A hot tub needs a flat, level, solid base that can carry its full weight, typically 1.5–2.5 tonnes when filled with water and people. A reinforced concrete slab around 100–150 mm thick is the best option. Well-laid paving slabs and properly engineered decking also work. Grass, gravel alone or loose slabs do not.
Hot tub base options compared
| Base | Pros | Cons |
|---|---|---|
| Concrete slab | Strongest and longest-lasting | Needs curing time; permanent |
| Paving slabs | Looks good, often already in place | Must be level and on a solid sub-base |
| Decking | Can sink the tub flush for easy access | Must be designed for the load |
| Spa pad / interlocking base | Quick, no concrete | Best for inflatables and small tubs on firm ground |
Base size and preparation
- Make the base at least as big as the tub, ideally a little larger.
- Check it is level in both directions with a long spirit level.
- Think about drainage so rain does not pool under the cabinet.
- Leave room for the cover lifter and steps.
Irish garden tips
Wet winters mean soft ground. Never put a hard-shell tub straight onto grass or soil, and avoid low spots where water collects. If your garden slopes, a built-up slab or reinforced deck is the way to go.
More help: choosing a hot tub size and installation in Ireland.
Frequently asked questions
Can I put a hot tub on grass?
Not a hard-shell tub. Inflatable tubs need a level, protected surface too, ideally a pad on firm ground.
How thick should a hot tub concrete base be?
Typically 100–150 mm, reinforced, on a compacted sub-base.
Can a hot tub go on an existing patio?
Often yes, if the paving is level, well laid and not cracked or sinking.
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