The single most important maintenance habit is drying the sauna after every session — vents open, door ajar. Everything else is secondary. A sauna that is allowed to dry between uses will look and smell good for decades with minimal intervention; one that is closed up wet will stain, develop odour and eventually grow mould, regardless of how often you scrub it.
Beyond that, sauna maintenance is light: wipe the benches after use, wash them monthly, restack the stones and sand the benches annually. This guide sets out the full schedule and the specific problems that come up.
The golden rules
1. Dry it out after every session. Open the vents fully, prop the door open, and let air move through for an hour or two. Some owners run the heater for a further 10–15 minutes with the vents wide; this is the fastest method and costs very little.
Bleach, ammonia, detergents, disinfectant sprays and multi-surface cleaners all soak into bare timber and then vaporise at 190°F, straight into the air you are breathing. Water, a soft brush and mild soap where genuinely needed is the complete toolkit.
3. Never seal, varnish, stain or paint interior timber. Sauna wood is left bare, or treated only with paraffin-based sauna oil on bench tops. Any film-forming finish will blister, discolour and off-gas at sauna temperatures.
4. Always sit on a towel. Body oils and sweat absorbed into bench wood are the primary cause of the dark staining that makes old saunas look tired. A towel prevents nearly all of it, and this one habit does more for the appearance of a sauna over ten years than any cleaning routine.
5. Do not pressure-wash the interior. It drives water into the timber and behind the cladding.
The maintenance schedule
After every session
- Open vents fully and prop the door open
- Wipe down benches and backrests with a damp cloth
- Empty the water bucket — essential in freezing weather outdoors
- Hang or remove towels and bench covers
- Give the room an hour or two to dry before closing up
Two minutes of work, and it prevents nearly every problem in this article.
Weekly (or after heavy use)
- Wash the bench tops with warm water and a soft brush
- Rinse the floor, or lift and rinse the duckboard
- Wipe the door glass with water — never glass cleaner
- Check the bucket and ladle for mildew and rinse them properly
Monthly
- Wash benches, backrests and the lower parts of the walls with warm water and a small amount of mild, unscented soap; rinse thoroughly
- Lift out the duckboard and clean underneath — the most commonly missed spot in a sauna and the first place odour starts
- Vacuum the floor and corners
- Check for any darkening or spotting on the wood and deal with it early
- Inspect the heater guard and surrounds
Annually
- Restack the stones. Remove them, discard any cracked or crumbling, vacuum the fines out of the basket, rebuild the stack loosely. Fifteen minutes and the highest-return maintenance in a sauna. See sauna stones.
- Sand the bench tops lightly with 120–180 grit to remove surface staining and raise a fresh surface. Vacuum the dust thoroughly.
- Apply paraffin-based sauna oil to bench tops after sanding, if you use it. Thin coat, wiped back.
- Check all fixings — bench supports, backrests, door hinges, guard rail.
- Inspect the door seal and adjust hinges if the door has dropped or sticks.
- Check vents are clear and the adjustable one still moves freely.
- Test the heater's controls and safety cut-off.
- Outdoor saunas: inspect cladding, roof, flashing and the base; re-oil or re-stain the exterior if you maintain a finish; check that ground drainage still runs away from the building.
- Wood-fired saunas: sweep the chimney. Non-negotiable — sauna fires burn hot with resinous softwood and creosote accumulates faster than in a typical domestic stove. Also check the spark arrestor and firebox gaskets.
Every 1–3 years
- Replace the stones when they crack, crumble or shed grit, or when steam quality has declined
- Replace bench covers and headrests as they wear
- Check heating elements for corrosion or deformation
Specific problems and fixes
Dark stains on benches
Cause: absorbed body oils and sweat. Almost always from sitting directly on the wood.
Fix: sand with 120–180 grit until the discolouration lifts, vacuum thoroughly, and re-oil if you use sauna oil. Deep stains may need 80 grit first.
Prevention: always sit on a towel or a bench cover.
Musty smell
Cause: the room is not drying between sessions. Usually a ventilation problem, a duckboard that has never been lifted, or a damp towel left in the room.
Fix: remove everything from the sauna, lift and clean the duckboard, wash the benches and floor, then run the heater hot with the vents wide open for 45–60 minutes. Repeat if needed.
Prevention: dry it after every session, and check the ventilation is actually working. See sauna ventilation.
Mould or black spotting
Cause: persistent moisture, poor ventilation, and often a failed or missing vapour barrier behind the cladding.
