Building Homes or Extensions/Beam size and material

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Expert: Ted Barnhill (Principal, Design45 LLC) - 2/11/2009


Question
Dear Ted
I want to build a beam out of 2x10 or 2x12 spruce or fir. This beam needs to span 40 feet with 2 tele post and the basement walls. The floor size is 26’ x 40’. I’m using 2x10 spruce for the floor joists. Can you tell if this is possible?
Thanks
Chris


Answer
Chris,

According to the 2006 IRC, the maximum span for a built-up 4-2x12 beam (of #2 Spruce Pine Fir) in a home 26' wide is 10'-7" if supporting one floor only, or 7'-5" if supporting two floors.  This is the largest built-up beam rated.

If you are supporting only one floor on this beam, you could add a third post to get your span down to 10' or so.  Otherwise, go to engineered lumber (LVL) to achieve your original two-column solution.

I hope this helps.  -Ted

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Ted Barnhill (Principal, Design45 LLC)

Expertise

I can answer questions about architectural design, how to work with a designer, and best construction practices for most trades. I specialize in cold-climate design (I'm in Minnesota), older home renovation, and energy-efficient/sustainable design.

Experience

As a Principal of Design45, I design and detail new homes and remodels. I am formally trained in architecture, but have also been a contractor and have experience with many trades. I strive to provide beautiful, durable, and efficient homes for clients and communities of all types and budgets.

Education/Credentials
Undergraduate work at Princeton University (Mathematics), Master's work at the University of Minnesota (Architecture)

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