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Parapet wall, box gutter, pitched roof - is this ok?

Discussion in 'Roofing and Guttering' started by Naknah, 16 Mar 2019.

  1. ^woody^

    ^woody^

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    You need 35° minimum for slate, and that drawing looks like about 15.

    The box gutter will need a ply base going up the slope to make sure that no water runs back up and under the slates.

    No cavity tray or DPC appears to have been specified at the parapet. I hope your builder is clued up about these
     
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  2. Naknah

    Naknah

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    It's just over 6 metres long. The roofer suggested doing it in fibreglass rather than lead (cost). It is working out at about 26 degrees on site. My understanding is that you can go down to 20 degrees with natural slate.

    I'll check those points with the chippie and brickie tomorrow. Thanks for the pointers.
     
  3. Leofric

    Leofric

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    Gutter waterproofing should go up under pitched finish roof to a height of 150mm according to NHBC, 100mm according to Lead Sheet Association.
    ( unable to copy and paste detail drawings ) distance on the slope depends on pitch.
     
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  4. Naknah

    Naknah

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    Cheers Leofric I’ll look that up. That doesn’t sound too bad
     
  5. Makie

    Makie

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    Lead could be done if it is welded together with an expansion joint. I see it done quite often in Edinburgh.
     
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  6. Naknah

    Naknah

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    If it can be done would you go for lead over fibreglass Makie?
     
  7. ^woody^

    ^woody^

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    Yes they are sold. But why would you use a product that is only warranted for 10 years (due to the rubber joint and glue) when lead is designed to last more than 80 years?
     
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  8. datarebal

    datarebal

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    As far as pitch is concerned you can use a natural slate to 20 degrees with the correct headlap

    Gutter , Up the slope I would opt for 300 mm, and a slate over lap of 150 mm over this. That would give you a cushion for snow etc

    To fit lead properly without T pren you will not have enough space for correct weir formation.
    you could use T Pren hardly worth the expense here
    You could use Torch on felt or Epdm or GRP.
    There are also the hard metals that could be used...
     
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  9. Naknah

    Naknah

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    Thanks datarebal that's really helpful. It sounds like GRP is the way to go.
     
  10. catlad

    catlad

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    I'm not sure I would have bothered with slates and skylights
    on such a small area
    could you not have just glazed it instead.
     
  11. Makie

    Makie

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    It depends on a few things I suppose. I know in Edinburgh and some listed buildings I've worked on in central Scotland lead is required most of the time.
     
  12. Leofric

    Leofric

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    What sort of rainwater outlet are you providing to the gutter , an outlet on the gutter or discharging via a shute to a hopper head perhaps ? Just a thought , but something that needs to be detailed correctly.
     
  13. Naknah

    Naknah

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    Good question Leofric, I've no idea. This is the drawing but it doesn't seem to shed any light on the question! I'll have to google the options you mention there/ask the roofer.

    catlad - it's so long since this was designed that I can't fully remember why we went for this design but I think it came down to concerns around keeping it clean (it's not easily accessible), cost, heat.
     

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  14. Leofric

    Leofric

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    It would be interesting to see a side elevation or cross section and a roof plan to show how your designer intended this to work. Is this abutment gutter open at each end and sloping two ways from the middle or just sloping front to back ? Not enough information to tell what is what. Is it intended to discharge the gutter on to a pitched roof ? Ask the designer how it is supposed to work.
    p.s. the rear wall is annotated as being rendered but shown as brick coursing !
     
    Last edited: 22 Mar 2019
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