I am in the process of refininshing my basement. I would like to remove one (preferably two) lally columns. The foundation measures 24' x 42' (exterior), all floor joists are 2x8's; main beam is 3) 2x8's spiked together; knee wall is stick built 2x4 construction; lally columns about 6'-11" apart (5 of them).
My plan is as follows: 1) Have head room to add 2) 16'- 2x12's to both sides of beam (6'-8" headroom under). 2) Add bearing wall from 15'-3" to next post (@ approx. 21' [CL] point along main beam). 3) According to tables I've read, span for 4) 2x12's (from memmory, don't have tables handy) is about 12'9".
My question(s), If I were to support gable end of beam by the foundation thickness (~10"), and leave existing beam in place, and bolt through all 7) 2x's [2 rows staggered, 3 1/2" apart, @ 16 o.c.) and attach together with 1/2" hardware, can I extend new beam to about a 15'-3" span and remove the two columns, (or only the first one) and still maintain the required structural support for the floor above (Split level home).
According to some old (1940/50's vintage) Audel books I've read, and doing some quick Pcs calculations found there, I should be able to. Don't really know for sure. Would like a little back-up.
If my idea is not valid as it stands, any other suggestions as to how you may have solved a similar situation?