Chimney leak in a new roof...please help

9 Aug 2022
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United Kingdom
I've had a complete reroof done (new membrane, same tiles, new guttering, a few rafters reinforced and a new render around chimneys). I did that as a preventative measure as the roof membrane was very old, but had no leaks. 3 months after the roof was done a serious leak developed on the top of the chimney breast in my 1st floor bedroom. No sign of moisture in the loft and no water coming down the chimney on the ground floor.

The roofer who did the reroof inspected twice and concluded it's nothing to do with his work and advised me to cap the chimneys (which makes no sense as for the 4 years prior I had uncapped chimneys and no leaks). The leak has now been unresolved for 8 months and is stopping me form replastering the bedroom. I took photos of the chimney in question from the outside and the leak on the inside. Is anyone able to diagnose this?

A builder I trust (who looked at the chimney from the ground) said it's to do with the wrong type of render used and flashing not being installed correctly - does anyone concur? I would be grateful if someone is able to shed some light (photos attached)

Thank you
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With your builder on this. AFAIK profile tiles should be step and cover to guarantee waterproof, using render is a hostage to fortune, especially when its just been trowelled over the original.

It's possible that water is running down within the brickwork (not the surface) and bypassing any flashing.

But yes, that render repair looks well dodgy, and not even render sand, but building sand.

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