An outdoor sauna in the UK works best built like a garden room: insulated, weatherproofed and with a sheltered place to change. Garden cubes and wood-fired saunas start at £12,995, excluding VAT and builders' work. Skip the changing space and it goes unused in winter.
Key takeaways
- In a British winter, a sheltered changing and cool-down space is what keeps an outdoor sauna in use.
- Three routes: quick-install cube or barrel (Aqua Spazio Cubo), off-grid wood-fired (Aqua Spazio Legna) or a fully bespoke garden-room sanctuary (Aqua Spazio Benessere).
- An existing garden shed can often be converted or replaced, as in our Holland Park, Hammersmith and Wandsworth projects.
- Outbuildings often fall under permitted development, but height and boundary limits apply; check with your local authority.
- Ventilation in an outdoor sauna is fairly straightforward, but it still needs designing.
Why do garden shed saunas fail?
We have seen our fair share of garden storage sheds that started life as a sauna. The pattern is familiar. A thin-walled cabin goes in at the end of the garden with no changing space, no shelter and no proper cool-down. In August it is a novelty. In January, walking across a wet lawn in a towel to a cold cabin that takes ages to heat loses its appeal, and the sauna slowly fills with garden furniture.
A garden-room approach fixes that. Think about the whole routine: where you undress, where you leave dry clothes, where you cool off between rounds, how you get back to the house. Then build the sauna inside a structure that handles British weather, with insulation and a vapour barrier just as you would have indoors.
What are the three ways to build an outdoor sauna?
Feature
Garden cube or barrel (Aqua Spazio Cubo)
Wood-fired (Aqua Spazio Legna)
Outdoor sanctuary (Aqua Spazio Benessere)
What it is
Quick-install barrel or box, door straight to the garden
Off-grid sauna with HARVIA M3 wood-fired heater
100% bespoke wellness complex
Heat
HARVIA Wall electric heater, 3–9kW
90–100°C+, 80–120kg of stones
Hybrid heating options; red light option
Base
No foundation; level pavers
Concrete base pre-cast on site
Bespoke
Timescale
Quick install
Delivery 2 weeks, build 2 weeks
Delivery 4 weeks, build 4 weeks
Price (ex VAT)
From £12,995
From £12,995
Price on application
Cube or barrel (Aqua Spazio Cubo). The fastest option, with walls typically 40–48mm thermo-wood or spruce and spruce cladding. A barrel shape reduces air volume by up to 23% compared with a square room, and a barrel takes 45–50 minutes to heat. We are honest that this format trades some comfort and efficiency for speed and simplicity.
Wood-fired (Aqua Spazio Legna). A HARVIA M3 heater with a stainless or black chimney, British Western Red Cedar outside, a metal-clad roof and Aspen or Alder inside. A wood-fired stove holds 80–120kg of stones compared with 20–40kg in a typical electric heater, so it retains heat for hours and suits long, social sessions. It needs a concrete base pre-cast on site and is best installed in dry weather.
Outdoor sanctuary (Aqua Spazio Benessere). The full garden-room approach. It has four elements: a hot zone with tiered seating and panoramic glass, a cold plunge right by the sauna exit, a weather-sealed transition anteroom for changing that acts as a thermal buffer, and a social lounge with terrace, deck or fire pit. Interiors are dark black thermo-ash contrasted with aspen benches.
What planning and building rules apply?
Many garden outbuildings in England fall under permitted development, but the limits are specific. According to the Planning Portal, an outbuilding must be single storey with a maximum eaves height of 2.5 metres and a maximum overall height of 4 metres with a dual-pitched roof, or 3 metres for other roofs. Within 2 metres of a boundary, the maximum height drops to 2.5 metres. Outbuildings cannot go forward of the principal elevation of the house, together they must not cover more than half the land around the original house, and listed buildings and designated land have tighter rules. Electrical work, including the supply to a sauna heater, must meet Part P of the Building Regulations. Always check with your local planning authority before you build.
How do you ventilate an outdoor sauna?
Ventilation in an outdoor sauna is fairly straightforward compared with a basement, because fresh air is right outside. It still needs to be designed: fresh air in, stale CO2-laden air out, and good circulation so the top bench is not scorching while your feet are cold. A sauna that feels stuffy will not get used, however beautiful the cladding.
What did we build in Holland Park?
Holland Park was our first outdoor sauna. The owner is a keen sauna user with a sauna in each of his homes. His town house was fully extended, so the only space was an existing garden storage shed. We kept the shed roof, reclad the outside in ready-painted black cladding and fitted a new door and window. Inside, Thermo Aspen is laid horizontally, and a glass front and door connect the sauna to a cold water shower for cooling off after a session. Colour-changing ambient lighting runs on a separate controller, and the heater is a HUUM CLIFF with Wi-Fi control.
For a larger example of the garden-room approach, our Wandsworth project replaced an old shed sauna and added a matching changing and storage area, with the ceiling outside the sauna finished in the same timber.
FAQs
How much does an outdoor sauna cost in the UK?
Our quick-install garden cube (Aqua Spazio Cubo) and wood-fired sauna (Aqua Spazio Legna) cost from £12,995 fully installed. Prices exclude VAT and builders' work.
Do I need planning permission for an outdoor sauna?
Often not, if the building meets permitted development rules for outbuildings in England, such as a 2.5m maximum height within 2 metres of a boundary. Listed buildings, designated land and anything forward of the house need permission. Check with your local planning authority.
Can I turn my garden shed into a sauna?
Often, yes. In Holland Park we converted an existing storage shed, keeping the roof and recladding the outside. In Hammersmith we converted a tiny shed using a compact HUUM DROP 4.5kW heater.
Is a wood-fired sauna a good idea in a London garden?
It can be, if you have the space for a chimney and a concrete base and are happy to tend a fire. A wood-fired sauna runs off-grid at 90–100°C+ and holds heat for hours. In a smoke control area, wood can only be burned in a Defra-exempt appliance, so ask your council whether your street is covered and check the stove's status before choosing one.
Why does an outdoor sauna need a changing area?
Because in winter nobody wants to undress in the rain. A sheltered changing and cool-down space makes the sauna practical all year, which is why our outdoor sanctuaries include a weather-sealed anteroom.
Talk to a sauna designer
Planning a garden sauna? Book a free design consultation, or email photographs and dimensions of your garden to info@saunacompany.co.uk for an initial assessment. See our outdoor sanctuary page.
Planning one for your own home? See our luxury outdoor saunas page for options and recent projects, or book a free design consultation and we'll talk through your space.
Sources
- Planning Portal: outbuildings, planning permission: permitted development height, boundary and curtilage limits.
- Planning Portal: Part P electrical safety: Building Regulations guidance on electrical work.
- GOV.UK: Smoke control areas, the rules: wood may only be burned in exempt (Defra-approved) appliances in smoke control areas; ask your council whether you are in one.