My partner and I have had our current mattress for about three years. It's a queen-size hybrid. For the past several months, my side has developed a noticeable dip, while their side still looks and feels basically flat. We rotate the mattress every six months like the manual says. I'm around 240 lbs and my partner is closer to 140. Is this just inevitable because of the weight difference? I'm trying to figure out if we need a new mattress already or if there's something else going on.
Mattress Sag
Why does my side of the bed sag but not my partner's
Weight difference is almost certainly the main factor. Foam, and hybrid mattresses break down faster under concentrated pressure. Rotating helps but it doesn't stop the heavier side from compressing more over time. Three years sounds about right for a heavier sleeper on a hybrid that wasn't specifically built for higher weights
Are you a back sleeper or side sleeper? That can matter too. Side sleepers concentrate weight on a smaller area, so the Sag shows up faster.
Do you both get in and out on your own sides? I used to sit on the edge of the bed to put socks on every morning. That alone wore down the edge and a strip near my side before anything else showed.
Rotating every six months might not be enough in your case. If one person is significantly heavier, some manufacturers suggest rotating every three months. Also check whether your foundation or bed frame is still evenly supportive. A slat that's bowed or a box spring that's giving out under one side will make the mattress look like it's sagging when it's really the base.
Pull the sheets off and measure the dip with a straight edge across the mattress. Most warranties have a threshold, often around 1.5 inches. If it's past that, you might have a claim. If it's less, they'll probably tell you it's normal wear.
Warranty claims are a pain though. They usually want photos with a straight edge and proof of the foundation you used. Worth trying, but don't count on it.
This is exactly why we switched to a mattress with zoned support. The middle and edge zones are firmer. It doesn't stop the sag completely, but it slows it down a lot for a heavier sleeper.
Could also be that the hybrid has a foam comfort layer that's just too soft for 240 lbs. Once that top layer compresses, it doesn't bounce back. The coils underneath might be fine. A topper won't fixx a dip, but a firmer comfort layer from the start would have lasted longer.
Seconding the foundation check.We had a similar issue and it turned out one of the center support legs on our bed frame had bent. The mattress was fine, the frame wasn't.
How old is the mattress exactly? Three years is early for a hybrid to faio unless it was a budget model or the comfort layer is low-density foam. Do you know the density specs?
If you do end up shopping again, look at mattresses rated for higher weights. Some brands list a recommended max weight per sleeper. A lot of standard hybrids are only rated to around 250 lbs per person, and that's for even distribution over the whole surface.
One more thing: are you both sleeping in the same spot every night, or does your partner sometimes roll toward the middle? Body heat softens foam too, so the side that gets more consistent heat and weight will break down faster.
At 240 lbs, three years on a hybrid with a soft foam top isn't surprising at all. I'd measure the dip, check the foundation, and start looking at firmer options. Rotating more often might buy you a little time but it won't reverse the compression.