5mx5m mono pitched roof, help please.


2 Dec 2014
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United Kingdom

Can anyone offer some advice on my new garage roof.
The garage will be constructed using a single skin block wall.
The roof will be a mono pitched roof that will span just under 5m x 5m
which is quite a span and I would like some advise on joist materials.
I was going to use wood joist but was thinking about steel perlins as these will be much lighter but i have no experience of using steel perlins.

Many thanks,

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Any advice would much apperciated.

Show us a proposed drawing of the garage and ask specific questions.

Your original question is too ambiguous to answer.

There are a billion combinations of roof layout and a billion combinations of materials.

Steel is used where timber becomes impractical, i.e. when spans become so great as to warrant a small forest in order to span a certain distance.
I would love provide a plan but I'm not very good with computers to do that.
Sorry if I was vauge in my post.
Bascially it will be a single skin block construction 4.8 meters by 4.8 meters with an up and over door that is 4.2 meters wide and 2.1 meter high.
The roof will be a single pitched roof (mono roof) and covered by corrugated roof sheets/cladding so.
The pitch itself will be as shallow as building regs allow.
The joists will run across the width with the fall running to the rear and its highest elavation will be at the front above the door.
I hope this is better.
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Corrugated sheeting requires a series of purlins spanning in opposite directions to the sheets and with a facility to either hook the sheet fixings (angle iron) or be able to receive twist nails (timber).

My thoughts are a series of angle iron purlins with hook fixings although I'm not a designer. You may then need a series of trusses (1/4 spans?) to support the purlins.
So the span is actually 4.6m? I would just go with timber joists, 50x195 @ 450 centres will be OK. I wouldn't faff about with purlins myself, a timber one would have to be huge and a steely fella would likely need some SE input.
Thanks guys for the replies.
I'll be sticking with wood joists. The guy at my local TP said he thought 6x2 inch C16 timber would be ok but I thought it sounded a little on the small side.
I'll go with the 50x195.

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