Sauna Maintenance, Part 1: The Interior

Sauna maintenance intimidates people. It shouldn't.

Here's the truth: a sauna is one of the lowest-maintenance things you'll ever own. Heat and cedar do most of the work for you. There's no filter to swap, no chemistry to babysit, no weekend lost to scrubbing. What cleaning a sauna actually asks of you is small — a little rhythm — and in return it stays beautiful for decades. Treat it well and your sauna outlives you.

A little wear is part of it, too. Wood ages, water leaves its marks, and none of that is damage — it's a sauna that's been used. So the goal isn't a museum piece. It's a clean, dry, good-smelling room you're glad to step into. Save this for your next reset day. Here's the whole sauna cleaning routine, start to finish.

The one habit that does 90% of the work

Leave the vents open. Always. This is the foolproof one — I leave mine open all the time and never think about it again. A sauna that can breathe stays dry, and a dry sauna doesn't grow anything, doesn't hold odor, and doesn't rot. No propping doors on a timer, no routine to remember. Open vents, walk away. (It's one more reason we love an outdoor sauna — keeping it dry and clean is so much easier than an indoor build, where the moisture has nowhere to go.)

That's really the whole secret. Everything below just keeps it looking sharp.

One optional add, for the tidy types: sitting on a towel keeps sweat off the wood, so the benches stay lighter and your deep-cleans get easier. I'll be honest — I rarely bother. I'm easygoing about it and the cedar handles it just fine. But if you like things neat, it's the cheapest win there is.

Step 1: Vacuum first

Start dry. Pull out the loose stuff — debris, cobwebs, and the fine rock dust that collects around the heater.

That dust is normal. Sauna rocks slowly crack over time from the heat, and if you're sweating frequently you can expect to swap them out every few years. It's not a problem, it's just physics. While you're in there, pull the rocks and re-stack them loosely — over time they settle and choke the airflow around the heater, and a loose stack lets the heat move the way it's supposed to. Vacuum up the dust and move on.

Step 2: Check your hinges

Two-minute job, huge payoff. Spring self-closing hinges lose tension over the years, and a door that doesn't pull itself shut nice and tight is bleeding heat every session.

Give the door a test. If it's not closing snug on its own, re-tension the hinge. Small adjustment, big difference in how the room holds heat.

Step 3: Rinse it down

Now the actual cleaning. Warm water, a couple drops of a mild, sauna-safe soap, and a good natural fiber scrub brush — natural bristles are gentle on cedar and won't leave plastic residue behind. Work the dirt spots — the floor and the benches take the most abuse, so that's where the effort goes. Everything else is basically along for the ride.

See dark streaking? It's not a stain. That's the cedar's natural tannins collecting where water runs down the wood. A little soap and a quick scrub and it washes right out. The wood is fine — it's doing exactly what cedar does.

Step 4: For bad smells, reach for vinegar

Every so often a sauna picks up a smell that a normal wash won't touch. When that happens, skip the fancy cleaners and grab plain white vinegar — diluted with warm water, wiped or scrubbed on, then rinsed. Vinegar neutralizes odor at the source instead of just covering it, and it's completely safe for the wood.

How do I know? A boy I know — who may or may not be related to me — once decided the sauna was close enough to a bathroom. It was bad. We tried everything, and the only thing that finally pulled it out of the wood was vinegar. Lesson learned, and now you get it for free: when a smell won't quit, vinegar wins.

Step 5: Leave the wood alone — never seal cedar sauna benches

This is the one people get wrong, so hear it clearly: never coat the benches with stains or varnishes.

We build exclusively with Northern White Cedar, and it's the right wood for a sauna for a stack of reasons: it's light in color, so the benches don't soak up heat the way a dark, dense wood would — they stay comfortable to sit on instead of scorching. It's strong. And it's full of natural oils that protect it, give it that smell, and let it shrug off heat and moisture year after year. Seal it with a varnish or stain and you trap heat against a finish that was never made for it, and you smother the very thing that makes the cedar work. (This is about the inside. Many of our saunas are stained or colored on the outside — that's a different story, and it's covered in Part 2.)

If you ever do want to treat the interior wood, the rule is simple: anything you put on it must be specifically labeled sauna-approved. Nothing off the general hardware-store shelf. When in doubt, water and a brush is all the bench ever needs.

Optional: sanding, and only as a last resort

Most stains and rough spots come off with a scrub and a wash — so try that first, always. But every once in a while a mark digs in and won't budge. That's the only time to sand: a light pass with fine-grit sandpaper on the stubborn spot takes you right back to bright, fresh cedar in a couple of minutes. It's a last resort, not a routine. If a wash handles it, you're done.

Your sauna cleaning routine, at a glance

• Every session: leave the vents open (a towel down is optional, for the tidy types).
• Vacuum the loose debris and rock dust, and re-stack the rocks now and then.
• Check the door hinges and re-tension if the door's gone loose.
• Rinse the floor and benches with warm water, a sauna-safe soap, and a natural fiber brush.
• Smells? Wipe it down with diluted white vinegar.
• Leave the benches bare — cedar's own oils are the finish. Sauna-approved products only, if anything at all.
• Sand only when a scrub and wash won't lift a stubborn mark.

A little rhythm, and the heat handles the rest. Don't overthink it — the point of a sauna is to make life simpler, not to give you one more thing to fuss over.

What about the outside of the sauna?

Everything above is the inside. The outside plays by completely different rules — and it depends on which Nightjar you've got. Some of our saunas are left as bare cedar and weather into a beautiful silver-gray. Others are stained a rich dark or a color, and those hold their tone with a little upkeep. Two different paths, both easy.

We gave the whole exterior its own guide.

👉 Read Part 2: Caring for Your Sauna's Exterior — Natural Gray & Stained »

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Got a cold plunge too? Don't miss Part 3: Cold Plunge Maintenance »

Want a sauna built from cedar that's meant to be lived in? Explore our handcrafted saunas and cold plunges.

— Nightjar Sauna, Grand Rapids, Michigan

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