I'm about 260 lbs and my current mattress (a memory foam from a big box store) has developed a noticeable dip right under my hips after about a year. It's not a huge crater, but I can feel it every night and it's starting to mess with my lower back. Is this just something that happens with foam, or is there a specific reason it's so localized? I rotate it every couple of months, but it keeps coming back.
Mattress Dip
Why does my mattress dip where my hips rest
Memory foam softens with heat and pressure, so heavier areas like hips will break down first. Rotating helps but doesn't stop it. A lot of foam beds just aren't dense enough for higher weights
What's the density of the foam? If it's under 4 lb/ft³, it's probably not going to hold up long for someone your size. Also, is it a pillow-top? Those tend to sag faster in the hip area.
I had the same issue with a Leesa. The dip was exactly where my hips were. When I cut it open, the foam under that spot was visibly compressed, and crumbly. For heavier sleepers, you really need a hybrid or something with coils for support.
Could also be your foundation. If the slats are too far apart or the box spring is old, the mattress will sag in the middle regardless of foam quality.
Good point about the foundation. I once had a dip that turned out to be a broken slat. Easy to check before blaming the mattress, though.
Foam just does that. Latex or coils are getter for heavy folks. My last foam bed lasted 14 months before the hip dip showed up.
I'm around 240 and switched to a hybrid with pocket coils and a thin comfort layer. Two years in, no dip. The coils take the weight and the foam doesn't get crushed as much. Might be worth looking into if you're replacing.
Also, are you using a mattress protector? Some of the waterproof ones trap heat and make the foam softer. Not saying it's the main cause, but it can accelerate the breakdown.
Before you toss it, try putting a piece of plywood between the mattress and foundation. If the dip goes away, it's the foundation. If nott, it's the foam.
Thanks for the foundation tip. I checked the slats and they seem fnie, but the box spring is pretty old. I'll try the plywood test this weekend. The foam density is 3.5 lb/ft³ according to the tag, which I guess is on the lower side for my weight.
3.5 is low for 260 lbs. That foam is going to compress over time. You might be able to get a warranty replacement if the dip is over an inch, but they often prorate it.
Warranty claims are a pain. They'll ask for photos with a straight edge and often deny for "normal wear." But worth a shot.
If you do replace, loook for something with a coil unit and a higher-density foam in the transition layer. Also, consider a latex hybrid. Latex is more resilient and won't soften as much.
And don't forget a proper foundation. Even the best mattress will sag on a weak base. A platform bed with closely spaced slats is usually best.
I'll try the plywood first, then maybe see about the warranty. Replacing isn't in the budget right now, so I'm hoping it's the box spring. If not, I might try a mattress topper to fill the dip temporarily.
A topper might help short-term, but it won't fix thhe underlying sag. Still, if budget is tight, a firm latex topper could add some support and reduce the feeling of the dip.