Outdoor saunas have become one of the most popular garden projects in Cornwall. After a sea swim, a surf or a wet winter walk, there's not much better than warming up in your own sauna. But a sauna is a building that gets very hot, sits outside all year and often needs power or a flue, so a bit of planning goes a long way. This guide covers the rules, choosing a spot, the base, heaters and what affects the cost.
Do I need planning permission for an outdoor sauna?
In many cases a garden sauna can be built under permitted development as an outbuilding, provided it's for use incidental to the house. As general guidance, the main limits for houses in England are:
It must not be in front of the main front wall of the house.
It should be single storey, with a maximum eaves height of 2.5 metres.
Overall height is limited to 4 metres with a dual-pitched roof or 3 metres otherwise, reduced to 2.5 metres if it's within 2 metres of a boundary.
Outbuildings and extensions together must not cover more than half the garden.
Tighter rules can apply in the Cornwall National Landscape (AONB), in conservation areas and at listed buildings, and flats and holiday lets with restrictive conditions are different again. Our guide to building in an AONB or conservation area explains more. If you're unsure, check with Cornwall Council before you buy or build.
Building Regulations and safety
A small detached outbuilding often falls outside Building Regulations, but parts of the work usually don't:
Electric heaters need a dedicated circuit installed and certified by a qualified electrician.
Wood-fired stoves need a correctly installed flue with safe clearances to timber and a suitable hearth.
Siting matters for fire safety, especially near boundaries, hedges and other buildings.
A sauna for business use, such as at a holiday let, may raise extra planning, licensing and insurance questions.
Choosing the right spot
A good location makes a sauna more enjoyable and longer-lasting. Things to think about:
Shelter. Cornwall's coastal winds can strip heat from a sauna and drive rain into doors and joints. A sheltered spot or a windbreak helps.
Drainage. Avoid low, boggy ground. Water needs to drain away from the base.
Access. A short, well-lit, non-slip path from the house matters in winter.
Privacy and views. Think about neighbours and where you'll want to sit and cool off.
Services. The distance to your consumer unit affects the cost of running power.
Getting the base right
Most problems with garden saunas start at ground level. The sauna needs a level, solid, well-drained base. Common options are a concrete slab, a timber frame on ground screws, or a paved or gravel pad with suitable supports. On sloping Cornish gardens, some groundwork or a retaining structure may be needed first. Our groundworks and foundations team can prepare bases for outbuildings of all kinds.
Types of sauna and heaters
Barrel saunas
The classic curved design. Compact, quick to heat and popular as a self-contained garden feature.
Cabin and bespoke saunas
Square or rectangular buildings, sometimes with a changing area or shower. These can be designed to match the house or combined with a home gym or garden office.
Electric or wood-fired?
Electric heaters are convenient and controllable. Wood-fired heaters give a traditional feel and work off-grid but need a flue, a fuel store and more care with fire safety.
Dealing with coastal weather
Salt air and wind-driven rain are hard on timber and metal. Choosing durable timber, protecting it with a suitable exterior finish, using stainless steel or coated fixings, and keeping roof coverings in good condition all help a sauna last.
How much does an outdoor sauna cost in Cornwall?
As general guidance only, a simple barrel sauna kit can start from a few thousand pounds, while a larger cabin or a fully bespoke sauna building with a changing area can run well into five figures. On top of the sauna itself, budget for the base, electrics or flue, any paths or lighting, and delivery and access. Narrow lanes and steep gardens can add to installation costs. The only reliable figure is a quote for your site.
Outdoor sauna FAQs
How long does it take to install a garden sauna?
A kit on a ready base can go up in a few days. A bespoke building with groundworks and electrics usually takes longer.
Can I put a sauna near my boundary?
Usually yes, but height limits are lower within 2 metres of a boundary, and you should think about fire safety and neighbours.
Does a sauna need a cold plunge or shower?
Not necessarily, but many people add one. Plan water supply and drainage at the start if you might want one.
Ready to plan your sauna?
We design and build outdoor saunas in Cornwall, including the base, power and finishing. Call Cornish Building Company on 01208 816991 or send us a message.
