The industry standard recommendation is no more than 2.5 to 3 inches between slats for foam and hybrid mattresses. For innerspring mattresses, up to 4 inches is generally acceptable.
Many bed frames — especially budget metal frames and flat-pack wooden frames — ship with slat spacing of 4–6 inches. This is fine for a box spring (which bridges the gaps) but problematic if you're placing a mattress directly on the slats.
Grab a ruler and measure the gap between two adjacent slats. Over 3 inches for foam mattresses, or over 4 inches for any mattress — your foundation needs attention.
Placing a bunkie board on top of your existing slats immediately eliminates all gaps. It takes under 2 minutes to install, requires no tools, and works with any slat spacing — even extreme gaps.
This is the most popular fix because it requires zero modification to your bed frame and works instantly. Our 10mm slim bunkie boards are available in all standard sizes — Twin through King.
If you want to address the slat spacing directly, you can buy additional wooden slats to fill the gaps. This requires finding slats that match your existing ones in width and thickness, and may require drilling new mounting holes in the frame rails.
A sheet of 3/4-inch plywood cut to your mattress dimensions can be placed on the slats as a makeshift solid base. It works well but is heavy, difficult to move, has no ventilation for the mattress, and has no fabric cover. It's a functional DIY solution but less refined than a purpose-built bunkie board.
A bunkie board costs $30–$80, installs in 2 minutes, looks finished with its Oxford fabric cover, is lightweight and easy to move, and protects your mattress warranty. It's the best solution for wide slat gaps for the vast majority of people.
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