I’ve got a bit of a conundrum with my roof and thought I’d run my little theory past you guys. Hopefully this theory may hold water or not as the case may be. Had some roofing issues over the last few years, not with damage or leaking as such, but more with issues of condensation. Mid terraced house with up and over roof, the original double Roman clay tiles , Bridgewater 17s . Shared chimney stack with neighbours with four flues each. I felted and battened the roof forty or fifty years ago and it didn’t leak then and I don’t think it’s leaking now (sort of) Chimney stack is rendered up to a face brick corbel / drip. All the flues in my house have been removed up to bedroom ceiling level in front and back rooms. Attic had raised flooring with a foot plus of insulation hiding the base of the remainder of the stack, but stack was never supported fully and was on my list of things to doo one day.
So I’ve had a scaffold put up and stripped the roof, refelted with a modern breathable membrane. I’ve added three vent tiles to the rear elevation just below ridge height, over fascia continuous 25mm vents along with pvc bottom course roof detail complete with birdstops front and rear. I’ve also fitted 50mm circular pvc vents up behind the eaves gutter every second rafter, all to aid air flow and minimise or defeat the condensation issues. The stack on the outside appeared mostly in good shape but I rebuilt some of the brickwork on the top course and repointed the rest. I also cleaned up the top and reflaunched the stack. Inside the loft / attic I removed about four or five courses of brickwork just above ceiling level and fitted a pair of steel angle iron gallows brackets along with supporting spars to bring the stack up to spec.
First big storm, we got a leak???
Looks like it’s coming down the stack, so my first thought is the render has aged and possibly cracked, get up there on a borrowed roof ladder and flash band some tiny tiny cracks, more to prove it that anything else. Still leaked but only during violent windy storms. So I’ve thought long and hard about this little issue, and little it is. The water coming in amounts to less than an inch in the bottom of the two buckets over the course of the storm and looks to be mostly , if not completely through the two central flues, which originally would have been the two downstairs fireplaces. So I’m now putting two and two together and hopefully not coming up with twelve. The two central flues have asbestos terminals from ancient gas fires long before I bought the property and my latest theory is that when the stack and it’s flues were congested at the bottom because of the stack being hidden in insulation there was no through passage for draft, along with the lack of roof space ventilation so stormy weather wasn’t blowing through my loft. Now I’ve removed the lower parts of the stack allowing air circulation and passage along with increasing substantially the air movement with wonderful ventilation, have I now introduced an air stream letting rain blow into my flues ???
This picture is off the top of the stack prior to me cleaning it up about fifteen years ago when I noticed we had a bit of a roof garden going on. The section of black downpipe is the termination of my rear most flue, the two middle flues have these asbestos terminals and you can just see my front flue has a bit of pipe too. The concrete double Roman tile is on next doors fide as is the gardens of Babylon. The stormy weather invariably comes from the direction of the way I’ve pictured this. So I’m now proposing that the internal reduction of the stack and increase in air passage is allowing rain to be blown through these two terminals. Plus a tiny tiny bit through the black pipes. Apologies for the boring prologue.
Ozziedog,,,,,,,,,Thoughts???
So I’ve had a scaffold put up and stripped the roof, refelted with a modern breathable membrane. I’ve added three vent tiles to the rear elevation just below ridge height, over fascia continuous 25mm vents along with pvc bottom course roof detail complete with birdstops front and rear. I’ve also fitted 50mm circular pvc vents up behind the eaves gutter every second rafter, all to aid air flow and minimise or defeat the condensation issues. The stack on the outside appeared mostly in good shape but I rebuilt some of the brickwork on the top course and repointed the rest. I also cleaned up the top and reflaunched the stack. Inside the loft / attic I removed about four or five courses of brickwork just above ceiling level and fitted a pair of steel angle iron gallows brackets along with supporting spars to bring the stack up to spec.
First big storm, we got a leak???
Looks like it’s coming down the stack, so my first thought is the render has aged and possibly cracked, get up there on a borrowed roof ladder and flash band some tiny tiny cracks, more to prove it that anything else. Still leaked but only during violent windy storms. So I’ve thought long and hard about this little issue, and little it is. The water coming in amounts to less than an inch in the bottom of the two buckets over the course of the storm and looks to be mostly , if not completely through the two central flues, which originally would have been the two downstairs fireplaces. So I’m now putting two and two together and hopefully not coming up with twelve. The two central flues have asbestos terminals from ancient gas fires long before I bought the property and my latest theory is that when the stack and it’s flues were congested at the bottom because of the stack being hidden in insulation there was no through passage for draft, along with the lack of roof space ventilation so stormy weather wasn’t blowing through my loft. Now I’ve removed the lower parts of the stack allowing air circulation and passage along with increasing substantially the air movement with wonderful ventilation, have I now introduced an air stream letting rain blow into my flues ???
This picture is off the top of the stack prior to me cleaning it up about fifteen years ago when I noticed we had a bit of a roof garden going on. The section of black downpipe is the termination of my rear most flue, the two middle flues have these asbestos terminals and you can just see my front flue has a bit of pipe too. The concrete double Roman tile is on next doors fide as is the gardens of Babylon. The stormy weather invariably comes from the direction of the way I’ve pictured this. So I’m now proposing that the internal reduction of the stack and increase in air passage is allowing rain to be blown through these two terminals. Plus a tiny tiny bit through the black pipes. Apologies for the boring prologue.
Ozziedog,,,,,,,,,Thoughts???
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