How to Make a Mattress Firmer

Do you sink into your mattress when you lie down or find yourself feeling trapped when you try to move? Even worse, do you find yourself waking up with a bad case of lower back pain? The culprit might just be a too soft mattress.

Softening and sagging can occur as mattresses age, and their materials lose support. While this loss of support is a good sign that it’s time to replace your mattress, it may not be feasible to replace your bed immediately. There are ways of firming up a mattress that will make your bed feel comfortable and supportive.

Ten Ways to Make a Mattress Firmer

1. Check Your Mattress’s Sleep Trial and Warranty

One of the simpler ways to replace a too-soft mattress is by checking the attached sleep trial and warranty policies. A sleep trial for a bed in a box mattress should last for the first few months, and some companies offer a full year to test out your mattress. If you’re sleeping on a new mattress and find it’s too soft, see if you can exchange it for a firmer mattress model.

If your mattress is no longer new and has grown soft and started to sag, you might be able to file a warranty claim for repairs or a replacement mattress. Measure how deep any indentations are, and see if they’re deep enough for your warranty to cover.

How deep a mattress must sag to be covered varies by company. Some will replace your mattress if it’s under 1 inch, while others will only offer a replacement once sagging exceeds 2 inches.

2. Buy a Firm Mattress Topper

Mattress toppers aren’t just for softening up a bed. You can also buy toppers with a firm feel to fix a sagging mattress. While a good topper can cost up to a few hundred dollars, it’s still far more affordable than buying a new mattress.

Toppers are usually made from memory foam, latex, or poly-foam. Be sure to compare features and prices and look at customer reviews, like you would when shopping for a new mattress.

3. Add or Replace Plywood

Slipping a piece of plywood or particleboard under the mattress can give the mattress a firmer feel. A solid or slatted foundation keeps a mattress lifted and deters sagging.

The downside to a plywood board is that the solid construction can limit airflow and promote mildew growth in your mattress. We recommend shopping for moisture-resistant plywood and keeping your mattress encased in a waterproof protector.

4. Move the Mattress to the Floor

A hard floor can provide the same uniform support as a plywood board and is a suitable method for firming up your mattress if you need an immediate solution. However, leaving your mattress on the floor is not the best solution in the long run because it can expose your mattress to dirt, pests, and mildew.

The floor presents the same problem as a piece of plywood, preventing air from circulating through the bottom of your mattress and collecting absorbed moisture. This moisture can build up and let mold grow in and around your mattress. Too much humidity can also soften up your mattress.

Is keeping your mattress on the floor for a while unavoidable? Then lift it once a week and lean it against a wall to let airflow through the mattress.

5. Change Your Box Spring

Box springs often last longer than mattresses, but they will need to be replaced eventually. The inner coils will eventually lose support and sag, providing uneven support. Most box springs shouldn’t be used for more than a decade, and you should check their condition if you hear squeaks or creaks or if the wood smells.

Using a box spring with a mattress can also cause the bed to sag prematurely if the box spring doesn’t provide the full support the mattress needs. Memory foam mattresses shouldn’t be placed on a box spring, nor should any other type of foam mattresses such as latex and poly-foam.

Removing the box spring and replacing it with a solid or slatted foundation for a memory foam mattress can make your bed feel firmer.

6. Lower the Room Temperature

Some mattresses are temperature sensitive, such as memory foam beds. Memory foam mattresses are designed to soften up when exposed to heat, which lets the mattress conform to your body for pressure relief. This sensitivity means the bed can also feel firmer in colder temperatures.

Try lowering your thermostat, turning on a fan, or opening your window to firm up your mattress a little

7. Give it Time to Breathe

It’s not just body heat that can soften a mattress—retained moisture can soften up a mattress as well. If you live in a humid climate, your mattress may absorb moisture throughout the day and night.

Try carrying your mattress outside so it gets exposed to some sunlight. Sunlight evaporates moisture and helps eliminate the germs, mildew, and allergens that a mattress can accumulate.

8. Rotate and Flip the Mattress

Do you tend to lie down on the same spot night after night? Many of us do, and the repeated wear and tear can cause that section of the mattress to sag. Rotating your mattress will change where you’re lying on the bed, evening out the mattress’s feel.

Not all mattresses made are flippable, including most foam and hybrid mattresses. But if you have one of the rare flippable foam or hybrid mattresses, flipping the mattress can even out the wear and tear on your bed.

You should rotate and, if possible, flip your mattress every three to six months.

9. Flatten Your Bedding

If you want a firmer bed, make sure your fitted sheets lie smooth. A tight fit puts pressure on the mattress that can harden its feel.

And if you use a mattress pad, you might want to skip it since it can add a touch of softness to your bed. If you want a protective layer between your sheets and mattress, consider a mattress protector instead.

10. Replace Old Layers

This is only an option if your mattress has a removable cover, as some latex and memory foam mattresses do. If you can unzip the mattress and move its layers, you should be able to remove any worn-out layers and replace them with a new one. Ask your mattress company’s customer service if you can special order a new foam layer.

Finding the Right Mattress Firmness

The best mattress firmness depends on two factors, your favorite sleeping position and your body weight. If you shop with these two considerations in your mind, you’re much less likely to choose a mattress that’s too soft or too firm.

Sleeping Position

Your sleeping position affects where and how much pressure is placed on your body. It also determines what support your spine needs. These variances are why there’s a different firmness range best suited for each sleep position.

Side sleepers are often supported by their shoulders and hips, so those two areas are where pressure points tend to build up. A mattress for side sleeping should have a soft to medium feel for optimal pressure relief.

