Building Homes or Extensions/Rafter Length

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Expert: - 7/10/2011


Question
I am planning to build a carport attached to my shop.  I plan on using 16'  2 x 6's, on 2' centers, from the shop to a support beam 14' from the building.  Would a spread this long cause the 2 x 6's to sag?

Answer
Floyd, I think you are way past the limits for a 2x6, but let's take a look at :
http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

I entered southern pine (strongest framing lumber) using a 20# snow load (you didn't tell me where you are, but this is a  small number for where I live) and a 10# dead load (minimum) and the maximum span would be 11'-2".

If you go to the "calculate span options" link on the same page, it tells you that to span 16' would require Select structural or #1 or #2 2x10's.  This allows an L/360 sag which is 192"/360= a bit over 1/2" which is code minimum.

Another way to accomplish what you are attempting would be to reduce the span by adding another beam at mid span which would either require posts or beams on each end.

If I've not answered your question, please ask again.  

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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.

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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.

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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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