Bloody obvious.

You have a flat roof and **** all flashing on the stack.,


Go up and prise up the lead. Bet you its all wet underneath.


You need to take roofing felt an carry it up the sides of the stack, to
where the flashing starts, and probably mastic it in, then put in new
flashing and dress it several inches out along and over the roofing
felt. So that driving rain under the flashing has to go a long way and
then UP to the flashing top, before it meets the brick.

Yu might also, as others have suggested, at the same time repoint the
stack and remortar the cowl top.


Personally I would scaffold up, or whatever, and demolish the stack top,
and start again and build a new top, done properly.

I take it the flat roof is part of the new conversion? If so its been
badly done.

It should be redone in conjunction with the chimney.




I'd go along with most of that, tho If it were me and it seems that the
water doesn't take that long to appear, I'd prolly chop a bit out of the
wall where damp and then try a hose at the bottom sides of the chimney
and see if thats where its at and if not the top, might just might show
up where its leaking...

But as its just been done why isn't the builder sorting this out?..

--
Tony Sayer