# Forum Home Renovation Pergolas, Gazebos, Strombellas & Rotundas  Advise need on timber size and span for diy pergola

## wonderland

Hi everyone,
I am looking into building a timber pergola attached to the house, all with treated pine. The area is 6m x 5m. The 6m will be attached to my brick house. My plan was to have 3 post (100x100 H4) @ 3m apart. The beam I'm using will be 6m long (170x45) and rafters will be 170x45 @ 900mm apart. For battens, I will be usin 170x45 but instead of putting them on top of the rafters, I was planning on putting them inbetween the rafters, like blocking.  
I was wondering whether my span and timber size is correct? I tried looking up span tables but its harder to find, and the ones I've found, I find it hard to understand the table. :No:  
Also, can I use H3 treated pine for the pergola or do I need to use H4? I will be painting the pergola once completed. 
Any advice or suggestion would be greatly appreciated. 
Thanks :Biggrin:  
P.S. I've also included a really novice drawing of where the pergola will be located so that its easier to understand what I'm trying to do.

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## wonderland

Anyone have any advice?! Please?

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## dukekamaya

H3 treated pine is fine.  -  Is there a roof going on this?
If the rafter span is 5 metres 190x45 would be a safer option. Its unusual to see 170x45 I've not even seen it listed for a long time
100x100 rough sawn treated pine posts are not structually graded generally, you would be better with 90x90 F7/GL8 posts.
You would need solid blocking between the rafters regardless - if you are putting a roof on I would use 70x45 battens on top of the rafters

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## wonderland

Thanks Duke, I think we've chatted before at homeone! :Biggrin:  This is exactly what I needed! 
With regards to the post, what does 'rough sawn' mean? 90x90 sounds like a better option anyways because it's smaller in size, therefore wont stick out so much like an eyesore! Another question with regards to the post, if i decide to put two post instead of 3, would that be alright? 
With regards to block, i was wanting to do something like the picture below. I have seen a few display homes with this style of pergolas, but I could never work out how they made the blocking stick to the rafters. I knew they didnt use rafter hangers because at close range inspection, i couldnt see it. And i dont know how they would hammer it in as the rafters and blocks are too thin. Any ideas?   
I am still debating whether I want a roof or not. I'm worried that if i put lazerlites, it might be too hot under there during summer. Are battens put in purely to secure the roofing? If i decide not to have a roof, would I still need battens?  
Thank you, much appreciated! :Biggrin:

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## dukekamaya

The better quality Laserlite ranges do not let heat in like the cheaper ones do so you won't cook under them. 
Rough-sawn means exactly that, how it comes off the saw after being cut from a log. 
The roof in your pic may have had the rafters and blocking notched into each other for the seamless look. Some of the qualified chippies on here may have a better idea of the method.
You could have 2 posts though you will need a fairly hefty engineered beam for the span. I can check it out if you like.

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## wonderland

Thanks Duke.  
With regards to the roofer, what distance apart should the rafters be to accommodate roofing? It was 700mm wasnt it? If i have two post, the beam would have to span 6m. Can you please look into this and see whether it is possible? When you say it needs to be 'hefty engineered', it sounds really expensive. I guess I'll have to wait and see how much it would cost. If its considerably more, i guess i can always deal with having 3 post there ha ha 
Anyone else have any idea how they would do the rafter and blocking as seen in the photo above?

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## dukekamaya

You could have the rafters 1000mm apart with 70x45mm battens if going that way.
I'll check the beam out

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## dukekamaya

A Tilling SmartLam GL18C 330x65mm beam looks to be a minimum as far as size goes - its a hardwood engineered LGL, wouldn't be cheap.
For the sake of a post in the middle you could use a 190x45 MGP10 treated pine beam at $60 rather than over $600

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## mijati

Just a thought.....there's not much load so a condideration could be to beef up the beam against the wall a bit to say a 240x45 and cantilever the 2m overhang eliminating that post (assuming you might want it gone)....
Good luck with it.

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## cherub65

Blocks would be skew nailed, notching would mean increasing rafter size by depth of notch.
What is the pitch of the roof?
Also for the look your after you should used treated pre primed as its smooth compered to rougher header treated pine

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## wonderland

Thanks everyone for your advice! 
@duke, I think you're right, i will steer clear of the engineered beams. I would rather have the post there for $60 than not for $600!! LOL 
@mijati, can you please explain more what you mean? Thanks 
@cherub, I thought the blocks would be skew nailed as well but at close inspection, I couldnt see any nails. Unless they puddied it up really well. Also, if I were to skew nail it in, is the rather thick enough to do that? What do you mean by 'notch'?

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## wonderland

Hi everyone,
its me again! I was just wondering whether anyone can see and tell me what size battens these are in the picture below? Or what material it would be to get that brown colour? 
I've decided that instead of having the battens as blocking with the rafter, I might just put the battens underneath the rafters like this picture. Is this ok to do? 
Thanks.

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## wonderland

Just bumping this topic! Thanks 
I'm really interested in building my pergola this way now with battens on the bottom of the rafters instead of the top. Is this secure? As my rafters will be spanning 5m without any support in the middle, will it sag later down the track? Will the battens help in preventing the rafters from also warping later down the track? 
Any advice would be GREATLY appreciated!! Thanks  :Smilie:

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