Bench Slats and Gaps: Why They Are Spaced

Why slatted benches have gaps

Sauna benches are often built from parallel wood slats with spaces between them, not solid boards. That spacing is deliberate. It serves two main purposes: airflow and drainage. In a hot room where your body sweats and you may splash water on the rocks, a bench without gaps would trap heat and moisture against the wood and your skin.

The gaps also prevent the bench from acting as a solid heat sink. With open spaces, hot air can rise up through the slats and the wood stays closer to the room temperature. This makes sitting more pleasant and reduces the risk of overheating the wood fibers. Over a long session, a slatted bench feels noticeably cooler than a solid one because air moves freely around your legs and back. The even distribution of heat also helps you relax without the discomfort of hot spots.

Traditional sauna design has always favored slatted benches for these reasons. The Finnish sauna tradition, which emphasizes the interplay of heat and steam, relies on good air circulation to maintain the dry, gentle warmth that defines a proper löyly. When you sit on a slatted bench, the air that reaches your skin is the same air that has been heated by the stove, not air that has been trapped under a solid surface.

Airflow and dry heat

Traditional saunas operate at low humidity, typically below 20 percent, as noted by the Cleveland Clinic. Gaps in the bench allow hot air to move freely around your body and the wood, so the environment stays dry and comfortable. Without spacing, the bench would block air movement and create a hot, humid microzone right under your thighs. That trapped air would also feel stuffy and might cause you to overheat more quickly.

Good airflow also helps the bench dry out between sessions. After you leave the sauna, the remaining moisture on the wood evaporates faster because both the top and bottom surfaces are exposed to air. A dry bench is also more hygienic, since bacteria and mold need moisture to grow. The open gaps discourage their development, making the sauna a healthier space for repeated use.

For more on how ventilation works in a sauna, see sauna ventilation basics. That article explains how intake and exhaust vents work together to keep the air fresh and the temperature even. Bench gaps complement that system by allowing the air to move around the entire room, not just across the ceiling and floor.

Drainage and cleaning

Sweat and any water you ladle onto the hot stones will eventually condense or run down. A slatted bench lets that moisture pass between the slats and fall to the floor, where it can be wiped or drained away. Finnleo notes that a sauna does not strictly need a drain, but a non-absorbing floor is recommended for traditional use. If the bench were solid, water would pool on the surface, making it slippery and hard to clean. It would also soak into the wood grain and leave stains, especially if you use essential oils or other additives.

The gaps also make it easier to wipe down the bench and allow the wood to dry quickly after each session. You can simply run a damp cloth over the top surface, and the water and sweat will drip through the gaps. For a deeper clean, you can use a soft brush to reach between the slats. Keeping the wood dry is one of the best ways to prevent mold and mildew, which is a key reason why sauna benches are never built as a completely sealed surface.

If your sauna has a removable bench, you can take it out and rinse it thoroughly. Some benches are hinged at the back, so you can lift the front and wipe the underside. Check your manufacturer's instructions for cleaning recommendations. Regular maintenance also includes checking the screws and brackets that hold the slats, as they can loosen over time with the constant expansion and contraction of the wood. For more on floor care, see sauna floor mat and duckboards.

Protecting the wood

Wood in a sauna expands and contracts with changes in humidity and heat. If moisture is trapped against a solid board, the wood can warp, crack, or develop mold over time. Gaps allow the wood to breathe and release moisture on all sides, which helps it stay stable and last longer. This is why most sauna manufacturers choose to space the slats rather than butt them tightly together. The small space between each slat acts as a buffer zone, absorbing the movement without stressing the joints.

The spacing also reduces the contact area between the bench and your skin, which means less sweat is absorbed into the wood grain. Over many sessions, that makes a real difference in how the bench ages. A solid bench might show dark stains and odors after just a few months, while a slatted bench remains cleaner and fresher. The wood also dries faster, which is especially important in a traditional sauna where the humidity rises when water hits the stones.

