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Hi All, I have a few larger then our usual pergola builds coming up and trying to minimize my support to the out corners. How can get 18ft span out of 2x8 or 2x10. I'v gone as far as 16ft with 2x8 dbl's but with 4x4 block sandwiched in between which matched the outside 4x4 corners were the cedar was attached to the non notched 4x4 post also have notched and filled in the space with a block as well to keep it locked up. I was expecting to have call backs for saggy cedar but still no call backs and still keep in touch with clients.
Remember I'm in the city so we keep the designs very simple and clean here.

Feel free to post picts I'm sure we would all appreciate some deck****.

Thanks
Yanni
www.citydecksinc.com
 

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If you take as an example 1- 2x10 Cedar with a LL @10 PSF and DL @ 10 PSF you can span that 19' with Deflection Limit @ L/360

I don't think it will be a problem going 18'-20' with a double 2x10 for the beam... But also keep in mind how much shading you want to have, and how will you run your rafters 12",16",18" OC etc. The more lumber you use on top, the more lateral force the structure will take.

With that said, the bigger the span the less points of bracing you will have. On 18' span you will have bracing at 4 corners, everything in between will move and cause friction when wind hits. The best way to go about this is to break up that span and will have a more sound structure that will last a long time and that would be also in the best interest of your clients.

Good luck
 

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I think that you could span double 2x10's that far, but you are stretching the limits. Try to limit the # of knots in the cedar.

I've pretty much gone to 3x or 4x material for my pergola's, I think it looks much better and adds just a tiny bit more strength and stiffness.

I've got to find a ad blocker or I'm done here, to small of screen.
 
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