After some advice again chaps, after getting confuzzled by google and the sagulator. Long story short - I need to build a carport in a hurry, ie next weekend ideally. Nothing fancy, quick and dirty will be fine. Going for a simple timber frame with onduline corrugated roofing sheets on the top. Panels may be trellis in between in due course at one end and 1 bay.
Plan is as follows:
10.2m long by approx 3.6m wide. What I would like to do, is have 4 posts down each side - 3m between each post (on centre) and 0.6m overhang at each end. Posts will be 4"x4" fence posts with the tops notched to take the rails. My question is - what size do these rails need to be to prevent sag? I plan to have diagonal braces at the top of each post, probably 450mm out from the post, which will bring the unsupported span down to 2.1m maximum. I would prefer to have a single rail sitting in a notch cut out of the fence post rather than bolt a rail to each side of the post. Would a 2" x 6" treated board sag over 2.1m and if so by how much? I can live with a bit of sag - we are going for rustic here, not perfection.
Cross members ie spanning the carport width ways will be either 3m if I sit them between the rails on joist hangers, or I could go 3.6M and sit them on the rails. There would be no weight on these other than the roof sheets plus snow load / leaf load from a tree. Again, I could use diagonal braces at 450mm on those that align with the posts, but not for intermediate cross members - these intermediates would really only be something to screw the roofing sheets to rather than for any form of structural integrity. What dimensions would you recommend for the cross members - 2 x 6 also?
The diagram below is an old draft from way back when - it doesn't have the diagonal braces in it and only shows 3 posts not 4, and cross members do not line up with the posts, but might help show option 2 (cross members on the rails) if my explanation is not clear:
Any thought appreciated - most google hits deal with decking rather than carports and these have a much higher load bearing weight. Pergola sites are an option but these are open to the sky so also not exactly what I am after either.
I need at least 1 3m span to allow both car doors to open without fouling on a post - I could possibly go 0.6m overhang, 2m, 3m, 2m, 2m, 0.6m overhang to put in an extra post but my gut feeling is this would look odd......
Many thanks,
Steve
Edit:
This site seems to show 6 x 2 spanning over 4 meters, which I would have some concerns over
https://www.jacksons-fencing.co.uk/prod ... O&timber=1