Damp loft wall

[daveaspy]

When we moved in 18 months ago there were some brown patches on the wall in converted loft - previous owner said something along the lines of it had been damp which was fixed but the wall needed some kind of sealing coat to stop the marks coming through. Nothing felt damp or soft (this wall is dot and dabbed plasterboard against the party wall, with chimney behind in the middle).

Now, time to get around to doing something with it! I noticed very tiny bubbles around the light switch (this area is quite solid, must be a big chunk of plaster around the back box) which when pressed would express a small droplet of water. This concerned me so I started to open up the paint a bit and it started coming off in big sheets - it looks like some kind of rubber layer (maybe PVA?) was painted on the plaster before being painted and there isnt much holding it to the plaster any more. I took a picture and you can see the plaster underneath is pretty damp:

View media item 73556
So my first question is, could this be due to very old water being held in the wall between the plaster and the rubber layer? If there is something sealing in the water how long can it stay there?

10 days later (having run a dehumidifier in there quite a bit) I took another picture and it has dried out quite a lot:

View media item 73557
I guess the obvious suspect is the chimney but I did have somebody around last year and they said all looked ok with the pointing and flashing. I think I need to wait for some more big downpours to see if the damp patches come back.

Anything jump out I might have missed?

 

[ree]

Is your neighbour having similar problems?

Chimney stacks are the immediate suspects, and should be methodically examined again. Ask whoever examines it to take pics for you.
Perhaps post pics of both front and rear roof planes and chimney stack?

Is your roof covering eg. tile, different from your neighbours roof material eg. slate?

If you read up on recent posts about this very kind of thing, and stacks and flues, you would be well ahead.

The "rubber layer" is probably some remedial measure, or camouflage, that the previous owner painted on. They never work in the long run.

Try not to use the switch.

The "old water" theory is irrelevant, the water has somehow come from somewhere.

 

[daveaspy]

thanks ree. I have had the switch open and no visible dampness or water inside.

I was wondering about old water in case it was from an old problem that has been fixed - my side of the chimney looks to have been repointed although hard to tell when. Previous owner said they had the flashing seen to at some point but I dont have any dates for that either. I'll try and get a picture of the chimney area out of the velux window on the right hand side of the damp wall and post it tomorrow.

I'll also have a look at the previous posts you mentioned

 

[tony1851]

Assuming the stains are on the chimney breast?
If so, are the flues in use?
If they have been blocked up in the past, they should be ventilated top and bottom.
If they are unused, condensation can form if they are not properly vented. The resulting water combines with deposits on the surface of the flues to give the characteristic brown stains.

 

[daveaspy]

Assuming the stains are on the chimney breast?
If so, are the flues in use?
If they have been blocked up in the past, they should be ventilated top and bottom.
If they are unused, condensation can form if they are not properly vented. The resulting water combines with deposits on the surface of the flues to give the characteristic brown stains.

Yes they are more or less in line with the chimney. The front room flue is used occasionally, the back room one is never used but ventilated (although it didn't used to be, the bottom was covered with a sheet of plasterboard and thick insulation which I took off a while back in case it was causing a problem) - they both end up in the same stack on the roof though.

Would the brown stains from condensation in the stack make it through to a dot & dabbed plasterboard though? I can imagine it on a traditional plastered wall.

 

[daveaspy]

Here are a couple of pictures of the chimney that may be the culprit - anything obviously need attention from this angle?

View media item 73584 View media item 73585
Both roofs are concrete tiles I believe.

 

[ree]

The roof tile and ridge look to be in good nick. Likewise the flashing.

The stack pointing isn't all that bad - its a very thin bed in stock brick, and needs to be diamond disc'ed out to a depth of 25mm to 30mm, thats if you go for re-pointing.

What really needs examining is the flaunching. Vegetation is growing there, a sure indication of neglect.

You have a redundant (?) TV cable and a "wire" that points up for no purpose?

I'd suggest that you and your neighbour make it a joint repair.

You would both do well to sweep your flues.

How salts and moisture could transfer across to a D&D plaster board is sometimes achieved by non-remedial D&D adhesive having been used. But its only a possibility.

If the process of elimination fails then you will have to open up the plaster board as the next step.

