General ideas on finding sourse of damp inside chimney

[StephenStephen]

We opened up an old chimney, and have had a woodburner installed (with a flue)
We have a damp patch on the back of the fireplace recess (about 4' above the hearthstone), which was there for some time before the burner install, and is still there some months afterwards. We find drips of water on the hearthstone. It seems worse when the weather is wet.

I'm wondering if anyone has any rules of thumb as to the sequence of checks to generally run through to find the source of the water? For example:

-single storey flat roof behind chimney
-chimney breast in the attic
-chimney stack
-roof
-the other obvious things I've missed out because I don't know what they are!

Sorry to ask such a vague question, I just realise I've been putting off investigating because I don't know where to start. Thank you for reading.

 

[Doggit]

What's the ground level like outside, and can you see a DPC in the chimney breast. Pictures will help.

 

[StephenStephen]

Thank you for your reply.
The house built, we think, in 1725 so no DPC - chimney is granite and lime, single story extension added behind it in 20th or 21st century.
The water is, I think, coming down or through, rather than up - the back of the fireplace recess is dry below the damp patch 4 feet up.
My best guess is that the water is dripping down to that area (it's slightly proud of the back of the recess further up) from somewhere above, but I can't work out where, and it could be coming through from behind (though the surface of the wall behind in the extension seems dry).

 

[StephenStephen]

Photos - the damp is on the darker stones which are seen in the pictures to the left of the flue - we also get spots of water which have dripped down onto the hearthstone below
[GALLERY=media, 99292]DSCN3705 by StephenStephen posted 14 Feb 2017 at 10:51 PM[/GALLERY][GALLERY=media, 99291]DSCN3704 by StephenStephen posted 14 Feb 2017 at 10:51 PM[/GALLERY][GALLERY=media, 99290]DSCN3703 by StephenStephen posted 14 Feb 2017 at 10:51 PM[/GALLERY]

 

[Doggit]

You'll have a closure plate above the stove, but do you have a liner, and is there a chimney cowel fitted.

 

[StephenStephen]

liner yes,
cowl I don't know -I'll need to dig out the paperwork from the installer

 

[Doggit]

You'd see if there was a cowl by looking up at the chimney, but if you've got a liner, then there should be one. If there wasn't, then that could allow water to come down the chimney, and drip from the back of the closure plate, so unless there's a source of water that's dripping into the chimney flue (especially as it's worse when it's wet) then you need to maybe look at the single storey behind the chimney, and check to see if the roof is letting any water through. So pictures of that needed next.

 

[StephenStephen]

Thank you, much appreciated - flat roof next - hopefully tomorrow
Yes - they did install a pot hanging cowl

 

[StephenStephen]

a couple of photos at last: