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Messy roof interface
https://photos.app.goo.gl/DWZzekDYZfTkqKp17
This is the interface between the original pebbledashed house, an old extension with a flat, fibreglass roof, and a 5 year old extension with render. Unsurprisingly the internal wall beneath this junction is damp.
I’m thinking of fitting lead flashing strips vertically from underneath the grey roof tiles of the extension, overlapping onto the pebbledash, down to the flat roof. I’ll set a few strips to overlap the lip of the flat roof entirely (towards the white cowl) and stick it all together with lead mate or similar.
Does this sound like a sensible solution?
I can buy flashing in a 3 metre roll in 150 or 240mm widths, the thinner will be cheaper but will require more strips, and therefore potential leak points?
Anything else I should consider? Do I need to buy tin snips to cut the flashing or Will other tools work? Is it worth puttin patination oil on?
All the black gunk is a bodge repair I did in the summer consisting of expanding foam an bitumen roofing paint.
Looks like there could be a number of contributing factors to your damp wall here:
Big chunk missing at top of lead flashing
Flat roof doesn't look like it drains well so standing water on an old roof
Dead cat up against the wall keeping it wet when all around is dry
Water ingress between pebbledash and render join
Water ingress where that big black pipe comes out the wall (toilet waste?)
Gap under all the tiles at the edge of the roof
Crack between render and roof on new extension
I'd be looking at the tiles and the join between the house & new extension first, but a) I'm not a builder and b) I don't know exactly where the dampness is in relation to that pic.
You can get fibreglass flashings which are easily installed.
I'm not overly sure from that poc if it's a Flashing issue however
The rendered wall butts up against the wall of the old extension, it is the old extension that is damp. I think that maybe when the tender gets wet from rain, it seeps down to the flat roof joint and beyond. The idea is to cover the tender above that point with the lead flashing to stop the tender getting wet, but also to create a better seal at the joint between the flat roof and rendered wall. Alternatively I cut a groove in the tender horizontally above the flat roof / wall join and put a horizontal flashing strip there, however I fear that is more invasive and could cause other problems with water that maybe seeping in to the tender.
There is no dampness on the new extension side.
Could it just be a badly built, poorly ventilated extension (the old one) and this roof joint junction has nothing to do with it?
In that case I'd be looking at the state of that flat roof. Standing water and an old felt roof could be leaking in any number of places. And speaking with the experience of my own internal damp issues don't assume the damp is directly below the leak; water can track a long way before it shows itself.
Get up there and clear off all the stuff that looks like sand, work out why water is pooling and address that, look at the seal between the roof and the wall and check the general condition of the roof material itself. Might be worth redoing the whole thing in EPDM.