Replacing Bed Slats With Plywood: What You Need to Know

Whatever your reason, you may decide that the slats under your mattress just aren’t doing the job anymore. Perhaps the slats you have need replacing, or maybe you’re hoping for more support for your back while you sleep.

Replacing bed slats with plywood is a viable option. Plywood can support your mattress, and if yours is older and perhaps sagging, the plywood will act as a stopgap measure. There are downsides to using plywood, but it’s not an option that anyone looks at with horror.

Let’s take a look at why we use slats or any other kind of support for our mattresses and why people choose to use plywood in some cases instead of those slats.

Do You Need Bed Slats?

If you are not using a box spring, you will need bed slats under your mattress. Without slats, you will need to have another system to give that support. Without support for your mattress, it will sag at best. At worst, it may slip out of the bed frame and come to rest on the floor.

The most common bed frame is the kind that is a rectangle made of metal rails. Since the rails only support the edges of the mattress, without bed slats or some other way of holding up the center of the mattress, it will sag.

Slats can also provide support for your back. People with back problems often find relief by adding slats so fewer areas of the mattress dip down toward the floor.

Can You Replace Bed Slats With Plywood?

Replacing slats is a must. You can’t just get rid of the slats and hope for the best. You might be able to get by with a sagging mattress if you’re sleeping on a twin, but anything wider will almost certainly sag to the floor, and its edges will slip off the bed frame.

Using plywood instead of slats is a viable alternative. In fact, a sheet of plywood can supply more support to a mattress and make it sleep more firmly.

Slats are generally crafted from 1×4 lumber and occasionally from 1×3 boards. Many people often overlook that the actual size of lumber is a bit smaller than the sizes we call them. A 1×4 is ¾” thick and 3 ½” wide. So if you place your mattress on pieces of wood that are not quite 4” wide, you’ll need to use enough slats to support it.

If you place the slats, say, 4” apart, your mattress will have support but may begin to sag in those 4” spaces. For that reason, you’d want to place them closer together. Since a queen-sized bed is 80” long, if you place the slats 2 ½” apart, you’ll need 14 slats.

Using plywood instead means fewer pieces. If you move often, that might be a real selling point. More pragmatically regarding sleeping, though, there will be no give at all between the slats because there will be no 2 ½” spaces.

Can You Put Plywood Over Bed Slats?

You can certainly do it, but putting plywood over slats is a bit of overkill. You won’t get huge returns on that investment. Sure, plywood isn’t a huge expense, but why would you spend money if you don’t have to?

Again, you’ll have no give with the mattress oozing through the gaps in the slats, but the added support you’ll get from the plywood won’t be enhanced by the presence of the slats beneath it. If you’re going to use plywood over slats, you might as well dump the slats and use plywood instead of slats.

Is Plywood Strong Enough for a Bed?

Using plywood that’s thick enough not to give will ensure that the sheet will be strong enough to support your sleeping surface.

The correct thickness is at least ¾”. Plywood any thinner will not resist bowing beneath the mattress, which means the creeping in of sagging. Since you have chosen plywood for its added support, having a too-thin piece will defeat the purpose of replacing the bed slats.

The ideal piece of plywood for this application is what’s known as 3/4AC pine. The 3/4 refers to the thickness, “pine” obviously designated the kind of wood, and “AC” means that one side of the wood is a bit more finished than the other. You’ll have a good side and a rough side.

If you use a piece of CD — both sides are rough and unfinished — you risk the rough wood damaging the bottom of your mattress. Small tears in the fabric add up, and since a mattress can be a costly purchase, you’ll want to do your best to preserve and protect it.

Is It OK to Put a Mattress on Plywood?

In general, using plywood is not ideal for supporting your mattress. Even with a piece of AC plywood, the unfinished wood can damage the fabric of your mattress. Remember that the finished side of AC plywood isn’t sanded smooth. It’s just a bit cleaner than the other side.

But more than that, mattresses are designed to have some give in them. If you put them on plywood when they weren’t designed for such a support system, you’re adding to the wear and tear on your mattress.

Even if you have a box spring under your mattress, this will still be the case since many box springs are intended to be somewhat flexible. Plywood eliminates the give the boxspring should have, which can lead to your mattress getting compressed by your body weight.

Your weight pushes down on the mattress, the mattress pushes onto the box spring, and if the box spring doesn’t have a way to dissipate that pressure as it would while laying atop slats, this can eventually damage the mattress.

Finally, without slats, the mattress (laying on a solid piece of plywood) can’t breathe. Moisture can collect under it, and once mold sets in, you have a whole new set of problems.

There are pros to plywood, though. It’s not like using plywood instead of bed slats is an all-around terrible idea. Using plywood can:

  • Prolong the life of your old mattress by adding support to it that its age is preventing it from providing.
  • Be a cheaper solution than replacing your mattress.
  • Give good support to a memory foam mattress if you’re not using a box spring with it.

Using Plywood Instead of Bed Slats

If plywood remains something you want, you’ll need to do a couple of things. First, determine the size of your bed since that will dictate how much plywood you need. Plywood is normally sold in 4’x8’ sheets, although oversized sheets that are 5’ wide are available.

The chances are good that you know whether your bed is a twin or a California king, but if you don’t know, find out. Unless you have a twin bed, you will most likely need two sheets of plywood.

Type of bedWidth (in inches)Length (in inches)
Twin XL3880
Full (or double)5375
California king7284

As you can see, a full-size bed is 5” too wide for a 48” wide piece of plywood. Once you have determined how much plywood you need, cut the wood to size. You will most likely want to sand the edges of the wood at least, and you probably want to pay some attention to the face of the wood, too. Even AC plywood is still a bit rough, so sanding the A-side will cut down on the wear it may apply to your mattress.

If your bed is a double or larger, you will want to put a support under the middle of the plywood. Even a sheet that’s ¾” thick will sag under the weight of the mattress and sleepers if it remains unsupported.

If you do not want to use slats but now wonder whether plywood is a good idea, an alternative that might work well for you would be something like the Mayton Support Wooden Bunkie Board (available at Amazon).

A bunkie board can come in a few varieties, but this one is a collection of slats that are connected to straps to hold them in place. A bunkie board ensures that the distance between slats won’t change as you use your bed.


Plywood serves as a replacement for bed slats, though it is not an ideal solution. While you might get some more support than from widely spaced bed slats, the plywood itself won’t be good for the health of the mattress over a long time.

Most of us will spend nearly a quarter of a million hours sleeping over the course of our lives. That’s a long time, so your mattress matters. If your mattress is at the end of its life, plywood can help, but over the long haul, plywood as a replacement for bed slats is not ideal.


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