Combined with hot temperatures, extreme moisture, bodily fluids, and bacteria, how does a typical sauna not completely rot or develop mould? Seems like the wood would be turned into mush with all of these factors.
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Properly selected wood, and coverings should prevent this. Certain woods are extremely resistant to your mentioned issues. Things like a nice layer of lacquer or varnish can protect wood from moisture.
Wood is a durable material that does not rot easily. Saunas are typically made with cedar or other types of wood that are resistant to rot and decay.
Not an expert (read not scandanavian) but Saunas are hot and low humidity. I would expect this is near perfect condition for the wood. Any moisture you sweat soon evaporates off the wood. Any bacteria or pests would soon die from the cooking
Very interesting question.
We usually use pine and aspen trees for construction and the benches, aspen trees usually on the benches and pine in the construction.
The main reason a sauna can stay good and healthy is because of the heat the fireplace radiates, that combined with the sturdy wood that has a lot of resin acids makes them very very durable. The resin leaks out like sap when the wood shrinks because of the heat and creates a natural protection of the wood.
And you will also have the sauna running after that you are done(recommended) for maybe half an hour so it will dry up the excess steam and water that has been accumulated while steaming/sauna-ing
Finn here:
The saunas are let to dry properly. The wood is impregnated with parafin oil regularly to ensure that nothing goes in to the grain of the wood. Then you also wash the sauna after use and properly regularly and you let it dry and keep it dry when not in use.
However here is the thing: They do rot away slowly, you have to do maintenance of them. When you see rot or decay, you have to take action and remove it to preserve the overall structure.
The sauna gets dry and cool in between uses. Rot and mold requires extended periods of warm and moist conditions.
Also saunas typically get hot enough to destroy some of the microbes. While the sauna is being heated it is not wet, in fact it is very hot and dry before you start throwing water on the stones.
Saunas should actually be really dry. The humidity is generally around 5-10% with some saunas going to 20%. Any higher will literally start to cook you as humid air conducts heat way better into your body.
The water splashes on the heating element are done to temporary raise the humidity a bit, so the sauna will start to feel hotter (due to the increase in heat conductivity). These spikes in humidity are generally not long enough to let moisture soak in the wood.
There is not extreme moisture in a sauna. It is very dry. That’s the fundamental behind it, very hot dry air makes you sweat. A steam room is made of tile because it would rot if it were wood. Tile breathes.
Humidity is not even that high. Its up to 100 Celsius in there, no amount of water will create significant relative humidity to hurt wood. Bacteria and mold are killed at that temperature, so they can not damage the wood either.
You don’t need to make saunas out of cedar like others claim. In fact, most saunas aren’t. Reckon the discrepancy in answers here is because non-Scandinavians tend to think of any sufficiently hot room as a sauna, which is simply not true. Many varieties of wood will do, including very basic ones like pine and fir, though deciduous trees are generally favored because conifers may emit resin.
The real answer is that it’s all about proper ventilation design, wood treatment (waterproof sealant), and regular maintenance. If you skimp on any of these three, a sauna very well can, and will, rot or get moldy.
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