My construction company does a lot of renovation work, including new foundations under old buildings. This typically involves jacking up the house, with big beams carrying the load, and then stacking cribs of railroad ties under the beams to support them while we work on the foundation.
I recently had a project in the mountains a couple of hours from home, and railroad ties were not to be had anywhere nearby. I did, however, have access to some 1-1⁄8-in. plywood, 3-1⁄2-in. galvanized screws, and tubes of construction adhesive. With advice from my structural engineer, I made a bunch of plywood boxes up to 2 ft. sq. and 3 ft. tall. I could make them larger than the railroad ties. They also weighed a lot less, so they were easier to move into place. I used the boxes as short, stout posts, tailoring their heights to fit the dimensions required. They were so handy that I’ll use them on purpose next time, even if I can get railroad ties.
—Brian Brophy, Lockeford, CA
Edited by Charles Miller
From Fine Homebuilding #236
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The strength of plywood when loaded edgewise is phenomenal. I've designed box beams to carry the weight of of a concrete slab placement over a 20' opening in the floor below that resulted in minimal deflection.