In a flat, permission and outdoor-unit location often decide what is possible before equipment choice does. Tenants and leaseholders should obtain written landlord or freeholder consent and check planning requirements before any fixed split installation. Portable exhaust-hose products avoid refrigerant pipework through communal fabric, but still need a safe window arrangement and can be noisy. Passive cooling should be addressed first.
Start with the building and lease
External walls, roofs, balconies and windows may be demised or controlled differently under the lease. Drilling through a wall, placing equipment on a balcony or altering a window can require consent even where planning permission is not needed.
Ask the managing agent or freeholder what information is required. A useful proposal includes model details, indoor and outdoor positions, pipe and drain routes, fixings, electrical arrangements, visual impact and noise information.
Use passive cooling without creating new risks
Manage blinds before direct sun reaches the room, reduce appliance heat and ventilate when outside conditions are favourable. External shading may need consent because it changes the facade.
Window opening must account for falls, security, traffic noise and outdoor air quality. Do not prop open fire doors or interfere with smoke-control and communal ventilation systems to move cooler air.
- Check lease and tenancy clauses in writing.
- Keep fire and ventilation systems unaltered.
- Consider traffic noise and pollution before night ventilation.
- Coordinate any facade change with the building manager.
Portable options and their limits
A portable air conditioner rejects heat through a hose. Sliding or sash windows may accept a removable panel, but the arrangement must be stable, secure and consistent with product instructions. Warm air leaking around the opening reduces performance.
The compressor remains indoors, which matters in compact flats. Condensate handling varies by product. Never direct water over a balcony or create a hazard for people below.
Fixed split systems in shared buildings
A fixed split can be quieter indoors, but the condenser cannot simply be put in a communal corridor, enclosed balcony or service cupboard. It needs suitable outside airflow, maintenance access and an approved location that avoids noise and vibration nuisance.
Planning controls can be more restrictive for flats than householders expect, and permitted development provisions have conditions and limitations. Obtain project-specific advice and use qualified contractors. Agree who owns and maintains the installation before work begins.
Frequently asked questions
Can I put an outdoor unit on my balcony?
Only if the leaseholder or tenant has the necessary consents, planning requirements are satisfied, and the location meets airflow, access, structural, drainage and noise needs. A balcony is not automatically suitable.
Do I need freeholder consent if planning permission is not required?
You may. Planning status and private property consent are separate. Check the lease and obtain written approval before altering the building.
Can a portable unit exhaust into a communal hallway?
No. Heat and moisture should be rejected outdoors through the arrangement specified by the manufacturer, not into another internal or communal space.
What if the building has no acceptable condenser location?
Focus on shading, glazing management, lower internal gains, safe ventilation, fans and a suitable portable option. Do not force a split installation into an enclosed or unauthorised space.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.