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

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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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.
 
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.
 
Cheers Leofric I’ll look that up. That doesn’t sound too bad
 
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How long will that box gutter be? It can't be done in lead if more than 1m long unless it's stepped.

Lead could be done if it is welded together with an expansion joint. I see it done quite often in Edinburgh.
 
If it can be done would you go for lead over fibreglass Makie?
 
Lead could be done if it is welded together with an expansion joint. I see it done quite often in Edinburgh.
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?
 
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...
 
Thanks datarebal that's really helpful. It sounds like GRP is the way to go.
 
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.
 
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?

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.
 
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.
 
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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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 !
 
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