The choice between an undermount and drop-in sink is both a utilitarian and stylistic one. Drop-in sinks have been around since plumbing was a thing, whereas undermounts came on the market when solid synthetic countertop materials, such as Corian, Silestone and engineered quartz, became popular. An undermount is decidedly the more elegant choice, but it isn't suitable for every type of countertop. Moreover, it's more expensive and more difficult to install than a drop-in sink.
Rimmed vs. Rimless: The Visual and Aesthetic Difference
Another name for a drop-in sink is a top-mount, and the names tell you the main difference between this type of sink and an undermount. You install a drop-in from the top of the sink cabinet by lowering it into a cutout opening, whereas an undermount is attached to the underside of the countertop form inside the sink cabinet. A drop-in sink has a rim that rests on the countertop to support it, but an undermount relies entirely on support anchor posts that must be installed prior to mounting the sink.
This difference affects the appearance of the entire countertop. The rim of a drop-in sink punctuates and highlights the area around the sink, while the undermount's absence of a rim creates a visual space that promotes the natural beauty of the countertop, which is why undermounts were invented in the first place.
Pros and Cons of Drop-In Sinks
The drop-in sink was once the only type available, so it comes in all sizes and shapes and can be made from virtually all common sink materials, including stainless steel, enameled cast iron, ceramic, porcelain, stone and engineered stone. Here are some of the reasons you might want to choose a drop-in sink over an undermount or farmhouse sink.
- It's the least expensive option. A drop-in sink costs, on average, about 50 percent less than an undermount of the same size and made from the same material.
- It's easy to install. You simply cut a hole in the countertop (if there isn't one there already), drop in the sink and fasten it in place with special clips.
- It works with all countertop materials. The rim hides the edge of the hole you cut in the countertop, so you can install it on stone, engineered stone, laminates with a plywood core, and even metal.
- The rim collects dirt. When installing the sink, you fill the gap between the rim and countertop with caulk, but this caulk doesn't last forever, and even before it fails, it can turn black with sediment and mold.
- The countertop is harder to clean. The rim forms a barrier around the sink opening, preventing you from wiping water and debris from the countertop directly into the sink.
- You lose working space. The rim takes up valuable real estate on the counter.
Pros and Cons of Undermount Sinks
People are attracted to undermount sinks for more than stylistic reasons. Undermounts come in most of the same materials as drop-ins, except for the heavier ones that are difficult to support. An undermount also has utilitarian advantages over a drop-in, provided the countertop is a good candidate for one.
- It's more sanitary. The sink edge is below the countertop, so there's no rim to collect debris and prevent you from wiping crumbs and liquids directly into the sink.
- It looks better. Undermounts were invented to capitalize on the aesthetic appeal of polished stone countertops, and they look great with most other countertop materials, as well. An undermount sink can add to the resale value of your house.
- It increases countertop space. The absence of a rim creates a small but significant amount of extra working space on the countertop.
- It doesn't always work**.** Because the edge of the countertop overhangs the sink and is left exposed, you can't use an undermount sink on a countertop with a plywood or MDF core, which includes laminates and tile. Moreover, you can't install a heavy undermount on a countertop made from a material that can't support it.
- It can sag. An undermount depends on the support posts and brackets that hold it, and if they should fail for some reason, the sink can sag or even fall.
- It can leak. The rim is sealed against the countertop with caulk, and if the caulk fails, water can seep through the gap. This is particularly an issue with positive-reveal sinks for which a small portion of the rim is visible.
Replacing Your Sink? Keep This in Mind
If you're replacing an existing sink, your choice of sinks may be limited by the dimensions of the existing hole. Assuming you can find both a drop-in and undermount sink that fit, keep in mind that it's more difficult to install an undermount sink, which means you may want to hire a pro, adding to the already higher cost. Also remember that the undermount won't look good if the existing hole doesn't have smooth, straight edges. If the hole that held the drop-in sink was cut roughly, you'll be wasting your money installing an undermount unless you're prepared to invest extra time and money into fixing the hole.
If you're determined to use a particular undermount sink, it is possible to replace just the portion of the countertop that has the cutout hole. This allows you to cut a new hole instead of trying to modify an existing one. You can even make the hole smaller than the original to accommodate a more compact sink. Using this option, you could install an undermount in a laminate counter—which normally isn't an option—by replacing the central part of the counter with a butcher block drainboard and installing the sink in the butcher clock.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at Hunker.com.