Most stainless steel undermount sinks are installed when using a granite, concrete or other stone countertop. Established undermount sink companies should offer good advice regarding the mounting of their sink, but this article will explain the most popular methods.

There are several ways to install these sinks.  Most all are good methods and the one used generally depends on the way the installer learned to do it.  Some use clips or brackets and some are just glue in installations.

The clips that are shipped with most sinks are simply a strip of metal about an inch long with a hole in one end and a screw and holder which is seated in the stone around the outside of the sink.  These work well, but need to be installed at the shop and not at the jobsite.  The risk of using this type of clip is that if the fabricator is not experienced or does not have the proper equipment, the stone can become cracked or broken.  The hole for the screw is drilled into the stone from the bottom about half way through to insert the plastic for the screw.  The metal strip then extends over the edge of the sink and is tightened to hold the sink.  There are generally about 10 of these clips around the outside of the sink which means about 10 more holes part way through the stone which can crack now or later.

This type of installation also requires additional space around the outside of the sink which can limit the size of the sink that can fit into the cabinet.

There are also brackets available to installers that run from the front to the back of the cabinet before installation.  These brackets also have screws in the brackets to hold the sink up against the stone from the bottom.  There are generally two of these per sink installation. They do require that the installer put two small notches in the cabinet to hold the bracket, one on the front and one on the rear of the cabinet.  The notches are not visible in the finished product unless you look from below the level of the cabinet.  No additional holes are required in the stone for this type of installation.

The most widely used method of installation is gluing the sink to the stone.  This sounds like a poor way of securing the sink, but it actually works very well.  It is also the best method if you ever have to remove the sink.  After the top is installed and secured the sink is installed from the bottom of the cabinet.  The installer will use the two part epoxy that is used in the stone countertop industry to glue seams and put several portions around the edge of the sink in about six or eight places and then go completely around the edge of the sink where it will contact the stone with clear structural silicon.  The silicon will also form the seal between the sink and the countertop.  This has to be silicon and not latex caulking.  The latex will not hold.  The stone must also be very dry.

The sink is then pulled up from the top and held in place with clamps through the sinkholes and a 2X4 across the counter.  In about 2 hours the clamps can be removed, but the silicon, which is what really holds the sink, needs 24 hours to dry.  Do not hang the garbage disposal on the sink during this time.

For additional security often small pieces of stone (about the size of a silver dollar) are glued underneath the sink overlapping the edge of the sink and the stone.  These can be knocked off it the sink has to be removed for any reason.

Installers who deck the cabinets with plywood underneath the stone often just clamp the edge of the sink between the decking and the stone.  This is a simple installation, but the sink cannot be removed without taking the countertops off.

This represents most of the methods of installing stainless steel undermount sinks.  You can discuss this with you fabricator before installation to know how he is going to do yours.  The clips generally ship with the sink.  The brackets do not and will have to be purchased separately.  If he glues the sink in, he should have everything that is necessary for the installation.

ARTICLE SOURCE: http://www.articlesbase.com/kitchens-articles/what-holds-my-undermount-sink-in-place-1304652.html
AUTHOR: Ron Freeman