 

[daveaspy]

thanks Ree. Yes there is a redundant aerial pole there with no aerial on it (on my side).
The "wire" that points up is actually the remnants of what was a beautiful sunflower growing there last summer! (and yes I guess that may have caused some damage to the pointing it was nestled in)

 

[daveaspy]

The front of this dry wall is drying out quite nicely now the paint has been peeled off. However I was a bit concerned about what was behind so cut a couple of holes to see...

This is over the chimney breast area, board seems very close to the brickwork but nothing too scary here. The back of the plasterboard was black although not sure if that is dirt/mortar or mould
View media item 73907
Another hole on the edge of the chimney breast and the alcove - nothing obviously wet but the inside of the plasterboard is damp, it is like a quite dry paste when you sheeze it between your fingers.
View media item 73905
The bit concerning me is when you poke inside this second hole. It is mainly nice and dry, some cobwebs etc, but the top of the plasterboard looks horribly mouldy:
View media item 73906
I think this whole dry wall should come down and be replaced? Are there any special precautions to take with the mouldy plasterboard or just get it into some plastic bags?

 

[ree]

No special precautions required for removing mouldy plaster board. Wear a mask?

You have to find out what caused the damp and mould. Its no use simply re-instating plaster board without solving the damp issue(s).

You seem to have had a mixture of studs and dot and dab. The dabs on view have been flattened out without adhering to the plaster board.
There are remedial adhesives available for D&D work, for what they are worth.

 

[Flyboytim]

It is a loft room, therefore at the top of the house where warm air rises to.
It has a chimneystack in poor condition, with historically damp brickwork.
It has D&D and battened dry lined plasterboard that "needed some kind of sealant coat".

The dry lining is showing signs of damp especially around a light switch and in the "10 days later after dehumidifier" picture, possibly where plasterboard nails or screws have been used to fix the board. The area of wall around the switch is "quite solid" and there seems to be a diagonal area/line of damp leading to the junction of the beam (purlin?) with the ceiling, probably where the light switch cable has been chased into the plasterboard, and plastered in.

These bits of metal are possibly conducting heat from the room to the cold space behind the plasterboard, and not conducting water from the wall into the plasterboard.

The cold spots around the metal are allowing condensation to form and penetrate the emulsion/vinyl paint coat into the plaster skim.

There is damp from 2 sources working on both sides of the plasterboard - cold damp brickwork, and warm damp "top of house" air.

Ideally, the chimney needs to be fixed as ree pointed out, and any cowls fitted to prevent direct ingress of water down chimneys that no longer are dried out by fires below, as originally intended when the building was built. This should be done to all flues, neighbours included. All flues should be adequately ventilated to prevent moisture build-up.

The loft wall should have a vapour barrier and insulation behind the dry lining. there are many ways to do this. One way to prevent cold bridging by fixings is to use Airtec Double Insulation: http://www.screwfix.com/p/airtec-double-insulation-1-5-x-25m/50913
http://www.free-instruction-manuals.com/pdf/p4761334.pdf

In the recommended configuration, there are 2 sets of battens forming a cavity, insulated and barriered by the Airtec membrane, with joints sealed with aluminium tape. The internal dry wall fixings are all into the insulated side of the barrier, and the electrical box can either be fixed with a plastic dry wall box, or a surface box.

Finally, some form of ventilation is required to extract the warm "top of house" air if it becomes too warm and humid. Humidity controlled extractor fans are readily available, and a suitable roof vent could be fitted when the chimney work is being done. A well fitting door to the rest of the house will also help control humidity in the loft room.

 

[daveaspy]

thanks for the input Ree and FlyBoytim - very useful stuff to bear in mind.

I had a guy round a couple of days ago who thinks it looks like water is still coming in somewhere around the chimney area so he is coming back this week in the daylight to get on the roof for a proper look.

The other 3 walls in the room (with eaves storage areas behind them) do have a vapour barrier and insulation behind them but this party wall doesn't for some reason. There is insulation attached to the brickwork either side of the chimney breast but not on the chimney breast itself (there isnt much room as the wall would come too close to the top of the stairs for anything thick, but that Airtec stuff looks like it would do the job)

The reason there is a mix of D&D and studs is because the wall is wider than the chimney breast so some framework is there to support the sides - personally I would rather have had it just around the chimney breast to give a little more storage room in the alcoves but what do I know (although thinking about it I guess further down the wall the chimneys are wider as they come from front/back room and join together in the one stack)