The short answer
In a flat or leasehold home, fitting air conditioning usually needs written consent from the freeholder under the lease, and the planning rules for flats differ from those for houses. Freeholder consent and planning are separate questions.
On this page
A flat shares its walls, roof and outside space with other homes, and the parts of the building an air conditioning system touches often aren't yours alone. That's why flats usually involve more permissions than houses. The lease usually matters as much as the planning rules, and the two work independently.
Planning rules for flats
In England, the permitted development conditions for heat pumps on houses, set out in Do you need planning permission?, don't simply carry over to flats. Flats follow different rules, so check with the local council before assuming an outdoor unit can go up without planning permission.
The same applies if the building is listed or in a conservation area, where the rules are stricter again. Wales, Scotland and Northern Ireland set their own planning rules.
What the lease says
Most leases say something about alterations. Some ban alterations to the structure or outside of the building outright. Others allow them with the freeholder's written consent, which is sometimes called a licence for alterations.
It also matters what the lease says you own. In many leases the external walls, roof and shared areas belong to the freeholder, even though they enclose your flat. An outdoor unit on an outside wall, or pipework through it, then involves someone else's property.
Things to look for in a lease:
- any clause about alterations, additions or fixing things to the building
- which parts of the building are included in your flat, such as a balcony
- rules about using shared areas like gardens, yards and roofs
- any rules about noise or nuisance to other residents
Freeholders and managing agents often have a set process for consent, which may ask for drawings, details of the equipment and the installer's information, and may involve a fee. A solicitor can explain what a particular lease allows.
Written consent needs to be in place before work starts. Leasehold houses work the same way: the lease can restrict alterations just as it does for a flat.
Where the equipment could go
| Location | What to check |
|---|---|
| Outside wall | Usually the freeholder's; consent needed |
| Balcony | Whether the lease allows equipment there |
| Flat roof | Usually the freeholder's; safe access for servicing |
| Shared garden or yard | Consent, and neighbours' windows nearby |
Wherever the outdoor unit goes, the refrigerant pipes and the condensate drain need a route from the indoor unit, usually through an outside wall. In a block, neighbours' windows are often close by above, below and beside, so position and noise need particular care, and anti-vibration mounts help reduce vibration carrying through the structure.
Walls and floors between flats are designed to slow the spread of fire. Any hole through one of them has to be sealed properly afterwards, and the freeholder or managing agent may have their own requirements for work inside the building.
When an outdoor unit isn't possible
If the lease or the building rules out an outdoor unit, other types of system are sometimes an option.
- Portable air conditioners stand in the room and vent warm air through a hose, usually out of a window. They don't alter the building, though a window kit that's screwed or drilled into a frame is an alteration. Portable air conditioners covers how they work and their trade-offs.
- Through-the-wall units have no outdoor unit but usually need two large holes through an outside wall, so the same lease and consent questions apply. Through-the-wall units without an outdoor unit explains them.
Scotland, and selling later
Property law in Scotland is different. Flats there usually aren't leasehold: they're owned outright, and the title deeds set out the rules for shared parts of the building, such as external walls and roofs.
Wherever you live, keep the written consent with the rest of the system's paperwork. A buyer's solicitor is likely to ask for evidence that alterations were approved, as covered in Selling a home with air conditioning.
Related guides
- Do you need planning permission?Usually not in England, where air-to-air heat pumps that aren't used only for cooling count as permitted development if conditions on number, size, position and noise are met. Listed buildings, flats and protected areas follow different rules.
- Air conditioning in rented homesTenants usually need the landlord's written permission before fitting fixed air conditioning, and a flat's landlord may need the freeholder's consent too. Portable units usually don't need permission, as long as nothing is drilled or altered.
- Noise rules and your neighboursIn England, a heat pump fitted without planning permission must be no louder than 37 dB(A) at 1 metre from a neighbour's nearest habitable-room window or door, worked out with the MCS 020(a) calculation. Councils can also investigate noise complaints separately.
- Portable air conditionersA portable air conditioner is a self-contained unit on wheels that cools a room and sends the heat outside through a hose, usually out of a window. It needs no professional installation, but it is noisier and less effective than a fixed split system.