Demon roof pt2

[kev123]

Hi guys i posted thread while back about damp upstairs chimney breast. Took advice and got stack rebuilt was real happy with stack but damp got worse. Roofer came back put wider lead painted fiber glass on top and coated sides and put better breathable membrane down. 2 weeks later still damp. Chimney sweep said possible problem is rain is getting in between pot and chimney liner so recomended a suspension cowl that covers the gap. Roofer said we may need ventilation caps as old 2nd chimney breast is blanked off.

 

Neighbour has same problem in same place didnt have the damp until new stack was built but i did.

 

Edited September 25 by kev123
Wrong photo

[joe90]

Is there any sign of damp on the stack in the loft?

[Dave Jones]

are there soakers under that flashing ? it will leak without them.

[kev123]

Hi guys i dont know if soakers were fitted. Cant tell if loft bricks are damp as little brickwork showing. 

[kev123]

Loft bricks are not wet managed to get to them 

[DannyT]

Lead flashing is only protecting the gap between roof tiles and brickwork.

Water will be driving in, Soaking the bricks and running down inside of the chimney.

The only way of stopping it is one piece lead at the highest and lowest point where the chimney hits a roof.

I would say your best bet here, rather than dismantle the chimney is coat the brickwork with some water sealer so it beads off rather than soaks through mortar and bricks.

 

drawings from work

[Mike]

On 25/09/2024 at 19:33, kev123 said:

i dont know if soakers were fitted

Soakers wouldn't normally be used with profiled tiles; the lead is dressed into the tile valleys as expected. The side flashing would normally wrap round the front a little more, but from your internal picture the leak is more generalised than that. The roofing felt should have been turned up behind the flashing but, you can't see if that was done. Also you can't see the depth to which the lead is turned into the brick joints (it should be at least 25mm), or what's going on with the back gutter behind the chimney, or on top.

 

It is certainly possible that the porosity of the bricks and / or mortar joints that haven't been fully filled result in driving rain soaking the brickwork and bypassing the flashing. The builder could have added a horizontal lead damp proof course level with the top of the flashing to to reduce the effect, though it's not often done. As @DannyT says, a vapour-permiable brick sealer would be an option to avoid rebuilding it (again), though a second best option on new work.

 

I'd let the roofers investigate further - it's their work and their responsibility to get it right.