How to Fix a Failing Bathroom Floor
From demolition to installation, how to repair old, water-damaged floor joists.
Synopsis: Because bathrooms are subject to such high usage under extreme conditions, they often end up having to endure the trickiest, most difficult repairs when things go wrong. For this project, builder Mike Lombardi visited the FHB Project House to prepare its bathroom floor as the first step in a major face-lift. To start, Lombardi and his crew removed the old, damaged floor joists. It’s important to take apart the floor carefully, starting with the subfloor, so that you don’t cut into any plumbing or mechanicals under the subfloor. The next step is fitting the replacement joists. In a bathroom, take steps to ensure that your work won’t be undone by future water damage, and be sure to reinforce the framing under the toilet and the tub. This article includes sidebars about prepping for a mortar bed and about working with the right number of people on a demolition job.
In a perfect world, there would never be a battle between framing and plumbing. The reality, though, is that bathrooms are often small, and there frequently is precious little space to fit all the incoming and outgoing plumbing necessary for the tub, shower, vanity, toilet, and other fixtures. Without forethought in the design phase, upfront communication between subcontractors in the rough-in phase, and a willingness to do the job right in remodels, sacrifices are often made.
These problems usually are found in the floor system: Joists are notched carelessly, cut through, or drilled incorrectly, sometimes directly under a bathtub or toilet, where there is an added load on the framing. In the bathroom shown here, water leaking from the joint between the tile floor and the tub apron had rotted the floor sheathing, the original joist below, and a new joist that had been sistered in place…