Download PDF version (193.1k) Log In or Register to view the full article as a PDF document.
Q.I'm about to pour a slab on a site where several stumps were removed, leaving 2- and 3-foot-deep holes about 4 feet across. The backhoe operator went ahead and filled in the holes with dirt from the site (sandy loam, pretty good stuff), drove over them a few times, and leveled it up. Question: I have a small plate compactor. If I run that over these ex-stump holes for a good while, will that suitably compact the subbase? Or should I re-excavate and compact the soil in 6-inch lifts? I plan to put Mirafi and then a foot of clean stone under the slab.

A.Jay Meunier responds: Don't bother re-excavating those areas to compact the fill in lifts. Instead, grab a hose and lightly saturate the areas with water. You want the soil to be damp but not full of water. Let the water percolate down through the soil to eliminate air pockets, then run the compactor over it. Do all of the areas once, then start over again. This should do a good job of providing a stable subgrade. When you're pouring the slab, lay a grid of 1/2-inch-by-6-foot rebar (two pieces in one direction, two perpendicular) across those areas as additional cheap insurance.

Jay Meunier is an estimator for Pizzagalli Construction in Burlington, Vt., and the former owner of a residential concrete business.