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shamrock33 03-19-2008 03:14 PM

Basement Beam and Columns.....
This is a bit backwards from the normal question on removing beams and posts – I want to add them. I am getting ready to refinish a basement in a 100year old foursquare colonial. I have noticed on the first floor, that there is floor sag in about the middle of the house. You can tell that it has been here for quite some time by the molding work done in a kitchen remodel by the previous owner 10 years ago.

Before I refinish the basement, I want to insure the sag does not get worse. The sag seems to originate from the center beam in the house which looks to be about 2 2x8 sistered, 2x6 on each side of that, and then 2x4 on the outside of that. The floor joists come off the exterior foundation and are notched to this profile. The there are 2 beam sections butted together, the back of the house resting on 1 beam and front on the other and meeting in the middle. They had one column supporting were the two butt ends of the beam meet. There are also columns mid span of each beam. Over time one outside corner of the plate at the top of this middle column failed (actually cracked off). This allowed the outer 2x4 to rotate ever so slightly on the one side of the beam(about 1/8-1/4” at the top). This transferred the load to the upper notch in the joists and in a couple of joists, you can actually see where the top notch cracked.

Here’s what I would like to do (and I actually have headroom and space to do it):
1) Replace the current column (it is an old 4in diameter column with a new 4 in column). Shift it about 2 inches so it is only handling one beam. The current column rests on a concrete pad that is about 2” off the concrete floor. None of my columns look to be recessed into the floor.
2) Add a second 4” diameter column next to the current column to handle the other half beam.
3) Add a W6-15 steel I beam (it will be 14ft long) right next to the current beams and put 3 3” diameter columns under it. This beam just happens to equally overlap the original beams by about 7’.

Anyone see any issues with this plan or have any suggestions. Is this over or under kill?

concretemasonry 03-19-2008 05:03 PM

The only problem I see is that you will have to first level the house and then the put right sized new supports where you want to.

You have no idea what the loads will be when you shift the loads to level it and add new columns.

You need a professional to give you some options on what to do. Do not ask a contractor since he just wants a job to walk away from.

Adding interior columns is a real change in the structure and they can pick up much more load than you get at a beam sitting on an exterior wall (more area above). Any new columns have to be on a new foundation since you have no idea how thick the slab is, how strong it is or if there is even soil suporting it instead of a void cause by years of settlement.

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