# Forum Home Renovation Pergolas, Gazebos, Strombellas & Rotundas  Attach pergola to metal posts

## mg2307

Hi all, 
I have three 100x100 metal posts in the ground currently holding a shade sail.  We intend to swap the sail and put up a pergola and hope to use the existing metal posts.  
My question to you all is what is the best way to attach the timber beam to the posts?  I am thinking of getting some brackets welded to each post.  Does that sound like a reasonable approach and if so, why type / size bracket should I get welded? 
Thanks in advance, any advice appreciated.    
MG

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## InsaneAsylum

are the posts supporting the shade sail straight or angled away from the shade sail?
if they're straight, I'd drill some holes in them and bridge a timber beam between them using 2 coach bolts. I'm not sure if that's best practice or legal though, just my personal opinion.

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## mg2307

Thanks for your reply, as much as I can tell they are straight, haven't put a spirit level against them, however to the eye they are straight.

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## r3nov8or

If you decide to bolt through, don't overtighten as you could crush the hollow posts. You can use small pipe inside the post, through which the bolt goes, to stop this happening

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## Marc

Depending on the size of timber you need and the span I suppose. Pergola can be 90 x 45 or 290 x 45. 
I would avoid welding. The chances to get a poor weld up there are high, plus you will burn the galvo. 
Drill through is the way to go, unless you want to use U bolts to avoid drilling, but such would give it an industrial look you may not like. 
Use HDG bolts 12mm or bigger, paint the holes in the SHS with cold galvo and like r3no said, don't overtighten. You can overcome crushing the wall of the SHS by drilling close to the edge, just enough for the washer to be flush with the side ...  and stagger the bolts. 
U bolts on the other hand require no drilling in the metal pipe and you can get away with just one per post if you get the right size and set it diagonally.

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## mg2307

Thanks so much for the great responses R3no and Marc, really appreciate it. 
The span for one section is 2800mm and for the other 2850.  Ill investigate the bolts.  If I was to drill through, how many bolts per post would you suggest?

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## Marc

Two bolts if drill. 
One U bolt but ... it needs to be 150 wide and 160 long to set it diagonally providing you use 140x45 timber. If you use larger timber you need a wider U bolt to set it diagonally and keep the bolt holes further apart. 
otherwise you need two U bolts 100x160 per post.

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## InsaneAsylum

2 coach bolts per post. I built a timber pergola like this. I think 190x45 treated pine should be suitable for your spans

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## r3nov8or

M10 bolts should be enough, but I'd better suggest M12 since we know little about "what's what" design-wise  :Smilie:

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## lino28

I would rebate /check the posts so the beam partially sits on the post - if you look at the attached link and look closely at patios with timber posts you will see what i mean. https://www.instylepatios.com.au/our-work 
Same principal for steel and looks a million times better than face fixing a beam to a post

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## mg2307

thanks lino28 - by rebate you mean cut out a section of the steel post, I agree that looks much neater and appears to be better from a load bearing perspective (I'm no engineer).  I assume I would still bolt the posts as suggested by Marc and r3nov8or in previous posts or would I need to do something different?  Cheers.

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## lino28

> thanks lino28 - by rebate you mean cut out a section of the steel post, I agree that looks much neater and appears to be better from a load bearing perspective (I'm no engineer).  I assume I would still bolt the posts as suggested by Marc and r3nov8or in previous posts or would I need to do something different?  Cheers.

  
Yes cutout a section of the steel post. Depending on the width of the beam you are using, you dont have to rebate the whole width of the beam, it can overhang the rebate a bit.
Yes still use 2 bolts per beam to post connection.

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## mg2307

Thanks very much lino28

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## Bart1080

If its a hip, (wood hip to metal post) see my post https://www.renovateforum.com/f204/v...st-how-124681/ 
Otherwise as per r3nov8or advice, 2 x M12 bolts.   
I should put up some finished photo's but with mine, I used a spade bit to counter sink the gal cup head bolts so they were flush with the outside beam.  Why, only because I put on a colorbond flashing over the beam so I never have to paint them ....NEVER!!!!  :Smilie:  
Are you lining the veranda?  if so, be careful on how low the bottom bolt is otherwise it will could show after the lining has been installed and quad installed around the edges

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