questions about Lead Flashing

BluePlanet · 20-01-2022 10:44PM #1

I have a shed/conservatory/lean-to structure that needs the roof replaced and i'd like to use multiwall polycarbonate sheeting.

But it also needs the roof pitch increased. There's not a whole lot of scope to do that.

Regarding Lead Flashing:

A YouTube video said not to run flashing in long lengths but to break it up into pieces 1.2m wide. Yet i see long lengths of lead flashing all the time way in excess of that. Is this something to be concerned about?

Chase depth? (i have a concrete render over stone, and plan on only go into the render, hope that's deep enough?)

-what sort of stuff do i seal the Chase with when i have the lead in place and how thick should the Chase cut be? I was hoping the width of my angle grinder disc, give or take, but the YouTube videos in the UK all go very wide with the Chase.

Drop? The goal here is to raise the height of this roof and there's a stone window cill about 15cm above existing so this doesn't leave much for a Drop. Can i cheat here and go pretty small like 5cm?

Overlap what i gleaned online, should be 125mm. This shouldn't be a problem.

I'm not sure how to flash the corner (shed roof meets boundary wall).

jack of all · 20-01-2022 10:58PM

I did a similar lead flashing job with my brother on a lean to roof not so long ago. We used a lead guide that was available free online and followed it to the letter as far as was practicable for the job in hand. We did stick to the max. 1.2m length, not worth compromising on this I think- plenty of examples of failed flashings and valleys. We used a special Sika mastic to point the chase after and treated it with the patination oil, including the underside and overlaps. Not a very difficult job once you take care to measure and plan out the joints and have a good bossing tool for working the lead.