Roof lights how to and if it’s sensible

Alantstroud · 16 Jan 2018

hello everyone

I have just started extending my house with a ground floor flat roof garden room with two largish roof lights in it. My double glazing supplier has suggested that if the flat roof is built with a kerb to frame the window, a 10 degree fall and an internal bead he can supply stepped double glazed units to be inserted then weathered in (it will be a fibreglass roof). One roof light is 2.5m x 1.5m and the other is 1.5m x 0.75m.

Does this sound like a sensible idea or will I get problems later? The first quote I got for a bespoke roof light was over 3 grand!

Thanks

catlad · 16 Jan 2018

It is possible just to use stepped glass and then weather
it to your situation, however its going to be a challenge
getting a piece of glass that size on the roof.

freddiemercurystwin · 16 Jan 2018

Sounds like you're planning some kind of hybrid made up on site affair, probably doomed to failure! How do you plan on detailing it? Not to mention would Mr BC even sign it off?

But that aside yes weight for the DG unit alone for the biggy would be about 75-112kg depending on the glass thickness. Or should it be triple glazed - at those sizes? Though you'd have to get the DG unit up there even if you buy a proper window so that's a separate issue. Not to mention the cleaning of it and the safety issue.

The £3K price sounds about right to me.

Notch7 · 16 Jan 2018

If you make the large roof light 2500 x 1500 and put in a central rafter, your glass will be a sensible size.

If you try to get a unit 2500 x 1500 it cant be done with 4mm glass, Im not even sure if you can do it with 6mm glass.

You could do with stepped units -1 step on 1 side only for a drip

Set the glass on rafter gasket and make the rafter gasket extend out beyond the glass at the the lower end by an inch or so, that way if there are any leaks the water can escape.

you could use capex gable end bar for the 3 sides (mitre at corners) and standard rafter bar down the central rafter.

here is an example showing the sectional detail:
https://www.questhardware.co.uk/cap...les-c450/capex-cgf-50-gable-end-profile-p1293

Make your roof with flat timbers and then fit the rafter gasket and then spacers to form a glass rebate, make spacers narrow leaving gaps to the glass for water to run out.

On the bottom edge where you have the stepped glass, you will need some form of fascia -this can be a board, with a draught seal so when the glass sits down, the seal touches where the stepped glass is. You will need to cut out some small rectangles in the fascia so that the rafter gasket can poke through -that will then allow any condensation and any water ingress to escape.

Allow for the thickness of the GRP when you set out the lanterns so that the gable bars can sit over the grp upstand.

datarebal · 16 Jan 2018

I have seen this done many times large glass size too and on GRP flat roofs.
In fact I have seen much longer glass panels used on a Fulham side extension over a kitchen..
It was imported from Switzerland at a cost of £14000.00

noseall · 16 Jan 2018

freddiemercurystwin said:
The £3K price sounds about right to me.

Me too. I just priced a Velux (leccy) dome, quite a lot smaller than that and it was coming out at £1.5K

Alantstroud · 16 Jan 2018

Looking at the panoroof website now!

pilsbury · 17 Jan 2018

Got my triple glazed roof lights and kerbs from panoroof.

2 x 1.8m x 0.9m
1 x 1.8m x 0.8 m
1 x 0.9m x 0.9m

Came to a few quid over £1200

They do any size you want and they seem to do the trick.

Alantstroud · 18 Jan 2018

pilsbury said:
Got my triple glazed roof lights and kerbs from panoroof.

2 x 1.8m x 0.9m
1 x 1.8m x 0.8 m
1 x 0.9m x 0.9m

Came to a few quid over £1200

They do any size you want and they seem to do the trick.

Thank you everyone, pilsbury, any chance of some photos?

pilsbury · 18 Jan 2018

Not finished article but you get the jist. Easy as pie to fit although heavy.

garyo · 18 Jan 2018

Any chance of some photos of the drip detail Pilsbury? What stops the water rolling around the top and edges and causing problems?

pilsbury · 18 Jan 2018

I could take pics tomorrow. But grp goes up to top of wooden kerb then the roof light is simply dropped in place with lashings of low modulus silicone. Then the edges where the glass meets the top of the kerb are also gunked up with that same silicone creating a seal.

garyo · 18 Jan 2018

Sounds nice and simple. I'm probably putting one in over summer and a flat one like that would do me fine.

Alantstroud · 18 Jan 2018

I think I will go with the local option, for the two I needed the quote was over 2k, glass supply only is less than a quarter of that, provided mr BC officer is happy

pilsbury · 18 Jan 2018

garyo said:
Sounds nice and simple. I'm probably putting one in over summer and a flat one like that would do me fine.

They are all over eBay. Also via their website they can make any size. Call them. I talked their already competitive prices down. I could find nowhere coming close on price.

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Roof lights how to and if it’s sensible

Alantstroud

catlad

freddiemercurystwin

Notch7

datarebal

noseall

Alantstroud

pilsbury

Alantstroud

pilsbury

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