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What is an Undermount Tub? 2024 Guide to Undermount Tubs

Shopping for the perfect bathtub can be a hassle and with so many options on the market, it’s hard to find out which is the right fit for you. For those looking for something different than the standard bathtub, there’s the undermount bathtub. A bathtub that is non-intrusive, blending seamlessly with your bathroom while still giving you the benefits of having a nice surprise for your guests. Today, we will be discussing if an undermount bathtub is the right fit for your home. 

What is an Undermount Tub?

An undermount bathtub is a bathtub that is installed underneath a rim, meaning that the surrounding deck or area is covered so that the bathtub itself is supported by the floor structure underneath. This is in fact, very similar to a drop-in bathtub except that a drop-in is placed above the rim, whereas an undermount is installed underneath it. 

The Difference between Undermount and Drop In Tubs

An undermount and drop-in bathtub are actually very similar if not identical. The bathtubs themselves are identical in design, the only difference being their method of installation. Undermount bathtubs are installed beneath a rim so that the bathtub’s weight is distributed between the floor structure and the rim. Drop-in bathtubs are installed above the rim, placing much of their weight on the rim itself. Lastly, is their appearance, with drop-in bathtubs usually containing a raised lip as they are installed above the rim, making their sides plainly visible whereas undermount bathtubs are finished on all sides so their edges are hidden from view. Aside from that, these two bathtubs are nearly identical in terms of price and size. 

Pros and Cons of Undermount Tubs

Undermount bathtubs offer an elegant, smooth aesthetic, which looks really well in all kinds of bathrooms. Also, undermount tubs provide design flexibility with numerous shapes and upgrades, which can be interesting for those homeowners who would like to customize their bathtubs to fit their needs and preferences. Not to mention that this also makes it a great choice compared to other bathtub types as you’ll be able to find a model for any amount of space you might have. Lastly, one of the great benefits is that undermount tubs allow for deep, relaxing soaks.

When it comes to cons of undermount tubs, keep in mind that they can be difficult to get in and get out, so if accessibility is important for you, this type of tub might not be the right choice. Also, if your undermount tub is made from marble or granite, it will probably require more floor support.

Styles of Undermount Tubs

Undermount bathtubs come in a variety of styles to suit almost any style of home. Whether you have a large bathroom or a more modest offering, there is enough variety in terms of style to cater to almost any bathroom. The three most prevalent styles are Standard, oval and corner. 

Standard style of undermount bathtubs or drop-in

This is an undermount bathtub that is placed in an ingress before an outer rim is placed above it, hiding the edges of the bathtub itself. This style will mesh typically with the standard bathtub sizes, providing a longer bathtub, with a raised platform or rim generally taking up an equal amount of space as a normal drop-in bathtub. 

Oval undermount bathtubs

These tubs are for those that prefer a longer, more relaxing soak in a small area as these bathtubs are generally rounder, providing a wider area to lounge while still being small enough when compared to the traditional bathtub. These are typically made into hot tubs or jacuzzis as their shape is countered to allow a person to bathe more comfortably than other designs. 

Corner bathtubs

Cortner bathtubs are quite similar to oval bathtubs as they are both round in shape, but where oval bathtubs are made to be much more comfortable to sit in, a corner bathtub is designed to save space. Whereas an oval bathtub is round, a corner bathtub is generally triangular in shape, giving you a more compact bathing area without losing much in terms of comfort.

Common Materials Materials

Undermount bathtubs come in a wide variety of materials ranging from lightweight materials such as acrylic to heavier set options such as cast iron. The quality of your bathtub will ultimately depend on the materials used, but keep in mind that some material will be heavier than others, making them much more difficult to accommodate, especially in smaller bathrooms. With undermount bathtubs in particular, bear in mind that the rim or surrounding tile will be more visible than the bathtub itself, so many homeowners choose a cheaper material for the bathtub while spending more money for a more aesthetically pleasing surround instead. 


Cheap, lightweight, easy to install and simple to maintain. Fiberglass is a desirable material since it lends much flexibility in terms of installation compared to other materials on the market, making it suitable for all bathroom sizes. That being said, it’s flexibility comes at a heavy cost as it is perhaps the least durable of all other materials and it is porous, meaning it will not retain heat well and it will eventually absorb enough water to crack and become unstable.

Cast iron

A classic material, cast iron is one of the most durable materials on the market, while also being one of the heaviest materials on the market as well. It is constructed from molded iron which is then coated with porcelain enamel. It has excellent heat retention and is incredibly durable, but as stated before, the trade-off is that the material is very heavy. Additional floor supports are recommended if you choose to buy a cast iron bathtub. 


A good compromise between the high and low end of the material spectrum, acrylic offers a material that blends the versatility of fiberglass while still being much more durable for a relatively low cost. It is also non-porous, meaning it has better heat retention and will certainly last much longer than fiberglass.

Cost of an Undermount Tub 

Discussing the cost of an undermount bathtub is a bit different than comparing the price of other bathtubs on the market, and that is because the bathtub equates about half the price you are expected to pay. That is because an undermount bathtub requires a platform or a raised area to install, requiring a fair bit of tile which will end up much more expensive than simply buying a drop-in bathtub. That being said, the average cost of an undermount tub ranges from $200-2000. Small and medium bathtubs will range anywhere from $200-1200, respectively, with larger bathtubs filling the rest of the spectrum between 1200-2000. For the tile installation or platform modifications, you are looking to spend an additional $700-1200, depending on the material used and the size of the platform itself. 

Undermount Tub Sizes

Undermount tubSize
Small-sized undermount tubs30×45
Medium-sized undermount tubs50×30
Large-sized undermount tubs72×30

Equally important to finding the right style or material is of course, size. Bathtubs come in a wide variety of sizes to fit just about any bathroom, so it’s best to determine what your bathroom needs before purchasing. The common sizes of undermount bathtubs are 30×45, 60×30, 54 inches, 60 inches, and 72×32. 30×45 is considered the smallest size, with 30×72 being slightly larger. Medium sized would be 50×30, to 60×30, with the largest sizes ended at 72 inches long with a width of 30 inches. 

Installing an Undermount Tub

Installing an undermount bathtub or any bathtub is a simple job, but not an easy one. Like everything else, if you are unsure of any step, consult a professional before proceeding to DIY this project.

  1. Clean the area where you wish to install your bathtub. Ensure the area is structurally sound, removing any obstructions and sand/smooth out any rough edges. 
  2. Measure the area, giving you an appropriate size of the bathtub that will fit in the area. Construct the tub frame using 2×4 inch lumber to mark the wall sections. 
  3. Place two pieces of lumber apart, cutting 2×4 inch studs and placing the boards on center between the plates. Now, using 3 inch screws, secure the sections, then apply construction adhesive to attach the frame to the wall. Install drain assembly per manufacturer’s instructions. placing boards 16 inches on the center.
  4. Install the legs on the tub and place it in the enclosure. Make sure the weight of the tub rests on the floor. 
  5. Check for proper level. Use wood shims to level the tub if necessary. Apply mortar to the subfloor around the legs and bare floor to help steady the tub and keep it in place. Connect the tail pipe into the trap.
  6. Cut along the dotted lines on the template, which came with the tub, for the dimension of the cutout of the plywood. 
  7. Sand the edges and create a smooth surface before applying the finishing material.
  8. Test the lines for leaks before applying silicone sealant along the joints. 

For those looking for a non-intrusive and stylish option, an undermount bathtub is a great choice, providing a bathtub that is easy to install and doesn’t steal the show from the grandeur of your bathroom.

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