Where to put a hot tub and what goes underneath
Load capacity comes first
Work out the weight: volume in litres, plus about 80 kg per person, plus the empty weight of the tub.
- Tub for 2: 250-600 l → 500 to 900 kg
- Tub for 4: around 1 000 l → 1 200 to 1 400 kg
- Tub for 6: 1 300-1 700 l → 2 000 to 2 400 kg
That load is concentrated on 3 to 5 m². A timber deck of ordinary construction will not carry it, and slabs laid on sand settle unevenly, tipping the tub.
Which base works
A concrete slab 10 to 15 cm thick with reinforcing mesh, 20 cm larger than the tub’s footprint. The safest option, effectively a requirement for large models.
Paving on a compacted sub-base – 15 cm of gravel compacted in layers, then the laying course. Works up to around 1 200 kg.
A reinforced deck – only if it was built to carry 300 kg/m². Get that confirmed; it is not a given.
What does not work: bare soil, lawn, slabs laid loose on sand, a timber deck without reinforcement.
Access, water and distance
Access. The tub is delivered in one piece. We need a passage 20 cm wider than its diameter – so 240 cm for a 220 cm model. If that is impossible, a crane is needed, which costs extra.
Drainage. The tub is emptied from time to time, and that is 1 000 to 1 700 litres at once. Plan where the water will go – not against the house foundations and not onto the neighbour’s land.
Distance from the house. With a stove, allow clearance for sparks from the flue and for smoke. A tub with a stove does not belong under a bedroom window.
Trees. A tub under a deciduous tree means leaves in the water every autumn. The thermal cover only solves part of that.
Frequently asked questions
Does the base have to be perfectly level?
Yes, the tolerance is 5 mm per metre. A tub standing at an angle has the water higher on one side, which loads the structure and looks wrong.
Can the tub stand on a lawn?
No. It sinks unevenly, the wood rots in permanent damp and water collects underneath. Always a prepared base.
How far away can the electrical connection be?
For a whirlpool, as close as possible – a long supply means voltage drop. Sockets and distribution boards must not be closer than 2 m to the rim; that is a code requirement.