Avoiding overhang at boundary

RonnyRaygun · 11 Feb 2016

I will soon be drawing up a mate's rear extension.

He wants to build right up to the boundary on both sides to maximise his available space, but obviously there cannot be any overhang to the neighbours' land from roof tiles etc.

The extension will most likely be a simple lean to and I am thinking we will need to step in 50mm or so to allow for the roof tiles to overhang the side walls but I am wondering if there is any detail that allows for the wall to abut the boundary and not require a overhang of any description??

Thanks!

Deleted 224857 · 11 Feb 2016

flat roof on boundary side and lean to on the other half.

RonnyRaygun · 11 Feb 2016

?? Don't quite follow...

It will be a full width lean to - was thinking one possibility is a parapet both sides with once weathered coping, but thought that would need a small overhang even on the high side.

Obviously a pitched roof needs a 40mm or so overhang for the tiles even on the non gutter ends?

Deleted 224857 · 12 Feb 2016

had a simiar issue. did not want to go through the hassle of PWA.As I am end terrace did a full width extension. highway side lean to and split the roof in 2 sections,with neighbour side flattie.

no overhang or anything. you could go for a hip on neighbour side , but that would mean going full width of party wall

RonnyRaygun · 12 Feb 2016

How do you do a flat roof with no overhang whatsoever? Surely even with a flat roof there will be a small overhang where the felt or whatever laps down and around the wall - it can't just stop flush?

Do you have and photos as I still can't quite work out what you mean.

Cheers!

jeds · 12 Feb 2016

We sometimes do a small parapet in that situation.

freddiemercurystwin · 12 Feb 2016

You can fit a coping stone and have it flush provided waterproofing (ie dpcs in appropriate positions etc) is adequate. Though there will likely be excessive staining. You could also do a lead capping flashing that could be flush, again if detailed correctly it will be fine apart from staining. Or even a metal coping with just say a 10mm overhang would be better than nothing and you could get a drip too then, albeit less effective.

Or just give your mate a reality check and set it 30mm off the boundary or whatever the overhang is. Maybe spend your time more usefully by designing as thin a wall as possible instead if not already. Been discussed on here a couple of times.

Though there are plenty of buildings out there with timber cladding that have a completely flush lead cap at the top and they don’t appear to suffer from excessive staining.

^woody^ · 12 Feb 2016

The main issue is water staining, and even a parapet will require a drip as wide as any verge should be.

I can't see why a verge can't be flush, and to deal with staining perhaps have three course of blue or red engineers in a band on a raked cut of the main wall. Possibly with a 10mm oversail, but flush if need be.

But if space is the issue, have a normal verge and just design a thinner wall to the sides.

jeds · 12 Feb 2016

How much water do you imagine is cascading off this coping. Just use a flush system - like in freddy's example - no overhang required.

chappers · 12 Feb 2016

I agree, just build a parapet capped with once weathered copings with the drip overhang onto your side of the parapet , just slim the cavity down by 20mm to allow for a slight overhang on the copings, could always use GRP to cap if you're worried about staining.

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Avoiding overhang at boundary

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