Fix, for surface mould: wash with warm water and a mild soap, rinse, then sand the affected area back to clean wood. Dry the room thoroughly with the heater running and vents open.
It soaks into bare timber, vaporises at sauna temperatures and does not reach mould that has gone below the surface. If the mould keeps returning, the cause is structural — inadequate ventilation, or moisture migrating into the wall because the vapour barrier is missing or compromised. Cleaning will not fix that. See DIY sauna vs professional installation.
White crusting on stones
Cause: mineral scale from hard water.
Fix: cosmetic only. Most of it falls away when you restack. Filtered or softened water in the bucket prevents recurrence.
Weak or thin steam
Cause, in order of likelihood: degraded stones restricting airflow; stones packed too tightly; not preheating long enough for the stone mass to saturate; or too much ventilation.
Fix: restack the stones first — it solves most cases. Then try preheating 15 minutes past the thermostat's cut-out. See how hot a sauna should be.
The heater trips its cut-out
Cause: most commonly an overpacked stone basket restricting airflow around the elements. Also blocked ventilation, or a failing element.
Fix: restack the stones loosely with visible gaps. If it continues, have the heater checked.
Wood cracking or opening up
Cause: normal seasonal movement, accelerated by very dry operation and by a room that swings between bone dry and soaking.
Fix: minor checking is cosmetic and normal. If joints are opening noticeably, moderate the peak temperature and use löyly rather than running the room bone dry at 195°F.
Door sticking or not closing
Cause: seasonal swelling, hinges dropping, or the room being slightly out of square.
Fix: adjust the hinges first. Plane sparingly and only as a last resort, since the door will shrink again in the dry season. Outdoor doors are the usual culprits.
What to use, and what never to use
Use
- Warm water — the primary cleaner, and sufficient for most jobs
- A soft-bristled brush for bench tops
- Mild, unscented soap, sparingly, rinsed thoroughly
- Sandpaper, 80–180 grit, for staining and refreshing bench surfaces
- Paraffin-based sauna oil, made for the purpose, on bench tops only
- A vacuum for dust, stone fines and under-bench debris
- Sauna essence, in the water bucket only, a few drops
Never use
| Product | Why not |
|---|---|
| Bleach | Soaks into bare wood, vaporises at temperature, does not reach subsurface mould |
| Ammonia or multi-surface cleaners | Same problem; harsh fumes at 190°F |
| Varnish, lacquer, polyurethane | Blisters and off-gasses; wood must breathe |
| Stain or paint on the interior | Discolours, off-gasses, and cannot be sanded back easily |
| Standard wood oils (linseed, teak, danish) | Not formulated for sauna temperatures; can go tacky or rancid |
| Pressure washer | Drives water into the timber and behind the cladding |
| Glass cleaner on the door | Residue vaporises; warm water is enough |
| Steel wool | Leaves particles that rust and stain |
| Air fresheners or scented sprays | Vaporise into the air you breathe |
Heater and component care
Stones — restack annually, replace every one to three years, always loose with air gaps. This is the maintenance with the largest effect on how the sauna performs.
Elements — no routine maintenance beyond keeping the stone basket loose. Elements typically last 5–15 years in residential use; premature failure is nearly always caused by restricted airflow.
Control panel and sensor — wipe the sensor housing clean during the annual check; dust and grime on a sensor affects its reading. Verify the safety cut-off functions.
Guard rail — check fixings annually; it takes knocks.
Door glass — water only. Tempered glass does not need anything else.
Duckboard floor — lift, clean underneath, and let both dry. The most commonly neglected part of a sauna.
Wood-fired stoves — ash out regularly, chimney swept annually, gaskets and firebox inspected once a year, spark arrestor kept clear. See electric vs wood-burning.
Outdoor cabins — annual exterior inspection, roof and flashing checked, drainage confirmed, door seal checked. See the outdoor sauna buying guide.
Seasonal and situational care
Before a period of disuse. Going away for a month, or shutting an outdoor sauna down for winter? Clean it properly, run the heater hot with vents open for an hour to dry everything thoroughly, remove all textiles, empty the bucket, and leave the door slightly ajar and the vents open. A sauna left closed and slightly damp for six weeks is how odour problems start.
Bringing one back into use. Wipe everything down, check the stones and restack if they have not been touched in a year, run the heater empty of people for 30–45 minutes with the vents open, and check the door and hinges. Outdoors, also check for water ingress, insects and any animal that has decided the space under the benches is a good home.
