Large skylight repair - flashbanding?

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We have a large (c. 5.33m x 1.68m – measured internally, so I’m guessing nearer 5.5m x 1.8 or more externally) singled glazed angled roof light. It appears to be made from two sheets of glass.

1) The seals are failing and need replacing/repairing. The roof material is made from fibreglass sheets, corrugated to look like fibreglass.
2) We then plan to secondary glaze it with four (or possibly two) cast acrylic sheets on the inside, secured with a wooden frame.

Photos here: https://www.amazon.co.uk/photos/share/0dJCw4rC1TRQn5ifhpQpJogkP2suc9WdwUb3tE60Pi4
A less extensive set attached to this post.

Replacing the whole unit with a double or triple glazed one isn't economically viable (quotes so far have been £9k-£14k+)

Any tips on how to go about 1 and 2 (particularly the first) would be much appreciated. It might be as simple as clearing it all up, applying flashband primer paint, and wide flashband tape. But (a) that seems a bit temporary and (b) I suspect I’m missing something! E.g. Any sense in plastic/fibreglass edging strips underneath? e.g. like this . Or another approach entirely? Lead? Lead alternatives? E.g. Wakaflex Rapid Flashing, Ubiflex, Masterform by Nicholson. Stainless steel? (All probably beyond my skill set, unlike it's quick to learn for someone practical).
If flashband, even as temporary measure, I'd need to wait for reasonably warm (and dry) weather for the adhesives to work properly. So I can't really crack on with it as quickly as I'd like!

Despite contacting 30+ roofers, most haven’t responded (despite chasers and lapse of several months) at all and those that have got in touch have said they're too busy or only doing total re-roofing projects. Given heat loss / poor insulation, extensive condensation and insane gas bills, it looks like I’ll need to get my hands dirty! Though if anyone has recommendations on people that might be able to help (near Crystal Palace), that’d be appreciated too.

Any tips much appreciated.
 

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What's your appetite for roofing over it?

It's single glazed, so even if it doesn't leak it'll probably generate as much moisture as a leak would just in condensation
 
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Might be hard to find something to replace this, you really could do with some sort of flashing kit, might have to be made for your window due to size, probably combined with some leadwork.

Flashband has it's uses, but it's no long term solution for your roof.
 
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Fwiw it's a decra roof system . Metal not fibre glass . Fair few of the panels are bent probably foot traffic .
Many thanks! That's handy to know.
In case it helps, here are a few other shots of it. It may be two different systems going on (?). And it may be it needs some TLC ... Certainly the fascias do - I was considering possibly uPVC overcladding rather than replacing the timber (or perhaps both).
 

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What's your appetite for roofing over it?

It's single glazed, so even if it doesn't leak it'll probably generate as much moisture as a leak would just in condensation
Almost no appetite, I'm afraid - it's a (/the) key feature of the property.

Condensation is occasionally a problem (though not nearly as bad as on other single glazing in the property) as set out at 2 above, there's a plan to install an secondary inner glaze (in cast acrylic). But I'd like to get it sealed as best as possible from the outside first.
 
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Might be hard to find something to replace this, you really could do with some sort of flashing kit, might have to be made for your window due to size, probably combined with some leadwork.

Flashband has it's uses, but it's no long term solution for your roof.
Thanks. So far I'm struggling to find anyone who'll even inspect it, yet alone advice on how to address it!

For a flashing kit, would the glass have to be lifted and reinstalled? I ask because that may not be viable - you'd probably need a crane, in which case it'd need a 30m arm, given the location. Or can it be retrofitted in place. I'm afraid I'm pretty clueless when it comes to roofing ... ! But willing to learn.

The quote I've had so far for an installed replacement are in five figures, which isn't on the cards. So it's unfortunately a case of trying to make the best of what we've got (even if that means periodically having to re-flashband it). A roofer I spoke to on the phone today (but who'd seen these photos) said he'd not touch it (too busy with other work) but DIY flashband might me the best economical bet.
 
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Once upon a time about 8 years ago I needed to replace about 48sqm of roof glazing; single pane, aluminium T supports and asbestos rope gaskets. The local double glazing guys weren't interested, the bigger name guys further away quoted just shy of £30k+VAT..

