Figured out why my concrete crew kept messing up the slabs

Ran a job in Austin last month where the slab edges were consistently off by 3/8 of an inch. I kept blaming the crew thinking they skipped the layout. Finally walked around the site with a senior foreman and noticed the laser level was set on a spot that had settled overnight from the morning rain. The ground shifted just enough to throw everything off. Now I check the tripod position first thing every day before anyone starts pouring. Has anyone else dealt with tools shifting on soft ground and how do you prevent it without losing time?

2 comments

2 Comments

nathang6711d ago

Yeah man, that ground settling thing is brutal lol. Had a crew in Houston lose a whole afternoon to that same crap once.

river_wright10d ago

Wait, are you saying the tripod itself settled into the ground or the whole laser level shifted from the base moving? Because those are two different problems. If the tripod legs sank into soft dirt, that's a setup issue where you gotta use those wide foot pads or even throw a piece of plywood under each leg. But if you're talking about the ground itself settling under the tripod's weight over a few hours, that usually means you're on fill dirt that's still compacting. The real trick is to set up on a concrete curb or sidewalk if you can, or drive a stake into the ground next to the tripod and check the level against that stake every hour. I've also seen guys set up two lasers and cross-check them against each other which sounds like a pain but catches this exact problem. Honestly though, 3/8 of an inch over a whole slab is a lot for just ground settling - could be the laser didn't auto-level properly too if the ground shifted while you were walking around.