Birch & Berg

Trade

Saunas and cold plunges for holiday lets, gyms and studios (UK)

Adding a sauna or cold plunge to a holiday let, gym or studio? Safety signs, supervision, insurance, electrics, water hygiene, planning and a spec checklist.

By Birch & Berg. Last checked .

Short answer: once guests or customers use your sauna or cold plunge, it's part of your business, and health and safety law applies. Before you buy:

  1. assess the risks, and write down what you'll do about them;
  2. plan signs, rules and supervision;
  3. tell your insurer and check you're covered;
  4. use a registered electrician;
  5. set up a water-care routine for any plunge;
  6. ask your council whether you need planning permission.

This guide covers health and safety law in Great Britain, and building regulations, planning and fire guidance in England. Wales, Scotland and Northern Ireland have their own rules for some of these.

Holiday letGym or studio
Risk assessmentYes, covering guests (section 2)Yes, covering members and staff (section 2)
Fire risk assessmentYes, recorded (section 3)Yes, reviewed regularly (section 3)
ElectricsPart P and BS 7671 section 703 (section 5)Electricity at Work Regulations and BS 7671 section 703 (section 5)
Plunge waterMaker's routine, plus HSE's legionella duty (section 6)The same (section 6)
PlanningMay need permission for paying guests: ask the council (section 7)No householder rights: ask the council (section 7)

1. Why the rules change when it's a business

  • Employers must make sure, so far as is reasonably practicable, that people who aren't their employees, such as guests and customers, aren't exposed to risks to their health or safety. This is section 3 of the Health and Safety at Work etc. Act 1974.
  • Self-employed people have health and safety duties if they employ anyone, even temporarily, or if their work could put other people at risk. HSE's guide for the self-employed explains.
  • HSE's hot tub guidance shows where the line falls. A privately owned hot tub in a holiday park unit, used only by the owner, family and occasional guests with no financial gain, is outside the Act. Hot tubs a site owner rents out are part of its business.

In Northern Ireland, health and safety law is enforced by HSENI, the Health and Safety Executive for Northern Ireland.

2. Assess the risks

Employers must make a "suitable and sufficient" assessment of the risks to their employees and to people who aren't their employees. With five or more employees, you must record the significant findings. This comes from regulation 3 of the Management of Health and Safety at Work Regulations 1999.

Things to think about:

  • Sauna: the hot heater and stones, steam, fire, slips on wet floors, people using it alone, children, and people who've been drinking.
  • Cold plunge: cold water shock, slips on wet steps, children getting in, water hygiene (section 6), and electrics near water.
  • Both: how someone gets help in an emergency, and what happens at night or out of hours.

HSE's spa-pool guidance says the most immediate danger to hot tub users is accidental drowning after slipping or tripping. Plan for slips around a plunge too: non-slip steps and flooring, a handhold and good lighting.

Review the assessment whenever anything changes, such as new equipment, longer opening hours or more users.

3. Signs, rules and supervision

Signs. Put clear rules next to the sauna and the plunge, and in your welcome pack or induction. Start from the maker's safety warnings. HSE's example notice for hot tubs asks users to shower first; not to use the tub after a heavy meal, alcohol or sedatives; to seek medical advice if they're pregnant or have health problems; and to supervise all children. Adapted for a sauna and plunge, a sign might say:

  • Shower before use.
  • Don't use the sauna or plunge alone, after drinking alcohol, or if you feel unwell.
  • Cold water can cause cold water shock. Get in slowly and keep your first sessions short.
  • If you're pregnant, or have a heart condition, high blood pressure or any other medical condition, ask your GP before using.
  • Children must be supervised by an adult at all times. Follow the maker's minimum age, if it gives one.
  • Don't touch the heater or stones. Only put water on the stones, and only if the maker allows it.
  • Get out if you feel unwell.
  • Put the plunge lid back on and lock it after use.
  • In an emergency, call 999. Give the address and postcode on this sign.

Supervision.

  • Gyms and studios: decide in your risk assessment when the sauna and plunge are open, how often staff check them, and how someone on their own can call for help.
  • Holiday lets: you won't be there, so build the supervision in. Use a lockable lid, heater controls with a timer or automatic switch-off, and clear written instructions. Check everything at each changeover.

Fire.

  • Holiday lets (England): if you let to paying guests, you must carry out a fire risk assessment of the premises and record your findings, under the Regulatory Reform (Fire Safety) Order 2005. This includes self-catering lets. The Home Office guide asks you to consider the risks from heating in your property, so include the sauna heater or wood-burning stove. Wales has separate guidance, and Scotland and Northern Ireland have their own law.
  • Gyms and studios: the person responsible for business premises must carry out a fire risk assessment and review it regularly. Include the sauna.

4. Insurance

Tell your insurer before you install anything. Ask them to confirm in writing that your policy covers:

  • guests or customers using a sauna and a cold plunge;
  • the equipment itself, including damage and theft;
  • any conditions they attach, such as signs, inspections or supervision.

Don't assume a home insurance policy covers paying guests. If you employ staff, you usually need employers' liability insurance by law, with cover of at least £5 million.

Check the maker's warranty too. Make sure it covers commercial or rental use, because some warranties are for home use only.

