Can I install air conditioning in my flat?

The two permissions a flat needs, the planning rule most people have not heard of, and the practical limits on where the outdoor unit can go.

Shameet PatelDirector, NVK Air
  • REFCOM certified, REF1025662
  • Daikin registered installer

The short answer

Usually yes, but a flat needs two separate permissions. The first is from your freeholder or managing agent, because your lease almost certainly controls what can be fixed to the outside of the building. The second is planning. A system that heats as well as cools is permitted development on a block of flats, so no planning application is needed, but only for one heat pump per block. If another flat in your building already has an outdoor unit, a new one falls outside permitted development and needs a planning application. The outdoor unit also cannot go on a wall facing the road above the ground floor without one.

On this page

Permission one: your lease

Most flats are leasehold, and GOV.UK's guidance is that your lease sets out whether you need permission to make alterations and who is responsible for repairs. Your lease also says what you own. If the outside wall or the balcony is not included, fixing anything to it needs the freeholder's agreement, even if you are the only person who uses it.

Where a lease says alterations need the landlord's consent, section 19(2) of the Landlord and Tenant Act 1927 says that consent to improvements is not to be unreasonably withheld. The landlord can still ask for reasonable costs, and some leases ban external fixtures outright, which is a different thing. Read your own lease, and if it is unclear, ask the managing agent in writing before you book anything.

Some blocks already have a position they allow units to go in, or a rule that they cannot go on the front. Asking that question first saves a wasted survey.

One heat pump per block

The permitted development rules for air source heat pumps, which is what a heating and cooling air conditioner counts as, allow no more than one on, or within the curtilage of, a block of flats. The count is for the whole building, not for each flat. In a block where any neighbour already has an outdoor unit, yours needs a planning application.

Permission two: planning

These are the Class G limits that matter for a flat in England. Fall outside any of them and you need a planning application, which is a separate process from your lease and can still be granted.

It must heat as well as cool

Since 29 May 2025 the rules have said the heat pump must not be used solely for cooling. Every unit we fit heats and cools, so this one is met.

Size of the outdoor unit

On a block of flats the outdoor unit, including its housing, must not exceed 0.6 cubic metres. Daikin's 2.5kW and 3.5kW Comfora outdoor unit is about 0.14 cubic metres and the 5.0kW about 0.28, so a domestic unit is well inside it.

Not on a wall facing the road above the ground floor

Outside a conservation area, a unit cannot go on any part of a wall that fronts a highway above ground floor level. For most upper floor flats, that rules out the front of the building and points to the back or the side.

Conservation areas

Inside one, the unit cannot go on any wall or roof that fronts a highway, at any height, or nearer to the road than the building itself.

Roofs

Never on a pitched roof. On a flat roof, it must be at least one metre in from the edge.

Noise

The installation has to pass the MCS 020 (a) sound calculation, which checks the noise from the outdoor unit at the nearest room a neighbour lives in. In a block, that neighbour may be a few metres away, above or below, so the position matters.

Listed buildings

There is no permitted development for a heat pump on a listed building or within its curtilage. That always needs an application, and listed building consent as well.

The practical limits

Once you have both permissions, the building itself decides how the job is done. All of these are priced in your quote before you agree, never on the day.

How far the pipes can run

Every unit has a maximum pipe length and a maximum height between the indoor and outdoor units. For Daikin's 2.5kW and 3.5kW Comfora that is 20 metres of pipe and 12 metres of height; the 5.0kW allows 30 and 20. An outdoor unit on the roof of a tall block may be out of reach for a small unit.

Pipework beyond the first 3 metres

Our starting prices include 3 metres of pipework. In a flat the outdoor unit is often further away, and each extra metre is £45 per metre.

Where the water goes

The indoor unit produces water when it cools. On upper floors there is often nothing for it to drain down to, and a condensate pump is needed, at £160.

Getting to the wall

Ground and first floor outdoor positions are a normal day's work. Above that needs access equipment, which we plan and price at the survey.

The fuse board

A 2.5kW or 3.5kW unit runs from a fused spur. From 5.0kW up it needs its own circuit from your fuse board, and older boards in converted flats sometimes have no spare way for one.

The order to do it in

  1. Read your lease and ask the managing agent

    Ask whether external units are allowed, where, and what they need from you. Get the answer in writing.

  2. Check whether anyone in the block already has one

    Look at the outside of the building. If there is already an outdoor unit on it, assume a planning application is needed and ask your council.

  3. Get a survey

    We look at the room, the route for the pipes and where the outdoor unit can go, and write a quote with every extra priced. If the managing agent asks for the installer's details, we can give you our SafeContractor and REFCOM certificates and our insurance details to pass on.

  4. Book the install

    A single room install is normally one day. Where access needs equipment or the pipe run is long, we say at the survey if it will take two visits.

What we do and do not do

We do not apply for planning or deal with your freeholder on your behalf. We do give you the unit's make, model and dimensions, where it will go, and our credentials, so the forms can be filled in accurately. We are a REFCOM certified company (REF1025662) and SafeContractor approved (MD8663), and we are fully insured.

None of this is legal advice. Your lease and your council's planning team are the only sources of a binding answer for your flat.

Sources

The ranges this applies to

Every price is fully installed and includes the unit, the installation, the electrical work and VAT.

Samsung Cebu S2

Samsung Cebu S2

The entry Samsung. Inverter heat pump, Wi-Fi in the box, and the cheapest way onto the wall.

From £1,995 fitted
Daikin Comfora

Daikin Comfora

The compact Daikin. The narrowest box we fit, quiet from 19dB(A), and the cheapest way to reach 7.1kW.

From £2,195 fitted

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Instant estimate

Want a price for your flat?

The estimate asks which floor you are on and gives you a starting price, from £1,995 fully installed. Or call and ask about your building first.

Call 020 3822 0118

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