What does building a sauna depend on?

First variable: volume

Everything starts from the cubic metres of the room. Volume sets the heater's rating — roughly a kilowatt per cubic metre — and the rating decides whether an ordinary supply is enough or a dedicated circuit and heavier cable are needed.^[1]

Which leads to something that surprises people: a few extra cubic metres can move the whole electrical job into another class. A small sauna and a slightly larger one are not linear in price.

Nor is it worth adding volume for safety's sake. A large sauna heats more slowly, uses more, and feels empty with two people in it.

Second variable: new space or conversion

Converting an existing room and building a new one are different jobs. In a conversion the walls, floor and drainage are already there, but they were built for something else; often most of the work is taking them out.

In a new space nothing is ready, but nothing is wrong either. It is usually more expensive and more predictable; a conversion is cheaper and more prone to surprises.

A third option is a separate building — a garden or lakeside sauna. Then foundations, a flue and possibly a permit come into it, and the work is closer to a small construction project than to a renovation.

Third variable: the heater and what it requires

An electric heater needs an adequate supply and installation by an electrician. A wood-burning stove needs no electricity at all, but it needs a flue — and a flue is structure, not equipment.^[1]

The choice is not only taste. In a block of flats a wood stove is usually not an option. At a cottage with limited electricity it may be the only sensible one.

The heater's installation instructions also set minimum clearances to walls, benches and everything around it. Those figures affect how large the room has to be, so the heater is worth choosing before the benches are drawn.^[1]

Fourth and fifth: ventilation and materials

Ventilation is not finishing work. The inlet and outlet are designed at the same time as the walls, because they pass through the structure. Added afterwards, the same thing is demolition.

With materials, price and experience travel together: panelling, benches and floor are the three where the choice shows and is felt every time. The cheapest panelling and the dearest do not cost the same and do not feel the same when hot.

This page gives no rates per square metre. Material prices move with the season, the supplier and the quantity, and a figure that was right here today would be wrong by spring.

Permits are decided by the municipality

Whether a permit is needed depends on what you are building and where. A change inside a dwelling, a separate building in a garden and a sauna on a shoreline are three different cases.

The answer comes from your own municipality's building control, and cannot be read off any general page — including this one. Distances to boundaries and to the shoreline are set locally.