5. Electrics

  • Holiday lets in England: Part P of the Building Regulations covers electrical work in homes, including gardens, garages and sheds. A holiday cottage or flat will usually count. A new circuit, such as one for a sauna heater or a new supply to the garden, is notifiable. So is adding to or altering a circuit in a room containing a sauna heater, which counts as a "special location". Use a registered electrician, who can self-certify the work. Our electrics guide has the detail.
  • Gyms and studios: the Building Regulations set standards for electrical installation work only in dwellings. Work in commercial buildings is covered by the Electricity at Work Regulations 1989. These require electrical systems to be built and maintained to prevent danger, so far as is reasonably practicable.
  • Everywhere: rooms and cabins containing sauna heaters have their own section of the UK wiring regulations, BS 7671 section 703. Use an electrician who knows it. Ask them how often to inspect and test the installation with heavy use.
  • Chillers: plug into a weatherproof, RCD-protected socket, never an extension lead, as the maker specifies.

6. Water hygiene for cold plunges

What HSE's hot tub guidance covers. HSE's guidance HSG282 is for spa pools: hot tubs, whirlpool spas and similar. It describes a spa pool as warm, agitated water, usually heated to 30–40°C, with air jets. It covers domestic-type hot tubs used in a business, for example in holiday park rentals and hotel rooms. A still, chilled cold plunge doesn't fit that description, and HSG282 doesn't mention cold plunges. So HSG282 isn't written for them.

What still applies. HSE says employers and those in control of premises must assess and manage legionella risks. HSE lists the conditions for a foreseeable legionella risk:

  • water between 20°C and 45°C;
  • water that's stored or recirculated;
  • breathable droplets, such as spray;
  • nutrients for the bacteria, such as rust, sludge, scale, organic matter and biofilms.

A chilled plunge normally runs below 20°C. But it stores and recirculates water, users add sweat and skin to it, and it can warm up if the chiller is off, fails or is set to heat. So include the plunge in your risk assessment. HSE says a simple risk assessment may show the risks are low and properly managed.

Our recommendation. Follow the maker's routine, and borrow HSE's principles:

  1. Use the sanitiser the maker approves, at the dose and test frequency it gives. Test more often with heavy use, and keep a written log.
  2. Clean or replace the filter on schedule.
  3. Ask the maker how often to change the water for your level of use. For comparison, HSE's guidance for hot tubs used in a business says to replace all the water each week, or after each group of users if that's sooner. It also says to check the pH and disinfectant at least twice a day, depending on the risk assessment and use. It's written for hot tubs, but it's a useful benchmark.
  4. Treat UV and ozone as extras alongside a sanitiser, not instead of one.
  5. Ask users to shower first, and keep the lid on between sessions.
  6. If the chiller stops or the water warms up, close the plunge and ask the maker what to do before reopening.

Our chiller guide explains filters, UV and ozone.

7. Planning permission (England)

  • Permitted development lets householders put up outbuildings, including sauna cabins, without a planning application, within set limits. The rights cover uses "incidental to the enjoyment of the dwellinghouse", and they apply to houses only, not to flats, maisonettes or other buildings.
  • A garden sauna that paying guests use, or that you rent out by the session, may not count as incidental. It may need planning permission.
  • Gyms and studios in commercial premises don't have these householder rights. A new outdoor sauna cabin or plunge area may need permission.
  • Ask your council's planning department before you buy. If you want written certainty, you can apply for a Lawful Development Certificate. It isn't compulsory.
  • Listed buildings, conservation areas and other designated land have extra limits (see our planning guide). Wales, Scotland and Northern Ireland have their own rules.

A chiller hums, so site it away from neighbours' windows. Our chiller guide explains.

8. Spec checklist for heavier use

  1. Commercial rating: if the maker offers a commercial-rated heater or chiller, choose it.
  2. Warranty: confirm it covers commercial or rental use.
  3. Controls: a heater timer or automatic switch-off, and controls that guests or members can't change.
  4. Lockable lid: on every plunge, locked whenever it's not in use.
  5. Water care: a chiller with filtration, and a sanitiser the maker approves. Ask about automatic dosing.
  6. Easy draining: a drain valve, and a plan for where the water goes, for frequent water changes.
  7. Safe access: non-slip steps and flooring, a handhold at the plunge, and lighting for evening use.
  8. Sauna door: a glass panel so you can see in, and a door that opens outwards and can't be locked.
  9. Thermometers: easy for users to read, in the sauna and the plunge.
  10. Power: the heater supply and chiller socket planned with your electrician (section 5).
  11. Signs: room for the rules beside each one (section 3).
  12. Finishes: surfaces that are quick to clean between users.

Trade enquiries

Birch & Berg takes trade enquiries from holiday lets, gyms, studios and other businesses. Email hello@birchandberg.co.uk and tell us about your premises, how many people will use the sauna or plunge, and when you need it.

FAQs

Does HSE's hot tub guidance (HSG282) apply to a cold plunge?
Not directly. HSG282 is written for warm spa pools and hot tubs. HSE's duty to assess and manage legionella risks still applies to employers and those in control of premises. So include the plunge in your risk assessment and follow the maker's water-care routine.

Do I need planning permission for a sauna at my holiday let?
Possibly. Permitted development covers outbuildings used incidentally to a house, and a sauna that paying guests use may not count. Ask your council before you buy.

Can I use a home sauna in my gym?
Ask the maker first. Heavy daily use may be outside what a home model and its warranty are designed for. If the maker offers a commercial-rated heater or chiller, choose it.

How do I supervise guests at a holiday let?
You can't be there, so reduce the risks by design: a lockable lid, heater timers, clear signs, safety information in the welcome pack and checks at each changeover. Your risk assessment sets out what's suitable.

General guidance for Great Britain (health and safety) and England (building regulations, planning and fire safety), checked on 29 September 2026. It isn't legal, insurance, electrical or medical advice. Check with your council, your insurer and a registered electrician, and always follow the maker's instructions.

Sources

Keep reading