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Column Load over a beam

Column Load over a beam

Column Load over a beam

Hey gang,
I'm working on one of those traditional "open up an interior load-bearing wall" remodel projects. The wall is on the main floor of a house over a basement. There is a second story above the wall I'm opening and that wall is also load-bearing to the roof. The load calcs put just under 11,000 lbs on each bearing column at the ends. If we were to follow the traditional rules, I'd take the load for each column directly down to the basement slab with another column directly below, dig an appropriately sized footing, adequately tie the two columns to each other with mechanical straps, fasteners and solid blocking in between and call it a day. However, I'm a bit leary of tearing into the existing concrete slab as this has been one of those remodels where everything I touch seems to open up two more issues, so I'm trying to be minimally invasive.

Is there a viable option to spread this column "point" load over the existing wall and subsequently the existing concrete slab by putting a beam in the top of the basement wall under the column? This would be embedded in the existing load-bearing wall (co-planar) and then putting 2x4 studs under that beam on 8" centers. When I run the numbers, I wind up needing 840 lbs per foot (tributary) of the beam plus the 11,000 lbs column load. Assuming that each vertical 2x4 stud in the wall can support around 3000 lbs (8' tall and braced), I wind up needing 3.5 lineal feet of beam with the 2x4s on 8" centers underneath it. The math is 42" / 8" centers = 5 support studs under the beam or 15,000 lbs of strength. The load would be 840 plf *3.5 ft = 2,940 lbs (tributary). Add to that the 11,000 lbs for the column for 13,940 lbs total load.

It's a 2x4 wall so that puts the bearing surface at 3.5"x42" = 147 in2 where the sole plate meets the top of the slab or about 95 psi on the concrete at the surface. The slab is at least 9" thick on gravel under the wall (I ran out of drill bit length on my hammer drill). Assuming a 45-degree angle of spread that makes for (3.5+9+9)*42/144 = 6.27 sq-ft of bearing surface at the soil or about 2,222 psf which should be below my soil strength.

Is this approach viable or am I still at risk of punch-through or some other failure? Anything I'm missing here in how I approach this?


RE: Column Load over a beam

check spunching shear

RE: Column Load over a beam

In wood I've never considered load spread that way. The load will take the stiffest path, that being the posts/studs directly below the column until something gives way,either the studs or the slab,then it will move to the next stud causing a zippering type failure.

Just cut out the slab and put an appropriate sized footing.

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