What to put under a memory foam mattress
Hi, we’re John and Mimi. “What do I put it on?” is one of the first questions we get after someone picks a mattress. The good news: a memory foam mattress doesn’t need anything fancy underneath, just a flat, solid, even surface. Here’s what works, what doesn’t, and what to do with the bed frame or box spring you already have. Our mattresses and foundations are below at today’s prices: same factory models, lower price than other online retailers.
The short answer
- Flat, solid and even. The setup instructions on our mattresses list three proper surfaces: a continuously solid surface, an adjustable base, or slats no more than 2" apart that can support the mattress and the people on it.
- Good choices: a platform bed, a slatted frame or foundation with gaps of 2" or less, or an adjustable base.
- Slats too far apart? Lay a bunkie board or a sheet of plywood over them.
- An old box spring can work only if it’s flat, firm and not sagging. A sagging one will make a new mattress sag too.
- The floor is fine for a short stretch, but for every night a frame or foundation is usually the better home, because air can’t move under a mattress lying flat on the floor.
Check what you have now
| What’s under it | Will it work? | What to do |
|---|---|---|
| Platform bed with a solid deck | Yes | Put the mattress right on it |
| Slatted frame, gaps 2" or less | Yes | Check that no slats are cracked or loose, and that a queen or larger frame has center support |
| Slatted frame, gaps wider than 2" | Not as is | Add a bunkie board or plywood on top, or add slats |
| Old box spring, flat and firm | Often | Check it with a straightedge first; see the box spring section below |
| Box spring that sags or flexes | No | Replace it with a foundation or platform |
| Metal frame with side rails only | Not by itself | It’s made to hold a foundation; put one on it, or use a foundation with its own legs |
| The floor | Short term | Clean, dry, hard floor; air it out; move to a frame for everyday use |
| Adjustable base | Yes | Mattress goes right on the base, with no box spring in between |
| Bunk bed, loft or trundle | Yes, within the label | Follow the bed’s maximum thickness; a board counts toward it |
Why memory foam needs solid, even support
A memory foam mattress has no springs or wire border to bridge gaps. It rests its whole weight, and yours, on whatever is underneath, and it slowly takes on that shape. Over a flat surface it stays flat. Over wide gaps, a broken slat or a dip in an old box spring, the foam can sink into the low spots, and you feel that as a sag. That’s why the setup instructions ask for a continuously solid surface, an adjustable base, or slats no more than 2" apart. The same instructions apply to our hybrids, so this guide works for them too.
Even support also helps a mattress last. Our how long does a mattress last guide covers the other habits that matter, like rotating it and using a protector.
Platform beds
A platform bed is the simplest match: a frame with a built-in deck or slats, so you don’t need a box spring or foundation at all. If the deck is solid, you’re done. If it’s slatted, measure the gap between two slats. At 2" or less, the mattress can go right on top. Wider than that, add a bunkie board or plywood, or ask the frame maker whether extra slats are available.
Platform beds often sit lower than a traditional bed, so think about height too. Bed height is the frame plus the mattress, and a 12" mattress sits 2" higher than a 10" on the same frame. Our how thick should a mattress be guide helps you pick.
Our 10" Rose, 8" Daisy and 12" Lavender Firm list a non-skid bottom fabric, which is handy on a smooth platform deck.
Slatted frames and foundations
- Measure the gaps. Use a tape measure between the edges of two slats, not center to center. The setup instructions call for no more than 2".
- Check the slats themselves. They should be firm, sit flat and stay in place. Replace cracked or bowed ones.
- Look for center support on a queen or larger frame: a center rail with legs down to the floor keeps the middle from dipping.
- Need a foundation? Our Express Mattress Foundation has wood slats and 6" faux wood legs under a fabric-covered frame, goes together with no tools, and can be used as a stand-alone upholstered bed frame.
Can I use my old box spring?
Our setup instructions don’t list a box spring; they list a solid surface, an adjustable base, or slats no more than 2" apart. So the real question is what’s inside yours.
