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Installing an undermount sink requires careful planning and coordination between subcontractors

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The demand for undermount sinks is growing. Even if you haven't had to install one yet, it is probably only a matter of time before a customer requests one. Because undermount sinks - also called undercounter sinks - are generally used only with stone or solid-surface countertops, they tend to be found in high-end kitchens. This raises the stakes for the builder, who is likely to face a more demanding client, and will need to coordinate the work between several subcontractors. Customers who like the elegant appearance of undermounts are willing to pay an up-charge for them - not only for the countertop, but also for the cost of the sink and the additional installation time. Because sink manufacturers know that undermounts are used only with high-end countertops, they see no reason to market budget-priced undermount sinks. In general, the price of a double-bowl stainless steel undermount sink starts at $400, and heads north from there. For less-expensive laminate countertops, a drop-in sink - also called a self-rimming sink - is usually required, because the sink cutout exposes the vulnerable particleboard substrate. However, Counter-Seal is now marketing a system for installing undermount sinks with laminate countertops (see sidebar, ).

A Wide Range of Materials

Like drop-in sinks, undermounts come in a wide range of materials, including cast polymer, stainless steel, enameled cast iron, enameled steel, vitreous china, copper, brass, and solid stone. Cast polymer Cast polymer (plastic) sinks make up a growing share of the market. Sink manufacturers generally divide cast polymer sinks into three different categories - cultured marble, solid-surfacing, and composite (see sidebar, ). Although cultured marble is relatively inexpensive, it is less scratch resistant than other types of cast polymer, and is not recommended for use in the kitchen. At least one manufacturer, Lippert, makes an undermount bathroom lavatory out of cultured marble. Solid-surfacing. Most manufacturers of solid-surface countertops also manufacture sinks out of the same material. Solid-surfacing, unlike cultured marble, is uniform throughout the entire thickness of the material. Any scratches can be sanded out, with no degradation of the finish, using 180- to 300-grit sandpaper. Solid-surfacing is less stain resistant than most other sink materials. "There are certain stains that none of the solid-surface materials can resist," says Steve McNally, director of government and regulatory affairs for the International Cast Polymer Association, an industry group. "Cherry Kool-Aid is one. It is a very aggressive stain. In writing the national standards, we don't include resistance to cherry Kool-Aid, because nothing would pass if we did." Stains in solid-surface material, like scratches, can be sanded out.

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Figure 1.When a solid-surface sink is used with a solid-surface countertop, it is usually fused with the countertop, making an integral unit. This oval solid-surface lavatory (left) is manufactured by Swan. Solid-surface kitchen sinks are also available as apron-front models, like this single-bowl sink from Corian (right). Solid-surface sinks for both the kitchen and the bathroom are available from several manufacturers, including Avonite, Corian, Fountainhead, Lippert, Swan, Transolid, and Wilsonart (see Figure 1 above). Solid-surfacing fabricators can also make custom sinks in almost any size. Composite sinks. Manufacturers usually use the term "composite" to describe a hard, scratch resistant type of cast polymer sink made with a filler of quartz or granite. High quality composite sinks, like solid-surface sinks, tend to have a high percentage of filler, resulting in a relatively high density. Blanco, Franke, Moen, and Schock all make composite undermount sinks (Figure 2).
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Figure 2. Cast-polymer sinks with acrylic resin and quartz filler are often called composite sinks. This kitchen undermount is made by Blanco, which calls the material Silacron.