What Goes Under The Mattress? A Simple Guide to Mattress Support

If you’re asking “What Goes Under The Mattress”, you’re usually trying to figure out what kind of support, base, or layer belongs beneath your mattress for the best comfort and longevity. This guide walks through the most common options, what each one does, and what to avoid.

Why Does What Goes Under The Mattress Matter?

What sits under your mattress is more than just furniture. It affects:

  • How your mattress feels (firmer, softer, more or less bouncy)
  • How long it lasts (sagging, wear, and tear)
  • Airflow and freshness (moisture build-up vs. ventilation)
  • Whether you keep your warranty valid (many require a certain type of support)

Understanding what goes under the mattress helps you match the right base to your mattress type and sleeping needs.

What Are the Main Types of Mattress Support?

1. Box Spring

A box spring is a fabric-covered wooden or metal frame that may contain springs or a rigid structure.

  • Often used with innerspring mattresses
  • Adds height and a slight bounce
  • Works best on a bed frame with side rails
  • Less common with modern foam or hybrid mattresses, which often need firmer, more even support

2. Slatted Bed Base

A slatted base uses evenly spaced wooden or metal slats across a frame.

  • Common under many types of mattresses
  • Provides airflow and generally firm, even support
  • Slat spacing usually needs to be narrow to prevent sagging (many manufacturers specify a maximum gap)
  • Works under foam, hybrid, and innerspring mattresses when the slats are strong and close enough

3. Solid Platform or Foundation

A platform bed or solid foundation is a flat, sturdy surface—usually wood or a rigid board-based structure.

  • Creates uniform support across the entire mattress
  • Often recommended for foam and hybrid mattresses
  • Can be a low-profile option if you prefer a lower bed height
  • Needs some way for air to circulate (gaps, breathable materials, or occasional airing out of the mattress)

Do You Need Anything Between the Mattress and the Base?

Many people asking “What Goes Under The Mattress” are really wondering if they should add an extra layer between the mattress and its support.

1. Mattress Protector or Encasement

A mattress protector goes directly on the mattress, then the fitted sheet goes on top of that. Technically it’s “on” the mattress, not “under,” but it plays a similar protective role.

  • Helps guard against spills, allergens, and general wear
  • Can extend the appearance and cleanliness of the mattress
  • Should be breathable so it does not trap excess heat

2. Bunkie Board

A bunkie board is a thin, solid platform placed on top of slats or inside a bed frame.

  • Adds extra firmness and evenness under the mattress
  • Commonly used when slats are too far apart but you don’t want a full box spring
  • Useful for foam or hybrid mattresses that need a smooth, uniform surface

3. Non-Slip Mat

A thin non-slip pad can be placed under a mattress, especially on smooth platform beds.

  • Helps prevent the mattress from shifting or sliding
  • Particularly useful with lighter mattresses or adjustable bases

What Should Never Go Under The Mattress?

Some surfaces may seem convenient but can cause issues over time.

  • Directly on the floor (long-term):
    • Can limit airflow under the mattress
    • May allow dust and moisture to build up more easily
  • Weak or widely spaced slats:
    • Can allow parts of the mattress to sag between gaps
    • May affect comfort and durability
  • Uneven or unstable surfaces:
    • Can create pressure points and uneven wear
    • May cause the mattress to feel lumpy or tilted

How Do I Match My Mattress Type to the Right Support?

While recommendations vary by brand, here are general patterns many consumers follow:

  • Innerspring mattresses
    • Often paired with box springs, solid foundations, or slatted bases with enough support
  • Memory foam or latex mattresses
    • Tend to work best on solid platforms, strong slatted bases with narrow gaps, or bunkie boards
  • Hybrid mattresses
    • Commonly used on solid foundations or closely spaced slats

If you’re unsure what goes under the mattress you already own, check its care instructions for any specific support or spacing requirements.

✔️ Quick Mattress Takeaways

Key points consumers should understand about What Goes Under The Mattress

  • The answer to “What Goes Under The Mattress” is usually a box spring, slatted base, or solid platform/foundation.
  • Support quality matters: firm, even support helps maintain comfort and shape.
  • A bunkie board can smooth out or reinforce slats.
  • A mattress protector sits on top of the mattress but plays a similar role in protection.
  • Avoid weak, widely spaced slats, uneven surfaces, and long-term floor placement when possible.
  • Always consider airflow, stability, and manufacturer guidelines when choosing what goes under the mattress.

Choosing the right setup under your mattress is mostly about stable, even support and good airflow. When you understand what goes under the mattress—and why it matters—you can set up a sleep surface that feels comfortable and helps your mattress perform as intended.