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Polycarbonate rooflight modification

Does what it says on the tin
mc2fool
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Re: Polycarbonate rooflight modification

#424733

Postby mc2fool » July 4th, 2021, 5:29 pm

jfgw wrote:"Standoff" might be a better search term. There are plenty on eBay.

Most are metric, 25mm and 30mm lengths are available, e.g.,

https://www.ebay.co.uk/itm/332366408497

Thanks, that'll help the search :D. Not sure that nylon ones are a good idea for this application though as, from what I read, unless it's been specifically treated to do so, nylon breaks down over time with exposure to UV.

mc2fool
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Re: Polycarbonate rooflight modification

#438443

Postby mc2fool » August 30th, 2021, 4:29 pm

Update, and next question... :D

Phase 1 is now complete. As it turned out, with a brand new HSS drill bit and a corded drill (as opposed to a battery one), it wasn't so difficult to drill holes in the iron frame, so a lot of the previous discussion was solved simply by bolting on some brackets to attach the "overhang" at the front of the polycarbonate sheet to and to fix through it to the dome above that.

Image

Now, phase 2: the upstand is metal and also gets a lot of condensation on those certain days in winter. As can be seen, it's roofing-felted on the outside and painted (Sandtex 10 Year Exterior Satin) on the inside. It's just the angled part (possibly clearer in the photo below) that's metal.

So, I'm thinking of attaching some polystyrene to the inside of the angled part. I've yet to go to Wickes to examine the stuff but I think something like: https://www.wickes.co.uk/Kay-Metzeler-G ... m/p/210823

So, assuming that's suitable, how to attach it? Glue would be one way, and I am thinking lashings of PVA might be suitable from the point of being able to easily cover the entire surface, so there are no gaps between the painted metal and the polystyrene for condensation to form between them, but as for the adhesiveness of PVA for polystyrene to satin paint ???

If that won't stick then possibly PVA over most of it for the filling effect and some more suitable glue around the edges and in odd dabs in the middle? But which?

Another thought would be to sandwich the polystyrene between the metal and a piece of ply (5mm? 9mm?) on the inside, attached by bolts drilled through to the outside (with suitable amounts of sealant applied). Obviously a lot more faff (the ply would have to be painted too), but I am tempted by this idea for at least the front, as that's where we climb out (from a temporary ladder inside) and without some protection it's inevitable that chunks of the polystyrene will be kicked off at some point or another.

Thoughts, ideas, suggestions? :)

Image
Yes, replacing the foam seal is also on the to-do list! :D

Both photos copyright me!

Itsallaguess
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Re: Polycarbonate rooflight modification

#439659

Postby Itsallaguess » September 4th, 2021, 1:45 pm

mc2fool wrote:
So, I'm thinking of attaching some polystyrene to the inside of the angled part. I've yet to go to Wickes to examine the stuff but I think something like:

https://www.wickes.co.uk/Kay-Metzeler-General-Purpose-Polystyrene-EPS70---2400mm-x-1200mm-x-25mm/p/210823

So, assuming that's suitable, how to attach it?

Glue would be one way, and I am thinking lashings of PVA might be suitable from the point of being able to easily cover the entire surface, so there are no gaps between the painted metal and the polystyrene for condensation to form between them, but as for the adhesiveness of PVA for polystyrene to satin paint ???

If that won't stick then possibly PVA over most of it for the filling effect and some more suitable glue around the edges and in odd dabs in the middle? But which?

Another thought would be to sandwich the polystyrene between the metal and a piece of ply (5mm? 9mm?) on the inside, attached by bolts drilled through to the outside (with suitable amounts of sealant applied). Obviously a lot more faff (the ply would have to be painted too), but I am tempted by this idea for at least the front, as that's where we climb out (from a temporary ladder inside) and without some protection it's inevitable that chunks of the polystyrene will be kicked off at some point or another.

Thoughts, ideas, suggestions?


