Sauna

How it is calculated

In the generator a sauna is a building, so the frame, cladding, roof, insulation, windows and doors are calculated as for other buildings. The north part across the full width is the steam room, the rest is the dressing room, and the heater stands by the partition.

From the steam room dimensions the system calculates the volume, adds 1.2 m³ for every square metre of glass (Harvia rule for a glass door) and chooses a heater whose manufacturer range covers it. If no such model is in the catalogue, it does not make up a power rating; it warns instead. The bill of materials includes the heater with stones, an insulated chimney with pass-throughs, a spark arrestor, fire protection, steam room lining with vapour barrier, benches, a glass door and ventilation.

Heater and chimney

- At least 1,250 mm must remain in front of the firebox to any structure (KKŠT item 41). In a small sauna this is usually possible only when firing from the dressing room; the system checks it.

- The chimney must be at least 3 m above the bottom of the firebox. Its top depends on the distance to the ridge: within 1.5 m, 0.5 m above the ridge; 1.5–3 m, not below the ridge; further, not below a 10° line (KKŠT items 22, 24).

- Single-wall uninsulated chimneys are banned (item 28). An F_ROOF(t1) roof covering needs a spark arrestor (item 35).

- Non-combustible floor protection of at least 700×500 mm is required in front of the firebox (item 42).

- We have not yet read the electric heater installation requirements, so the system warns about them.

Permits and distances

- A sauna is an ancillary building: it may only be built as an accessory to a main building (house) (STR 1.01.03 Annex 1 row 9.1).

- Group I is up to 50 m² and 5 m, group II up to 80 m² and 8.5 m. A group II sauna in a city needs a permit.

- The distance to your own house on the same plot is not regulated; to a neighbour's buildings it is 10–15 m (Basic Fire Safety Requirements, item 93).

- Closer than 1 m to the plot boundary needs the neighbour's consent. Between 1 and 3 m it does too, if the building is higher than its distance to the boundary (STR 1.05.01 Annex 7 item 4).

Barrel sauna

In the generator a barrel sauna is a separate object: a horizontal barrel of 44 mm staves held by stainless steel bands, resting on cradles and blocks. The steam room with the heater is at the rear end, a glass door is at the front, and a dressing room can sit in front of the steam room.

The steam room volume is the circle area minus the part below the floor. For example, a 2 m long barrel 2.37 m in diameter has about 7.2 m³ of steam room, 8.8 m³ with the glass door, so a Harvia Legend 150 is chosen. When firing from the steam room, about 1.4 m remains in front of the firebox (≥ 1.25 m needed). The chimney exits through the rear wall and rises to 3.7 m above ground, because it must be ≥ 3 m above the firebox and ≥ 0.5 m above the barrel top.

- A barrel assembled in a factory and delivered may be treated as a product, not a structure. This is an assumption: we found no official interpretation. Assembled on site it is a sauna, i.e. a group I ancillary building (K ≈ 76).

- On the market 2–4 m barrel saunas cost about €2,200–5,100. The system's bill of materials prices the materials separately, so it may differ.

Barrel with a dressing room

With a dressing room the heater can be fired from it, and the chimney then rises through the roof next to the partition. The system checks that at least 1.25 m remains in front of the firebox in the dressing room and that the steam room is at least 1.5 m long.

Shapes and terrace

Besides the round barrel you can choose an oval (elliptical) or a square body with rounded corners. The calculation is the same, only the cross-section differs: a square body is wider at floor level, so it fits wider benches and has more volume. A square body is held by a frame, so there are no bands in its bill of materials.

A covered terrace is the body extended in front of the door: the door wall is set back and the terrace floor is level with the inside. K is calculated including the terrace.

The starting dimensions come from market offers: oval 2.4 × 2.5 m, square 2.43 × 2.42 m (with base).

Square sauna

A square 3.5 m sauna with a 1.4 m dressing room: the heater is fired from it and the chimney rises through the roof.

Mobile sauna on a trailer

The barrel can sit on a trailer. Instead of blocks and gravel the estimate then has a braked class O2 trailer (single axle up to 3.5 m, twin axle for longer), tie-down straps and registration at Regitra. The system checks:

- the width (up to 2.55 m on roads) and height above the road (up to 4 m) — if the chimney is taller, its top must be removed for transport;

- the mass: a sauna with a trailer is almost always over 750 kg, so the trailer is class O2, braked, with a roadworthiness test after 3 years and then every 2 years;

- the driving licence: a combination up to 3,500 kg — B, up to 4,250 kg — B with a test, heavier needs BE.

A trailer on its own wheels is treated as a vehicle, not a structure, but there is no official clarification. The sauna mass (about 300 kg per metre) is an assumption. If you do not give the trailer tare, the market median is used: 390 kg for a single-axle braked platform, 590 kg for a tandem. The exact figure is in the trailer registration certificate, so it is better to enter the maker's data.

Sauna with a hot tub (2 in 1)

A hot tub can be added on a deck beyond the door. The estimate includes a fibreglass or acrylic tub with an external or integrated stove, a base (deck, paving or gravel), a non-combustible stove base, a drain pipe and a spark arrestor. The system works out the water volume (about 1,080 l in a Ø 1.8 m tub) and the heating time (about 3 h).

- Solid-fuel domestic stoves may be used no closer than 6 m to buildings. Whether this covers a hot tub stove has not been officially clarified, so the system shows a warning rather than an error.

- A filled tub with people loads the deck at about 6–7 kN/m², so the joists under it must be designed by an engineer.

- Drain the water within your own plot; with chlorine, discharge limits apply.

Smoke sauna

A true smoke sauna without a chimney is not allowed in new construction: smoke must exit through a vertical flue, and firing with the stove door open is prohibited. Similar soft steam comes from a heat-storage stove with a chimney (e.g. Aito AK57 ST, for 9–20 m³ steam rooms, 130 kg of stones). The system picks it by steam room volume, adds a concrete pad under the stove, the chimney and longer installation, and reminds you of the maker's clearances to combustibles and more frequent flue cleaning. If you choose a smoke sauna without a chimney, the calculation stops with an explanation.