Hot tub

What the system works out

You enter the tub's inner diameter, liner depth and material, the stove (external or built-in), the base and where the water is drained. The system works out:

- the water volume and how long the stove takes to heat it from 10 to 37 °C;

- the base around the tub: paving on gravel, gravel or a timber deck;

- a non-combustible stove base, a spark arrester and the drain pipe;

- labour hours: the base and the chimney.

Is it a structure

A hot tub without a roof is a structure only when K = S × H³ ≥ 10 (STR 1.01.03 p. 30). A typical Ø 2 m tub has K of about 3, so no construction documents are needed.

Stove, base and water

- Solid-fuel outdoor stoves may be used no closer than 6 m to buildings (BGST p. 25). 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 weighs about 2 tonnes (5.7–7 kN/m²). A timber deck under it must be designed by an engineer.

- Water without chemicals may be drained on your own plot, but not onto the neighbours'. If chlorine is used, the discharged water may contain no more than 0.1 mg/l.

- In frost, drain the water from the stove.