Replacing a Garage's Lally Column
The Lally column in my detached garage is rusting, and its concrete base is crumbling. Can I replace it, or is that beyond the scope of a homeowner? —Norm Watkins, Bedminster, NJ
Tom Silva replies: I don’t think the work will be too difficult, but you may want to get some help figuring out what needs to be done. With all the variables to be considered, you should have an inspector, engineer, or experienced contractor assess your situation and the steps required to fix it before you tackle the job.
That input will be especially important if there are cracks in the base or in the slab around the column. A crumbling base may need only a cosmetic fix, but a cracked slab is an indication that the footing is inadequate or nonexistent and that a new one needs to be poured. Since you don’t mention cracks, it’s likely that your column rests on a proper footing, making this a much easier job.
Here’s a general overview of what should be done, assuming you have a basic, single-story garage with a single Lally column supporting a beam that runs the entire width of the space.
Before you can begin, the beam will need temporary support. For a single beam, a couple of 2x6s nailed together and a hydraulic bottle jack placed a couple of feet from the post will be sufficient. If there are two beams that overlap at the post, then make sure each one has a temporary support on either side of the post.
Place a steel Lally plate on top of the bottle jack, steady the 2x6s on the plate, then hold them in place by jacking them up against the underside of the beam. Check that the 2x6s are plumb. Now unbolt the plate connecting the column to the beam, gently jack the support up just enough to relieve the weight on the column, and unfasten it from the base. Save the old column so that you can cut the new one to the same length.
You could install another grout-filled steel Lally column, but a pressure-treated 6x6 post might be a better option because it’s easier to cut and won’t rust. You’d anchor it to the concrete with a galvanized-steel post base held in place with expansion bolts, and fasten it to a metal post cap with structural screws. All this hardware is made by Simpson Strong-Tie.
Use a 4-foot level to make sure the post is plumb before lowering the temporary support and fastening the cap to the beam with more structural screws.