A.George Smith
responds: You’re not the only one
who’s struggled with this problem. You can
beat yourself up trying to cut a door or window
through a foundation wall.
The easiest way is to rent one of two specialty
saws, if available. A Partner ring saw can cut to a
depth of about 10 inches (Partner Industrial
Products, 905 W. Irving Park Rd., Itasca, IL 60143;
708/773-2801). Or RGC makes a concrete chain saw
that cuts to a full 15 inches (RGC Construction
Equip., P.O. Box 681, Buffalo, NY 14240;
716/895-1156). Both run on a hydraulic power pack
and require special (read "expensive") diamond
blades.
We don’t have access to these saws here
on Tortola, where everything is built with
concrete. So we make do with a standard 14-inch
concrete saw (we use the Bosch).
To support the saw, make this simple rig: Build
an A-frame out of 2x4s, either screwing the top of
the frame to the joists, or attaching a third leg
to make a freestanding tripod. Throw a rope over
the cross rail of the A-frame, tying one end to the
front (top) handle of the concrete saw and the
other end to a 5-gallon mud bucket. Then fill the
bucket with enough sand or rubble to counterweight
the saw.
The counterweight will not only make it easier
to keep the saw elevated, but it will allow you to
apply light, even pressure as you cut. When cutting
concrete, you don’t want to bear down on
the saw. If you hit rebar, you’ll see the
sparks. Back out, then go back into the cut very
gently.
A 14-inch saw has a depth-of-cut of about 4 7/8
inches, so you’ll have to cut from both
sides of the wall. Before you begin, drill holes at
each corner, keeping the hammer drill as straight
as you can. Then you can draw layout lines on the
wall to align your cuts on both sides. If the wall
will be plastered, overcut the corners. If not, cut
to the corner holes, then bust the remaining pieces
out with a sledgehammer and cold chisel.
Most of the time we use a silicon-carbide
abrasive blade for concrete and masonry. Diamond
blades are nice, but very expensive ($400 to $800
each).
George Smith owns Island Equipment on
Tortola, British Virgin Islands.