Old 05-12-07, 06:50 PM
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Join Date: May 2007
Location: USA
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Hello, I'm a newbie here. My wife wants me to build a pergola in our back yard. I am fairly adept at home improvement (carpentry, woodworking, etc.). My problem is that the area we have to put up a pergola requires that my posts be placed at approximately 10' by 20' spacing. I need to know what size lumber to use for the 20' span. Any help would be appreciated.

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Old 05-13-07, 07:00 AM
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Join Date: Apr 2001
Location: Island Lake, IL
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Welcome to the forums.

You will probably need to come up whith a way to support the middle (or close to) of the 20' span. Any size dimensional lumber will eventually sag.

An engineered joist may work, but I haven't seen any that are suitable for oustside projects, being that they are not made from treated lumber, and not very moisture tolerant.

Good luck!
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