Mattress sag: How to fix a sinking bed
Why does your mattress dip in the middle? Find out what's causing the sag and take steps to remedy it
Some people love a firm mattress, others love a soft mattress, but no-one loves a saggy mattress. When your bed gives you that sinking feeling, you may be tempted to throw your mattress out. However, some sagging can be fixed and, to an extent, may even be covered in your warranty.
Mattress sag is basically a big dent that shouldn’t be there. Even a soft mattress should support your body consistently: if it doesn’t you could end up dealing with a sore back.
While the best mattresses we’ve reviewed come with warranties that last at least 10 years, it’s worth noting that these don’t cover issues that you’ve caused yourself. You may be causing your bed to sag every night without realising it, for example by sleeping without a mattress protector or by using an unsupportive bed base.
In this article we’ll reveal why your mattress may be sagging, offer some ways to fix it, and reveal how to ensure your next mattress stays supportive for years.
Why is my mattress sagging?
Some sagging is an inevitable result of a mattress’s age. Any bed that’s been slept on by a 60kg human (or two) every night for more than a decade will feel and show the effects, chief among which is a saggy middle.
Mattresses tend to sag in the areas that get most pressure, normally under your bum and shoulders. If you continue to sleep on a sagging mattress, your back won’t get enough support and this will negatively affect your sleep quality.
Not all mattresses age (and sag) at the same rate, of course. The various types of mattress we test here at Expert Reviews are constructed in ways that offer different levels of durability and resistance to sagging. Sprung mattresses tend to lose tension over time, and memory foam softens over the years.
Hybrid mattresses, which contain both springs and foam, can be more robust. Their sprung layers are wrapped securely in layers of foam (as in the Simba Hybrid Pro, pictured above), often with foam reinforcement along the sides as well, and this multi-layer construction makes them especially resistant to sagging.
Why does my mattress sag already?
If your mattress has started to bow in the middle after just a few years (or even months) after you bought it, there may be many things going on. Here are a few causes of premature sag:
1. You haven’t rotated your mattress
Most hybrid and bed-in-a-box mattresses are not designed to be flipped, but many need to be rotated every few months to prevent sagging. By rotating your mattress from head to toe, you avoid putting too much pressure on any one single area.
Rotation is so important that most hybrid mattress manufacturers make it a condition of their guarantee. For instance, Otty requires that you rotate their mattresses once a month for the first year and every three months thereafter.
2. Your mattress has been jumped or walked on
It seems obvious but please don’t jump on your mattress. Even a small child bouncing around on a mattress can damage its springs, compress its foam, weaken its edges and break its seams: all of which will lead to premature sagging.
If you try claiming on the guarantee after your mattress has been used as a trampoline, you’re unlikely to get a replacement. Otty’s T&Cs even prohibit standing on your mattress, too.
3. You’ve exceeded the maximum recommended weight
Many mattress warranties state a maximum weight limit of around 130-140kg (20-22 stone) per person on each side, or a combined weight up to 280kg. Exceed this regularly, and your mattress may dip as a result.
This weight recommendation seems to be fairly standard regardless of mattress size. If you’re particularly heavy or tall, we recommend choosing a king size or super king size mattress: it will be much more comfortable as well as less likely to sag.
4. The mattress has got wet
Moisture causes foam to degrade, so it’s important to avoid getting your mattress wet if you want to avoid sagging.
In our guide to cleaning your mattress we warn against getting foam or hybrid mattresses even the tiniest bit wet; instead, spray cleaning liquid onto a sponge and use that to clean the surface. Make sure it’s all completely dry before putting any bedclothes back on, or you’ll risk a mouldy mattress as well as a droopy one.
Body fluids are a fact of life, especially when you’re sweaty in summer, so we recommend always using a mattress protector to keep your bed safe from moisture and stains.
5. Your bed base isn’t supportive enough
If a supportive and durable mattress is your priority, it’s worth investing in a bed that will help avoid sagging. The best anti-sag bed frames are solid beds such as divans. If your bed has slats, it will provide most support if the slats are sturdy and close together, and the bed either has a solid frame or six legs. A slatted bed with just four legs may not provide enough support to prevent a double or bigger mattress from sagging prematurely.
Most mattress manufacturers give guidance on the bed style you should be using, and many mattress warranties even specify a maximum size of gaps between slats.
We certainly don’t recommend stacking mattresses on top of each other, as tempting as it might be as a space-saving solution. This puts their structures under too much pressure and will damage the support in both of them.
6. There’s a manufacturing fault
The springs, foam and other components of a mattress are carefully constructed to provide optimum support throughout the warranty period, but things can and do go wrong.
If you’ve done everything right to keep your mattress in great shape but it still starts to sag within its warranty period (typically 10 years for a hybrid mattress), then you can make a claim for a free repair or replacement.
The cause of the sagging would have to be a manufacturing problem such as damaged springs or split seams, and the sagging would need to go beyond the reasonable “sinkage” that occurs from daily use. For example, Otty defines “significant” dipping as more than 25mm after the first year, 40mm after three years and 50mm after five years.
It’s also worth noting that all the bed-in-a-box mattresses we review come with free trial periods (with some lasting a full 365 nights), allowing you to try the mattress out in the comfort of your home rather than a showroom. If there’s something wrong with it such as a sagging middle then you should be able to get your money back within the free trial period, as long as you didn’t cause the damage.
READ NEXT: Emma vs Simba: Which is better?
How can I fix my sagging mattress?
If you can’t have your sagging mattress fixed or replaced under its warranty, there are still things you can do to sort the sag. These fixes are temporary, but they could make all the difference to your night’s sleep:
Rotate your mattress
Rotating is an important way to prevent sagging, as we’ve said already, but it can also give you relief from an annoying dent. Rotate the mattress 180 degrees and enjoy the relief of a fresh sleeping surface.
Switch to a solid bed base
Changing your bed base can make a surprising difference to the way your mattress feels. If you switch from a slatted base to a solid bed base such as a divan, or even the floor, it can give a sagging mattress a temporary support boost.
Be aware that mattress manufacturers don’t recommend keeping your mattress on the floor in the long term (and neither do we), because the air can’t circulate and you may get mould and mites.
Use a mattress topper
A good mattress topper won’t fix a sagging mattress, but it can help you sleep more comfortably by creating a more even sleep surface.
Lie on a pillow
Placing a pillow under your back, hips or legs can make your mattress much more comfortable, especially if it’s sagging. A pillow with good shape retention, such as those we included in our roundup of the best memory foam pillows, may be a good choice.
We don’t recommend putting a pillow under your mattress to try to even out its surface, because this can interfere with the structure of the mattress and make the problem worse.
There do exist “mattress correctors” (such as this one from Meliusly), that are designed to be placed underneath your mattress to remedy sagging. However, it’s not a hugely affordable solution, nor can we really vouch for its effectiveness.
What if I can’t fix my sagging mattress?
Using a pillow, a solid bed base and other remedies to make your mattress less saggy will only help in the short term, and won’t restore your mattress’s original supportiveness. If your mattress is sagging so much that it’s uncomfortable, it may be time to replace it.
Disposing of an old mattress can be a wasteful and costly business, so it’s worth looking out for companies that offer to recycle your old mattress when delivering a new one. For instance, Simba charges £50 for this service and Mattress Next Day charges £39, but Panda will collect your old mattress for free – and “recycle it responsibly” – if you’re buying a new mattress from them.
