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help with pergola design

Posted by dmirza (My Page) on
Fri, Jul 20, 12 at 15:12

I am building a paver patio in the back yard of my northern California home and want to incorporate a freestanding pergola.

The pergola will be built from redwood and will cover an area of 20' X 16'. There will be 3 posts on each of the long sides, measuring 6"X6". I plan on sandwiching those posts with two 2"X10" boards and then putting on 2"X8" rafters across the 16' span.

Does this sound like it would work? My concern is that the 16' rafters will sag. I can have the posts span a 12' distance and then cantileaver the otehr 2' on each side, is this needed?

Thanks for the help in advance!


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RE: help with pergola design

If I deduce correctly, your outside corners will be, in effect, on 12 x 16 centers. Center posts make two 12 x 8 areas. With the 2' overhang you then get a 16 x 20 shaded space.

So, your longest unsupported span will be 12' with 2 x 8 lumber.

What is your on-center plan for the rafters? You don't need to worry about snow load in your climate (just wind)and the span chart I looked at indicates with 16" centers, using 2 x 8 lumber, you can span approximately 23'; and on 24" centers, 21 feet.

From the linked photos you can see our pergola. The posts are on 8' x 12' centers with a 2' overhang on the corners. All lumber is 2 x 12 but with the rafters "nested", each is in effect, 2 x 6 though I have a lag screw at each intersection to tie the members together. No problem after 5 years and I reside in a snow zone.

Plan to install footings for the posts before building the paver patio. Hope this information helps. Good luck.

Here is a link that might be useful: Pergola


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RE: help with pergola design

I wanna see 2x8's spanning 23'. Sounds bogus to me.


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RE: help with pergola design

most on a 2x8 should be about 12' span if I remember correctly


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