Poly over chimney?

14 Jan 2008
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United Kingdom
Hello all,

flaming damp / condensation / ingress in loft!

All at one gable end, which is west-facing, and also has the (redundant) chimney stack there.
Roof is closed eave, so I put air bricks in each gable end to allow some through flow.
Lagged the living daylights out of it.
Fitted dry verge to prevent tile lift in high winds, but also ingress at verge.
Thomson weathersealed stack to prevent ingress there.
Had closed pepper pot fitted to chimney.
Checked flashings - appear fine.
Dulux weathershielded the walls (they're rendered) - to prevent ingress there.
I can't see any cracked tiles.

Timbers still damp / wet in loft at one end (and one side of chimney breast). Plaster darker in top corner of room below. Just redecorating (again!)

Has anyone wrapped their chimney breat in 1000g polythene for the winter, just to rule out a problem with the stack / flaunching / flashings?

Short of having the stack knocked off, ridge replaced with vented, and vent tiles added, I'm lost.

Anyone near Cannock help?
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If you want to go down that route you put one of those large bags that sand gets deliver in from the builders yard they have straps on so you could tie it down as long as the stack is redundant.
That, my friend, is a beautifully faff-free idea! I'm on it! (although not at this time of night

went up there yesterday morning and tied a tarp over the stack. It's not airtight by any means, so no risk of sweating under there.
Due to having no means of securing the tarp over the flashing on the south-facing narrow side of the stack, the lowest course of brickwork and flashing is still exposed to the elements; however, the vast majority of the stack is now much-better shielded from the direct elements.
The damp patch is still there in the bedroom, so will have to give it a few days to see if things get better, worse, or no change.

I tried to get photos of the stack, but they were a bit blurry - I'll try and get some better ones when I'm off over christmas. I've put the rubbish photos up anyway.

I'm guessing that the "best" solution would be to have the stack taken off, and the roof re-made over (as I have next-to-zero intention of using the fire). What sort of ball-park figure would that cost please?
Failing that, I think I'd be looking at re-flaunching, pointing, flashings - again, what sort of guesstimate?

Finally, if (which I doubt), it's condensation, the 9 x 6 airbricks in either gable end haven't worked, so I'd be looking at vent tiles, and perhaps ventilated ridge. Current tiles are Marley double roman concrete pantiles - again, ball-park would be most appreciated :)

Any other helpful wisdom again would be received with thanks!
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I did not see any pictures,but if you post some pictures there are plenty of people who can help. I do not think there will be much difference in price for removing the stack or pointing flaunching and new lead work
Thanks for the reply catlad :) pictures in album (click on my username).
would say £300 be a realistic price, or higher / lower?
I have seen a lot worse chimneys than that. you could keep it covered for a while and see if it improves. Take a look in the loft when it rains. If there is no ventilation at all then it could be condensation.
I'll get up there and have a look.

I'll try and post some photos from up there - I did put some anti-condensation measures up there, mainly to try and give a bit of an air gap between the felt lining. Those, along with the (admittedly a bit feeble) air bricks were the best I could do, condensation-wise.

Once I am certain the outside is weatherproofed, I'll probably batten out the affected wall, and put some insulated boards up there (my uncle dot-n-dabbed the previous boards, and where the damp is most pronounced feels most solid i.e. I'm guessing straight over a blob of adhesive).

Being on a bit of a hill, and fairly exposed, is it likely that rain can be driven under the roof tiles and in by the prevailing wind, or would that not realistically happen?

Cheers for replies
The roofing underlay should take care of any driving rain. have a look in the loft when it rains, and if you take some more pictures not so close up.

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