6 Common Undermount Sink Problems

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Bathroom vanity quartz countertop with white rectangular sinks

The bathroom needs to be as functional and convenient as possible due. When doing a remodel or upgrade people spend a lot of time on bathroom fixtures, one component that is often overlooked is the type of sink. That should not be the case since the style of sink has a major aesthetic impact and may or may not fit in with the rest of your overall bathroom style. 

When it comes to sinks, you might have already heard of the undermount design. This type of basin features a rimless design which gives it a streamlined appearance with the countertop. That said, you should know that several problems can arise with having an undermount sink – as is the case with other types of basins. 

In this article, we will list the possible issues that you may encounter with an undermount basin to help you better prepare and avoid said problems. 

What is an Undermount Sink?

As the name implies, an under-mount sink is a type of basin that installs from underneath the counter. This type of basin attaches from underneath the countertop and requires a custom-cut hole, unlike the drop-in sink. However, the drop-in version is already compatible with the standard measurements of a pre-cut hole on the counter. 

Having it installed from underneath helps give the sink and counter a streamlined appearance as there will be no extra notable rims that separate both. Visually, this is an excellent feature for those who want a smooth and sleek appearance for their bathroom. 

Clean granite sink in bathroom of model home

What are the Advantages of an Undermount Sink?

So, why should you pick the undermount sink over the standard drop-in sink? 

  • Seamless Design

As noted earlier, the most significant and most notable advantage of this type of sink is the streamlined design that makes it appear as if part of the countertop. In addition to having that nice seamless aesthetic, it is also functional in that this type of design makes cleaning easier and faster as crumbs won’t get lodged in the rims. 

  • Customizable

Another big draw of the undermount basin is its versatility. This sink is fully customizable and comes in two single-bowl and double-bowl, depending on your countertop or vanity design. Also, this basin comes in different designs utilizing a variety of materials such as porcelain, ceramic, stainless steel, cast iron, and more. 

  • Added Countertop Space

Drop-in or top-mount sinks take up a few extra inches with their rim or lip, which is not the case with an undermount basin. Therefore, there will be no 1 to 2-inch sink rims that take up countertop space or break the design of the counter and basin. 

What are the Disadvantages of an Undermount Sink?

Of course, everything pretty much comes with a shortcoming, undermount basins included. Here are some of the cons that come with this type of sink.

  • Trickier Installation

Since the sink will be attached from the bottom, it is crucial to follow proper installation. The basin needs to be properly bolted to the bottom of the counter, even more so if you have a cast iron sink that is significantly heavier. 

  • Takes Up Extra Space Under the Counter or Vanity

While it is true that undermount basins free up extra space on the surface, it does the opposite underneath the counter. Due to its installation method, this type of basin will take up more space underneath – to the point that it pretty much takes up most of the cabinet space in your counter. In addition, if you have an iron cast sink, even more space will be taken as extra support is required for the weight. 

  • Replacement Can Be Expensive

Unlike top-mount sinks that utilize a pre-cut hole, undermount basins require a custom one to accommodate its measurements. Because you will need to custom cut a hole, if you need to replace the sink in the future, you must find one that uses the exact measurement. Additionally, undermount sinks usually install the faucets to the wall, which further limits your replacement options unless you want to reinstall a new tap as well.

Two sinks on white countertop with plant beside tray of cotton and soap in jars

6 Most Common Problems of Undermount Sinks

Along with the pros and cons of this type of sink comes several problems rooted in the drawbacks. Understanding the possibility of coming across these issues can help you prepare and take the necessary steps to avoid them. So, here are the most common issues we know of regarding the undermount basin.

1. Difficult Installation Process

As we have already brought earlier, the installation procedure of the undermount sink is a bit more complicated than the drop-in model. First, the installation process will require special basin supports, which will be bolted to the counter. Afterward, cement will be applied to add that extra layer of support and stability to the basin. 

Because of the specific way of installing this sink, we highly recommend you hire a professional. Of course, this means extra cost, but at least you can rest easy that your undermount basin won’t be crash down. 

2. Installation Takes Up More Time

As you would expect from the rather complex installation required for this type of basin, the whole process can also be quite time-consuming. From cutting a precisely measured hole on the counter to applying and letting the cement dry – the entire process is pretty much double the time of a top-mount model. 

3. Quite Expensive

Seeing that the installation process requires a couple of extra steps and hiring a professional is highly recommended, you can bet this will translate to more cost. Yes, undermount basins can be pretty expensive, with even the cheapest brands having almost double the price tag of a drop-in sink. 

4. Overflowing Problem

Take note that this type of sink does not include an overflow hole or rims that will help prevent water from overflowing. Also, make sure not to leave the faucet running as this could cause major water damage. Why don’t all sinks have an overflow?

5. Countertop Material Issues

Alas, the undermount sink is not an option for those who have laminated countertops as it simply won’t be strong enough to support this type of basin. Only those with cement or stone counters will be able to install an undermount basin. 

6. Susceptible to Mold Buildup

Because this sink is installed on the countertop, water might leak inside the basin and counter. If it does, expect to have mold problems in the near future. Due to the minimal space between the joints, cleaning this area can also be quite tricky and hiring an expert might be needed. However, proper maintenance can effectively avoid this problem. 

This problem is even more prevalent in cases wherein the sink is not correctly installed and sealed—another reason to hire a skilled professional for the task. 

As you can see, this type of sink adds a certain level of style to the bathrom, which can undoubtedly increase the resale value of your house in the future. It is also quite aesthetically pleasing. That said, it does come with certain specific issues that you might need to address in the future. Regular maintenance and proper installation should prevent most of these problems, though. 

Installation Methods of the Undermount Sink

There are three ways to install the undermount basin, each with its own strengths and drawbacks. 

  • Flush Mount

The most common installation is the flush mount, which forms a perfect seal between the basin and sink. This style helps prevent any moisture or crumb from seeping underneath the counter, eliminating the mold problem. 

  • Negative Reveal

If you prioritize aesthetics, the negative reveal installation might be something you should check out. With this method, the counter slightly hangs over the basin, which provides a truly seamless appearance. However, this installation method also has the highest chance of mold growth due to the slight opening between the countertop and sink. 

  • Positive Reveal

With the positive reveal method, the basin’s rims are made visible, which allows for easier detection of leakage. However, this method also makes the sink lips vulnerable to mold build-up and crumbs. Therefore, this installation method is the least used in most homes that feature this type of sink. 

Should You Choose an Undermount Sink?

Personally, I feel the main reason to install an undermount sink is its aesthetic value and ability to increase the overall resale value of any house. In addition, the uniqueness of this kind of basin has a certain ‘pizzazz’ that makes it a pretty sought-after feature for some potential house buyers. It is definitely a bathroom fixture that exudes a luxurious appeal.