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Question DetailsAsked on 8/5/2013

Looking for help respanning a 3-car garage structural beam

Hi, I have a three-car garage that has bedrooms above it. To support the upper floor, there is a structural beam along the ceiling of the garage with two 4x4s between each of the 3 stalls. These 4x4s make it impossible to open the rear doors of cars parked inside, so I want to replace it with an engineered beam or I-beam that spans the whole width of the garage. Has anyone had help getting this done? I'm not sure what time of companies would do this type of structural remodeling. Thanks!

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Start with a structural engineer, or an architect with a structural engineer on his staff. Probably about $400-600 to look at the issue and come up with a design - about $150-200 for the visit and advice on whether it is worth doing, rest for design and cost estimate.

First, I would check on headroom - for that span you are talking an 16-24 inch deep steel beam or probably 30-36 inch engineered wood beam - 2-1/2 car garages use 18-24 inch wood glulam beams, so you are going to be well beyond that for a 3 car span. Highly unlikely you have that kind of headroom and still be able to get a tall vehicle like a pickup or SUV in, and for resale (and probably building code) purposes you don't want to prevent that even if you do not need that headroom yourself.

Therefore, to make it work it would have to fit up into the existing floor space (which your current one may do, also), with the floor joists butting into hangers on its side rather thann sitting on top of the beam. This means temporarily supporting ALL the floor joists at the same time, on both sides of the beam, while a new beam is put in - basically putting the new beam under the spot, building a load-bearing wall on each side of the beam, dropping the old beam down, lifting the new one into place, hanging the joists, then removing the temporary supports and old beam.

Doable, but the last time I worked a beam replacement like this (due to a burnt beam in 2-1/2 car garage fire), the cost was about $7000, and that was with no engineering cost because it was just a replacement.

I am not sure opening the car door while in the garage is worth that much to you. I suppose backing in does not solve the problem, just makes it so the front doors will not open ?

Would replacing the 4x4 posts with a single smaller steel column at each bay solve the problem - MUCH easier to do, and probably about 1/4-1/3 the cost, depending on whether it would require special footer or if the slab can carry the load OK. Either way, would need a structural engineer design to do it.

Actual work would be by a general contractor or a large (multi-person) rough carpentry firm - if you want drywall repair and patch painting, or if going with pipe columns, then a general contractor is probably your best contractor type.

Answered 6 years ago by LCD

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