Garden sauna base options UK 2026: concrete, paving, timber or ground screws?

What the base has to do

Sauna retailers all ask for a firm, level base. Polar Recovery says the base for its 3–5 person Sauna Cube must support 1,000kg in total (the structure plus an allowance for people), and lists concrete, paving slabs, tiles, patio decking or reinforced gravel as suitable if the surface is level, stable and weather-resistant. It warns against slopes and places where water collects. Its warranty excludes damage from installation on uneven or unprepared foundations, so the base matters for the warranty too.

A Derby groundworker, Tradesmart, recommends keeping a garden building base 100–150mm above the surrounding ground, so rain runs away rather than pooling against the timber.

The options compared

Base	Published price	Good for	Watch out for
Concrete slab	£60–£80/m² laid; 2 × 3m £500–£600; 3 × 4m £800–£1,000 (JobPrices, 2026). Reinforced £90–£140/m² (Tradesmart, 2026)	Most saunas, heavy cubes, long life	Access for a mixer or pump; spoil to remove
Paving slabs	£45–£75/m²; about £340–£560 for 3 × 2.5m (Tradesmart)	Lighter saunas on firm, well-drained ground	Must be laid on a proper sub-base and checked level
Timber bearer base	£40–£70/m² (Tradesmart)	Light buildings on level ground	Rot, and whether it’s rated for about 1,000kg
Ground screws plus frame	£1,200–£2,800 for a typical garden room (Tradesmart); £1,260–£3,000 installed for a 6 × 3m structure (Checkatrade, 2024); DIY screws and tool hire £450–£550	Slopes, tree roots, poor access, no digging	Load rating of screws and frame; stony ground
Existing patio	£0 if it’s sound	Saunas on a strong, level patio	Cracks, slope and drainage falls

Concrete slab

The default for a heavy garden sauna. JobPrices (checked 5 November 2026) puts a laid concrete base at about £60–£80 per m², or £500–£600 for 2 × 3m and £800–£1,000 for 3 × 4m. Tradesmart quotes £90–£140 per m² for a reinforced slab. Extras can include a skip (£230–£350) or a concrete pump (£250–£400) where a mixer can’t reach. Checkatrade’s shed base guide gives £500–£750 for a 6 × 4ft concrete base and £1,000–£1,500 for 12 × 8ft.

Paving slabs

Tradesmart quotes £45–£75 per m² for a paving slab base, or about £340–£560 for 3 × 2.5m. Paving can work for lighter saunas if it’s laid on a compacted sub-base and stays level. Check the sauna maker accepts slabs; Polar Recovery does for its Cube.

Ground screws

Steel screws are driven into the ground, typically 800mm–1.5m deep according to Tradesmart, and a timber or steel frame sits on top. There’s no digging and little mess, which helps on slopes, near tree roots or where access is tight. Tradesmart quotes £1,200–£2,800 for a typical garden room. Checkatrade’s guide (cost table last updated May 2024) gives £1,260–£3,000 for ground screws with installation under a 6 × 3m non-load-bearing structure, averaging £1,875, or £450–£550 for the screws plus tool hire if you DIY.

For a DIY kit, B&Q’s website lists the Shire Gorilla 8-screw kit with frame for £1,064, sold and shipped by Dagless Limited (online only). It’s designed for sheds from 8 × 6ft to 10 × 10ft. Check its load rating and the frame’s bearing points against your sauna before you buy.

Before you pour or screw

1. Get the loaded weight from the sauna retailer, and the footprint including any terrace or porch.
2. Check access. Some saunas arrive by crane or forklift (Steam & Oak’s Ruutu 200) or tail-lift lorry and pump truck (Polar Recovery’s Cube), which affects where the base can go.
3. Plan the cable route. If your sauna is electric, ask the electrician whether to lay a duct before the base goes down. See sauna electrical requirements.
4. Keep it low. In England, a raised platform over 0.3m takes an outbuilding out of permitted development. See planning permission.

For the full budget, including base, electrics and assembly, see garden sauna costs or try the sauna cost calculator.