# Forum Home Renovation Pergolas, Gazebos, Strombellas & Rotundas  Which grade timber to use for pergola

## wonderland

hi everyone,
Sorry to start another thread but I wasn't really getting much response from the other one. 
Anyways, I'm in the process of researching on how to build pergolas. I want to build a pergola out the back which is 6mx5m. The 6m will be attached to the house. Here is the materials which I'm using: 
Post H4 90x90 treated pine
Beam 190x45 treated pine
Rafter 190x45 treated pine 
Although I know what size timber to get, I'm abit confused of what grade timber to use. :No: . With regards to the post, can I use the H4 rough header treated pine? With regards to the beam, can I get the MGP10, or do I need MGP12 or F17 KD Hardwood, or the LVL F17, or the rough header treated pine? Same thing as with the rafter. Which grade of timber would i need? As the rafter needs to be a continuous single span of 5m, I want a timber which isnt going to sag. 
Thanks for all your help!! :2thumbsup:

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## wonderland

Any have any advice? Any advice would be greatly appreciated!!  :Smilie:

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## r3nov8or

> Although I know what *size* timber to get, I'm abit confused of what *grade* timber to use

  These things are actually closely related and together affect the decision. Let's assume you use F7 KD treated pine all 'round. I think for a pergola you are right with 190x45 for the rafters (can check later tonight), but need to know the span between your posts to help spec the beam.

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## wonderland

Thanks r3nov8eor for your help. 
The pergola will be 6m wide x 5m long. The rafters will run 5m with only support on both ends. The post will be on the 6m side. Therefore I will use 3 post, 3m apart from each other.
Thanks.

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## r3nov8or

> Thanks r3nov8eor for your help. 
> The pergola will be 6m wide x 5m long. The rafters will run 5m with only support on both ends. The post will be on the 6m side. Therefore I will use 3 post, 3m apart from each other.
> Thanks.

  Span tables for verandah beams with 3m span to take rafters spanning up to 6m say a 240x45 beam

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## wonderland

Wow 240x45? That's such a large beam. So I can't get away with 190x45? Is the rafter alright at 190x45? 
Thanks but i still don't know which grade timber I should use?

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## r3nov8or

The span tables I have don't specify *pergola* rafters and beams, but *verandah * rafters and beams and the below assumes a sheet roof will be installed. It always best to go for the larger dimension or higher grade, but that you won't have a roof sort of compensates for you. If you plan to roof this thing one day, choose wisely. 
Re the beams - at 3m span the span tables specify the same dimension (240x45) for grades MGP10, MGP12 (~F7) and F17.  190x45 is stated for F27 (not even sure you can buy F27?). If you add an extra post (3 openings at 2m each) you can go down to 170x45 as low as MGP10 grade. 
Re the rafters - at 4.8m span, span tables state 190x45 for MGP12 (~F7) and F17. For 5.4m span it states 240x*3*5 for  MGP12 (~F7), F17 and F27. Your rafter length (5m) falls in between, and you'd normally go up not down, but the unroofed aspect may convince you of 190x45.. 
Use MGP12 or F7 for all and you should be OK. This is probably the most available grade for your dimensions anyway. 
You should also block up your rafters to ensure they stay perpendicular - a slight fall will create sag. 
Now, where's one of those Disclaimer signature thingos...
Here it is - Seek professional advice and read the PDS before purchasing this free advice

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## girlpower

> The span tables I have don't specify *pergola* rafters and beams, but *verandah * rafters and beams and the below assumes a sheet roof will be installed. It always best to go for the larger dimension or higher grade, but that you won't have a roof sort of compensates for you. If you plan to roof this thing one day, choose wisely. 
> Re the beams - at 3m span the span tables specify the same dimension (240x45) for grades MGP10, MGP12 (~F7) and F17.  190x45 is stated for F27 (not even sure you can buy F27?). If you add an extra post (3 openings at 2m each) you can go down to 170x45 as low as MGP10 grade. 
> Re the rafters - at 4.8m span, span tables state 190x45 for MGP12 (~F7) and F17. For 5.4m span it states 240x*3*5 for  MGP12 (~F7), F17 and F27. Your rafter length (5m) falls in between, and you'd normally go up not down, but the unroofed aspect may convince you of 190x45.. 
> Use MGP12 or F7 for all and you should be OK. This is probably the most available grade for your dimensions anyway. 
> You should also block up your rafters to ensure they stay perpendicular - a slight fall will create sag. 
> Now, where's one of those Disclaimer signature thingos...
> Here it is - Seek professional advice and read the PDS before purchasing this free advice

  Hi there. I'm brand new to this so apologies in advance! Was reading this post- I have similiar dilemma... want to build pergola with minimum posts ie. beam span of 4.5m  (2 posts) to support rafter span of 5m, off a roof other end... so should i b using 290x45 treated pine beams with 240x45 rafters. Will this ensure no sag?
Tks

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## wonderland

Thanks R3nov8or!!
What is the difference between a verandah and a pergola? So I guess I cant get away with 190x45 beam? With regards to block, can I just use battens to stop the rafters from warping, or do I need to block? 
Thanks.

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## r3nov8or

As explained earlier, a verandah has a roof.  Re blocking, if you block (or support with a steel bracket) one or two rafters (e.g. the end rafters) the battens should do the rest, but make sure each rafter is perfect while attaching the battens.

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## jb2020

G'day,
came across this post because I'm looking at building a flat roof pergola with 5m rafter span. 
I found this table specific to pergola rafter & beam spans:  http://www.tabma.com.au/documents/TA...n%20Tables.pdf 
it says you can span 190 x 45: F5 5.2m, F7 5.6m & MGP10 5.8m (at 900 centres)
Is this table correct? seems to have much longer spans that what some people are saying on various forums or am I misreading it? 
I don't quite understand why the spacing of the rafters effects the max span if you only have say laserlite on top?  
Cheers
John

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