Damp on chimney breast wall

[596adam]

Hi, hoping someone can help me with this problem as it’s been happening for over a year now and is driving me mad!

The chimney breast from the gas fire downstairs comes up through our first floor bedroom. About 12 months ago we noticed a leak on the bedroom wall (the chimney wall) with some water tracking down it on the internal face of the wall.

Upon investigation in the loft, we found a pool of water coming through from where the roof tiles meet the chimney. We called a roofer who fixed the flashing and the pools of water in the loft stopped. At this point we assumed the leak is fixed completely.

The Chimney breast wall in the bedroom that had gotten wet never dried out though!

Original damp patch after leak:

Original damp patch after leak

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We eventually called in a damp proofer, who chiselled off the plaster where the damp patch was (around 1m from the ceiling down), applied waterproof screeding and then replastered. At this point again we thought the problem was solved.

Water proof screeding :

Waterproof screeding

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The problem now is that the few centimetres under the original patch (below where the screeding now is) is now showing wet patches through the plaster.

Does this mean there is still a leak somewhere? If so, it must be coming on the inside of the chimney as there is no visible water on the bedroom wall or anywhere on the bits of the chimney I can see in the loft.

I’ve also been told it could be condensation? Or is it that the damp proof guy should have chiselled more of the plaster off?

I’ve had 3 roofers look at my chimney and none of them can see a problem with it. They’ve recommended a cowling but I’m not convinced that’s the problem.

Anyone ever seen anything like this before? Any help would be massively appreciated as I’m at my wits end with this now!

Thanks in advance.
New damp patches underneath where screening was applied:

79726283-DF6E-4FE2-B2B1-5CDBCE340732.jpeg (186.28 KiB) Viewed 2809 times

[wes56]

Is this chimney breast on an external wall? Any render?
How many terminals or chimney pots on the stack?
The damp could be coming down from a leaking stack back gutter?
What was this water proof screeding that the damp man applied? The finished patch looks rough.
Photos of the chimney breast in the loft - and the bedroom and the ground floor fireplace openings will show more.
Is the gas fire active and connected to a SS liner?

Try and get before and after photos of any work on your roof or stack.

[ayjay]

We eventually called in a damp proofer, who chiselled off the plaster where the damp patch was (around 1m from the ceiling down), applied waterproof screeding and then replastered. At this point again we thought the problem was solved.

The problem now is that the few centimetres under the original patch (below where the screeding now is) is now showing wet patches through the plaster.

If you think about logically, all that you've done is to shift the damp to a different area.

The damp comes in from outside - it can't show itself on the wall where it used to cos that's been rendered with a waterproofed product - so it does what water does - gravity take it a bit lower and it now shows below the waterproof area.

The remedy will be to find out where it's getting in and fixing that.

[596adam]

Thanks so much for your reply @Wes56.

To answer your questions:

The chimney is on an external wall and it is rendered yes. There’s one pot on the top.
The gas fire is active but doesn’t have a liner.
Not sure what the damp proof screeding was exactly I’m afraid but it seems to be ‘working’ in as much as no water is coming through there, im assuming water is now running inside the chimney, down the waterproof material and coming through the wall at the first opportunity it has.

The latest roofer I had round took a photo of the top of the chimney for me, which might help the investigation?...

[wes56]

The lead back gutter has failed so a fillet of sand and cement has been used as a stop-gap repair. It never works.
The wings of the back gutter dont look too clever.
Back gutters should have 6" to 8" of flat standing room and have been made in one piece.
The sides of the stack should have step-flashings and soakers - but i cant see the sides.

There's only one chimney pot for two flues - there should be an gas terminal inserted in the pot and the flue probably needs sweeping.
The flue from the bedroom is blocked off on the stack and no means of ventilation shown. Flues have to be left clean and ventilated bottom and top.
The flaunching is very poor and the render is not much better.

The odds are that the back gutter is the cause of the leaks but still none of the other interior pics that i asked for above?

The pointed valley on the house opposite roof - the pointing is failing and will eventually block at the bottom.

[596adam]

Hi @wes56 thanks so much again for the reply.

The annoying thing is, you’ve given me more practical information in one post, than the 3 or 4 roofers I’ve had round to look at the problem have combined!

Should I be getting a roofer or another trade in to come resolve the problems?

I’ll get those other pics you asked for over today.

[596adam]

@wes56

Photos as requested below.
To clarify, there is no fireplace anymore in the bedroom, I assume that was taken out be previous owners. Does it still need ventilation?

Chimney in loft

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Bedroom with damp

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Gas fire in living room

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[wes56]

The loft photo confirms the back gutter is leaking - the chimney breast brickwork and some of the rafter timbers are wet.

Best practice would be to remove the old flaunching and rendering on the stack - and then reflaunch with a 30mm overhang and re-set two chimney pots with gas and air inserts. Dont use any metal - only use clay pots and inserts.
The bed room fireplace needs opening up for sweeping and then a vent must be left in the breast for ventilation at the old fireplace opening.
And either a new stack pot and air ventilation insert fixed on top of the stack - or an air brick ventilating the bedroom flue in the side of the stack will provide through ventilation.

The back gutter will need stripping out and probably replaced with a new lead back gutter with cover flashing.
With the back gutter out its a simple matter to build a wider timber flat say 6" to 8" wide for a new back gutter.
Examine the side step-flashings and soakers.

Hack off all plaster from the face of the chimney breast from floor level to ceiling and then render with a sand and lime mix and a limelite skim finish - dont use any gypsum plaster. Check if the corner angle bead is rusty?
Closely examine the wall at the side of the chimney breast for any damp signs or disturbances to the decorations.

The ground floor gas fire will need temp. removing (use a GASAFE) and the flue swept.

A plasterer can do the internal stuff and a NVQ trained, pro roofer to do the roof work.

Thats quite a lot to do but I'm advising you on best practice for a proper job.