Short answer: Before fitting air conditioning in a flat, check your lease and get written consent from the freeholder or management company for anything fixed to or through the outside of the building. In England, permitted development allows only one outdoor unit of up to 0.6 m³ on a block of flats, so many installs need planning permission.
Your lease
Most leases reserve the external walls, roof and structure to the freeholder. Drilling through an external wall or fixing a unit outside usually needs consent.
Practical positions
Balconies are the most common outdoor unit location. Rear walls and flat roofs are alternatives where the freeholder allows and access is safe.
Renters
Tenants need the landlord's written agreement, and usually the freeholder's as well. A portable unit may be the only option on a short let.
Related services
Sources
More guides
- How much does air conditioning cost to install in the UK?
- How much does air conditioning cost to run?
- What size air conditioner do I need?
- Fixed split or portable air conditioning?
- Do you need planning permission for air conditioning?
- The £2,500 grant for air-to-air heat pumps explained
- F-gas rules: what homeowners need to know
- R32, R410A and R22: refrigerants explained
- Is air conditioning the same as a heat pump?
- What happens on air conditioning installation day
- Air conditioning noise and your neighbours
- Looking after your air conditioning: an owner's checklist
- Can you fit air conditioning in a listed building?
- Keeping a home cool in a heatwave
- Multi-split or separate single systems?
Reviewed October 2026. Rules and prices change; check the date and ask us if anything is unclear.