- 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.