In this video, we are leveling up and stiffening a sagging floor. The floor sagged over time because the builder didn’t provide properly designed trusses. We stiffened the trusses and jacked up the floor to fix the problem, and this is how we did it. The contractor is David Moore with Structures, Inc. I found in my analysis that the original designer didn’t take into account additional loads on the floor. Also, the installer cut the floor trusses improperly at the ends.

Over time the trusses began to sag, or “deflect” in engineering lingo. A typical solution is to place plywood on both sides of the trusses, but the problem we had was that there was ductwork, plumbing, and gas lines going through the trusses, so that didn’t work. So, we stiffened the trusses using strips of steel, and then we jacked them back up into place.

Leveling up and stiffening a sagging floor in this type of situation was difficult, and we only have one chance to get it right. So, to deal with this, we took as many measurements of the existing floor truss as we could, we had to work through a small hole in the ceiling at first. We modeled the floor trusses in 3d structural software (Bentley RAM Elements), and determined the problem. Doing some calculations, we found we could reinforce the trusses using strips of steel held in place by wood screws and glue. We needed glue to provide shear resistance to keep the steel strips from sliding.

You’ll see in this video that we jacked the floor in place to take the sag out of it, and then placed the stiffeners on the sides. This one was relatively simple for us to jack back up into place. It isn’t hard for you to jack a floor into place with the right equipment and reinforcement. Part of the floor will be a problem because there are walls above it that we will lift. We will do this over time to allow the wall to flex and not cause excess cracking.

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