Air Conditioning for Flats

Flats can get very warm. Top-floor flats sit under the roof, many have large windows, and some only have windows on one side, so there is little cross-breeze. Air conditioning is often possible in a flat, but there are more permissions to check than in a house, and the outdoor unit needs more thought.

Can You Install Air Conditioning in a Flat?

Often, yes. Two things decide it: permission from the owner of the building, and a suitable place for the outdoor unit. Where an outdoor unit is not possible, there are other options, each with trade-offs.

The Permissions You Need

Your lease and the freeholder

If you own a leasehold flat, the outside walls, roof and shared areas usually belong to the freeholder. Leases usually require the freeholder's written consent before you drill through an outside wall or fix anything to it. Check your lease first, then ask the freeholder or managing agent before you book an installation. Some blocks also have their own rules about where outdoor units can go.

If you rent

You need your landlord's written permission for any fixed installation.

Planning permission

In England, permitted development rules allow only one outdoor unit on a whole block of flats without planning permission. It must be no larger than 0.6 cubic metres and meet the MCS 020(a) noise standard. It must not be on a pitched roof and, on a flat roof, must be at least 1 metre from the edge. Extra limits apply in conservation areas and on walls facing a road.

If another flat in the block already has an outdoor unit, or yours cannot meet these limits, planning permission is likely to be needed, so check with your council before you commit. Listed buildings also need listed building consent. Our planning permission guide explains the rules in more detail.

Where Can the Outdoor Unit Go?

• On a balcony or terrace, on the floor or a low bracket, with enough space around it for airflow.

• On a flat roof, with the freeholder's consent and at least 1 metre from the edge.

• On an outside wall, on a bracket. On upper floors this may need scaffolding or a powered access platform to install and service safely, which adds to the cost.

• At ground level, in a garden, yard or shared area, with consent. Many wall units allow up to 20 metres of pipework between the indoor and outdoor units.

Wherever it goes, we position the outdoor unit with your neighbours in mind, away from their windows where possible. See our guide to air conditioning outdoor units.

Options Without an Outdoor Unit

• Through-wall units put everything in one indoor unit, with two holes through the outside wall. There is no outdoor unit, but they are louder and less powerful than a split system.

• Water-cooled units use a water supply and a drain instead of an outdoor unit. They start from £5,000 and are expensive to run, so they are usually the option of last resort.

• Portable units need no installation, but they are noisy and much less effective. See do portable air conditioners work?

Our guide to air conditioning without an outdoor unit compares these options in detail.

Noise and Neighbours

In a block of flats, neighbours are close above, below and beside you. Indoor units are very quiet, but the outdoor unit holds the compressor and main fan, so its position matters. Installations under permitted development must meet the MCS 020(a) noise standard, which sets a limit of 42 dB(A) at the nearest window of a neighbouring home. See the quietest air conditioners.

Drainage

Air conditioning produces water when it cools, and the outdoor unit produces water when it heats and defrosts. In a flat, that water must drain somewhere suitable, not onto a balcony below or a shared path. Where there is no natural fall, a small pump lifts the water to a suitable drain.

What Does It Cost?

As a guide, one room typically starts from around £2,500 and multi-room systems usually range from £5,000 to £10,000+. Access equipment for upper floors and long pipe runs can add to the cost. We give you a clear written quote after a free survey.

What to Do Next

1. Check your lease and speak to your freeholder or managing agent.

2. Book a free survey. We will measure the rooms, look at where the outdoor unit could go and give you a written quote. We can provide the details your freeholder or council will ask for.

3. Get written consent from the freeholder, and planning permission if it is needed, before the installation goes ahead.

Frequently Asked Questions

Can I put an air conditioning unit on my balcony?

Often, yes, with the freeholder's consent. The outdoor unit needs space around it for airflow, a safe way to drain water and a position that does not disturb your neighbours.

Do I need my neighbours' permission?

Not usually. If planning permission is needed, the council may notify your neighbours as part of the application. It is good practice to talk to them about where the outdoor unit will go.

Can I install air conditioning in a rented flat?

Only with your landlord's written permission. If permission is not given, a portable unit is the main alternative.

What about a top-floor or loft flat?

Rooms under the roof are often the hottest and may need a larger unit. Our guide to loft conversion air conditioning explains the options.

Call 01772 288651 or use the form below to book a free survey. We will measure the room, recommend the right system and give you a clear written quote.

Last updated: November 2026.