One of the most frequent comments I hear about mattresses is, “I can see impressions in my mattress – it’s defective!” Body impressions can be a sign of a mattress defect, but in many cases, they aren’t, so I’ll try to help explain the difference.
Nothing Lasts Forever
The most important thing to note is that all foams lose resilience over time and will soften with use. This is the case absolutely, and without exception. There is no “Everlasting Gobstopper” of foams.
All foams will eventually wear out and are generally the weak link within a mattress, and this is the main reason most people choose to replace their old bed. Here are some things to consider that will help you manage your expectations of durability and increase your chances of having a more consistent and durable mattress comfort life.
Density Is Key
The most important thing to consider is the density of the flexible polyurethane foam. Here in the USA we express this as pounds per cubic foot (the rest of the world tends to use kilogram per meter cubed). Simply stated, the higher the density of the flexible polyurethane foam, the more durable it will be. It’s an almost direct correlation.
True High Density flexible polyurethane foam would be technically described as 1.8 pound/cubic foot (1.8# foam). You may even find numbers up to 2.5# for some of the ultra-premium deeper upholstery layers used within a mattress. Visco-elastic foam (memory foam), while technically a flexible polyurethane foam, uses a different scale, with better memory foam typically being in the 4.0# – 5.0# range. The bad news is that most of the typical brands you find at department stores don’t use anything close to this quality of foam.
It’s important to note that the density and the hardness of flexible polyurethane foam don’t necessarily correlate. You can produce a very high quality and high density flexible polyurethane foam and have it be firm or soft. This allows a manufacturer to create a super hard or ultra plush mattress while still using higher quality materials.
Other common factors that come into play for durability include the hardness of the foam (harder foams tend to last longer than plush foams), the overall amount of padding material used, the quality of assembly of the product, the maintenance of the mattress (not keeping it clean will accelerate the degradation of padding materials), the frequency of mattress rotation (I recommend monthly rotations), and the size of the individuals using the mattress.
Body Impressions Are Normal
As for those body impressions, some of that is normal and to be expected, and is desirable. You need some conformation to allow your contours to sink into the mattress and have your weight distributed over an area to help with pressure point minimization. Some impressioning shows that the foams are doing their job.
Body impressions become problematic is when they are too deep, allowing you to sag into a mattress and “feel through” your comfort cradle. This can be the result of too much padding material within a mattress, the material being of lower density, or the padding material being just plain worn out.
Most mattress manufacturers allow for up to 1.5″ of body impression before they consider there to be a defect in the mattress padding material. This is standard warranty boilerplate within the industry. Some products using higher quality padding materials, such as latex mattresses, might allow for a shallower impression (such as 1″) before considering things to be defective. Conversely, I’ve recently seen some mattress brands extend this body impression allowance to 2″, which in my opinion is to make up for the lower quality foams they are using within their mattresses.
The reason mattress companies have this inch depth limitation is that they need to have some sort of empirical way to gauge padding material defectiveness. They can’t rely upon someone’s subjective opinion of comfort, as anyone could at any time cold say they found something uncomfortable and ask for a new product. This is why comfort is not part of a mattress warranty.
Phantom Body Impressions
This leads us to another type of body impression that I term “phantom body impressions”. This is the gradual softening of foam that develops in every mattress over time. While the mattress may visually appear flat, when you lie upon it you’ll feel softer areas where it’s been used more frequently. The difference in this foam softening may be more pronounced in harder mattresses and mattresses that are slept on only in one area and have very limited use patterns.
Most phantom body impressions are perfectly normal and are the result of the gradual softening of the flexible polyurethane foam with use. Where these phantom body impressions become problematic is when you sink in very deeply into the mattress, allowing for a negative alignment and increase in pressure points. Phantom body impressions are not covered under mattress warranties, so to help minimize these you should choose a product using higher density flexible polyurethane foams.
Is It Time For A New Mattress?
So, are your existing body impressions a reason to replace your existing mattress? I would suggest that you primarily focus upon your quality of sleep, comfort, and alignment as a guide, and not the overall appearance of your mattress. If you’re within your mattress warranty period and you have over 1.5″ of impressions, you certainly may wish to fill out a warranty request form with your mattress manufacturer. Using a straightedge, be sure to properly measure any impressions (not in the quilted stitching area), but it’s been my experience for over 25 years that most body impression claims are far less than 1.5″ (but most of the products I’ve offered have also used higher quality, higher density foams).
If you don’t have excessive body impressions but are still on the fence about looking for a new mattress, take a step back and evaluate your current mattress. Is it over a decade old? Is it stained? Do you still find it comfortable? Are you getting good restorative sleep? If you’re sleeping well and the only reason you’re thinking of replacing your mattress is because you perceive it to not look like a showroom mattress, I’d probably tell you to save your money and consider keeping your existing product a few more years.
There are people who replace their mattress, regardless of quality, every 4-5 years. There are others who keep very low quality mattresses for 20 years. How often a mattress is replaced is a very personal preference, and comes down to factors such as one’s sensitivity, level of flexibility, overall muscle tone, health, sleeping style and mass. While it may be stating the obvious, someone weighing 300+ pounds will go through a mattress of any quality much faster than someone weighing only 100 pounds.
How Long Do Mattresses Last?
Ultimately, how long will a mattress last? Well, what I’ve seen the past decade with the typical fare found at most department stores is people replacing these products after only 4-5 years. This is due primarily to the lower density foams that have become ubiquitous within the mattress industry, and the poorer quality of construction. I generally see over 10 years of comfort life with products using true high density foams and latex. But again, realize that this can differ quite a bit depending upon the individual.
Hopefully all of this helps explain the relationship between mattress body impressions, comfort life and mattress durability.