Not sure if it would be suitable, given the hinge-situation, but just throwing this one around in case it's useful -

Rather than some sort of 'sandwich' solution in this area, is there any scope for an 'enclosed' solution, with any insulation placed inside an appropriate size of rectangular 'ducting', with the potential benefit of the mechanical protection that you'd probably want in this area if you're climbing past it frequently, and also perhaps benefiting the fixing situation as well, given that you might then be supporting fewer 'elements' than the sandwich solution described above, perhaps?

This is a plastic flat-duct example of the sort of thing I was thinking about, but I assume metal versions would be available at different sizes as well, if you think it's something worth considering -

https://www.screwfix.com/p/manrose-204-x-60mm-flat-channel-1m/59769

Anyhow - just thought I'd mention the above in case you're still rattling round ideas..

Cheers,

Itsallaguess

mc2fool
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Re: Polycarbonate rooflight modification

#439677

Postby mc2fool » September 4th, 2021, 2:56 pm

Itsallaguess wrote:Not sure if it would be suitable, given the hinge-situation, but just throwing this one around in case it's useful -

Rather than some sort of 'sandwich' solution in this area, is there any scope for an 'enclosed' solution, with any insulation placed inside an appropriate size of rectangular 'ducting', with the potential benefit of the mechanical protection that you'd probably want in this area if you're climbing past it frequently, and also perhaps benefiting the fixing situation as well, given that you might then be supporting fewer 'elements' than the sandwich solution described above, perhaps?

This is a plastic flat-duct example of the sort of thing I was thinking about, but I assume metal versions would be available at different sizes as well, if you think it's something worth considering -

https://www.screwfix.com/p/manrose-204-x-60mm-flat-channel-1m/59769

Anyhow - just thought I'd mention the above in case you're still rattling round ideas..

Hi. Thanks for the suggestion, although I don't really see how it'd work out. There's zero chance of finding one that's the right height (width), which would mean that I'd have to cut it, width wise, and at that point it'd no longer be enclosed. There's also no chance of getting one the right thickness either. :D

However, you have given me an idea :!: being that I could get some of those and cut them to an appropriately sized "L" shape, and then use that instead of plywood for the inside "bread" of the sandwich. Cheaper than plywood and no need to paint too. ;)

Itsallaguess
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Re: Polycarbonate rooflight modification

#439683

Postby Itsallaguess » September 4th, 2021, 3:22 pm

mc2fool wrote:
However, you have given me an idea :!: being that I could get some of those and cut them to an appropriately sized "L" shape, and then use that instead of plywood for the inside "bread" of the sandwich.

Cheaper than plywood and no need to paint too. ;)


Result!

Cheers,

Itsallaguess

mc2fool
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Re: Polycarbonate rooflight modification

#554968

Postby mc2fool » December 15th, 2022, 1:05 pm

An update on this project ... in the end I attached the previously linked to Wickes polystyrene to the whole of the inside of the (metal) angled part of the upstand (see previous photos), using lashings of PVA and a fair amount of sealant, and also around the supports for the struts that hold the skylight vertical when open (also see previous photos!). Although I bought the aforementioned Screwfix channels and cut them to size I didn't fit them, on a let's see how it goes without basis, and they've just stayed unfitted. ;)

So, two winters in and it's been a massive improvement; no more condensation from the skylight itself or from the inside of the upstand, which previously on really bad days, as I said in the OP, "I tried to sponge it off and half filled a washing up bowl!". Almost total success with only a couple of very small occasional condensation drips, from the lowest point of the struts, on both sides, i.e. the bit below the lower of the right hand nuts in the photo below.

The bolt is attached (welded) to the metal support which is attached to the metal upstand, and so directly conveys the cold from the outside to the metal struts. There's nothing I can do about the strut and support arrangement itself, and insulating most of the struts themselves isn't on, although I suppose I could try gluing a small block of polystyrene to the bottom of the strut over the lower nut (not to it of course) but wondered if anyone here had any other ideas...? :D

Image


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