Red cedar, hemlock, spruce, and aspen are common bench woods, and all of them benefit from air circulation. Some woods have natural oils that resist moisture, but none are immune to rot if they stay wet. The gaps are the first line of defense. If you notice the gaps becoming clogged with dust or debris, use a vacuum or a small brush to clear them. This simple step can add years to the life of your benches. For more on wood selection, see which sauna wood is best.

What to look for in bench spacing

When you look at a sauna, check the gap size. It should be wide enough for air to pass easily but not so wide that you feel the gap under your thighs. A gap of about 1/4 to 1/2 inch (6 to 12 mm) is typical, but the exact size depends on the wood species and the manufacturer. The slats should be evenly spaced, with rounded edges to avoid splinters. Some manufacturers use wider gaps for traditional saunas where water is frequently poured, while infrared cabins may use narrower gaps because they stay dryer overall.

You can also look for benches that are removable or hinged for easy cleaning. If you are comparing models, read the spec sheet and look at close-up photos of the benches. Pay attention to how the slats are attached: are they screwed into a support frame, or are they set into routed channels? Screwed slats are easier to replace if one gets damaged. Also consider the depth of the bench and the height, which we cover in sauna bench height and heat.

If you are planning to build your own sauna, you have full control over the spacing. Use a spacer board when you screw the slats down to keep the gaps uniform. Test the gap with a finger to ensure it is comfortable. Remember that the gap will change slightly as the wood expands and contracts, so leave a little extra room if you live in a humid climate. Also round over the edges of the slats before installation to reduce splinter risk.

Bench spacing in traditional vs. infrared saunas

Traditional saunas, which are heated to 150 to 195 degrees Fahrenheit with low humidity, rely on gaps to maintain that dry heat. When you pour water on the rocks, the resulting steam raises the humidity briefly, but the gaps allow that moisture to rise and eventually condense on the walls and floor, not on the bench. Infrared saunas operate at a lower temperature, typically 110 to 135 degrees Fahrenheit, and do not use water on a heater. The gaps are still useful for letting the air circulate and for draining sweat, but the wider gaps are less critical because the room stays drier.

If you own or plan to buy an infrared sauna, you may see benches that are still slatted but with narrower gaps. That is fine, as long as there is some opening for airflow. Some infrared cabins have backrests and footrests that are also slatted for the same reason. When you compare models, consider how much time you plan to spend in each session. A longer session means more sweat, so a bench that drains well is always a good idea.

For hybrid saunas that combine infrared and traditional heating, the bench design follows the same principle. The gaps help with both heat distribution and moisture management. If you are deciding between different sauna types, the bench construction is a minor factor compared to the heater output and room size, but it still affects comfort. You can read more about the differences in infrared vs. traditional: which fits you.

What to pick for your use

Questions

Do all saunas have slatted benches?

Most saunas, especially traditional ones, use slatted benches. Some infrared cabins may have solid panels, but gaps are still common for comfort and airflow.

Can I change the gap size on an existing bench?

Not easily, since the benches are usually pre-drilled. If you build your own sauna, you can choose the spacing during construction. Modifying an existing bench might weaken its structure.

Do gaps affect heat distribution?

Yes, they allow hot air to rise and circulate. This helps the bench heat more evenly and keeps the room temperature consistent, especially near the upper benches where heat accumulates.

How do I clean between the slats?

Use a soft brush or a vacuum with a crevice tool. Wipe down the top surface after each session with a damp cloth, and let the bench dry fully. For deep cleaning, you can remove the bench if it is designed to be removable.

Can gaps be too large?

Very large gaps can be uncomfortable and may let small objects fall through. A gap that fits a finger is usually comfortable and functional. Also, too wide a gap might reduce the support your legs receive.

Does the wood type affect the ideal gap?

Softer woods like cedar are more prone to compression, so they may need narrower gaps to avoid bowing. Hardwoods like aspen can handle slightly wider gaps. But the difference is minimal for most users.

Why do some benches have gaps only in the front?

Some designs use a solid back section for comfort and gaps only where you sit. That still allows some airflow while providing a smooth surface for your lower back. The key is that moisture can still escape.