What Goes Under a Mattress? All About Mattress Bases

August 1, 2022 | Casper Editorial Team

Ever wonder what goes under a mattress? If you’re curious about that thing that looks like a second mattress underneath the first (and if you actually need one), you’ve come to the right place. 

Mattress bases, also called bed bases or mattress foundations, help support and extend the life of your mattress. There’s also the bed frame to consider — the framework that adds height and structural integrity to your bed. 

We’ll explain each type of mattress base, from box springs to bed frames. By the end, you’ll know which combo of bed base and frame is the dream team for your personal sleeping needs. 

Box Spring

One of the most well-known bases that goes under a mattress is a box spring. There are different types of box springs with various heights and materials, but a box spring is typically a metal or wooden frame with springs inside. It’s usually also covered in cloth. The box spring sits under the mattress to help absorb shock, add bounce, and give the bed some additional height. 

So, do you need a box spring? It depends on your mattress type. Box springs were popular when most mattresses were innerspring, or made with coils. Today, memory foam and hybrid mattresses are gaining popularity, but they aren’t compatible with box springs. 

Good for:

  • Adding bounce
  • Absorbing shock
  • Adding height

Compatible mattresses:

  • Innerspring


A slatted foundation is like the modern-day box spring. It’s made of a wood or metal base and includes supportive wooden slats instead of springs. The slats are spaced apart to allow for proper air circulation. This structure makes a more durable foundation base for modern mattresses. 

Foundations are replacing box springs because they are compatible with new, more complex mattress types like foam, hybrid, and latex. They also provide great under-mattress support and tend to last longer. 

Good for:

  • Longevity
  • Firm support
  • Modern mattress types

Compatible mattresses:

  • All

Our foundation provides exceptional support and stands the test of time. Not only that, but you can assemble the foundation in minutes without the need for any tools. 

Bunkie Board

A bunkie board is an ultra-low profile option that adds a small layer of support under a mattress. The thinnest base available, a bunkie board sits at around 2 inches high and can go above a box spring or on top of a platform bed. Bunkie boards are usually made of wooden boards covered in fabric. 

Good for:

  • Adding support without adding height

Compatible mattresses:

  • All

Platform Bed

A platform bed frame is a sturdy base that is modern and sleek. It’s made of a metal frame with wooden slats that provide a firm, even surface for a mattress. A platform bed is a unique type of bed frame because you can place your mattress directly on it (no box spring or foundation required). 

When weighing a platform bed vs. a box spring, remember that box springs are only compatible with innerspring mattresses, while platform beds pair well with any mattress type.

Good for:

  • Sturdy support
  • Keeping bed lower to the floor while still off the ground
  • Those who don’t want a box spring or foundation
  • Durability

Compatible mattresses:

  • All

The Casper platform bed is a clean, modern bed frame for stylish support — no foundation or box spring necessary. 

Adjustable Base

An adjustable bed frame gives you the ability to customize your sleep setup with the push of a button. You can raise an adjustable base at the head or foot to adjust your sleep position. This is a great option for those who find that adjusting their head or feet relieves back, neck, hip, or shoulder pain, or need to relieve symptoms of sleep apnea or acid reflux. 

You don’t need a special mattress for an adjustable base, but your best bet for optimal movability and durability is a foam, latex, or hybrid mattress. At Casper, our adjustable base is compatible with all of our mattress models. 

Good for:

  • Customizable comfort

Compatible mattresses:

  • Foam
  • Latex 
  • Hybrid (usually)

Our adjustable bases will help you find maximum comfort. Enhance your sleep setup with essential features to help you find the perfect position for sleeping or relaxing. 

Metal Bed Frame

Another type of bed frame is a metal bed frame, commonly made of stainless steel or brass. They come in styles ranging from ornate to minimal. Metal bed frames are sturdy and can easily hold a heavy mattress. You’ll just need to get a box spring or foundation to go between the metal bed frame and the mattress. 

Good for:

  • Sturdy and strong support

Compatible mattresses:

  • All (with box spring or foundation)

Our easy-to-assemble metal bed frame pairs with the Casper foundation and any Casper mattress to create a perfect sleep setup.

Wooden Bed Frame

An alternative to a metal bed frame is a wooden bed frame. They come in many different styles, making it easy to find one that matches your interior design preference. As with a metal bed frame, you will also need a box spring or foundation to go between the wooden bed frame and the mattress. 

Good for:

  • A soft and versatile look

Compatible mattresses:

  • All (with box spring or foundation)

Our sleek wooden frame has softened edges to give your bedroom a warm look. 

Considerations When Choosing a Mattress Base

Not positive which mattress base is right for you just yet? Here are some additional factors to consider to help you choose a bed frame and/or foundation. 

Mattress Type

Your mattress type is the top thing to consider. If you have a traditional innerspring mattress, you can pair it with an old-fashioned box spring. However, foam, latex, and hybrid mattresses are designed with more complex comfort layers, so they need stronger support. For these mattresses, opt for a strong foundation or a platform bed instead. 


The aesthetic of your mattress base should not be overlooked. After all, your bed should match your overall vision for your bedroom’s style. A metal bed frame can contribute to an industrial interior design look, while a wooden bed frame appears softer and more traditional. A platform bed is an excellent minimal, sleek option. 


Height is another consideration when choosing a mattress base. The standard bed height is 25 inches, but ultimately, your bed height is up to you. If you like a bed that’s high up or a convenient height to climb in and out of, adding a foundation under your mattress should pose no problem. If you prefer something closer to the ground, a platform bed is ideal. 


A good mattress is an investment, so you’ll want to support it with a high-quality setup that will last. Box spring coils tend to break down over time. When considering durability and longevity, a metal bed base or slatted mattress foundation is a better choice. 


I Need Something Under My Mattress?

nd add height. This setup will keep your mattress in good condition for a long time. Bed bases prevent mattress sagging, absorb shock, and add height. 

What Is the Box That Goes Under a Mattress?

If you have something that looks somewhat like a second mattress underneath your mattress, it’s likely either a box spring or foundation. 

What Can I Put Under My Mattress Instead of a Box Spring?

Box springs typically aren’t compatible with many modern mattresses, so there are plenty of other bed base options available. One option is a foundation, which is designed with more support and durability in mind. 

You can also opt for a platform bed frame, a low-profile bed frame that has the foundation built in. It doesn’t require a box spring or foundation; you can set your mattress directly on the platform bed frame. 

What’s the Difference Between a Box Spring vs. Foundation vs. Platform Bed?

A box spring is a base made of a metal or wooden frame with springs inside and a cloth covering. The box spring sits under the mattress to help absorb shock, add bounce, and give the bed some additional height. 

A slatted foundation has a wood or metal base and includes supportive wooden slats instead of springs. It’s a more sturdy box spring alternative. 

A platform bed frame is a bed frame with wooden slats that you can place your mattress directly on top of without the need for a box spring or foundation. 

Why a Good Base Is Essential

Now that you know what goes under a mattress, you can pick the best base for your needs. Since we spend one-third of our lives in bed, it’s important to choose a solid foundation to be the bedrock for a comfortable and long-lasting sleep setup. 

Engineered with solid wood, the Casper foundation has been rigorously tested for durability and proven to stand up to years of sleep. Our platform bed is made with strong aircraft-grade aluminum. With any of our bases, you’ll sleep soundly knowing your bed is supported by the best of the best.