Hot Tub Bases
Poured to manufacturer spec.
A 6-person hot tub weighs 2.5 tonnes filled. Our C28/35 reinforced slab is rated well beyond any domestic spa, and keeps your warranty valid.
The Mix You Need
C28/35 Reinforced Slab
- Mix grade
- C28/35
- Slump
- 75mm (workable)
- Aggregate
- 20mm
- Recommended depth
- 150mm
- Reinforcement
- A142 mesh (mandatory)
- Sub-base
- 150mm Type 1 MOT, fully compacted
Volume Guide
How much concrete for your hot tub?
Based on a 150mm slab. Always check your manufacturer's footprint, add 100mm to each side for a safe margin.
2-person hot tub
2.0m × 2.0m
~1,200 kg filled
4-person hot tub
2.2m × 2.2m
~1,800 kg filled
6-person hot tub
2.5m × 2.5m
~2,500 kg filled
8-person swim spa
4.0m × 2.3m
~4,500 kg filled
Why It Matters
Get this right and you won't redo it for 30 years
- A full 6-person hot tub weighs 2,500kg+ with water and people, that's three and a half cars sat on one spot of your garden.
- Hot tub manufacturers void the warranty if the base moves or cracks. A proper C28/35 slab with mesh keeps you covered.
- Paving slabs, decking, or a DIY concrete bag mix will not cut it. The tub needs a continuous, engineered slab, full stop.
- A 150mm slab with A142 mesh handles any domestic hot tub on the UK market, one pour and you're done for good.
Step by Step
How to prepare & pour
Check manufacturer's spec
Every hot tub supplier publishes a base requirement. Most specify 100-150mm of reinforced concrete. Use the higher of their spec or ours, 150mm with A142 mesh covers all domestic tubs.
Dig & compact
Excavate 300mm deep across a footprint 100mm wider than the tub on each side. Fill with 150mm of Type 1 MOT and whacker-plate in layers until it rings solid.
DPM & formwork
Lay 1200-gauge DPM with 150mm overlaps. Build formwork to finished level, get it dead-level because the tub sits directly on the slab.
Mesh on spacers
A142 steel mesh on 50mm plastic spacers, never lay it on the DPM. Overlap sheets by 300mm and tie with wire. The mesh must sit in the lower third of the slab.
Pour & finish
Pour C28/35 at 150mm. Tamp with a straight-edge, then float for a flat, smooth surface. No brushed or textured finish, flat means the tub sits true.
Cure before delivery
Wait 7 days minimum before the tub is delivered. 14 days is safer if the tub is being craned in, ask your supplier about the placement method.
FAQ
Common questions
Do I really need 150mm?
For anything above a 2-person tub, yes. A filled 6-person hot tub is a 2.5-tonne point load. 150mm with A142 mesh is the UK industry standard and every reputable hot tub manufacturer will ask for it.
Can I put the hot tub on paving slabs?
No. Slabs rock, crack, and channel point-loads through to unprepared ground underneath. Your hot tub supplier will void the warranty if they see it on paving. Concrete slab is the only supported base.
Can I pour it myself without mesh?
You can, but you shouldn't. A142 mesh costs around £40 for a 4.8×2.4m sheet and stops the slab cracking under cyclical loads (people climbing in and out). It's not worth the risk.
How far from my house should the hot tub be?
Check building regs if it's near a boundary or a combustible wall, but 1m from any structure is a good rule of thumb. Leave access to the equipment bay, usually one side.
Can you deliver if my garden is round the back?
Yes. We pour direct from the mixer where access allows (barrows up to ~30m). For tight gardens we arrange a concrete pump that can reach over a house. Call 024 7636 1448 for a pumped quote.
How long before I can fill the tub?
The slab is walk-on hard after 24 hours but wait 7 days before the tub is placed and 14 days before it's filled. Full cure is 28 days, by that point it's bombproof.
Ready to order?
Instant price in 60 seconds. Next-day delivery subject to availability. With volumetric, pay only for what's poured.