Using glass in verandah roof

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14th December 2006, 08:15 AM
tackon

Using glass in verandah roof

Can anyone help with ideas for design/ accessories?
I have a 1930s stucco (over timber frame) house with no eaves, so beautiful (demolition) Kauri french doors I had installed on the North side get a beating from rain and sun, and now they leak badly. To protect them, but not cut out too much light, I want to put a kind of tinted glass awning above them. But there are 3 steps outside the doors leading down to ground level (a drop of about 1 m) and these run the width of the two doors and a set of 3 windows too
For cosmetic and access reasons I want the 'awning' to span them all, (with doors open right back) a total of about 4m.

I already have 10 sheets of laminated smoked glass that I'd like to use as 'roofing', each one about 580mm x 1530mm. (I won't use laserlite or similar because a friend fell through a (painted) plastic roof and broke his back. Be careful out there guys!).

I figure I can run a beam against the wall above the doors and windows and attach rafters to that at about 600 centres (is that too wide? Should I use those metal 'hangers' nailed to the beam? Do they come with a standard 5 degree pitch built in?). Then lay the glass on the rafters (does it need to be inserted into aluminium joiners attached to the rafters? or what other method would allow expansion and still be weather-proof (and wind-proof?
Then, because of the steps ouside, the outer beam at the lower end of the pitch (5 degrees right?) needs to span almost the same distance without any intermediate supporting posts (or say 3 m with a 500mm overhang on either end, would that work? Is this even possible? - what size beam would it require? I was hoping for a lightweight look, because the view from the windows and doors is my best view. Could a metal girder be an alternative?)

Suppose I solve that problem, the last one I am aware of is this:
how do I prevent the glass from sliding down the roof, and yet avoid pooling of water at the base? I don't really want conventional spouting along the base: too heavy looking. I'm happy if rain just runs downm off the glass, its just sleeper steps and a paved area below.

With laserlite etc you can drill holes through the sheets, but not with glass like this. Is there some kind of metal edge / bead, channel or similar that could be attached along the length of the outer beam, with the glass slotting into it? Like what I'd use on the sides? Then would I drill holes in the channel, between the sheets of glass, for drainage?
Or can I set the glass against a wooden bead attached to the beam, so it is virtually flush with the top of the beam, and use a silicon product to seal it?

Any suggestions at all greatly appreciated.
23rd December 2006, 08:14 PM
GrantE

Glass awning project.

I just had a browse for the steel glazing bars we used to use for sawtooth factory roofs. No immediate joy.

There were a line of galvanised tee shaped 'Roof Glazing bars' with a bulb, the glass was fitted with a neoprene edge which was then secured by a galvanised section which locked to the bulb when pressed on.
Perhaps you could try a greenhouse manufacturer, industrial builder, or building recycler.

As for the carpentry, I'll leave that to the experts, but I'd be doing it in steel given the weights and probable uplift forces involved.

Regds
G.
31st December 2006, 09:44 AM
pawnhead

It sounds like you know what you're doing and you've got the right ideas.

I built a pyramid glass roof some time ago now and I didn't buy any special fittings to do it. I just used a small piece of heavy duty, non perforated hoop iron, bent back on itself (allowing a gap for glass thickness) and screwed it (housed in) to the top of the rafters at the bottom. The glass just sits in the hook and the hook stops it sliding down.
With your glass at 580mm wide, I'd be spacing the rafters at 590mm centres, which will give you a 10mm gap between sheets. Silicone the glass down, and silicone between the glass sheets before you cover the joint with a flat timber batten siliconed and screwed down between the two sheets and rebated over the hook at the bottom. If you want the glass to overhang the rafter slightly (stops water dripping from your rafters and looks good, but I wouldn't go over 50mm), then just make the hook longer and paint the bottom where it's seen, or you could leave the glass flush, or stop it short of the rafter end, according to taste.

With the outside beam, just get the smallest one possible, but I'd be installing it so the rafters finish flush with it at the top (not underneath, with the rafters sitting on top). It looks better, gives more height under the beam, and helps support the glass, but it's a bit more work because you'd have to house the rafters in at least 10mm > 15mm, for two thirds the rafter depth. At the top end, you can't get joist hangers on an angle, but you can notch them in to the underside of the rafter, or just use a multi grip on each side of the rafter instead. You can add an eaves overhang by just butting and screwing a rafter to the beam, and installing a tightly stretched (using a 3" nail) piece of hoop iron along the top extending from the rafter to the eaves overhanging rafter extension. In your case, leave it long enough to bend a hook on the end for the glass and you've killed two birds with one stone :ok: .

