It is not uncommon for a building more than 100 years old to have floors that are out of level, but to have those floors be out of level more than 2 inches is a challenge to fix. In this particular three-story, three-unit building, the load-bearing center beam had dropped, while the brick exterior perimeter walls had remained in place. The resulting 2-inch-plus drop is evident in all three of the stacked units, each owned separately.

Co-author Chris Hovious checks the framing for flatness after leveling an existing floor for a bathroom remodel. New framing and sistered 2-by stock was added to support the existing joists and help stiffen the floor.
Co-author Chris Hovious checks the framing for flatness after leveling an existing floor for a bathroom remodel. New framing and sistered 2-by stock was added to support the existing joists and help stiffen the floor.

Attempting to jack the center beam in a building this old would likely cause severe and unpredictable consequences. The most benign of these would be that interior doors might not operate and plaster would crack; the worst-case scenario would be brick-wall failure and plumbing breaks. At the same time, there is no guarantee that 100 years of sagging could ever be corrected by jacking.

So we had a 2-inch drop down the center of the building. This might be interesting character in living rooms and bedrooms, but in kitchens and baths, it’s a big problem. Tubs, vanities, and toilets need to be placed on a level surface. Imagine what your tub would look like with a 1 1/2-inch taper from left to right. Or envision a furniture-style vanity with more than an inch cut off one side of its legs. People certainly do it, but that doesn’t make it right.

In this bathroom remodel project, the floor dropped roughly 2 1/2 inches in 8 feet. To level from the highest point (the exterior wall) would leave an approximate 2 1/2-inch step up at the bathroom door threshold. Sure, this would yield a level floor, but a step that large would create an obvious and unacceptable tripping hazard. Instead, we chose to remove material from the uphill side of the existing joists.

After removing the existing flooring, a level laser line shows 2 inches of wood to be removed at the high end of the 3x8 hemlock joists (above).
After removing the existing flooring, a level laser line shows 2 inches of wood to be removed at the high end of the 3x8 hemlock joists (above).
Here, Hovious snaps a cut line along the laser line (above left), then screws a ledger guide to the joist (above right).
Here, Hovious snaps a cut line along the laser line (above left), then screws a ledger guide to the joist (above right).

Doing this requires increasing the load capacity of the remaining framing. In our case, we sistered additional support to the existing joists and added new framing between them. Because the renovated bath would have electric radiant heat, extra material was removed to account for the added finish-floor height.

Original Structure

The original floor joists were full-dimension 3x8 hemlock. The joists were spaced roughly 32 inches on-center (some were spaced about 31 inches, some about 33 inches). Instead of being supported by wood framing such as a rim or band joist, the floor joists were installed directly into the inner wythe of the exterior brick wall and locked into place with mortar. The joists spanned the entire 20-foot width of the building, supported by one load-bearing center wall.

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By ripping the joists back instead of packing them up, the authors were able to bring the bathroom’s final floor system flush with the existing floor in the adjoining living room. The final buildup, including two layers of subfloor, a layer of Laticrete Hydro Ban board, Laticrete Strata heat mat, thinset mortar, and ceramic tile, came to 2 3/4 inches.
By ripping the joists back instead of packing them up, the authors were able to bring the bathroom’s final floor system flush with the existing floor in the adjoining living room. The final buildup, including two layers of subfloor, a layer of Laticrete Hydro Ban board, Laticrete Strata heat mat, thinset mortar, and ceramic tile, came to 2 3/4 inches.

The existing subfloor was 7/8-inch-thick random-width plank flooring, presumably originally 1 inch thick, run perpendicular to the floor joists. The flooring was random-width wide-plank softwood (probably hemlock), also run perpendicular to the joists. Everything was installed with hand-cut nails.

Deflection. At a rough calculation, the original framing had a deflection rating of about L/600—surprisingly stiff. Technically, this would qualify the floor to support ceramic tile, when installed properly. (Natural stone requires L/720 or better, while ceramic tile requires only L/360).

However, just walking on the floor was enough to deter us from installing tile with anything but a taillight warranty: There was significant bounce and movement between the joists. But when we were done ripping down and sistering the joists and reinforcing the floor system with additional joists, its deflection penciled out at roughly L/1000—stiff enough for us to feel comfortable.