# Forum Home Renovation Pergolas, Gazebos, Strombellas & Rotundas  Confirm Pergola Batten spacing and query Post Set Down ?

## Ian G

Hi . I was hoping somebody could confirm if a batten spacing of 950mm is acceptable for this planned pergola . I have scoured the net and manuals but found nothing decisive. 
Please feel free to correct any other sizes/spacings,  . Just need this clarified prior to ordering timber. 
Region B ,N3 Wind 
Freestanding , gable roof pergola  10m x 5.5m
All wood treated pine F7 or MP10 
12 posts  90 x 90mm, 5 each side at 2500mm centers  and center of ends
Beams and Ridge 190 x 45mm   ( 2 x 5 m , joined center pole)
Rafters 120 x 45mm  x 3m  ( rafter span 2700mm  , overhang 300mm ) Spaced @ 900mm
Battens 45 x 75mm 
The battens were set at 750mm spacings but it seemed a bit over the top for the rafter span. 
Also i have read a few times that Posts are not finished level with top of Beam (post set down)
Why ??? and is it necessary 
Lastly , at this point i am thinking of Posts directly into concrete (after being treated some) for added structural strength.
Is this a big no no (vs Stirrups) or is there something to be gained in regards to being free standing structure . 
Hopefully someone can shed some light on my queries . 
Regards Ian

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## manofaus

think it depends on what you use for covering as in colorbond or trimdek or laserlite.... check their specific instructions. Especially since is N3 wind classification.

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## Ian G

Thanks for the reply manofaus  , never thought to mention covering which would be colorbond. 
The N3 wind class, was my interpretation of a web post example (Dongara /Geraldton WA  , 2.5 acre block ,slight slope , perimeter trees only) .
The submitted drawings to council are stamped Region B Cat 2.5. ? 
Cheers.

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## Ian G

I have attached a drawing of the planned pergola which probably should have been done to start with .
So hopefully someone can advise if Im heading in the right direction  
Cheers

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## stevoh741

I wouldnt be putting posts in ground. Stirrups def way to go.

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## Ian G

Thanks for the reply stevoh , certainly aware of the cons placing inground but thought there could be some extra stability being freestanding. don't know yet.
I have just ordered timber , but would really appreciate if someone could give me peace of mind with rafter size . I have learn't  a bit , but there is so much differing advice out there.
Is the Rafter span from Beam to Ridgeboard (unsupported apart from collar ties every second rafter )  OR  width between Beams (total width less overhangs) 
Any reply would be greatly appreciated.

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## shauck

As per AS1684.2 (2010)  
N3, F7 seasoned softwood gives span for 120x45 @ 900 centres, (roof/ceiling mass of 10k/m2) at 3400 with overhang 700  
MGP10 with all the above info - 3500 with 600 overhang

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## ausdesign

Rafter span is from ridge to beam.
Batten spacing for 0.47 corrugated is 1200 internal & 900 at ends of sheets.
Bracing of the posts is required either by diagonals between the posts or by the footings.
For footings the size of the hole & the amount of bulk concrete is determined by the (vertical) area of the roof & the wind catagory.
As an example - 900 deep * 600 * 600 bulk concrete each post with the post set down 800.
It is not possible to use stirrups for this type of bracing.
Generally an N12 rod around 400 long is drilled through the post around 100 up to cope with uplift forces.

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## shauck

I just opened your design/pdf. I went off the written info at the top or thread. You stated 120x45 then in design 120x35 rafters. for 120x35 - MGP10 - span 3100, 550 overhang and F7 - span 3000, 600 overhang.  
Closer to the max spans.

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## Ian G

shauck and Peter ,many thanks for your reply's . Sorry for the incorrect rafter size. I purchased the span tables and believed spans were OK only to read various quotes /articles disputing Rafter Span for this roof type. 
Peter , re the posts, as much as I wanted to keep out of ground ,I believe the whole structure would be sturdier than on stirrups. the posts will be receiving extra protection prior to erection.
The rods were planned. Bracing is going to be an issue , especially on the aesthetics of the project ,but understand its reqirements. 
Guys , again many thanks.

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## stevoh741

> I believe the whole structure would be sturdier than on stirrups.

  With everything tied in a braced their shouldnt be any lateral movement just uplift. IMO you are asking for a lot more trouble putting timber in ground than a percieved sturdiness with using stirrups. Stirrups are engineered and if used correctly are more than adequate for your needs.

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