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An important note, our Laserlite 2000+ Twinwall has UV protection on both sides. So either side can face the sun.
Another recent question:
Looking at using Twinwall 610 x 4000 x 8mm sheets, joined using H snap joiners. Can you please confirm the rafter centres measurement between sheets? I’m getting 640mm to allow for thermal expansion (610 + 15 +15).
Also, can i use the off cuts from the 5.8m H snaps and combine them on another sheet (as losing 1.8m per 4.0m sheet)?
Thanks for your email. 640mm is correct.
So if the sheet goes flush to the edge of the first rafter, it will need to be 625mm from the outer edge of that rafter to the middle of the next rafter. Then each subsequent rafter can be 640mm from the centre of that rafter.
Depending on how square the structure is, you may want to make it 10-20mm narrower (or more). Sometimes you may need to make it slightly out of square in order to accommodate existing house/walls etc. Especially over 4m.
It’s much easier to trim the sheets down a bit (with a sharp knife or handsaw) than it is to be slightly too narrow in some places!
But if you’re confident it’ll be completely square and won’t need to trim the sheets then 640mm is right.
You can also use the H snap joiner off-cuts. If you cut them dead square then they but together fairly well. You can use a bit of sealant (suitable for polycarbonate) if you like. But otherwise, even if a very small amount of water gets in through the join it’ll just run down the inside of the joiner channel and out the end.
Thanks for your enquiry.
This is for the 8mm grey at 610mm wide. They are easy to trim to size with a sharp knife or hand saw. We can usually get them trimmed at factory, but unfortunately this isn’t an option for our South Island orders.
You’re correct about the joiner. If that’s sitting on a rafter, then you can put a screw through the bottom plate of the joiner, every 400mm or so. You won’t require a fastener through the Twinwall sheet itself (since it’s only spanning 610mm) as that will be held down by the joiner, once you snap the top plate into place.
I’ve also included the aluminium F channel. This can be used flange facing down on your outside edge. You can fasten the flange through the barge capping on the outside edge, to hold that edge down.
You can then use another F channel on your inside edge. You’d put this one flange facing up the plywood wall, so it would work like an apron flashing. You can also fasten the flange through the plywood, or simply glue it if you don’t want to pierce the cladding.
Lastly, I’ve put some sealer and dust tape in (sealer tape goes at the top edge, dust tape at the bottom edge). The U end cap fits over both tapes to protect it and hold it in place (including under the ridge capping).
I’ve included a 6m ridge capping, the one I think would be most suitable.
We’re pretty limited in the type of polycarbonate flashings we can get. You’re probably better going for a metal one (from a roofing company), with a soft edge. Then you’ll be able to form the edge to the various pans and ridges of the Custom Glaze butting up together.
Normally you have purlins every 1500mm max, but since your one will be just over 2m total, you’d put a purlin at the mid point i.e. 1m.
If you’re using glulam wider than 70mm (the width of the ridge on the Custom Glaze), and you put them at 600mm centre to centre, then the sheets will join directly over the rafters, and fasten directly into them.
In which case the mid purlin would just be there to stop flex, and would not need to be substantial. If necessary you can put a screw through the mid pan to stop it flexing up from wind coming underneath.
There is a tolerance with the sheets, and they have been known to be 595mm centre to centre, not 600mm. So I would suggest waiting until the sheets are in stock first, and measuring them, before putting the rafters up.
Client is looking for the custom glaze…
Will be tricky on the change of pitch/ridge (1 side 10 degrees, 1 side 5 degrees…and not a true 45 degree angle).
We are also looking for direction on the centers and size of rafters required? Sheet length will be 2m.
(I had thought using glulam for rafters and thus getting a cleaner look, which would then be painted to look good).