I am building a pergola. What size of beam will span 20 feet. There will be no load on the beam aside from the weight of the beam itself

Question

This is my first time here and I have looked at other questions regarding pergolas. However, my situation is unique. There will be no load on the beams. The pergola is 20 foot x 20 foot. It only contains 4 posts and 4 beams. There will be no rafters or lattices.

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score 1 · Answer 1 · answered Mar 25 '20 at 02:46

For a beam that long deflection will control over strength. A 2x6 HF#2 would pass code with 0.6" sag in the middle if you are ok with that. Going with a 2x4 will result in a deflection of about 1-3/4" and it will want to roll over in the middle since there are no bracing members. If you go with cedar or pressure treated, it will be more.

score 0 · Answer 2 · answered Mar 25 '20 at 02:01

0

Just use 2x4 (eg:fence rails) they'll span 20 feet wiith no load.

answered Mar 25 '20 at 02:01

Jasen

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I am building a pergola. What size of beam will span 20 feet. There will be no load on the beam aside from the weight of the beam itself

2 Answers2