How to span 3m for corrugated plastic roof

Esho

There's a 3 m wide X 2.5 m deep space between the kitchen wall and the end wall.

I want to cover it in to make space.

I was thinking of heavy joist hangers and 4x2s to span between them, to screw the corrugated plastic sheets into.

Would this work or is there a better way to do it?

Lumen

15m of 4x2 rafters (+sheeting+fixings+purlins?) is only weigh something like 100kg, which isn't much, but....

Are there windows above the planned roof on the kitchen wall? If so you might need to engineer the roof as a means of escape, with associated imposed loads, and then I would definitely look at a product which can be jumped on (e.g. polycarbonate).

Consult some span tables:

https://www.timberbeamcalculator.co.uk/en-ie/span-table/flat-roof-joists?load=0.75&class=C16

You should also account for maybe 0.32kN/m2 snow load (source).

I am not an engineer and this is not structural advice.

Also think about gutters and downpipes.

The Continental Op

Also consider wind load. Are you creating a wind tunnel that could take off in a storm?

Esho

https://www.boards.ie/discussion/comment/119583171#Comment_119583171

Thanks for that link -

Good one about the snow load, water runoff and the emergency exit.

There is a drain on the end of it, so no issues. Theres only a non opening bathroom window above it , so should be ok.

I'll check the specs on the joist hangers and try and with out what that can cumulatively support.

Really useful advice - thanks, very much appreciated

Esho

https://www.boards.ie/discussion/comment/119583186#Comment_119583186

That crossed my mind alright. Think it'd be ok as there is no where for the wind to go through. Im going to give it a goggle - thanks

Esho

https://www.boards.ie/discussion/comment/119583171#Comment_119583171

Wow - the joist table is excellent. Thanks again