New Floor System
In the basement, the center bearing would include both 4-inch Lally columns and a framed bearing wall. Rather than create individual piers for the columns, we poured a 24-inch-wide by 12-inch-deep reinforced trench footing down the center of the basement. There was no easy access to the basement, so we dug the trench by hand. Luckily, the old basement floor was no more than a thin coating of cement over the dirt, so we could easily cut it up with a demo saw and a diamond blade. Other than hitting some large rocks, digging the footing was easier than expected. We moved the soil directly into a dumpster outside with a rented conveyer belt, and then, after placing the rebar, we placed the concrete using a chute through the basement windows.
Demolition. First, we demolished all of the nonbearing walls. Next we removed as much of the flooring and subflooring as we safely could, to get as much weight as possible off the framing and expose any potentially dangerous conditions. We started on the first floor and worked our way up. We removed the floor framing in thirds, starting at the front of the building and working toward the back.
To support the second-floor framing while we tackled the bearing walls, we posted down to the basement floor through holes cut in the flooring. My little 16-inch Husqvarna chain saw got a workout — we went through a half-dozen chains, but it was a lot faster than using a reciprocating saw.
As we removed each floor section, we replaced it with new framing before moving on to the next. Thanks to the trench footing and center bearing walls, the longest joist span was only 14 feet 2 inches, so we used 9-1/2-inch 230 series I-joists from Weyerhaeuser for the first-floor framing. On the second and third floors, we used 11-7/8-inch-deep I-joists so that we could cover existing 10- and 11-inch-deep beams without interrupting the ceiling plane.
LVL rim joists. Our initial plan was to hang the I-joists from LVL rim joists bolted to the 8x8 oak sill beams around the perimeter. But on discovering that many of the sills were rotting and would have to be replaced, we decided instead to hang the joists from a doubled LVL beam attached to a 2x4 PT plate sitting on top of the foundation wall inside the rotten sills. This way we could continue replacing the floor framing and replace the existing sill later, working from outside. We leveled the LVL band-joist assemblies with a laser, temporarily shimmed them in, then packed nonshrink grout in the voids.
The sills along the covered porches were still in good shape, so there we bolted a single 9-1/2-inch LVL to the existing oak beams using 3/8-inch-by-7-1/4-inch GRK lag screws placed 24 inches on-center in a staggered pattern. Not only are GRK lag screws stronger than conventional lags, but they install much faster because they don’t need to be predrilled and can be driven with a corded drill driver.
We needed to transfer vertical post loads from the old sill beam to our new double-LVL rim joist. So we had a local shop fabricate custom angle brackets from 1/2-inch steel plate. The horizontal flanges of the plates bear on top of the doubled LVL rim joist, while the vertical legs are bolted to the timbers with 1/2-inch lag bolts (see the illustration " Sill Retrofit
" on page 4 of the PDF).
I-joists. Once the new LVL rims were in place, we set the first third of the center girder on top of Lally columns, installed Simpson ITS 9.5/2.37 top-mount joist hangers, and started hanging the joists. These hangers are a little tricky because both sides of the joist must come down evenly to get the teeth on the bottom of the hanger to grab the bottom flange of the joist correctly. And once the joist is in place, it can be very difficult to remove if there are problems with the layout.
Bracing. After gluing and nailing down the 3/4-inch OSB subfloor on the first section of the floor, we nailed diagonal bracing down from the outside walls to the new first-floor deck and started working on the next section.
Once we’d completed the first-floor deck and securely braced the walls, we felt it was safe to remove and reframe the second floor, again working in sections. Here we were able to simply bolt the LVLs to the beam at the top of the first-floor walls. The 11-7/8-inch-wide LVLs were almost an inch taller than the existing beams, which were only slightly out of level, so we were able to install the new rim joists perfectly level while still covering the entire beam.