Air conditioning in a flat: consent, planning and where the unit goes

The short answerMost flats can have heat-and-cool air conditioning. You usually need two things: written consent under your lease from the freeholder or managing agent, and either permitted development or planning permission for the outdoor unit. Then it comes down to finding a good spot for that unit.

Flats get hot. Heat rises through the building, top-floor flats sit under the roof, and many flats only have windows on one side, so there is no breeze through. The same heat-and-cool system we fit in houses works in a flat. It just needs more planning first. This page covers that part. It is general guidance for England, not legal advice about your lease.

Do I need my freeholder's permission for air conditioning?

In most leasehold flats, yes. The lease usually keeps the outside walls, the roof and the structure for the freeholder. Fitting air conditioning means a hole through an outside wall and an outdoor unit fixed to the building, so it normally needs written consent first. Some leases call this a licence for alterations.

• Read the alterations clause in your lease, or ask your managing agent what they need.
• Expect questions about the look, the noise, the hole through the wall and who maintains the unit.
• Ask about fees and timescales. Some freeholders charge a fee or want their own surveyor to look.
• Share of freehold? The other owners or the company directors usually decide together.

Fitting without consent can put you in breach of your lease, so we always suggest getting it in writing before the fitting day. If the wording of your lease is unclear, a solicitor is the right person to ask.

Planning

Do you need planning permission for air conditioning in a flat?

Since May 2025, a heat pump on a flat in England can be permitted development, so no application is needed, as long as it meets every condition. The limits for flats are tighter than for houses:

• One outdoor unit only, and no bigger than 0.6 cubic metres (a house is allowed 1.5).
• Noise: it must pass the MCS 020(a) calculation, 37 dB(A) at 1 metre from a neighbour's nearest door or window to a habitable room.
• Heat and cool: the rules cover heat pumps. A unit used only for cooling needs permission.
• Position: not on a pitched roof, not within 1 metre of the edge of a flat roof, and not on a road-facing wall in a conservation area.
• Listed buildings need listed building consent.

The one-unit limit is a good reason to look at a multi-split: one outdoor unit can run two to five indoor units, so a bedroom and a living room share one unit outside. Our planning permission guide explains the rules in full. Remember that planning and lease consent are separate. You may need both.

Where can the outdoor unit go on a flat?

This is usually the deciding question. The options, roughly from easiest to hardest:

• On a balcony or terrace that is yours under the lease, on a floor stand with room to breathe.
• On the ground for a ground-floor flat, or in a communal plant area if the building has one.
• On a wall bracket on an outside wall. On upper floors this needs access equipment, and every visit to service it will too.
• On a flat roof above, with the freeholder's consent and at least 1 metre back from the edge.

Pipes can run a fair distance, within limits set by each manufacturer, and we plan the route against them. Some people ask about units with no outdoor unit at all. They are noisier in the room and need two large holes in the wall, so they still need consent. We will tell you honestly if one makes sense for your flat.

Keeping the noise down in a flat

Neighbours are closer in a flat, above, below and beside you. We keep the outdoor unit away from other people's bedroom windows, fit it on anti-vibration mounts, and never bracket it to a wall that backs onto a neighbour's bedroom. Indoors, the units we fit are quiet on low fan, so they suit a bedroom as well as a living room. More on that on our bedroom air conditioning page.