Treating rising damp on internal party wall

[sam78759]

Here's a photo of the fireplace - our neighbours are on the other side of the wall.

The damp runs along the same wall to the right hand side of the photo as well, where there's a second fireplace (although not a real one as it's the bathroom directly upstairs!)

 

[JohnD]

On the left hand side of the chimneybreast, light is poor, but I think the damp patch is highest close to the breast.

So not rising from the entire floor.

May just be residue from the wet rubble. It is not in a position where there is likely to be a pipe or drain, unless a leak is running down from the bathroom.

If you have a desk fan or room fan (not a fan heater) set it to blow on the damp areas, and scrape the paint off, and remove the skirting, to speed evaporation. If it has to be painted for appearance, use Dulux Trade Supermatt, which is porous to allow plaster to dry. Maybe a strip from dado height down. (Not a vinyl paint)

Taking off the plaster would be even better as @tell80 says.

If you mark the edges of the wet patch with a pencil you will see if it gets smaller.

The hearth slab, if still present, may continue to be wet after the chimney has mostly dried. If you can lift the wooden boards it can dry faster, and they might not warp and rot so much.

The hearth slab is laid on rubble, with no DPC, going down to the ground. The rubble is absorbent and draws up water by capillary action. You may have to break up the slab and dig out the rubble. When you lift the floorboards you will see more.

Under the floor will be damp so lift boards if you can. There may be more wet rubble.

Sooner or later you are going to have to take the floor up against that wall. The sooner the better.

 

[RandomGrinch]

Here's a photo of the fireplace - our neighbours are on the other side of the wall.

The damp runs along the same wall to the right hand side of the photo as well, where there's a second fireplace (although not a real one as it's the bathroom directly upstairs!)

View attachment 246819

Thank you for the photo
My questions now are:
Is the top of the fireplace boxed-in as the sides are?
Is there any ventilation to the chimney?
...and is the pot open at the top of the chimney?

 

[jacko555]

What's this fireplace like? Any damp? Does it share a stack with the damp one?

 

[conny]

They probably both share the same stack but, obviously, different flues. In my old house they went vertically as 2 separate flues until in the loft space and were then built towards each other to form one stack.

@sam78759 to lift your floorboards you need a broad chisel, called a bolster, to prise the boards up gently. Find where there is a join between 2 boards on the same line and work from that area. Prise one edge up a bit and then prise the other edge up. Work along the length of board so it raises evenly. After you have got it up stand it up in a corner and remove any nails left in the joists. You will now be able to see how much 'crawl' space you have underneath. To get underneath you will need to remove a number of adjacent boards to give you space to poke your head down or even climb down to inspect the joists for damp damage. If the crawl space is big enough you may be able to inspect all around under there without lifting more boards in various places.

 

[Harry Bloomfield]

@sam78759 to lift your floorboards you need a broad chisel, called a bolster, to prise the boards up gently. Find where there is a join between 2 boards on the same line and work from that area. Prise one edge up a bit and then prise the other edge up. Work along the length of board so it raises evenly. After you have got it up stand it up in a corner and remove any nails left in the joists. You will now be able to see how much 'crawl' space you have underneath. To get underneath you will need to remove a number of adjacent boards to give you space to poke your head down or even climb down to inspect the joists for damp damage. If the crawl space is big enough you may be able to inspect all around under there without lifting more boards in various places.

The floor looks as if it has laminate laid on top of it, which has been installed properly - under the skirting boards, so perhaps not as straightforward as that.

I think the op first needs to ascertain whether the floor is a solid one (concrete) or a suspended timber floor, either of which could be hidden by laminate.

 

[sam78759]

Thank you for the photo
My questions now are:
Is the top of the fireplace boxed-in as the sides are?
Is there any ventilation to the chimney?
...and is the pot open at the top of the chimney?

Yes the chimney is indeed boxed in (same material as the sides). Not sure about the ventilation and pot though as the house has three floors and we can't access the top.

This is what the survey said when we bought the house:
"The fireplaces to the lounge and dining room have been removed and the fireboxes left open but the flues sealed up above the former mantlepieces, while all four of the upper floor fireplaces have been removed, the openings infilled and made good with either plasterboard or plaster"

What's this fireplace like? Any damp? Does it share a stack with the damp one?

Yes some signs of damp along the walls and chimney breast. Here's a photo from Google Maps of the chimney stack - would this suggest both share the same one?

The floor looks as if it has laminate laid on top of it, which has been installed properly - under the skirting boards, so perhaps not as straightforward as that.

I think the op first needs to ascertain whether the floor is a solid one (concrete) or a suspended timber floor, either of which could be hidden by laminate.

Thanks - I'm told from our survey that the ground floor has a suspended timber floor.

 

[conny]

Yes the picture shows a shared stack but it will only be shared from inside the loft space.
Do you have laminate flooring in all the ground floor rooms? If not you may be able to access the crawl space from somewhere else and crawl to the affected area. Alternatively, if there are 'sleeper' walls under the floor, there may be gaps where you can shine a torch through and see from a distance what it looks like in the affected area.
Be prepared to get a bit dirty and dusty but thats one of the 'joys' of owning your own house.

 

[RandomGrinch]

As was suggested by mrrusty in post #13,
to me (..and I may be very wrong! ), this appears to be an issue caused by water ingress from the chimney; be that from an open pot, or another problem.

The water may be being diverted down the sides of the chimney breast, by whatever is sealing the flue above the mantelpiece (as mentioned in the survey).

There is also no ventilation to the flue, to allow it to dry out.

As has been suggested before, marking the damp line in pencil may be a good idea.
I would also suggest investigating the possibility of opening a ventilation channel in the flue.
This may be a simple and cheap way of proving us right, or wrong!

 

[mrrusty]

A bucket stood outside soon fills with rainwater. It is one of the mysteries of life that there are so many apparently uncapped, but disused chimney pots around. Where do peeps think the water goes?

 

[tell80]

sam787759 in the pic all the 6 pots on your stack have terminal ventilation cowls. the stack is not shared.


Dont touch your finished floor, maybe later.
You need to find the trap that lets you go under the floor, look under the stairs. then someone has to crawlto the fireplace and see is there a fender wall around the old hearth, is it filled with soil? Are any joists loose or rotting?Take video or pics down there.

You may as well knock off all the plaster on 3 sides of the chimney breast and some of the theback walls in both recesses, knock off from finished floor to coving. Judge how far to go on the outside window wall and right side return wall.
I think you have plaster contamination from soot chemicals coming through the brickwork from a dirty and maybe unventilated flueflue.You also have rising damp.

theres 6 flues , the report says 4 upper floor fireplaces plus you show 2 ground floor fireplaces for the 6 flue pots on your stack.
all the flues need vents at the fireplace blockings.

can you post a pic of the front wall at ground level?

 

[sam78759]

Thanks everyone for your replies!

I've attached a few new photos showing the damp coming through the recently painted walls (done around 2-3 weeks ago) - marked by red lines to make them more visible

First photo: left side of chimney breast in dining room

Second photo: right side of chimney breast in living room

Third photo: wall between the two chimney breasts in the living and dining rooms

 

[tell80]

I asked few questions and made a few suggestions?