What materials for building a pergola?

[ElvisGazz]

I’m about to build a pathway pergola similar to the picture attached and was thinking 100x100 treated pine posts 

with 140x 45 treated pine for the wall mounting plate and rafters? Does this sound ok size for the rafters?

 

[MitchellMc]

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

You're within the right ballpark. However, what determines the size of timber you can use is their span. Check out this helpful guide on How to understand deck span tables. 

So, if you can let us know how far out the rafters will span, we'll be able to answer your question. Anything under 1800mm should be fine. 140 x 45mm would typically be suitable for the mounting plate. Remember it needs to be fixed through any cladding into the structural members of the house.

100 x 100 posts would be suitable, and the number you require will be determined by the length of the structure and the size of the beam.

Here's a helpful step-by-step guide: How to build a pergola.

Please let me know if you have any questions.

Mitchell
 

[ElvisGazz]

Hi Mitchell 

thanks for your reply it’s very helpful 

Looks like I’m ok with the rafter size as it’s only 1100mm wide span and 8.5 long as it’s going along my garage over the pathway as per the photo 

thanks for your help 

 

[MitchellMc]

Keep us updated, @ElvisGazz, and reach out if you need further assistance.

Mitchell

[ElvisGazz]

Hi Mitchell I’m ready to do this project. So picking up from where we left. I’m using 140x45 h3 timber for everything like wall plate and rafters at 450-600 centres. So my question is how many 100x100 pine posts do I need for maximum span from post to post supporting the rafters above?

[JacobZ]

Hi @ElvisGazz,

It's great to hear you have decided to pick up where you left off with your pergola.

140x45 pine can span 2700mm while acting as a beam that supports rafters and roof sheets. You are right on the limit of needing a fifth post. If you bring the two end posts in 100mm and have a slight overhang at the end, then you will be able to use 4 posts comfortably, otherwise, you would need to use 5 posts.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob

[ElvisGazz]

Hi Jacob

Now that I know the span, I would rather the posts to be at each end and only have 4 x posts so I’ll upgrade the fascia beam to 190 x 45 and I should be fine shouldn’t I ?

Thanks for your help 

cheers 

George 

[MitchellMc]

Yes, that would be fine, George (@ElvisGazz).

Mitchell

[ElvisGazz]

Thank you so much for your help.

I’ll send some photos later 

[MitchellMc]

Can't wait to see @ElvisGazz!

Mitchell