Shoring a Sagging Floor, Images 1-8

Use the right tools and a methodical approach to get the job done quickly.

The home's central girder had been unprofessionally shored over the years with steel posts, pressure-treated 4x4s, and even a cedar log.

On this job, I ordered Springfield plates for the caps; these have a welded ring of steel that prevents the column from moving sideways.

Before doing anything else, I want to get a sense of how badly the girder is sagging. So I run a string 12 inches below the bottom of the joists from one end of the basement to the other.

At its worst, this beam had taken on a 3/8-inch sag — not enough to worry about, and certainly not worth jacking straight, which might cause problems upstairs with door swings and cracked plaster.

I measure along the string in 6-foot increments and mark off the centers of the new footings with a Sharpie.

Attaching my Tajima plumb bob to the beam at every mark, I plumb down and lay out the 24-inch-by-24-inch footings.

Laying out the footings

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