Box Springs & Foundations

Yes — every mattress needs proper support to perform as designed. A solid foundation or box spring keeps your mattress elevated, prevents sagging, and helps extend its lifespan. Without the right base, even the best mattress can wear unevenly or feel less supportive over time.

Traditionally, box springs contained metal coils inside a wooden frame to add bounce for innerspring mattresses. Today, most “box springs” are actually foundations — solid or slatted bases made from wood or metal that provide consistent, firm support for modern mattresses like memory foam, latex, and hybrids.

It depends on your mattress type and bed frame:

• Foam, latex, and hybrid mattresses: Need a solid or slatted foundation for firm, even support.
  
• Innerspring mattresses: Can use a traditional box spring if compatible, though most modern versions now work best on foundations too.
  
• Adjustable bases: Combine comfort and support in one — no separate box spring or foundation needed. Most modern mattresses are adjustable-base compatible, offering personalized positioning for better comfort and circulation.
  

Our Sleep Experts are available via Live Chat, by phone, or in-store to help you find the right solution.

No — adjustable bases act as both the support system and the foundation for your mattress. You don’t need a separate box spring or foundation underneath. Just make sure your mattress is adjustable-base compatible (most foam, latex, and hybrid models are).

The difference is height, not support. A standard foundation (around 9 inches tall) gives your bed a higher look, while a low-profile foundation (around 5 inches) keeps your bed lower to the ground — ideal for thicker mattresses or modern platform-style aesthetics.

It depends on its condition and structure. If your box spring or foundation is more than 8–10 years old, sagging, or squeaky, it’s best to replace it. Using an outdated base can reduce your new mattress’s performance and may void its warranty.

Most mattress sets are designed as a set to provide proper mattress support and to insure its proper flame retardant properties. Be sure to speak to one of our sleep experts when shopping for a new mattress.

A Euro-slat foundation (also called a European-style slat base) uses flexible wooden slats that curve slightly upward to contour to your body and mattress. Unlike a solid foundation, these slats provide gentle give and enhanced airflow under the mattress. This design offers adaptive support and helps extend mattress life by reducing moisture buildup.

Euro-slat foundations are a great match for foam, latex, and hybrid mattresses, and they’re often found on adjustable bases or platform-style beds. If you prefer a little flex rather than a completely solid feel, a Euro-slat foundation can be an excellent choice.

Unlike the standard king size mattress, which can use two twin XL box springs together, a California king size mattress requires a California king size box spring. City Mattress has a few of these foundations to choose from.

It depends on your bed design.

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  Platform beds often have built-in slats or a solid surface, so they don’t need a separate foundation.
  
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  Metal bed frames and many upholstered or wood frames do require a foundation or box spring to hold the mattress properly.
  
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  Adjustable bases serve as both the foundation and frame, so you don’t need anything underneath them.
  

If you’re unsure, check your frame’s construction—if it only has a metal perimeter and no cross-support, you’ll need a foundation.

Not usually. Most bed frames don’t have enough surface support for a mattress on their own. Unless your frame is specifically a platform style with closely spaced slats or a solid panel, you’ll need a foundation or bunkie board for proper support.

A bed frame is the furniture piece that holds and supports your mattress setup. It lifts your sleep system off the floor and adds style to your bedroom.

A foundation (sometimes called a box spring) is the supportive base that sits inside the bed frame, directly beneath the mattress. It keeps your mattress flat, firm, and properly supported for long-term comfort.

Think of it like this: the bed frame is the structure, the foundation is the support, and the mattress is where you rest.

Yes. A sturdy, properly supported bed frame helps your mattress perform as designed and prevents uneven wear. If your frame or slats sag or creak, your mattress will too. Always make sure your frame’s center support matches the size and weight of your mattress.

A Bunkie board is a thin, solid platform—typically made of wood, metal, or plywood and covered in fabric—designed to provide a flat, supportive surface beneath your mattress. Originally created for bunk beds (where box springs wouldn’t fit), they’re now commonly used with platform beds, daybeds, and trundle beds to add extra firmness and stability.

If your bed frame has widely spaced slats or you want to lower your bed height, a Bunkie board can help create even support—especially important for foam or hybrid mattresses that require a solid surface.

Note: You do not need a Bunkie board with an adjustable base. Adjustable bases already act as the foundation, and adding a Bunkie board can interfere with the base’s movement and functionality.

If you prefer a lower bed height or have limited space, a Bunkie board can replace a standard foundation while still giving your mattress the support it needs.