width of the c/breast and split into three centres - open the first measured flue centre and the next one is half a brick away.

 

[MisterFish]

If some of your flues are bricked up its difficult to know how they could have been swept?

It is difficult to imagine how they could have been swept after they were bricked up, but less so before they were. My point is that I have checked all the flues that haven't been bricked up and they have clearly been thougroughly cleaned. Your saying that the others haven't been is speculation that leads to a very dificult and expensive investigation .... unless you are diagnosing this based on something that I don't know about, in which case, please share.

Where necessary, units are simply removed, they are not "ripped out".

With respect you haven't seen the kitchen and you don't know what would be involved. I have and I do and my description was not fanciful.

You have possible access, at floor level, to two flues from the lean-to side of the main rear elevation wall, vents can be installed from there as well. Its a simple matter of removing a few bricks and later making good.

Thanks for that, that may well prove useful.

Even with the high ceiling, your outrigger roof pitch is well adequate for crawling thro - as a DIY'er you've entered the building trades and you accept dirt and uncomfortableness - you dont give up at minor obstacles.

More speculation? I can't get up there. You haven't seen the access hatch or the roof space. I am not an absolute beginner and I really don't need to be patronised.

Edit: just noticed your latest post. Measure the width of the c/breast and split into three centres - open the first measured flue centre and the next one is half a brick away.

Again, thanks for that, useful info.