- A flat, firm one that doesn’t give when you press on it, like many fabric-covered wood foundations sold as “box springs” today, acts as a solid surface. Lay a straightedge or a long level across it and look for gaps.
- One with real springs that flex, or one that sags in the middle, won’t give memory foam even support. An old, sagging box spring will make a new mattress sag too. Replace it with a foundation or platform rather than trying to fix it with a board, since a board on top of a dip still dips.
- Getting an adjustable base? Don’t stack it on a box spring. The base replaces it. Our do you need a box spring with an adjustable base? guide explains why and what to do with the old one.
What is a bunkie board?
A bunkie board is a thin, flat board, often wrapped in fabric, that goes between a frame and a mattress. It turns a frame with wide slats into a solid surface without adding much height, which is why it’s popular for bunk beds, trundles and low platform frames. We don’t sell bunkie boards; a smooth sheet of plywood cut to fit inside the frame does the same job.
On a bunk bed, loft or trundle, a board counts toward the frame’s maximum mattress thickness, so a 1" board under an 8" mattress counts as 9". Our bunk bed, trundle and daybed guide covers the labels and safety rules.
Can a memory foam mattress go on the floor?
For a few nights, like while you wait for a frame or for a guest, yes. A clean, dry, hard floor is a solid, flat surface. For every night, we suggest a frame, foundation or platform instead, for a few reasons:
- Moisture. Your body gives off warmth and moisture every night. With the mattress flat on the floor, air can’t move underneath, so moisture can get trapped, especially on concrete, over carpet or in a damp room. The care instructions say not to let moisture saturate the mattress.
- Dust. A mattress on the floor sits right where dust collects.
- Getting up. A bed at floor level is a long way down for knees and backs.
If the floor is your plan for now, keep the room dry, lift the mattress or prop it up now and then so the underside can air out, and check your mattress’s own care instructions.
An adjustable base is an option too
An adjustable base is one of the proper surfaces the setup instructions list, and memory foam bends with it well. It replaces the box spring or foundation, and our zero-clearance bases like the e3 can sit inside a bed frame with or without slats, on top of a platform bed frame, or stand alone on screw-in legs (3", 6", 9" or 12" on the e3). You get to sit up to read or watch TV and a one-touch zero gravity position.
- Choosing one? Start with our how to choose an adjustable base checklist.
- Which mattress bends best? See the best mattress for an adjustable base.
Mattress prices today
Our memory foam picks in full, queen and king at today’s prices. A dash means that size isn’t available right now.
| Pick | Best for | Model code | Full | Queen | King |
|---|---|---|---|---|---|
| 10" Rose | Medium all foam; non-skid bottom fabric | 10BNV-F |
$609 | $629 | $689 |
| 12" Copper Gel | Medium to medium firm; copper memory foam over a 7" Air Grid base | 12BNCOPPER-F |
$699 | $739 | $819 |
| 10" ActiveAlign Copper | Medium firm; base layer cut to flex on an adjustable base | 10REACTIVE-F |
$709 | $739 | $809 |
| 8" Daisy | Firm, lower profile; non-skid bottom fabric | 8BNV-F |
$569 | $589 | $639 |
| 12" Lavender Firm | Firm; non-skid bottom fabric | 12BNF-F |
— | $709 | $769 |
Prices are today’s prices, read live from our catalog, with free FedEx shipping included.
And something to put it on: a foundation, a bed frame with slats, or an adjustable base.
| Pick | Best for | Model code | Full | Queen | King |
|---|---|---|---|---|---|
| Express Mattress Foundation | Wood slats on 6" legs; can stand alone as a bed frame | UFG-F |
$269 | $279 | $389 |
| Tufted Upholstered Bed Frame | Upholstered bed with headboard; slat pack included | UBHUD-F |
$639 | $649 | — |
| e3 Adjustable Base | Replaces the foundation; zero clearance or legs | SBKD3-F |
$479 | $499 | $749 |
Prices are today’s prices, read live from our catalog, with free FedEx shipping included.
Compare every mattress side by side in the mattress comparison chart.
