Reinforcing existing basement beams for longer spans
Reinforcing existing basement beams for longer spans
(OP)
I have a situation where the owner of a home wants to remove the basement posts supporting the beams. The beams run along the center of the basement. the house is approx 3000 sq ft. there are 2 beams which are 8" deep (didn't get the exact size yet) that span from the top of the foundation to the center post (there are 3 posts total). The beams meet at the center post and bear on a cap plate (typical basement construction). The owner wants to remove the two posts the beams are cantilevering over. I'm not sure if I'd want to sign off on something like this as I have never encountered this situation. He doesn't want do decrease head height significantly so a WT welded to the bottom is out of the question. What about welding a 1/2" cover plate to the bottom of the beam? I don't think you could weld it while the beam is being stresses in it's current state. would you have to try to shore up the joists at least a bit to relieve some of the stresses before welding? Not to mention you would have to remove the two posts before welding the cover plate to the underside and end shear reactions.






RE: Reinforcing existing basement beams for longer spans
RE: Reinforcing existing basement beams for longer spans
RE: Reinforcing existing basement beams for longer spans
Another idea is to place additional 8" beams either side of the existing beam with additional columns and footings. If you have trusses bearing on the beams, be sure you modify them to accomodate a new bearing.
A larger issue might be the adequacy of the existing footing.
Good luck!
RE: Reinforcing existing basement beams for longer spans
You will have to do an analysis of the entire building. The code requires you bring all the forces (LL + DL) through the building (from the roof), its' walls, columns, beams, etc to the foundation, which has to be adequate.
You have to analyze the beams, the columns and the footers. I'll bet you will need a new footer in the center. I doubt if you can remove the posts and reinforce the beams if you have little headroom. You might be able to remove the beams and use flitch plates. Remember, the code dictates a minimum headroom in the basement.
I doubt if the original design was overdesigned.
Regards,
Dermott
RE: Reinforcing existing basement beams for longer spans
Mike McCann
MMC Engineering
RE: Reinforcing existing basement beams for longer spans
That being said, I've come across this bunches of times in the past. Realtors love to tell prospective buyers that it's "No big deal."
It can be done, but it gets expensive.
Forget about reinforcing the beam. It'll never work.
My preferred option, take the span from the center post to the outside wall, and divide it by 3 (It's divided by 2 now). Assuming the floor joists are on top of the existing beam, size a beam to span from outside wall to outside wall, perpendicular to the existing beam, at these third points. You want the deepest beam you can get to work out for your client. I typically get into the void of the floor joists. They'll have to shore the existing beam, & cut it for it to connect to the side of the new beam.
There's a whole bunch of other stuff to consider (footings, flange bracing, etc), but that's the jest of it.
Hope this helps.
RE: Reinforcing existing basement beams for longer spans