Freezing weather, outdoor saunas. Empty the bucket after every session without exception, make sure the floor drains rather than pools, and clear snow from the roof and away from the door. An outward-opening door blocked by drifted snow is both an inconvenience and a genuine safety issue.
Humid summers. In a humid climate an unused sauna can stay damp for days. If the room smells at all when you open it, run the heater for 20 minutes with the vents wide — it is cheaper than dealing with mould later.
Hard water regions. Expect scale on the stones and on the bucket. Cosmetic, and it comes away when you restack. Filtered water in the bucket removes it entirely if it bothers you.
Very dry climates. Timber moves more, so expect a little more seasonal checking of joints and a door that fits differently in summer than in winter. Adjust hinges rather than planing.
Heavy or shared use. A sauna used daily by several people, or in a rental property, needs the monthly clean weekly and the annual sand-and-restack twice a year. It also needs a commercial-rated heater if it is genuinely shared. See the commercial sauna buying guide.
The five-minute habit that replaces most maintenance
- Sit on a towel — prevents nearly all bench staining
- Wipe the benches when you get out — ten seconds
- Open the vents and prop the door — the single most important step
- Empty the bucket
- Come back in an hour and close up
A sauna treated this way needs a monthly wash and an annual sand-and-restack, and that is the whole maintenance burden. A sauna that is closed up wet after every session needs constant intervention and will still look tired in five years.
What it costs to maintain a sauna
Modest, and worth knowing so it can be budgeted rather than deferred.
| Item | Frequency | Typical cost |
|---|---|---|
| Sauna stones | Every 1–3 years | $60 – $200 |
| Sandpaper and consumables | Annually | $15 – $30 |
| Paraffin sauna oil | Annually | $20 – $40 |
| Bench covers / towels | Every 2–3 years | $30 – $120 |
| Replacement heating element set | Every 5–15 years | $100 – $400 |
| Chimney sweep (wood-fired only) | Annually | $150 – $400 |
| Exterior re-oil (outdoor only) | Every 2–3 years | $50 – $200 |
Annualised, an electric indoor sauna costs roughly $50–$100 a year to maintain. An outdoor wood-fired sauna is closer to $250–$500 a year, mostly the chimney sweep and exterior upkeep.
The most expensive maintenance is the maintenance not done. Stones left in place for five years choke airflow and kill an element early. A room never dried out stains benches that then need aggressive sanding or replacement. An outdoor cabin whose drainage was never checked rots at the base.
Frequently Asked Questions
How do you clean sauna benches?
Wipe them with a damp cloth after every session, wash them monthly with warm water and a soft brush — mild unscented soap only if genuinely needed, rinsed thoroughly — and sand them lightly with 120–180 grit once a year to remove absorbed staining. Never use bleach, household cleaners or any film-forming finish on sauna wood.
Why does my sauna smell musty?
The room is not drying between sessions. Common causes are inadequate ventilation, a duckboard floor that has never been lifted and cleaned underneath, and damp towels left inside. Strip the room, clean everything including under the duckboard, then run the heater hot with the vents wide open for 45–60 minutes.
Can you use bleach in a sauna?
No. Bleach soaks into bare timber and then vaporises at sauna temperatures into the air you breathe, and it does not reach mould that has penetrated below the surface. Wash with warm water and mild soap, then sand affected areas back to clean wood and dry the room thoroughly with the heater running.
Should you oil sauna benches?
Only with a paraffin-based oil made specifically for saunas, applied thinly to bench tops after sanding, once or twice a year. Never use linseed, teak, danish or other standard wood oils — they are not formulated for sauna temperatures and can go tacky or rancid. Walls and ceilings are left completely bare.
How often should you clean a sauna?
Wipe benches and dry the room after every session; wash benches and the floor weekly with heavy use; do a full clean including under the duckboard monthly; and once a year sand the benches, restack the stones and inspect fixings, vents and the door. Drying the room after each use prevents most of the problems the rest of the schedule exists to fix.
Time for fresh stones or a new bucket?
Sauna-grade stones, buckets, ladles, thermometers and bench accessories — the consumables that keep a sauna working properly.
Shop Sauna Stones Shop AccessoriesRelated guides
- Sauna Stones: Complete Guide
- Sauna Ventilation: Complete Guide
- Best Wood for Custom Saunas
- How Hot Should a Sauna Be?
- Outdoor Sauna Buying Guide
Published by Finest Saunas