Installing Stone Counters, continued
The sink should be installed flush with the subtop, because
the counter is supposed to land on or just above the flange.
Sink holes will vary, because they are ground and finished by
hand; they need a little bit of play. The hole in the subtop
should be slightly oversized, big enough to shift the sink 1/4
inch in any direction. This allows us to adjust the sink to the
opening when we install the counter. The counter usually
overhangs the sink, and the joint between the slab and flange
Unlike many fabricators, we will not cut a sink opening from
the paper template that comes with the fixture. Every now and
then someone will give us the wrong template, and we don't want
there to be any question about where the opening goes. We want
the sink to be in place when we template the cabinets so we can
trace the opening onto the template (Figure 6).
Figure 6. Here, a
fabricator is tracing the location of a sink onto the bottom of
a plywood template. The opening through the stone will be sized
down to create the proper overhang.
Stiffeners. Counters are
weakest at the narrow strips of stone along the front and back
of large cutouts. We sometimes reinforce these areas by
slotting them from the bottom and epoxying in a metal rod
(Figure 7). It's also a good idea to stiffen the subtop under
narrow strips of stone. You can do this by installing aprons or
posts inside the cabinet (Figure 8).
Figure 7. The edge of
this counter has been strengthened by gluing metal angles to
the back of the nosing. The entire slab has been reinforced
with a layer of fiberglass mesh and glue.
Figure 8. The stone
will be narrow at the front of this sink, so the carpenter
reinforced that area by installing a horizontal apron across
the top of the opening. A center stile would perform the same
function in a face frame cabinet.
A cast-iron sink is very stiff, so if it's held up by the
cabinet it will provide some support to the strips of stone
above. Stainless steel is another matter. I will not put stone
across the divider of a double-bowl stainless steel sink unless
there is some kind of reinforcing below.
Some fabricators drill the faucet holes in the field. They
fear that the counter, weakened by holes, may break in transit.
We prefer to drill holes in the shop, because drilling creates
a lot of dust and we haven't had much trouble with
We can't make templates until we know exactly where the
faucets will go. Faucets should be dry-fit in the subtop with
the sink in place. It's usually a tight fit, so it's important
to make sure everything works. Be sure to consider the
thickness of the backsplash. It's a good idea to temporarily
install the sink and faucet and show them to the clients. Let
them manipulate the faucet, and get them to sign off on the
location of everything. It's not hard to move things at this
point, but once we fabricate the counters the faucet locations
will be literally carved in stone (Figure 9).
Figure 9. Sinks and
faucets must be located and temporarily installed in the subtop
before the templates for the counter are made (top left and
right). Here, the author is verifying that the homeowner is
satisfied with the location of the faucet
Clearances. The holes
through the subtop should be the same size as the holes that
will be drilled in the counter. The faucets should be test-fit
with the sink in place, because you want to be sure they are
not too close to the flange. If they are, the plumber will not
be able to install the nuts and washers that hold them
Once the counter is templated, you may want to cut out the
material that's under the faucet holes. Most faucet stems do
not have enough thread to reach through the counter and the
subtop and stretcher below. If you remove this material, the
plumber can run the nuts to the bottom of the slab.
Cooktops and Vents
Cooktops are usually easy to put in, because they install from
above and have a flange. It's tougher if the client wants to
use a cooktop with a separate downdraft vent. Frequently the
two appliances come from different manufacturers, which can
make for a tight fit in the cabinet. Most vents are slightly
narrower than cooktops and are equipped with a minimal flange
(Figure 10). There's not much play, so you need to test-fit the
units to make sure they fit in the opening and that the flanges
will hide any gaps. Some vents have top and bottom flanges that
slip over the stone to hold the unit in place. They work fine
with dimensional stone but are not sized to fit thicker
material. If you want to put this type of vent in a 1 1/4-inch
slab, you'll have to cut off the bottom flange.
Figure 10. The top
piece is a 1/8-inch plywood template that has been cut to match
the opening in the subtop for a cooktop and downdraft vent. The
vent is not as wide as the cooktop, which is why the opening is
narrower at the back.
Sometimes there's an opening in the counter for a freestanding
stove. The stove will not be attached to the counter, but we
still expect it to be on site when we make the template. We
will not work from cut sheets because the dimensions are
frequently incorrect and appliances are allowed to vary
slightly from spec. Sometimes they are not even square. The
only way to get a good fit with an even reveal is to put the
stove where it goes and template to it (Figure 11). The stove
should remain in place until the counters are installed. That
way, we have something to align them to.
Figure 11. Freestanding
stoves should be installed before templating. Otherwise, there
could be an uneven gap between the stove and counter. The
fabricator is measuring to see if the stove is square to the
Even though it's not supposed to show, we polish the cut edge
of the counter that butts to the stove. If the stove is
slightly low, the client will see a polished edge.
Cover Your Costs
If you're the GC, you will need to carry something in the
budget for tasks that relate to the installation of stone
counters. Someone needs to build the subtop and to pre-install
the cooktop, sink, and faucets. The schedule will be affected,
too. The fixtures, faucets, and appliances need to be on site
earlier than usual. The client should be aware that there will
be a two- to three-week lag between templating and when the
counters go in.
Rick Stenberg is the
owner of Marin Marble in San Rafael, Calif.