..an outfit called Architectural Products Ltd in Tewkesbury quoted £3.5k for supply only of an industrial grade double glazed roofing system that suited the place well, so we got on with doing it ourselves. I see they're still around, perhaps they could supply something helpful; the dimensions you've quoted are definitely more their "shopping mall" bread and butter than residential
 
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I was wondering if you could buy flashing extrusions that you could doctor to suit. I've looked, but they are hard to find.

I'm sure some of the roofers on here might be able to advise on wether this could be carried out with lead... as it can be soldered/welded together. Down side is, your roofing is in sheets not individual tiles, so this will make it awkward, as they may need to lift them around your window.

I'll keep thinking! (y)
 
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1) The seals are failing and need replacing/repairing
The images don’t really give much of a clue how the structure was weathered when built.

Your problem is that the correct way to weather to an upstand or side abutment is to create a hidden valley under the roof tiles or some form of continuous soaker…..without seeing how it was constructed, it’s not possible to know if this was done.

With the glass in place your only option is to weather on the face of the tile.….which is not really correct, but it’s all you can do.

Your starting point is to create a rigid upstand for any flashing material to stick to - It looks like the glass overhangs, so you need to fix some timber under the glass to come out flush to the glass.

You can then fix maybe a cut plastic fascia board to form an upstand.

and the flashing will need to be a flexible material -mayber EPDM strip, if that can be stuck to the decra face.

Maybe a liquid roofing system

I wouldn’t use fibreglass - those decra tiles probably move too much.
 
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See above. You have inherited a diabolical roof, sorry. Decra tiles are like single use plates/cutlery that you sling after parties. They belong on shed roofs.
I feared as much!

The thing is, for the most part, the roofers that didn't respond didn't even know. Seems they're so busy that inspecting for more potential work doesn't even make the radar. I guess that's London for you ... and probably labour shortages, Covid backlogs, etc.

The roof is built over a bungalow which has been extended at various times over decades. About half of it was originally a flat roof (much of it seems to be something that looks like about 10" of compressed hay with a bitumen covering), with an angled cold roof (including the skylight) added on top. I think that at least that part of the many roofs (and probably all of them - see internal loft shots below) was only built to support a lightweight roof, which is what I imagine informed the choice of Decra Classic. I suspect this was all done quite some time ago (I'm guessing 40 years but really don't know).

Lots more photos here ...
- Inside the lofts
- Exterior roofs

Perhaps inevitably, the only roofers who've inspected have suggested reroofing the whole lot (maybe 350m2 of roof), either with:

- sheet metal (like this https://www.southernsheeting.co.uk/...-sb132b7pl00e53.html?filter_set[]=176,177,313 - which I suspect is the economy but pretty ugly option); or

- creating a warm roof covered in EDPM.

Quotes awaited, but the EDPM option seems likely to be in the £80k-£100k ballpark. Alas, don't have that to spare so - unless it's totally wrongheaded to try to do so - I'm likely to need to eek out the existing one as long as possible. However, if total replacement is a crushing inevitability, there's perhaps no point either patch repairing the roof (which doesn't currently seem to be a particular problem at the moment ... at least as far as I'm aware [famous last words!]) or addressing the skylight.

Thoughts welcome - and much appreciated.
 
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The images don’t really give much of a clue how the structure was weathered when built.

Your problem is that the correct way to weather to an upstand or side abutment is to create a hidden valley under the roof tiles or some form of continuous soaker…..without seeing how it was constructed, it’s not possible to know if this was done.

With the glass in place your only option is to weather on the face of the tile.….which is not really correct, but it’s all you can do.

Your starting point is to create a rigid upstand for any flashing material to stick to - It looks like the glass overhangs, so you need to fix some timber under the glass to come out flush to the glass.

You can then fix maybe a cut plastic fascia board to form an upstand.

and the flashing will need to be a flexible material -mayber EPDM strip, if that can be stuck to the decra face.

Maybe a liquid roofing system

I wouldn’t use fibreglass - those decra tiles probably move too much.
Many thanks. Seems like a sensible and practical solution, given the circumstances.

FWIW, the other side of other sky light, which has been flashed (I'm unsure when - I think it was originally installed c. 2006/2007) looks like this. I really should take some better photos ... and remove the leaves beforehand!
 

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