Skylight hole in verandah roof.

[jackruss]

Hi all,
I have a verandah roof. 7 deg pitch .42 corrugated colorbond roofing.
Span from wall to verandah plate of 4800.

Rafters are 150 x45 hyspan lvl at 600 centres.

For this section of verandah its about 5500 wide.

I want to install three sheets wide ( 762x3 ) Corrugated Polycarbonate over a section in the middle if this, running the full 4800 from wall to verandah plate.

My question is can I move the rafters that sit in the middle of the skylight to the edges of the opening, and so have a 2100 wide opening with only the battens spaning the opening.

Instead of leaving the rafters running through the middle of the skylight.


Hope this makes sense.

thanks
JR

[OBBob]

It might sage over time? The laser light would be made for 600mm ctrs. Presumably you would still need battens accross the rafters to attach the sheets ... maybe you could reinforce these with angl steel of aluminium over that section?

[ozwinner]

My question is can I move the rafters that sit in the middle of the skylight to the edges of the opening, and so have a 2100 wide opening with only the battens spaning the opening.

Instead of leaving the rafters running through the middle of the skylight.JR

Why?
What do hope to achive?

Al :confused:

[Barry_White]

Why?
What do hope to achive?

Al :confused:

A real hot spot under the verandah.

And you would probably have to increase the battens to 150 x 45 and fit them between the rafters.

[echnidna]

You would need larger rafters each side of the skylight and much larger battens (installed on edge as purlins)
So it won't be a cheap project.

[jackruss]

Why would cost isn't an issue. I am still using the same number of rafters, just nail laminating them either side of the opening??

The batten is just to hold the polycarb. roofing.

I know polycarb is not trafficable ( is that the correct spelling ?!). So the load on the battens will always be roofing material only, and poly carb is VERY light.

i don't expect uplift to be an issue either as it would just pop the fixings long before it lifted the batten.

Note the installation is in Sydney

I want to have a clean opening, that lets as much light in both on the deck and thru the kitchen window.

As you can imagine, a 4800 deep verandah will cut a lot of light.

For the record its a south east facing verandah, and the bulk will be covered in steel.

Beefing up the battens seems the best way to go, while still giving a clean line.

thanks

JR

[Barry_White]

Why would cost isn't an issue. I am still using the same number of rafters, just nail laminating them either side of the opening??

The batten is just to hold the polycarb. roofing.

I know polycarb is not trafficable ( is that the correct spelling ?!). So the load on the battens will always be roofing material only, and poly carb is VERY light.

i don't expect uplift to be an issue either as it would just pop the fixings long before it lifted the batten.

Note the installation is in Sydney

I want to have a clean opening, that lets as much light in both on the deck and thru the kitchen window.

As you can imagine, a 4800 deep verandah will cut a lot of light.

For the record its a south east facing verandah, and the bulk will be covered in steel.

Beefing up the battens seems the best way to go, while still giving a clean line.

thanks

JR

Jack it looks like you answered all your own questions without our help.

[jackruss]

Well Barrry

Yes and No.

I hadn't thought about the heat gain, or about beefing up the battens.

I was just looking for some input from the brains trust of the forum.

Thinking outloud so to speak, didn't mean to ask and answer my own question.

I know if I had made a glaring assumption, someone would jump on it.

I appreciate all the input.

Its all about the planning right, do it once and do it right.

Anyway Barry, I would think the thermal transfer thru the steel either side would be similar to polycarbonate, right?

JR

[journeyman Mick]

Jack,
it may or may not worry you, but I could just about gauarantee that it would not meet the requirements of the building code. Conducted heat would be less from the polycarbonate would be less but the radiant heat would be a lot more, enough to make it very uncomfortable on a sunny day.

Mick

[Barry_White]

Well Barrry

Yes and No.

I hadn't thought about the heat gain, or about beefing up the battens.

I was just looking for some input from the brains trust of the forum.

Thinking outloud so to speak, didn't mean to ask and answer my own question.

I know if I had made a glaring assumption, someone would jump on it.

I appreciate all the input.

Its all about the planning right, do it once and do it right.

Anyway Barry, I would think the thermal transfer thru the steel either side would be similar to polycarbonate, right?

JR

Jack

At the moment I do some commission work for Spanline and attached is a sheet we use to show the Solar Gain for various products. At the bottom you will notice the low number for Spanline roof sheeting. This roof sheeting because of its profile and colour coating has a very low heat gain compared to polycarbonate and Alsynite. Colorbond corrugated would not be as low as this but would certainly not be as high as the heat gain from polycarbonate or even Alsynite.

Spanline sheeting has an underneath gloss coat of between 55 and 80% which contributes to its low heat gain. We do very little in the way of dark colours with Spanline so it would depend on what colour you have on your roof as to what heat gain you will get out of your steel roof.

Normal Colorbond only has a wash grey coat on the underside which would be lucky to be 10% gloss.

If you want to increase your light in the house I would suggest installing some Solar Tube brand type skylights in the house. The Solar Tube brand is the best one on the market because it gives more light because of its highly reflective tube.

Hope this helps in your decision.

[Bleedin Thumb]

Have you thought of just removing the tin over the area in question and leaving it open to the elements - or even adding extra joists to get a pergola effect. You wo'nt have the heat problem but a bit damp during rain.:eek: