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cpav 01-29-2010 06:04 PM

span 16' without post midway?
i have a 5.5"w x 7"h beam running the entire length of my basement (36'). there are posts every 8'. my basement is 26' wide. i would like to bolt a piece of 1/4" x 7" flat bar (2 bolts 24" on center going completely thru both pcs of flat bar and wood beam) to both sides of the beam so i can remove the center post; beam would now span 16'. i have 2x10s, 16" on center, running the 26' above the beam. also a wall on the first floor running the whole length directly above. will this be strong enough to keep from sagging? i work in a metal fab shop and my boss, an engineer, and coworker all agree that it will be plenty strong, but my wife does not think it's safe. my boss also informed me his brother-in-law used one piece of 1/4" x 6" flat bar to span 20' and has had no issues. can someone help me out?

jlhaslip 01-29-2010 06:37 PM

I'll offer to help by suggesting that you have an engineer look at the situation and take his recommendation.
Might be okay, but get a stamped drawing before you attempt this modification.

It will cost you, of course, but then you (and the Mrs) can sleep at night.

Daniel Holzman 01-29-2010 08:48 PM

As noted, you should hire an engineer to review and stamp drawings. However, if you are legally allowed to perform your own analysis, or no analysis is required in your jurisdiction, you can google "flitch beam" and begin the process of understanding how your new beam will function.

You need to check the beam for flexural strength and shear strength (flex will probably control). You also need to check the strength of the bolts since the bolts will carry the horizontal shear of the composite beam. Also check the bolts for tear through. When you are done with those checks, you need to compute the deflection of the beam by treating it as a composite element.

This is what the engineer would do, and how they would earn their money. None of it is rocket science, but then again it isn't typically done by DIYers.

Scuba_Dave 01-29-2010 09:26 PM

I'd go the engineer route unless your work can calc the loads

Check this thread where another person had his basement beam re-inforced

Gary in WA 01-29-2010 09:34 PM

I fourth, the recommendation to hire a structural engineer to sign on the liability for your family's safety. And the others will pay to fix or replace a loss if it doesn't work? An S.E. will also check if there is any roof load on the center bearing wall, any point loads and where, if the 5-1/2 x 7-1/4" glue lam is 36' long or breaks on the center post, if the existing remaining posts are sized for the additional load, if the piers are sized for same, the paper-work for a future house sale, satisfying your Homeowners Insurance carrier work was professionally designed to honor any future claims of liability, etc.

Be safe, Gary

wnabcptrNH 01-30-2010 08:00 AM

26 feet? I would say if that is a main carrying load in your house 2 pieces of flat stock metal are probably not going to be enough. Typically and engineer is going to want a steel beam or a composite beam that includes LVL and steel. I design stuff for my family (note I am not a PE but have a structural degree and know how to size stuff).

I 5th the note for an engineer. They can imput the basic house loads and the computer will pop out a beam size based on whatever material they imput.

tpolk 01-30-2010 09:37 AM

just consider it your small contribution to raising the human intellegence quotient. thanks for that

wnabcptrNH 01-31-2010 08:16 AM


Originally Posted by tpolk (Post 391648)
just consider it your small contribution to raising the human intellegence quotient. thanks for that

who was this directed towards?

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