What wood to use for pergola?

mikewebb

I'm building a very small pergola (about 1.5 m by 2.5 m by 2m high). I will be covering the roof with Acyclic sheet. What grade and size of timber should I use for the rafters etc.

MitchellMc

Welcome to the Bunnings Workshop community @mikewebb. It's amazing to have you join us, and many thanks for your question about building a pergola.

Before you start the project, it would be best if you checked out this handy step-by-step guide: How to build a pergola frame.

It's quite easy to over-engineer your structures' timber, but if you are looking for the smallest calibre or most budget-friendly option, you'll need to examine timber span tables and consult building codes. If you run your rafters at 450mm centres, then 140 x 45mm L/M Outdoor Framing MGP10 H3 Treated Pine would be in the right ballpark.

I'd suggest you go with at least 190 x 45mm L/M Outdoor Framing MGP10 H3 Treated Pine for the beams, and you can use 90 x 90mm treated timber for the posts.

Here are some pergola span tables from Hyne timber for you to reference.

I'm keen to follow along with your project. Please let me know if you have further questions.

Mitchell

mikewebb

Thanks for that. Just the info I needed.

mikewebb

Thanks for the excellent info Mitchell. One further question: I am digging my post hole depth at 650mm for 90 x 90 posts. What size (length) post stirrups would be suitable to use?. Im told not to put them all the way into the hole but leave about 75 mm under the post stirrup. would 450mm be sufficient?.

EricL

Hi @mikewebb

It all depends on the type of post stirrup you're putting in. For example, the Pryda Post Anchor High Wind 600 x 90mm M12 has a flat bar indicating where the post is supposed to sit. Leaving 75mm under that should be sufficient to avoid trapping water underneath. Would it be possible for you to post a link to the 450mm post anchor you're planning to use? This will give us a better idea as to which product you're referring to and we can then make recommendations.

Please keep us updated with your progress, we look forward to seeing your pergola assembled.

Eric

mikewebb

Thank you for your reply. I was intending to use the Pryda Post Anchors Full stirrup.:Pryda Post Anchor Full Stirrup 450 x 90mm M10 - Bunnings Australia. Kind regards.

EricL

Hi @mikewebb

Thanks for getting back to me so quickly. Let me just do a little bit of investigation and confer with my colleague concerning the Pryda Post Anchor Full Stirrup 450 x 90mm M10 - Bunnings Australia. As soon as I have more information, I will get back to you.

Eric

MitchellMc

@mikewebb,

The distance from the top of the concrete to the underside of the post anchor saddle must not exceed 75mm. Embedment depth is to be designed by a structural engineer to suit uplift capacity, concrete edge beam design and stability of the structure. However, having your stirrup 375mm into a 650mm deep footer sounds like it could work. If you don't wish to consult an engineer, I'd go with @EricL's suggestion of using Pryda Post Anchor High Wind 600 x 90mm M12.

Please let me know if you have any questions.

Mitchell