Damp plaster over boarded fireplace - with photo

[Kathj]

Hi. I really need advice as so confused by this and don't know what trade to get in to help resolve it. In an upstairs bedroom there is a boarded up fireplace and it gets damp when the weather is wet . The chimney is capped. What is really odd is that the top of the damp patch is I believe is in line with the top of the original fireplace and when I pull the bed away from the wall the bottom of the damp is lined up exactly with the top of the headboard. Some , but much less below this. Why would it not be damp below the level of the headboard? The room doesn't smell damp , there is no mould just this fluctuating patch between top of headboard and likely the original boarded up section of the fireplace. Salt? Sulpherisation? Water ingress? But why in that pattern

 

[blup]

Some observations.

The headboard positioning is coincidence, I think.

The top of the old fireplace (mantlepiece?) is possibly in contact with the back of the plasterboard, and transmitting damp from the chimney, the remaing board is free from obvious damp because of the void left by the fireplace opening.

Short of removing the relevant section of plasterboard, it is difficult to diagnose the extent of the problem. Some would suggest a lime plaster that allows the wall to "breathe".

The capping of the chimney will have reduced the effect of the vent i.e less air movement to remove moisture that encourages the damp.

Blup

 

[Kathj]

That seems very logical thank you.

The whole wall sounds hollow (lath and plaster) but definitely more so below the lower damp line so that all makes sense. I have someone coming to check the chimney for me today to see if it possibly leaking and will then look at getting the plaster redone.

 

[bobasd]

is this a projectin external chimney?

why do you say "lath an plaster"?

lower down the wall ther are signs of maybe damp damage to the decorated surface.
why not pull the bed back an photo the surface with no shadow.

ther could be 2 or 3 flues in the chimney breast - all need to be through ventilated with ventin at the bottom an the top.

if you remove the hit anmiss vent cover an look into the opening you might see sooty surrounds or even a pile of sooty debris?

have you looked at the c/breast in the loft?

 

[Kathj]

Hi
Thanks for responding.
Not sure about your first question but yes there is an external chimney.

The walls in the house are all lath and plaster other than the bit over the fireplace which is likely plywood and plaster at a guess.

There is a very slight damp area below the obvious bit. I will get a better photo.

This room is upstairs and the room below has it's own flue which is still used for a log burner. This one with the damp issue has the vent you can see in the pic and the top has been capped with a vented cap.

I was thinking of moving that vent, not sure how, can't see any screws?

I cannot access the loft as have no hatch however am getting that done next month hopefully .

 

[Kathj]

I had someone out today and there were obvious signs around the chimney where water could be getting in so that has been repaired. Fingers crossed everything dries out

 

[bobasd]

better photos will help - plus a couple showin the outside chimney an chimney stack.

external chimneys stick out from the wall elevation - google pics.
external flues get well cool an without through ventilation can create a chemical condition that attracts damp on the interior decorated surface.

the vent you can see is a vent cover that snaps on to a vent frame - ease it back from one side an it will spring off.

a torch an a small miror will help you inspect a bit of the fire opening and flue.

why do you think its ply an plaster?

 

[bobasd]

you beat me to it!

afraid to tell you that youve not had any useful repairs.Why, because
all thats been done it seems is to smear sand an cement mortar on the lead flashings.
that flashing arrangement is well wrong for usin with slates - that one piece flashin is for certain kinds of concrete tile.
you have slate, so soakers an cover flashing should be used.
same with the parapet - no flashing can be seen.

the solid fuel chimney pot also needs a solid fuel cap.
how the pots are fixed to the stack,an the condition of the flaunching cant be seen - photos neededof the top of the stack?

that chimney is an internal chimney not a projectin external chimney. go in the loft when accessible an see.
BTW have the loft trap cut above a safe accessible landing or best place is in a room - not over a stair well.

 

[Kathj]

Ok. I see,
It's not an external chimney stack. The chimneys are within an approx 2ft wide wall.
The picture of the chimneys is before any work was done today, the picture was taken yesterday and has been like that the 2 years we have lived here. The work done today wouldn't actually show on the picture. The cement around the left chimney pot was very cracked and breaking away leaving gaps down the sides of it so that was repaired today. The guy showed me pictures on his phone he took to discuss with me and even I could see it was a mess. I think he called it haunching , flaunching maybe?
I will look into a new solid fuel cap thanks. Oh and the loft hatch will be above the landing.

I don't actually know if it is ply and plaster that's a bit of a guess tbh. I know the original parts are lath and plaster. I will maybe have more idea when I take the vent off.

Thanks for help. Sorry I don't have the pics of the stack but it was a bit of a mess in the photos.
I will look into what you are saying about the flashing etc also .

 

[blup]

You say you don't know which trade to get in - consider a building surveyor who should give objective advice and specify what works are required for the roofer that is ultimately employed.

Good luck!

Blup