I've done just this on my pergola which is laserlite on a 5 degree pitch with a 600 overhang, and I'll be posting up pics of everything probably this afternoon after I've put a post together for my thread on bifold doors. :2tsup:

edit : - The advice is probably a bit late to help tackon, but it might be useful if anyone else is interested.
3rd January 2007, 08:17 AM
tackon

Roof glazing. Further questions:

Thanks very much for the advice on this. Pawnhead, dDid you post the pics of your pergola? I did not find that message. I had a brainwave about a 'hook' myself, so will pursue this. May try to source aluminium to avoid rust/paint issues.
A couple of related questions: What size beam would I need to span a 4 m gap at the lower edge (with 10 rafters attached and 10 sheets of 7 ml glass?) (I imagine the rafters will be 100 x 50; or would 50x50 be adequate? )Can you advise?
And if I use timber battens over the sheets of glass, how can I reach them to fasten in? I mean: I' m not sure about putting my weight on the glass and frame. I guess I could fit a screw at the top, by hanging over the parapet of the roof, (Not sure if I can reach) and one at the bottom, from a ladder below. Is that enough? Or is it possible to work from side to side, putting in one sheet of glass, then screwing in the the cover batten, then sliding the next sheet in? Silicone as I go?
Thanks very much, :)
Helen
3rd January 2007, 12:02 PM
pawnhead

Quote:

Originally Posted by tackon

Thanks very much for the advice on this. Pawnhead, dDid you post the pics of your pergola?

Yes, I’ve posted details on my doors since they’re finished now. They’re quite lengthy posts that reached the site’s character limit, and the one you’d be interested in is the last post (wait for it to load and it will take you to the relevant post in the thread) which gives some details on the pergola that I constructed. You can see the hoop iron I’ve installed under the laserlite in this pic. It’s important to stretch the hoop iron tightly because it carries the weight of the overhang. Here’s some pics I just took illustrating how I stretched the hoop iron.: -
First you nail the hoop iron to the top of the overhang rafter (Don’t bend the nails. This is just a demo on an offcut)
Then you butt the rafter to the beam and screw it from the opposite side.
Then you drive a three inch nail on an angle into the rafter.
Then you bend the nail and drive it home by hitting the bend.
It pulls the hoop iron taught, and if you go too far you can actually tear the hoop iron, so be careful not to stretch it too tight. After nailing some clouts in you can remove the three inch nail. When fixing the battens, you'll have to drill through the hoop iron.
The heavy duty non-perforated hoop iron would be better, and I certainly wouldn't use that lightweight stuff for the hook.

This pic shows how I've booted my rafters to my hyspan beam. The rafters are at a five degree pitch so I notched the bottom into the boots. The other end (at the pergola beam) is housed 12mm X 2/3 the depth of the rafter because I didn't want to see ugly boots on my nice new pergola.

Quote:

Originally Posted by tackon

I had a brainwave about a 'hook' myself, so will pursue this. May try to source aluminium to avoid rust/paint issues.

Yeh, aluminium would look nice from underneath if you were overhanging the glass. In my case with the pyramid I built, the glass wasn’t overhanging, the batten covers the hook from on top, and the end of the rafter where you could see a tiny bit of the end of the galvanised hoop iron, was bogged up with gappo and painted. You could always just glue a batten of timber over it from underneath if you wanted.

Quote:

Originally Posted by tackon

A couple of related questions: What size beam would I need to span a 4 m gap at the lower edge (with 10 rafters attached and 10 sheets of 7 ml glass?) (I imagine the rafters will be 100 x 50; or would 50x50 be adequate? )Can you advise?

My brother has my NSW framing code at the moment so I can’t look it up, but I found these hardwood span tables on the net, and in this screencap you can see that you’ve got no problems with your rafters since a 100X38 will span 1800 and can overhang up to 770. I wouldn't go down to a 50X50 though.:o I'd just use a bit of 90X45 treated pine. Even though it's only rated at F7 and these tables deal with hardwood starting at F14. I think 90X45 pine will span up to 2100 as a rafter (from memory), but it could be 1800. You've got no problems since you're well under that.
In this screencap under ‘Roof Beams’ you can see that even with hardwood, you can’t span more than 3900. But the minimum roof span that they’re applying is 2400. You’d have much less than that with your glass roof which would weigh no more than a tiled roof. To calculate your E.L. (Effective roof length) you take half the span of your rafter plus the overhang. So if your sheets are 1530 long, and you incorporate an overhang of say 450, then your EL will be 1530 – 450 = 1080 /2 = 540 + 450 = 990. This is much less than 2400. What I would do is just whack in a piece of hardwood or treated pine, about 300X50 (or 290X45). It certainly won’t break but you could increase it to a 300X75 if you wanted to play it safe and if you’ve got a strong back and a couple of mates to help you lift it ;)
Otherwise you'd have to consult an engineer since the span tables don't cover your particular situation. They'll probably have you install a huge steel girder. :rofl:

Quote:

Originally Posted by tackon

And if I use timber battens over the sheets of glass, how can I reach them to fasten in? I mean: I' m not sure about putting my weight on the glass and frame. I guess I could fit a screw at the top, by hanging over the parapet of the roof, (Not sure if I can reach) and one at the bottom, from a ladder below. Is that enough? Or is it possible to work from side to side, putting in one sheet of glass, then screwing in the the cover batten, then sliding the next sheet in? Silicone as I go?
Thanks very much, :)
Helen

Yeh, you could easily reach over from the side and install one at a time since they’re only 580 wide. You should also be able to reach up from the bottom quite a way since they’re only 1530 long (If your ladder is high enough). If you’ve built it properly then the battens (and the glass itself) should be able to carry your weight. If they can’t then don’t invite me around to stand underneath it in a storm ;)

Any more questions, just give a holler.
Cheers, and good luck.