During home inspection, we found some termite damage in the basement: not ongoing, but significant. Un-finishing the basement a few months later, it became clear that the original wooden pillars supporting the house hadn’t been load-bearing in quite some time: two steel pillars were supporting the main beam, with a third under the staircase.

Since the goal is to get the house as original as possible, and steel posts are ugly, I wanted to swap in new wooden pillars for the old termite-ridden ones. The first step was to remove the old pillars to get an idea of the condition of the beam and footings. The beam was actually in three parts, kind of like this:

FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
 J  J  J  J  J  J  J  J  J  J
WBBBBBBBB BBBBBBBBBBB BBBBBBBBW
WW    S PPP    S    PPP S    WW
WW    S PPP    S    PPP S    WW
WW    S PPP    S    PPP S    WW
WW    S PPP    S    PPP S    WW
CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC

where C=concrete, B=beam, W=wall, P=wooden pillar, S=steel jack, J=joist (coming out of the screen), F=first floor. I needed to get a couple more jacks to put on the opposite side of each pillar, but then it was pretty easy to raise the house a fraction of an inch and remove the old pillars. The footings were crumbling (the moisture is probably why the termites thrived), and anyway the new pillars were slightly different dimensions. Speaking of:

These giant oak pillars have the same cross-sectional area as the originals, and a bit more surface area contact with the beam. I traced out the new profiles on the floor, cut away the old concrete with a diamond blade (grinder and skill saw), and poured a layer of concrete that would set the pillars about half an inch deep.

Once the concrete set, I adjusted the jacks until the first floor was as level as possible, measured the distances from the newly-poured surface to the beam, and cut the new pillars to size. To protect against termites, which destroyed the old pillars, I coated the end-grain with a napthalene solution.

Since I cut the old concrete out a lot wider than the footprint of the new pillar, it could be placed vertically inset into the floor, then slid under the beams. Carefully lowering the jacks until the beams rest on the new pillars, all that remained was to finalize the bases by pouring concrete into the space around the base, and then seal where the pillar meets concrete with silicon.

So far, the house hasn’t collapsed!