After redirecting the gas line, sewer pipe, and electrical wiring, we began work on the floor system. Lead carpenter Danny DuCouto hammer-drilled out four new beam pockets for the steel in the existing brick party walls.
The W6x9 I-beams weighed 180 pounds each, so they weren't too heavy; the main issue was their length. We managed to move the beams inside through an existing street-side window.
It took three of us to put them roughly in place, setting one end up in the 12-inch-wide pocket we had chiseled out of the party wall.
We shored up the existing floor system with temporary 2x4 stud walls, placing them around the steel ...
We lifted the W6x9s in place, pushing them into the 8-inch-deep pocket and at a slight angle along the horizontal plane at the wider, chipped-away side of the pocket. We then moved on to installing the Microlam beams.
In order to flush-frame the three new 3 1/2-by-6-inch Microlams, we had to cut away the existing 3x6 joists and notch the ends of the Microlams so they would fit between the flanges of the W6x9. We started at one end of the room and worked toward the street side. We cut the joists, then fit the first Microlam into place, posting it up at one end. The widened beam pocket allowed us to sledgehammer the steel into place, nudging it toward the Microlam until the web of the steel I-beam flushed up with the Microlam's notched end.
We did the same for the second Microlam. This time we had to insert the Microlam's leading end into the first W6x9, then pound the second W6x9 into place.
With steel and Microlams roughly in place, we shimmed the steel level and applied non-shrink grout at the beam pockets. We connected the existing joists to the Microlams with joist hangers and clip angles, then removed the shoring.
In an effort to create clear space in the apartment below, we removed the existing bearing wall at the stairwell.
We infilled the stair opening with new double 2x6s sistered to the existing 3x6 joists with through-bolts. Where we needed to pick up point loads from above (avoiding posts and pilasters in the basement), we swapped out a few 2x6s for Microlams ...
In order to redirect the floor and roof loads from above—leaving the new steel to support just the first floor—we used a 5 1/4-by-14-inch LVL beam in the second-floor framing and posted down to new footings in the basement. Once new subflooring covered the infilled opening, we started framing the powder room and closet.
With the structural work complete on the first floor, we moved on to the other floors, juggling the clients (who stayed in the house during construction) from space to space. The finished basement, though small, looked pretty slick.