Leaking roof

[monkman]

I am having problems with a leak above the chimney breast in a 1901 terraced upstairs flat (external wall). When it rained a thin glistening line appeared between ceiling and chimney breast. Some drops formed and ran down the wall and a damp patch on the ceiling became a permanent feature, with peeling paint. The following solutions were tried:
1. the chimney breast was repointed and sealant applied to the brickwork (chimney breast) - the problem continued.
2. the lead flashing was replaced - the problem continued.
3. the roof was replaced - the problem continued.
4. the chimney pots were removed and the chimney sealed. This has made some difference. Now there is only dampness when it rains but not running water.

What should I try next?

 

[middi]

What type of roof cover do you have, tiles, slate, thatch,etc..?

And, has it got felt ?

 

[monkman]

There were original slates; these have been replaced by concrete tiles. I don't know if there is felt but the new tiles do not sit directly on the wooden roof struts as the slate had done - there is a layer of something in between. Is this where felt would be?

 

[NT]

> There were original slates; these have been replaced by concrete tiles.

hope you had the roof structure strengthened to take the extra load

NT

 

[Penners]

There's always a temptation to assume that water leaks originate immediately above where they become evident. In your case, drips against the chimney breast are assumed (perfectly reasonably) to be something to do with the chimney or its flashing. However, it sounds as though you have pretty well exhausted the possibilities there.

Water can be a b*gger. Quite often small leaks can travel along beams or other surfaces and finally appear a considerable distance away from where they managed to sneak in.

Is the chimney breast on a party wall? If so, it's possible that the water could be coming through your neighbour's roof and finding its way around the chimney, to appear on your side.

Have you been up into the roof during a rainstorm and tried to find the path of the water? It's possible that - with the help of a good torch to make the water glisten - you might be able to trace it back to its source.

 

[middi]

It is quite possible also that the combination of new tiles and felt and the way the they are used is obstructing the breathing mechanism of the roof.

Condensation can form on the underside of the felt barrier an treacle down to the eaves, this would be more prominent against the stack.

Have a good look from within the loft if you can, and check as to how is all put together including any ventilation gaps if there.

 

[Moo]

"... and treacle down to the eaves "

What a lovely turn of phrase - sums it up exactly.

 

[Penners]

From an above-ground treacle mine, perhaps?

 

[Moo]

But of course.