When undermount sinks first hit the consumer market, they were expensive and considered difficult to install. But now that professionals are just as comfortable installing undermount sinks as they are with drop-ins, and prices of undermount sinks have become more competitive, the choice is that much harder.
Basic Sink Configurations
Drop-in sinks, also called self-rimming or top-mount, are still the most common type of kitchen sink. A drop-in sink has a visible lip around its perimeter that rests flat on the countertop. The sink basin drops straight into the countertop cut-out, and the perimeter lip holds everything in place.
Drop-in sinks are secured by hidden metal clips under the countertop as well as a bead of silicone caulk under the sink's edge.
Yet not all drop in sinks require clips to lock them down. Some cast iron drop sinks do not require clips since they are much heavier and use the weight of the sink, along with caulk, to make the seal. In some cases, two people are needed during the installation.
Undermount sinks mount to the bottom of the countertop and are held in place by heavy-duty clips and caulk or a special adhesive. An undermount sink does have a rim, but the rim is not visible because it rests up against the bottom of the counter. The edge of the countertop along the sink cutout is entirely exposed. For this reason, undermount sinks generally must be used with solid countertop materials, such as solid surface, natural stone, or quartz.
Undermount Sinks Save Countertop Space
With undermount sinks, the countertop extends all the way to the sink—even a bit more. If you're tight on room and need every possible square inch of counter real estate, undermount is the way to go.
However, there is one type of drop-in sink that can save some counter space: the drainboard sink. This has an integrated drainboard and/or food prep area that extends 8 to 10 inches beyond the side of the sink basin. If you're tight on counter space, this counterintuitive move—adding more sink rim instead of less—might actually be more economical on space.
Drop-In Sink: Easier Sink Cleaning
One of the more frustrating things about undermount sinks is the gap at the top of the sink, where it joins up with the counter. While this gap is filled with a bead of silicone caulk, it's usually not filled flush to the surface. A depression remains, and this naturally becomes a magnet for food buildup. Citing this issue, Greg Fox at Fox Granite Countertops recommends digging out the caulk and replacing it on undermount sinks every three to five years.
With drop-in sinks, all working areas of the sink are visible and accessible. However, it should be noted that the small, visible seam formed by the lip and the countertop can build up gunk as well. The only difference is that you have better access and more visibility when cleaning the drop-in sink.
Undermount Sink Best For Counter Cleaning
The clear winner in the category of countertop cleanup is the undermount sink. In fact, ease of cleaning is the number one selling point of the undermount configuration. Because there is no lip to form an obstruction around the sink, you can swipe food particles directly off the counter and into the sink.
Some drop-in sinks have lower-profile rims than others, making it easier to swipe from the counter into the sink, but it’s still nothing like the seamless undermount experience. Stainless steel drop-in sinks tend to have the lowest rims, while enameled cast iron sinks have a tall rim that you have to swipe around, not over.
Drop-In Is Easier to Install
Homeowners can install a drop-in kitchen sink on their own as long as it is a one-for-one replacement. After cleaning away any old caulk, lay down a bead of caulk, set the sink into the hole, center it, and secure it with clips underneath the countertop.
While an exact replacement in size is generally easier, there are things to consider. Removing the old sink is not always an easy task. There is potential damage to the countertop that can occur. The depth of the sink needs to be considered, too. This can result in having to alter the plumbing drain connection below the sink.
By comparison, undermount sinks require much more care for proper installation. They must be fitted in place and supported temporarily while the clip locations are marked. Holes must be drilled into the countertop (very carefully) and the clips installed. Then the sink must be caulked and mounted—with almost no room for error.
The cost of installing an undermount sink is higher, but only marginally, about $50 to $75 more. The savings with a drop-in sink can be much greater if you opt to install it yourself. Do-it-yourself installation of undermount sinks is not recommended because it’s too easy to damage an expensive countertop if you make a mistake.
Drop-In Works With All Countertops
Undermount sinks typically are recommended for all countertop materials except laminate (they can also be problematic with custom tile countertops). The laminate isn't the issue; it's the underlying base of particleboard or MDF. MDF does not hold clip fasteners well, and it is highly vulnerable to moisture damage. It’s possible to cover the sink-hole edge with laminate to protect the MDF core, but the seal between the sink and the laminate must be flawless to keep water away from the MDF.
By contrast, drop-in sinks can be installed on all types of countertop materials, including laminate, tile, solid surface, and all composite and natural stone.
Undermount Wins for Resale Value
Whether your kitchen has a drop-in sink or an undermount sink will not, by itself, change the resale value of your home. Resale value is affected more by major upgrades, such as additions, whole-house flooring, or finished rooms, than by single elements like a kitchen sink or bath vanity.
That said, undermount sinks clearly have a more custom, high-end look and feel compared to conventional drop-ins. As one building block of a highly valued designer kitchen, the undermount sink can be said to impart higher value to potential buyers than a drop-in sink.