Do memory foam mattresses sag?

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Memory foam is a durable material that retains its shape well over time. High-density memory foam is more resilient and less likely to sag. However, mattress sagging is to be expected over time. With correct mattress care, you can help minimise the effects of sagging and prolong the life of the mattress.

Memory foam is one of the most popular types of mattresses on the market. The material moulds and adapts to the body and then slowly recovers to its original shape when pressure is removed. Memory foam helps relieve pressure across the body, especially around the shoulders and the hips.

But as with most mattresses, memory foam is susceptible to sagging, despite its resilient properties. One of the downsides of memory foam mattresses is that they are single-sided, which means that as they cannot be flipped over, all the wear and tear is concentrated on a single sleeping surface.

Mattress sagging occurs naturally over time and is usually the result of normal wear and tear. After several years of use, the components in the mattress can start to break down in the areas that are exposed to the most pressure. Springs can lose tension, or the fillings become less durable and resilient.

A sagging mattress provides an uneven sleeping surface and a distinct lack of support. This can often result in discomfort, spinal misalignment and poor quality sleep. It can often make sleepers feel stuck in the areas where the mattress has collapsed, making it harder to turn over or get in and out of bed.

memory foam mattress on bed frame

How long does it take for memory foam to sag?

Typically a memory foam mattress should last at least 8 to 10 years with correct care. Sagging may occur sooner or later depending on the construction of the mattress, its usage and how it has been looked after.

Each manufacturer will use a different formula when making the foam, which will affect how it performs. Most memory foam mattresses are made using various layers of foam material. These layers will vary in density and depth. Typically, the higher the foam density, the longer it will retain its shape.

Memory foam can also be combined with springs. Durability depends on the type of spring unit used in the mattress and the density and depth of the memory foam on top. Pocket springs, consisting of individual springs encased in fabric, tend to be more supportive and durable than coil springs. The memory foam layer on top should be at least 5cm in depth, as anything less is unlikely to provide the support and durability you need. 

How the mattress is used can also be a factor in how long it lasts and whether it will sag. A memory foam mattress may wear out sooner when two people share a bed than a single person sleeping independently. A mattress may also sag quicker when used by a heavier person because the mattress is put under more pressure than it would be from a lighter person.

Premature sagging is often caused by neglect. This usually occurs by sleeping in the same areas each night. This eventually causes the material to break down under pressure from the sleeper’s weight. 

In some cases, premature sagging may be caused by a manufacturing defect. But this can be difficult to prove as so many factors can contribute to the mattress sagging.

How do I keep my memory foam mattress from sagging?

It is essential to follow the manufacturer’s care instructions. Doing so can minimise the effects of sagging and help extend the life of the mattress.

Memory foam mattresses are single-sided, which means that you can only sleep on the top side of the mattress. They cannot be flipped over as the underside is not suitable for sleeping on.

However, rotating your memory foam mattress head to toe from time to time can help to maintain an even sleeping surface and prolong its life.

Another reason why a memory foam mattress may sag is that it is not properly supported by the bed base it rests on. Memory foam mattresses tend to perform better on flat solid surfaces.  If the mattress is placed on an old-worn out bed base with an uneven surface, the mattress will quickly take its shape, causing it to sag.

Likewise, a memory foam mattress will sag if it is placed on a slatted bed base where the gap between the slats exceeds the manufacturer’s recommendations. Typically, the slat gap should not exceed 6cm, although each mattress manufacturer will provide guidance on slat spacing.

If the slat spacing on your bed frame exceeds the manufacturer’s recommendations, placing a sheet of plywood board directly onto the slats will ensure a flat solid surface. Drilling several holes in the plywood board will allow good air circulation and prevent moisture from accumulating.

You should avoid getting a memory foam mattress wet as this can damage and weaken the material resulting in sagging. A wet mattress can also provide the perfect environment for mould and mildew to thrive.

A memory foam mattress cannot be washed, sponged or dry-cleaned. But most memory foam mattresses have removable covers for cleaning. These can typically be machine washed, but you should always follow the cleaning instructions on the label sewn into the cover.  

You should also avoid using a hot water bottle with your memory foam mattress, as any leaks may result in the mattress getting wet or stained. Memory foam works best with your natural body heat, so using a hot water bottle is unnecessary. When taking a shower or bath, ensure you are properly dried off before coming into contact with the mattress.

The use of a mattress cover provides your memory foam mattress with an extra layer of protection against stains, spillages and accidents. It will help keep the mattress dry, clean and in good condition. The mattress protector should be waterproof and fully breathable. The material should be thin to allow for better body contouring.

How to fix a sagging memory foam mattress?

After use, body impressions and indentations may start to form on the surface of the mattress. This is expected and doesn’t necessarily mean that the mattress is sagging or failing to provide adequate support. Rotating a memory foam mattress from time to time should allow the mattress to settle more evenly.

However, when a memory foam mattress sags, it can give you the feeling that you are sinking to the bottom of the mattress. Mattress sagging is usually the result of normal wear and tear and is not typically covered by a mattress guarantee or warranty.

Unfortunately, there’s not much you can do about a sagging mattress other than to replace it.  However, there may be some temporary fixes that can help to minimise the effects of sagging until you replace your mattress.

What type of mattress doesn’t sag?

Tempur mattresses are an excellent choice if you’re looking for high-density foam that is less likely to sag. NASA first developed the material to help cushion astronauts during lift-off.

Tempur mattresses are backed with a 10-year guarantee and are more effective at relieving pressure than ordinary memory foam. They cost more money than other memory foam mattresses, but they offer good support and longevity.

Natural latex is a good alternative to memory foam. It has a slightly bouncier feel and is durable, resilient and recovers its shape quickly when pressure is removed.  The material is also breathable and generally cooler to sleep on than memory foam.

If you prefer the feel of a traditional sprung mattress, pocket springs are a good option. Each spring works independently and conforms well to the body. Unlike foam, pocket spring mattresses can be turned and rotated to help even out the wear on both sleeping surfaces. Higher-quality pocket spring mattresses often contain natural materials which provide a sumptuously soft and luxurious feel. Natural materials are durable and fully breathable.  

Final thoughts

Memory foam is a durable material that retains its shape well over time. High-density memory foam is more resilient and less likely to sag. However, mattress sagging is to be expected over time. Following the manufacturer’s care instructions provided with the mattress can help minimise the effects of sagging and prolong the life of the mattress.

About the author

About the author

Tony Brown is the founder and creator of The Bed Consultant. His career in the bed industry began in 2002. After graduating from university with a degree in Business Administration, Tony joined one of the largest independent furniture retailers in the UK as a bed consultant. Tony has helped thousands of customers find the perfect mattress.

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