Repairing a beam

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  #1  
Old 01-17-08, 04:27 PM
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Question Repairing a beam

I need advise about how to repair a load bearing beam in a crawl space. The "beam" is made of 3 2x8's with a 2" top plate. This beam spans 22' and supports the floor joists of the first floor. There are two floors of living space above made of bedrooms and bathrooms. Amazingly, this beam was only supported by one tempory jack stand in the middle of the beam. The floor has sagged above, and the beam has crushed in on itself where the jack was trying to support the whole load. There is signs of rot on the bottom 1/3 of 2 out of 3 of the 2x8s in a section about 6' long directly in the middle of the span where the jack is holding up the beam.
I have added two footings, one on either side of the original, to bring the spans within code for the "beam" (according to building inspector). Now I want to address the rot. Do you think this was caused by contact with the steel jack? There is no sign of insects or water leaking from above.
My plan was to temporarily brace the floor joists above, cut out the bottom half of two of the 2x8s, replace this with a 4x4, then sister 2x10s on either side of the beam, then jack up the whole thing and support the new full sized beam on 3 posts.
Is this a reasonable way to make the repair? Can I cut part of the beam and replace with a 4x4? Should I glue the new piece in? What glue would you use? Is it worth sistering in the 2x10s?
Any help would be great. Thanks ahead of time. Great site!
 
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  #2  
Old 01-17-08, 07:05 PM
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Location: Baltimore, MD
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Sounds like you do need to replace rotten sections, but your 4 x 4 idea is a little shaky. After SECURELY supporting the joists on *both* sides of the beam, cut the bad sections of 2" x 8" entirely out and replace w/ same so that the cuts are over a pier/post or what ever support you are using. The breaks (cuts) in the beam members should be in the center of a support post for load bearing purposes. Using glue is good, either a good grade of subfloor adhesive like OSI, or the PL Polyurethane glue. Inexpensive glues are frequently not worth the time or money, it's only a couple more dollars. Thru bolts are frequently used on bms also, check w/ your inspector. It would be a good idea to get the pressure off of the beam before cutting also by using jacks as you shore up the joists. Get a big beam, 6" x 6" at least, or maybe bigger-I can't judge from where I am, and attach to joists across effected area. Make sure it can't roll--secure with blocks or metal bracing, and raise slowly and evenly with adequate jacks. Keep jacks plumb and level to avoid rolling and/or kickouts. You really just want to make sure you've got all the weight on the temporary support before you cut to avoid a surprising disaster. You may have to keep the temp bm quite close to the existing one also to avoid merely bending the joists in the middle w/o actually lifting the weight off the beam.
 
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