20x15ft Pergola


Old 04-13-15, 05:51 AM
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20x15ft Pergola

Hi all,
In our backyard we have some trellises that have grapes climbing up and over them. They are constructed with 2" pipe, steel I believe.

We're planning a backyard kitchen under these grapes, and want to replace the steel pipe trellis with a wood pergola. This will nicer, and provide more shade.

The existing trellis is 20ft x 15ft, with just 4 posts on the corners, no support in the middle.
I'd like to try and keep the same general idea, 4 posts main construction.

So I'm thinking of 6x6 posts on the corners, and for the 20ft spans, using 24ft 2x12's, one on each side of the 6x6's, so 4 in total. Then run some 2x8's or 2x12's perpendicular across top.
I'd have some 6x6 supports on 45 degree angles on the corners along the long 20ft run to reduce that span a few feet.

We'd be using cedar or redwood.

This would be in Southern Ontario, Canada. There will be snow on it, in winter, but no solid roof. One edge will but up against our detached garage (along one of the 20 ft spans.

Any thoughts on this? I will get it reviewed by the city before I build it, but wanted to get some input from others if this is a feasible design.

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Old 04-13-15, 06:06 AM
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While I agree that wood looks nicer than steel, anytime you have vines growing on/over wood you'll trap moisture on the wood shortening both the coating's and wood's life ..... just something to consider.
Old 04-13-15, 06:56 AM
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I'd consult with the local permit office before moving forward. I doubt that they will allow a 20 ft unsupported span with dimensional lumber that will have additional timbers on top of it. Here is a copy of the code we use here in the states for decks. I would assume that spans on pergolas would follow the same.

Old 04-13-15, 07:47 PM
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I will be checking with the city before I do it, and looking around online a bit, it does look like doing a post in the middle, making it two 10 foot spans, would be better.
15 foot for the other direction doesn't seem like a problem with the 45 degree braces on it, but I'll plan 2 version of the kitchen so I will be ready either way.
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