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Do You Need a Foundation for a Mattress?
The Bedrock of Your Bed

Last updated on July 18, 2019

One of your remaining decisions is selecting the foundation your new mattress will rest on top of. Choosing incorrectly could void your warranty.

How Important is a Mattress Foundation?

A foundation is a support system that goes underneath the mattress. It is designed to evenly distribute the weight of the mattress and absorb some of the compression that it sustains in normal use. A well-made foundation will prolong the life of your mattress.

Mattresses and foundations are designed to work as a unit, so it is generally recommended that they be purchased together (new mattress plus new foundation). When you purchase a mattress, the manufacturer or retailer will recommend several types of compatible foundations. And in fact, many warranties specify that a mattress must be used with the recommended foundation or the warranty is void. Some brands say you must buy a foundation from them for the warranty to be valid. And we found several brands that specify you should specifically not use a box spring (see below).

Is a Mattress Foundation the Same as a Box Spring?

Mattress foundations and box springs are different in construction and durability, though they may look the same from the outside.

A box spring is a wooden box with heavy coil springs that take some of the load off of your mattress. Also made with metal, a torsion module foundation works similarly to a box spring, but instead of coil springs it has torsion bars, which are heavy wire bars typically bent at 90-degree angles (they still compress and bounce back, but at angles instead of circles). Both are covered with fabric so they have an upholstered look.

True box springs work perfectly well for most traditional innerspring mattresses, but they aren't supportive enough for today's heavier foam, latex and hybrid beds. Box foundations, on the other hand, look like a traditional box spring unit from the outside, but instead of springs, closely spaced wood or metal slats extend across the bed from side to side, creating a surface that can better support heavy mattresses. A box foundation is still covered with fabric, so it has the same appearance as a box spring.

Box foundations vary in height. Most are 8" or 10" tall, but you can also find 4" or 6" low-profile versions, handy if you have an extra tall mattress but don't want to be so far off the ground.

You can place a foundation right on the floor, or on a bed frame of your choice, depending on the look you're going for.

Below: Box foundation

Can I Put a Mattress on Slats?

Modern box foundations are made with closely spaced slats in a wood frame, covered with upholstery. You can also find simple bed frames with slats that will support your mattress. However, be careful what you are buying. You want a heavy bed frame with substantial, closely spaced (no more than two inches apart) heavy slats.

Also on the market is an accessory you can purchase: Wood slats you can install on an existing metal bed frame to turn it into a platform for your mattress. These vary greatly in quality. Some are meant as extra support for a box spring and mattress set, while others are heavy enough to support a mattress without any other foundation. Just be sure to check which you are purchasing, and consult your mattress documentation to be sure that it will be adequate support.

Below: Bed frame with heavy slats


Does a Mattress Need a Foundation?

You may not want to use the foundation that is recommended with your mattress because you plan to use a platform bed. Or you may wonder if you really have to spend the extra cash for a new foundation when your old one seems in perfectly good shape.

Before you decide not to purchase the foundation recommended by the manufacturer for your mattress, your first step should be to check the warranty terms. Most specify that platform beds or another solid surface are fine. Some mattress warranties will be invalidated if a specified type of mattress foundation isn't used.

Also consider that while your old box spring may look just fine on the outside, that does not mean that it is still structurally sound enough to properly support the weight of another mattress for 10 more years. And finally, consider that the cost of the foundation is generally a small percentage of the cost of the mattress. If you’ve considered all of these things and opt not to purchase a foundation, know that you’ll still need to support your mattress adequately in order to maintain its integrity over time, such as with a bed frame that is designed for use without a foundation.

Is it Bad to Put a Mattress on the Floor?

In most cases, no. A floor is a solid support for a mattress as long as you don't mind being so close to the ground. It will not hard your mattress to use it on a floor.

One consideration is airflow. Using a box-type foundation or a bed frame raises your mattress off the floor, alloying air to flow all around it. If your mattress is on the floor, moisture and humidity can't escape out the bottom. One idea is to periodically turn your mattress on its side and allow it to air out for a day before plopping it back on the floor.

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