Pergola Wobbly

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Old 06-14-14, 11:17 AM
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Pergola Wobbly

We have just helped a relative build a 23'x13'x10' pergola. It is not attached to the house. It is quite wobbly. We're not sure if it's because of the post bases, or because of the post caps, or because it doesn't have enough support. Everything is put together with screws, except for the lower 2x6s. We are amateurs at this and would appreciate any kind suggestions.
 
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Old 06-14-14, 01:51 PM
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Should have been 6 X 6's not 4 X 4's, main reason is 6 X 6's can be notched and through bolted where the beam is attached to the post.
Those horizontal 2 X 6's are doing nothing to stabilize the structure, should have been diagonals.
Looks like nothing but 2 X 4's where used to support the rafters, should have been at least 2 X 8's bolted to the post that where notched.
Also not seeing any blocking between the rafters so now the rafters can twist, curl, and bow.
Are there any hurricane ties on those rafters?
 
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Old 06-14-14, 02:17 PM
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Welcome to the forums Molly!

Installing a 2x8 or larger to the posts and top beam [all the way across] should help. I take it no permit or inspection was needed ??
 
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Old 06-14-14, 02:34 PM
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I see diagonal bracing in one direction but not the other. Still, there's an awful long stretch of 4x4 that is unbraced.

Are those 2x6" roof rafters? How far are they spanning? And, what is the horizontal beam? It looks like two 2x4" or a 4x4".
 
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Old 06-14-14, 02:37 PM
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Also screws never should have been used when framing.
Only ACQ approved nails should have been used.
 
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Old 06-14-14, 04:07 PM
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Sorry you are getting all bad news Molly, but everyone is only trying to help. Correct choices of materials and bracing is everything. I built a pergola/grape arbor and skimped a bit on sizes, had to go back and add diagonal bracing on all corners as well as a few supports.

You need better diagonal bracing, more support around the top, through bolts instead of screws, etc.

I have to ask....why so tall? Looks like 10 ft or so? Lower would have helped with making it more resistant to movement. Because of the height, you'll need to really beef up the rest. And since it's not solidly attached to the house, thats making movement even more likely.

Hold a 6" dowel in your hand and have someone try to push it side to side. Now do it with a 12" dowel. That the difference between shorter and taller posts.

You sure don't want it coming down on your head or blowing apart in high winds.
 

Last edited by Gunguy45; 06-14-14 at 04:30 PM.
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Old 06-15-14, 01:11 AM
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Sorry that the suggestions submitted aren't kind, but they are truthful. Sometimes the truth hurts, even though it's needed.

Beefing up the columns (possibly with stiffener flanges) or replacing them with 6 x 6s will help considerably. I'd also shorten them, unless there's a pressing need for the tall height. Beefing up the front beam would also help, as would adding upper diagonals perpendicular to the house, as would using through-bolts for all diagonal connections, as would adding beams from front to back (at each end) for connecting the perpendicular diagonals to.

A complete tear-down and rebuild using properly-sized members and connectors might be the easiest solution to eliminate wobble.
 
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Old 06-15-14, 04:35 AM
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After looking at the pic again, is the roof flat? will rain water run off of it?
A roof that is flat or doesn't have much pitch is more apt to leak
 
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