How to make bed slats firmer: 7 options

I have been getting a lot of questions on this topic recently so I thought the subject deserves an article. This also helps me as I can send those asking to this resource 🙂 You might want to also read my article about making bed slats stronger in 7 steps here.

Make bed slats firmer by fastening the ends to the bed frame, adding a center support beam, reducing gaps and adding slats, adding lumber to the underside of the slats, replace with 2×4 lumber or 3/4″ plywood, using a box spring.

A quick fix in 5 minutes with this Amazon support here.

Option #7 is the easiest and Option #5.2 is the strongest method to make firmer slats.

7 ways to make bed slats firmer

#1 Fasten slat ends to the bed frame

Simply adding screws to the ends of the slats to attach them to the side rails (frame) increases the sag resistance by 60%! That is an incredibly simple, fast, and cheap fix to make bed slats firmer and to hold their shape to resist sagging!

For a comparison of 12 types of wood (and five thicknesses for each of the 12) that sag when fixed (fastened) versus floating (not fastened) please see my article here.

#2 Add a center support rail and/or legs (including DIY with the Amazon legs)

This is the cheapest and easiest method to increase the strength of bed slats. Most of the adjustable support legs are manufactured in China, but what isn’t these days? For less than $20 you can have one of several designs show up at your door in a couple of days. See the list of adjustable height options on Amazon here.

You can also add a beam down the center of the bed, running from the head to the toe. Using two or three of the above adjustable support legs is an easy way to set the height for optimum strength. Fasten the beam to the slats for optimum strength and reduce movement and squeaking as much as possible.

#3 Reduce gaps and add more slats

You can simply buy or make more slats and add them to the frame to reduce the size of the gaps.

Another option is to remove all slats and rearrange them so that there is a larger gap at the head and foot of the bed. Perhaps 3 – 4 inches gaps in these areas as there is less weight here.

Then start reducing the gaps as you get closer to the center of the frame where most of the weight and action (movement) is. So perhaps reduce the gaps in the middle to about 1.5 – 2.5 inches.

#4 Add lumber underneath the slats

This is a very strong and sturdy solution, but it will cost a few dollars. Purchase a few 2×4 or 2×6 inch lumber (whatever is on sale is fine).

  • Remove the slats.
  • Add the lumber to the frame starting and finishing near the edge of the bed frame.
  • Fill in the middle with the 2×4 or 2×6 inch lumber with no more than a 6″ gap.
  • Reinstall the slats on top of the lumber. Make sure to fasten each slat to every board (lumber) below it to tie all the construction together. This increases the strength substantially and only takes a few minutes and a couple of dollars for screws.

#5 Replace slats with 2x4s

This can be accomplished in two ways:

  1. Remove the existing slats and install 2×4 lumber (which is actually only 1.5″ x 3.5″ due to the wood being planned, which makes it much easier to handle. Think fewer splinters!). If the span is 36″ or less you can space the wood at 3″ or less.

    If your span is greater than 36″ you should reduce the gap to 2.5″ or less. Fewer gaps over longer spans will prevent future mattress sagging.

    An advantage of gaps is that the bottom of the mattress can breathe with more available airflow. This reduces the chances of growing mold underneath between the mattress and the wood.
  2. Be lazy and install the lumber on top of the existing slats. This can provide advantages such as:
    • Less work
    • Less debris to dispose
    • Adds more strength than if the original ones are removed

The only disadvantage I can think of is that it will raise the height of the mattress more than in option 1 above.

For more information on adding 2×4 lumber to your bed frame you can read my detailed article here.

Scott Boyd

#6 Add plywood to the top of the slats

This is a popular choice because:

  • Requires only one or two cuts
  • It creates a solid platform for the mattress
  • Plywood is available in many types of wood and thicknesses to meet everyone’s needs.
  • Does not raise the mattress height as much as when using 2x4s

You can read more in-depth details about replacing bed slats with plywood in my article here.

DIY storage bed
Plywood instead of bed slats

#7 Use a box spring on top of the slats

This is the most expensive option, but it might extend the life of your mattress so it could be worth the investment, especially if you have an expensive mattress! Advantages of this solution include:

  • No tools are needed. Just remove your bedding and mattress, add the box spring, and toss the mattress onto the box spring. Viola finished.
  • This solution can reduce the firmness of your mattress, which can be a huge benefit if you find your mattress too firm.

As with every solution to a problem, there are disadvantages, and these include:

How thick should bed slats be

Wood bed slats should be a minimum of 3/4″ thick for any type of solid wood. OSB, MDF, and even plywood should not be used as slats as they will sag too much unless you add much solid lumber underneath. This is what I did when we built the biggest bed in Thailand.

We are actually working on this project in Thailand and are using 7/8″ (22mm) plywood, which is expensive and hard to find here!

Read my list of how much 12 types of wood sag for thicknesses of 1/2″, 5/8″, 3/4″, 7/8″, and 1″ here to help you decide what wood and thickness you need.

Scott Boyd

Should bed slats be solid?

Solid bed slats are superior to ones with gaps, especially when the gaps are more than 2.5″ wide. The reasons include:

  1. Much more sturdy. Not only is this design much more strong and sturdy, it also increases the overall strength of the bed frame. This design reduces noise and movement by greatly increasing the frame strength to reduce twisting during use by heavy or rambunctious bedtime behavior.
  2. Reduces inconsistent forces on the mattress that can cause uneven wear. And many mattress warranties are voided when the slat gaps exceed 2.5″, which many models do.
  3. Less likely to sag in the middle where most of the weight is located during use. Think about it, bed slats are always evenly spaced. Does this make any sense at all? NO, do your head and feet weigh the same as your torso? NO.

    So why have the same design/gap at the head and foot of the bed frame if most of the weight is in the middle? Perhaps there is a better design that includes 2.5″ gaps at the head and foot with less gap space as you get closer to the middle.

    Or just use a solidly built frame without any gaps at all!

Read my article Do Bed Slats Need to be Screwed Down here.

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