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pergola structure design/load help needed

Posted by Ladera05 (My Page) on
Fri, Sep 27, 13 at 12:13

Hello there.

I�m building a pergola ~13� square from post to post and would like to some help to see if it�s structurally sound. This is my first time building this and would like to ask for help from the experts out there. Our plan is to have either Wisteria grows on top of this structure or perhaps some table grape vines. This structure is located in Rocklin, CA (Sacramento). Ground is somewhat hard and have quite a lot of river rock in ground. Open for suggestions and modification to ensure structure sound and hope that cost won't go through the roof.

Already done:
Poured 12" concrete tub footing � at ~ 2 ft deep (5000 psi commercial concrete)
Bracket is embedded within concrete footing
It�s 3" off the ground from the base of the bracket

Planning to use the following lumbers but open for changes to ensure structure sounds and no sagging
Use Redwood for this structure( but considering Dougfir or treated fir if the expert recommend)

1. 6"x6" x 7� or 8� columns (4 columns) (I can either keep 8� height or can trim it to 7")
2. Stack on top of the columns are 2 cross beam of 6"X 8"X 16� (with ~13�.3" unsupported spanning)
3. Stack on top of the cross beams are 8 rafters of 4"x 6" x 16� (the intention is to have 2 ft spacing)�try to maximize the space without creating sag problem
4. 2"x3"x16 or 2"x2"x16� (32) for lattice � 4-5" spacing

Many thanks in advance,

Follow-Up Postings:

RE: pergola structure design/load help needed

A drawing would help us, but the building dept will definitely need a plan possibly stamped by an engineer in order to issue the permits. You are getting permits aren't you?

RE: pergola structure design/load help needed

Agree with millworkman that your questions need review by a structural engineer. Wind and weight are the factors that will determine the wood size requirements.

If you go to the 2nd page on the link below there are photos of our pergola being assembled. It is 8 x 12 on center with the posts which are 6 x 6 set into post brackets anchored to concrete footings. All the top structure is 2 x 12 but you'll note that they nest so strength is compromised. The posts are pressure treated and wrapped with cedar. All of the top structure is cedar. My footings are also 12" but we live in the upper Midwest so are 5 feet deep.

Hope this helps. Good luck.

Here is a link that might be useful: Patio and Back Yard

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