How we built the Forge Indoor.

A real stone heater, from Harvia.

The Forge Indoor runs on a Harvia Vega Compact 3.5kW, a stone heater from the Finnish brand. It warms a tray of sauna stones, the stones heat the air, and the air heats you. That is traditional sauna, the way it has always worked.

It reaches 170°F in about 25 minutes and goes up to 200°F. Two knobs on the front run it: a thermostat for the heat you want, and a timer that runs up to an hour at a turn.

Pour a ladle of water over the stones and you get löyly (say “lur-loo”), the burst of steam when water hits the stones. It is the soft wave of heat Finnish saunas are known for. The bucket and ladle come in the crate.

Every Forge Indoor heats with real stones.

Canadian Hemlock, inside and out.

Inside, the Hemlock is left natural: light toned, low resin and low odor, so the cabin smells like warm wood and nothing else. Outside, the same Hemlock is painted black.

• Bench with an S-shaped backrest. 2'2" high, 1'9" deep.
• Slatted wood floor for drainage and comfort.
• Louvered side panel for built-in airflow.

A full-length glass door. Light in any color.

The door is tempered glass, 65 by 24 inches, in a black frame with black hinges and handle. It shows off the Hemlock and keeps the cabin from feeling closed in.

An RGB LED strip runs under the bench and overhead. Warm white on a normal night, or pick a color for the room.

It fits where a fridge fits.

Outside, the Forge Indoor is 6'7" tall, 3'7" wide and 3'6" deep, so it fits under a standard 8 ft ceiling. Inside, you get 6'1" of headroom.