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Housing - Renovation: How tightly should lead flashing be dressed to a NOT flat old stone wall?

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  1.  
    Hi all

    I've finished installed soakers to my slate roof at a wall abutment, and I've cut the chase above ready for the flashing. The chase isn't mega straight, especially the bottom line This is mostly due to bits of stone and mortar falling away. And partly lack of skill ;) On top of that, the vertical bit of wall that will be behind the flashing undulates and is anything but flat.

    I've dressed the soaker upstands tight to the wall. Should I do the same with the flashing or does it not need to be dressed so tightly?

    Also, I was planning to keep the bottom of the flashing about 10mm above the slates. The upstand would then be around 115mm, with 35mm tucked into the chase. Where the chase is lower than 115mm, does it matter? IE - with the lead at 115mm upstand, but the bottom line of the chase only 100mm, there will be a small void behind the lead. Is that ok as is? Or should I look to pack it somehow?

    I hope this all makes sense! It's been a long day. I'll try and add some photos shortly.

    Any advice much appreciated.



    Many thanks
    • CommentAuthortony
    • CommentTimeSep 12th 2023
     
    10mm up is good. Nice if the flashing is let into the wall slightly up hill and pointed in nicely. I like the bend where it turns over into the wall to be fully supported, where it hangs down is ok not be touching the wall.
  3.  
    Hi tony.

    Yes, I did angle the cut as you suggest. As for pointing, I was actually planning to use Lead Mate or similar rather than point. I read that it is better because it is more flexible?

    Posted By: tonyI like the bend where it turns over into the wall to be fully supported


    What would you suggest I use to give it support behind the lower sections?

    Photos to be added in a mo.

    Many thanks for your help
    • CommentAuthorgreenfinger
    • CommentTimeSep 12th 2023 edited
     
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    • CommentAuthorphiledge
    • CommentTimeSep 13th 2023
     
    I'm not expert but that looks good work so far
    • CommentAuthorgreenfinger
    • CommentTimeSep 13th 2023 edited
     
    Posted By: philedgeI'm not expert but that looks good work so far


    Thanks for the vote of confidence :) I posted on another forum where the advice was to recut the top line and mortar up the bottom.

    So I'm currently deciding what to do best, although in all honesty I'd much prefer to not recut it, for various reasons.

    Any further thoughts much appreciated on my original post and/or whether anyone thinks it needs recutting...

    Cheers
  12.  
    Great work and it looks like you had the same issues as the one I did.
  13.  
    I also ended up painting StormDry on the wall above. It made a big difference in our case - driving rain was soaking into the soft sandstone and lime mortar and we had a little drip, this seems to have stopped it.
  14.  
    Thanks for the kind words Dominic. Perhaps I'm good to go with what I've done then, and the angle grinder can be put aside for now (would be great if so!).

    Thanks for the tip RE the StormDry. We removed a roughcast concrete render last year, along with all the sand/cement mortar which we replaced with lime (still got some to finish). So we're going down the breathable wall route and wouldn't want to add anything to impede that. However, unlike you, this wall is on the opposite side of the house that sees most of the weather. It's quite sheltered. And before it started work it just had a crude flashing cemented to the render and bent over the top of the slates, with no soakers or anything beneath. SO regardless I think this will be a big improvement.

    Thanks again
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      CommentAuthorfostertom
    • CommentTimeSep 13th 2023 edited
     
    Agree - tidy work so far.

    Isn't Stormdry or similar supposed to prevent liquid absorbtion but not impede vapour traffic in or out? I've always been dubious but wd appreciate words of wisdom and experience or whether this is an OK practice.
  16.  
    Thanks for the vote of confidence. Looks like I can crack on with the flashing today then :)

    Stormdry does say it's breathable in the product blurb (just had a quick look). But there are also forum posts discussing the merits of it and how breathable breathable actually means?!? Here's one for starters:

    https://www.periodproperty.co.uk/forum/threads/stormdry-brick-waterproofer-any-thoughts.14516/


    Thanks again
    •  
      CommentAuthordjh
    • CommentTimeSep 13th 2023
     
    FWIW, Stormdry works well on lime. I have some on a wall in my shower.
    •  
      CommentAuthorfostertom
    • CommentTimeSep 13th 2023
     
    Wot, just naked lime plaster + Stormdry? That's interesting.
    • CommentAuthorGreenPaddy
    • CommentTimeSep 13th 2023
     
    Pre-bend the lead on a piece of timber to give a square edge (or a bit more than 90o if you wish as Tony suggests)

    Butter the lower cut edge with mortar, to give the lead some support as you press it home.

    Tap in the fixings (I use folded lead off cuts, but clips are avail I believe)

    Fill gap with lead mate.
    •  
      CommentAuthordjh
    • CommentTimeSep 13th 2023
     
    Posted By: fostertomWot, just naked lime plaster + Stormdry? That's interesting.
    There's clay paint on the lime and then the Stormdry, FWIW. It only gets drops of water on it and they bead up and run off.
  21.  
    I got the tip for Stormdry off here. It seems to have helped in our situation - south elevation that gets the worst of the weather. I expect to have to reapply every few years.
    • CommentAuthorlineweight
    • CommentTimeSep 18th 2023
     
    Remember that the maximum length of a single run of lead flashing is supposed to be about 1.5m to avoid problems with expansion/contraction.
    • CommentAuthortony
    • CommentTimeSep 18th 2023
     
    Depends on thickness of the lead, I used 1.2m lengths with code 4 lead, others think 1.5m is ok , code 3 can be used in shorter lengths

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