Express Mattress Foundation with 6" Grey Wood-Style Legs
The simple answer if you have nothing underneath yet, or your old box spring is done. A foundation on its own legs, so it doesn’t need a separate frame.
- Wood slats and 6" faux wood legs
- Fabric-covered frame for a clean, streamlined look
- No tools for assembly
- Can be used as a stand-alone upholstered bed frame
From $269 (Full) · Queen $279 · See sizes & details
10" Rose - Medium Firmness - 10BNV
Our everyday memory foam pick. A medium 10" all-foam mattress with a non-skid bottom, so it stays put on a platform or foundation.
- 2" gel air memory foam top layer
- Non-skid bottom fabric
- Machine-washable zip-off cover
- CertiPur certified; 10-year limited warranty
From $539 (Twin) · Queen $629 · See sizes & details
Setup tips
- Set up the support first. The setup instructions say to place the mattress on its proper surface before opening it, then cut the plastic with scissors, never a razor blade.
- Sleep on it the first night. It can take up to 72 hours to fully recover its shape. More in our how long does a mattress in a box take to expand guide.
- Use a mattress protector, since liquid damage isn’t covered by the warranty.
- Rotate it head to foot to even out wear, as the care instructions suggest, and don’t stand or jump on it.
- Still choosing a mattress? Our memory foam vs. hybrid guide and thickness guide help narrow it down.
Shop this guide
Need something to put your mattress on, or a mattress to put on it? These are the ones we suggest most.
- Express Mattress Foundation with 6" Grey Wood-Style Legs, from $269. A foundation with wood slats and its own 6" legs; no tools to assemble.
- 10" Rose - Medium Firmness - 10BNV, from $539. Medium memory foam with a non-skid bottom.
- e3 Adjustable Bed Base with Wireless Remote, Memory Positions & Zero Clearance, from $449. Replaces a box spring; zero clearance, wireless remote and zero gravity.
Questions we hear a lot
What should I put under a memory foam mattress?
Something flat, solid and even. The setup instructions on our mattresses list a continuously solid surface, an adjustable base, or slats no more than 2 inches apart that can support the mattress and the people on it. A platform bed, a slatted frame or foundation with narrow gaps, or an adjustable base all work.
Do you need a box spring for a memory foam mattress?
No. Memory foam needs solid, even support, not springs. An old box spring can work only if it is flat, firm and not sagging, like many fabric-covered wood foundations sold as box springs today. If yours flexes or sags, replace it with a foundation or platform, because a sagging base will make a new mattress sag too. On an adjustable base, skip the box spring completely.
How far apart should slats be for a memory foam mattress?
No more than 2 inches apart, measured between the edges of two slats, per the setup instructions on our mattresses. The slats should be firm and flat, and a queen or larger frame should have center support. If the gaps are wider, lay a bunkie board or a sheet of plywood over the slats.
Can a memory foam mattress go on the floor?
For a few nights, yes, on a clean, dry, hard floor. For everyday use a frame, foundation or platform is usually better, because air can’t move under a mattress lying flat on the floor, so moisture from your body and the room can get trapped, especially on concrete or carpet. If you use the floor for a while, keep the room dry and lift the mattress now and then to air out the underside.
What is a bunkie board and do I need one?
A bunkie board is a thin, flat board, often covered in fabric, that turns a frame with wide slats into a solid surface without adding much height. You only need one if your slats are more than 2 inches apart or you need a solid surface on a bunk bed, trundle or low platform. On a bunk bed it counts toward the maximum mattress thickness. Not sure about your frame? Text John a photo at 805-617-6878.
Not sure about your frame? Just ask us
Send John a photo of your bed frame or box spring and the gap between the slats, and he’ll tell you honestly whether it will work or what to add. Text or call 805-617-6878, 6 AM to 9 PM Pacific, take the 60-second mattress quiz, or use Help me choose. See our Purchase Policy & Warranty for the details.
Written by John & Mimi Venti, MimiJohn. Specs and setup instructions from the manufacturer; prices update automatically. Always follow your bed frame’s own instructions and labels too.