Sleeping on your back distributes pressure evenly across your body and naturally keeps the spine in a neutral position. A firmer feel helps the spine remain aligned, so a good mattress for back sleeping should have a medium-firm to firm feel. A mattress with a medium feel can be considered if it offers targeted back support.

Stomach sleepers risk misaligning their spine if they sleep on a soft mattress. When they lie on their front, gravity pushes down on their belly. If their stomach has room to sink into the mattress, it overextends their spine. We recommend a bed with a firm feel to keep the stomach and spine lifted—although it’s even better to switch to side or back sleeping instead.

Combination sleepers move between two or even all three positions. A mattress for combination sleeping should have a medium feel to provide adequate support, no matter the sleeping position. It’s also a smart idea to look for a mattress with motion isolation to limit sleep disturbances.

Body Weight

Your body weight determines how much you press down on the mattress. Naturally, a heavier person places more pressure on a bed, while a petite person exerts less pressure than most sleepers.

If you weigh under 130 pounds, you should shop for a softer mattress. You’re lightweight enough that you should feel lifted on a soft bed, instead of like you’re sinking into your mattress.

If you weigh more than 230 pounds, try a firmer mattress for a bed that can withstand a lot of pressure. A firmer mattress should conform to your body without risking sinkage.

If you’re in between 130 and 230 pounds, then your body weight shouldn’t be a concern as you shop for your perfect mattress.

Buying the Right Mattress

While the methods we listed are all an excellent way to make a mattress feel firmer, they’re no substitute for sleeping on the right mattress for you.

While it’s important to shop for the right firmness, it’s also a smart idea to make sure you’re buying a mattress with the right thickness. Mattresses can lose their firm feel as the material wears away, and thinner mattresses usually contain less material to resist wear and tear. The best mattresses are generally at least 10 inches thick.

If you’re shopping for a mattress for a heavy person, you may need to consider a bed that’s at least 12 inches thick. A taller mattress can decrease the risk of bottoming out on the mattress’s support layer, thanks to thicker comfort layers and added transition layers.

And always make sure you buy a mattress with a sleep trial and an extensive warranty. A sleep trial lets you make sure a bed is right for you and is especially crucial if you’re buying an online mattress that you’ve never seen or felt before.

Frequently Asked Questions

Is there a firm mattress topper?

Yes, some toppers can firm up your mattress instead of softening it. Firm toppers can be made from memory foam, latex, poly-foam, and other materials. A topper isn’t the only way to firm up your mattress, but it is a more comfortable way to change a bed’s feel.

How can I make my sagging mattress firmer?

If your mattress is sagging and you’re not quite ready for a new one, there are a few ways you can even out its feel. A firm mattress topper is the easiest way, though usually, it’s one of the more expensive methods. You can also place firm pillows in any mattress indentations and cover the bed with a sheet to keep the pillows in place.

Finally, check your choice of mattress foundation. If it’s not offering consistent support, it may leave space for your mattress to sag. Bed slats should not be more than 3 inches apart, and a foam mattress should never be kept on a box spring.

Does putting plywood under a mattress make it firmer?

Yes, slipping a piece of plywood or particleboard that’s cut to fit your bed is an excellent way to make your mattress feel firmer. The drawback is that a solid piece of wood prevents air from carrying away the moisture that collects at the bottom of your mattress. We strongly recommend you buy wood that’s moisture resistant, or else you might end up sleeping on a mattress full of mildew.

You could also try setting your mattress on the floor to firm up the bed. To avoid moisture build-up, you can lift your mattress and lean it against a wall for a few hours. You should try to do this about once a week.

Can a bed that is too soft hurt your back?

You might find yourself waking up with back pain if you’re sleeping on the wrong mattress firmness. If your mattress is too soft, your back may bow into the mattress and add pressure on your spine. On the other hand, a too firm mattress can lift your spine out of its neutral alignment.

It’s best to shop for your ideal mattress firmness by considering your favorite position and body weight. Side sleepers and people under 130 pounds need a softer mattress. Back and stomach sleepers and those who weigh more than 230 pounds will usually rest better on a firmer mattress.

Is a firm bed good for a bad back?

Yes and no. A firmer bed is often good at easing back pain, but you don’t want to choose a bed that’s too firm. A 2015 study found that sleeping on a medium-firm mattress can relieve back pain.

Memory foam beds are among our top recommendations when you’re shopping for a mattress for back pain. The material’s conforming nature allows it to relieve pressure better than most other types of mattresses.

Did We Help?

There are multiple ways to firm up a mattress, such as using a piece of plywood or mattress topper, or by setting the mattress on the floor. A good care routine can help keep your mattress feeling supportive. Rotate the bed regularly and give it a few hours outside in the sun to eliminate moisture and other nasty things.

Buying a mattress with a sleep trial and warranty can help you ensure that you’re getting a bed with the firmness you need. If it’s not the right firmness, it’s usually simple to exchange it for a different mattress or return it for a full refund.

This article is for informational purposes and should not replace advice from your doctor or other medical professional.

James Nguyen, Sleep Expert James Nguyen

James Nguyen is Zoma's resident sleep expert and staff writer. James enjoys learning about the newest technologies in the mattress industry and doing deep dives into the science of sleep. He's tried nearly every gadget and gizmo in an effort to determine which sleep-promoting accessories can truly enhance your shut-eye. Outside of work, James takes his dedication to get healthy sleep seriously, and has even declared himself an "expert napper."

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