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Question
can i use 2x8x20 at 16 inch centers 20 foot span with 1/2 inch plywood on top for roof of patio
JOhn, here is an easy to use span table:
http://www.awc.org/calculators/span/reversecalc/reversecalc.asp
As I read the table, you will need 2x10
YOu should desing for L/360 deflection.
You need to decide if you are subject to snow loads.
Strongest lumbers available are Southern pine and Douglas fir.
Pay attention to the grading of the lumber for this long span.
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Answers by Expert:
Dan Griffin
Expertise
I can answer almost all questions related to the total construction process. My expertise is in commercial construction, though I can field most any residential question. I have hands on experience in concrete, heavy equipment, masonry, all phases of carpentry, interior finishes, and I am fairly strong in mechanical and electrical.
Experience
I have over 20 years experience as a commercial carpenter and commercial construction superintendent. I have another 20 years experience in facility management for a major school district.
Organizations
My favorite hobby for he past 12 years has been singing bass in a The OkChorale men's barbershop chorus and the Mature Moments quartet.
Education/Credentials
I hold a Bachelor's degree in English and Math. I have completed many continuing education hours in the building trades. I hold a Master Carpenter card from the AGC, Associated General Contractors.
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