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Welcome to the Bunnings Workshop community @Powerone. It's terrific to have you join us, and many thanks for your question about pergola spans.
If you have one post at 4.2 m and another at 2.1 m from the house, a 140x45 timber should be able to span those distances. That said, it would be helpful to have a quick sketch of your intended pergola layout. For example, if your pergola is 4.2 m by 4.2 m, each rafter might require a central post to span that distance safely.
Could you let us know the overall dimensions and where you plan to position the posts? That will help us determine the best timber sizes and spacing for your project. If you need assistance uploading an image of your layout, we can guide you through that as well.
Please let me know if you have any questions.
Mitchell
Thanks Mitchell. I may have gotten confused with width and length. Have attached a mud map and wanted to know what size facia I need to just have posts at either end as well as how many beams at 2.4 metres. Have put 5 on the mud map but that may not be enough. Any assistance greatly appreciated.
Great, thanks for that @Powerone.
So, no, 140 x 45mm is not capable of spanning 4200mm for your beam. You would need a post in the middle of that span to support at 2100mm. For a single span of 4200mm, you'd likely need to go up to a 290 x 45mm. 140 x 45mm would be suitable for your 2400mm rafters. Rafters need to be positioned according to the type of roofing you are using and its requirements. This would typically be around every 900mm. You'd then add purlins perpendicular to the rafters, and once again, their spacing would be dictated by the sheeting. For our Suntuf polycarbonate, that would be around every 800-1200mm.
Mitchell
