ᐅ Appropriate and Proportional Base for a Small Hot Tub

Hello everyone,

I would like to place a hard-shell whirlpool (not inflatable or similar) in my garden on an area currently covered with lawn (not recessed).

Base dimensions: 210cm x 160cm (83 x 63 inches)
Filled weight: 960 kg (2,116 lbs)
Surface load including people: 360 kg/m² (74 lbs/ft²)

Now, I have a question about the suitable subfloor. Pouring a 10cm (4 inches) concrete slab might be a bit excessive, right? Additionally, I would like to add XPS insulation panels between the subfloor and the whirlpool for thermal decoupling. These panels also help distribute the load slightly and compensate for minor unevenness.

The crucial question: What kind of subfloor should go under the XPS panels? Does it have to be concrete (if so, what kind of setup), or would well-compacted gravel be sufficient (if so, in what configuration) to then lay the XPS panels on top?

I would appreciate any guidance or advice!

Best regards

I installed XPS boards on top of the split, so my pool holds up without any problems. What you should consider more carefully is the edge—make sure there is a clear separation between the pool and the lawn or terrace.

Thank you for the feedback! Which size of gravel and base layer thickness should I choose? Around this area, a small planting bed with lava mulch will be created, then a standard garden edging will separate it from the lawn.

The question is how to border the gravel base from the lava mulch area to prevent sideways displacement. At the point where I would need to set edging stones with a concrete backing, it might be easier to just pour a full concrete foundation for the small area, right?