Pro tip: corrugated boxes lose half their stacking strength in 24 hours, and that changed how I build | Cardboard Box Forts

Kelly Kim · 2026-09-14T08:40:03.305641+00:00

I used to hoard moving boxes in my garage for weeks before a big build. Then I read on a packaging site that a corrugated box keeps only about 50 percent of its stacking strength after a single day of use, since the linerboard and flutes get crushed. That number stopped me cold because my last two-story fort in the backyard leaned hard to one side after a sleepover. Now I build the same weekend I grab boxes from the liquor store on 5th, and the walls hold way better. Anyone else notice fresh boxes just perform different, or is it only me?

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Pro tip: corrugated boxes lose half their stacking strength in 24 hours, and that changed how I build | Cardboard Box Forts - The Community Guide