How to get my builders to fix this...

[nforne]

On the whole I'm very pleased with the job my builders have done in constructing my dormer extension, but there's a leak by the chimney that just won't go away. Construction finished six months ago but whenever we have heavy rain, particularly when accompanied by strong winds, a wet patch appears on the new dormer ceiling by the chimney.

I've had the builders back every time it happens but I don't know what, if anything they're actually doing about it. Last night we had another storm and another wet ceiling, so I'm going to ask them to come back once again. But this time I'd like to tell them exactly what I expect them to do, so I'd be grateful if anyone could give me an idea of the steps they should be taking to trace the leak, and what the possible/probable causes might be.

Some further info... I replaced the pepperpot cowl with a vented cap a couple of weeks ago. When I went on the roof to swap it over I noticed the pointing and brickwork appears to be in good condition, as does the flaunching.

Hopefully the photos will explain better than I can.

TIA
nforne

 

[vinn]

Presuming the stack is shared with the neighbour's?
How is the stack flashed on the shed roof? Maybe its me but I cant see any flashing in photo3?
Photos of the stack flashing esp. the back gutter and surrounding tile would help?
If you go up on the shed roof then gently lift up the flashings including the back gutter, if any, and look for damp beneath them.

 

[nforne]

Yes, the stack is shared with next door (semi-detached bungalow).
The photos you see are from during construction so I'll take some new ones and close-ups as soon as the weather improves.

 

[catlad]

That was a mistake to incorporate the chimney into the construction.

 

[nforne]

That was a mistake to incorporate the chimney into the construction.

Okay, but why?

 

[Barris Roofing Ltd]

Hard to tell from the pics but some possible problematic issues could be: (not that these are problems I can see.. Just suggestions to check)

By process of elimination, I'd check:

1. Are there any soakers between vertical tiling and original roof slope.

2. Lead flashings & soakers
3. Back gutter
4. Chimney flaunching
5. Unsealed chimney caps
6. Verge overhang
7. Porous bricks to chimney
8. Minimum pitch of roof covering

If I think of any others I'll let you know.

From my experience, some builders overlook the use of soakers, so I'd check those first. I'm not tarnishing everyone with the same brush, mind.

 

[nforne]

Thanks for the replies so far. Just been up on the roof and taken some more photos...

 

[^woody^]

There should be a new DPC above the level of your new dormer roof.

 

[nforne]

Hard to tell from the pics but some possible problematic issues could be: (not that these are problems I can see.. Just suggestions to check)

By process of elimination, I'd check:

1. Are there any soakers between vertical tiling and original roof slope.
...

Thanks for the checklist, it's really helpful. As for point 1, it looks like they didn't install soakers on the dormer cheeks (new photo attached), so...

• Is it a big job to retro-fit them?
• Is it the responsibility of the builder to do this, or is it my fault for not specifying them?
• Is it worth doing the whole of the dormers, front and rear, or just the small section above the chimney where the leak is?

 

[nforne]

There should be a new DPC above the level of your new dormer roof.

That might be tricky with it being a shared stack. My neighbour isn't experiencing any problems and while I don't mind footing the bill, I think she'd rather I left her side well alone.

 

[^woody^]

There should be a new DPC above the level of your new dormer roof.

That might be tricky with it being a shared stack. My neighbour isn't experiencing any problems and while I don't mind footing the bill, I think she'd rather I left her side well alone.

Of course the neighbour won't be experiencing any damp if the original DPC is above her roof.

Your new roof is above those and if there is no DPC above the new roof, damp will come down the stack.

It's been inadequately designed.

 

[Barris Roofing Ltd]

Soakers (in this example) are a pain to retrofit, but do-able. I'd fit soakers everywhere they should be fitted, but if you're not getting an issue anywhere else.. its for you to decide.

You could try applying Stormdry to the chim to counteract damp issues. It's expensive, but the best I've used.

 

[Barris Roofing Ltd]

The faunching (on your updated pic upload) looks really damp and a bit suspect. Would be worth renewing that.

 

[nforne]

The faunching (on your updated pic upload) looks really damp and a bit suspect. Would be worth renewing that.

The flaunching and proofing is my responsibility but am I right in thinking the builder should foot the bill for the soakers? Or is it not as clear-cut as that.

 

[Barris Roofing Ltd]

It wouldn't be my place to comment on that.