Flat roof timber span

[th3joker]

I'm connecting the Garage onto the house and need to redo the roof.

The span length is 4930mm on top or 4780mm off hangers what size timbers would I need to buy.

Planning to use ply and rubber on top, in Cornwall so we basically get snow once every ten years and it's never deep.

I would rather use a thicker timber and less height if possible as height will be more of an issue than anything else, I could even close up the centres a bit more.

Thanks in advance for any help or suggestions

 

[tony1851]

You'd be looking at something like 7"x3"s at 400c/s, or maybe 6"x3"s if closer - say at 350c/s. The problem
here will be deflection rather than the timber being over-stressed.
Too much deflection and you get ponding unless there is a reasonable fall.