Fitting air conditioning in a flat, and why the lease decides

Most guidance about fitting air conditioning is written for somebody who owns the wall they intend to drill through. In a flat, you usually do not.

That single fact reorders the whole job. The planning question, which takes up most of the internet’s attention, is generally the easier half in a flat and is answered in an afternoon. The lease is the part that decides whether the work happens at all, and it is worth reading before you get a quote rather than after.

Three permissions, not one

A split system in a flat needs three separate things to line up.

Planning. Whether the installation is permitted development under Class G, or needs an application to the local planning authority.

The lease. Whether you are allowed to alter the building, and whose consent you need.

Building work consent from the freeholder. Separate from the lease covenant in practice, because it covers access, scaffolding, insurance and what happens to the fabric.

They are independent. Permitted development does not give you the right to drill through a wall you do not own, and freeholder consent does not make an installation lawful in planning terms.

What Class G gives a block of flats

The permitted development rules for air source heat pumps, which is what an air conditioner is in planning law, are tighter for flats than for houses.

Listed buildings and scheduled monuments are out entirely, and conservation areas add restrictions on any wall or roof fronting a highway. The system also has to meet the MCS planning standard for sound, and the unit has to be removed when it is no longer needed. The conditions are in Part 14 of Schedule 2 to the General Permitted Development Order.

One condition catches more flat owners than any other: the machine has to heat as well as cool. A cooling only unit is never permitted development at any size, which is covered in full in the planning rule that decides what air conditioning you can fit. Our planning permission checker walks the Class G conditions in order for a specific installation.

The lease is the real gate

Now the harder half.

In a typical long lease of a flat, what you own is the internal space. The external walls, the roof and the structure are usually retained by the freeholder. A split system puts a bracket and a compressor on the outside of that structure and runs pipework through it, so it is an alteration to somebody else’s property.

Leases handle that in one of three ways, and which one you have decides how much room you have to negotiate.

An absolute covenant. The lease forbids alterations to the structure or exterior, full stop. There is no implied duty to be reasonable and the freeholder can refuse without giving a reason. You can ask for a deed of variation, and you may be quoted a price for it.

A qualified covenant. The lease forbids alterations without the freeholder’s consent. Where the work is an improvement, section 19(2) of the Landlord and Tenant Act 1927 implies that the consent must not be unreasonably withheld. The freeholder may still require you to pay their legal costs, to cover any loss in value, and in some cases to undertake to reinstate the wall at the end of the term.

Silence. Older leases sometimes say nothing specific. That is not permission, because other clauses about not damaging the structure or causing nuisance usually still bite, but it does give you a stronger starting position.

Read the alterations clause and the nuisance clause together. A noise complaint from the flat below is the most common route by which a lawfully installed system becomes a problem, and the nuisance clause is what a managing agent will reach for.

What a consent application should contain

Freeholders and managing agents refuse vague requests, and a complete application is answered faster than a thin one. Include:

• The exact position of the outdoor unit, with a photograph of the wall or balcony and a dimensioned drawing.
• The unit’s sound power figure at the proposed position, which matters more than the model name to everyone reviewing the request. Our guide to what a noise figure tells you explains which number to quote.
• How the pipework passes through the wall, how the penetration is sealed and made good, and where the condensate drains to.
• The installer’s F gas certification and their public liability cover.
• A method statement covering access and any scaffolding.
• Confirmation of your planning position, whether that is permitted development or a granted application.

Expect to pay the freeholder’s reasonable legal and surveying costs for a licence to alter. That is normal, and section 19(2) contemplates it.

Where the unit can realistically go

Assume nothing about the balcony. Many leases demise a balcony to the flat but restrict what may be fixed to it or hung from it, and a compressor bolted to a balcony wall is still a fixture on the structure. A unit standing on feet on a balcony floor is a different proposition from one bracketed to the outside of the building, and is often the easier consent to obtain.

Ground floor flats have the most options and the fewest planning problems, because the restriction on walls fronting a highway applies above ground floor level.

Top floor flats often look promising and are not. A pitched roof is out for a block of flats, and a flat roof needs the unit at least a metre back from the edge, on a roof that is almost always retained by the freeholder and often covered by a maintenance regime that a new penetration would compromise.

If the answer is no

There are three routes left, and only one of them is a fixed system.

A monobloc unit. No refrigerant crosses the building fabric, but there are still two large ducts through a wall or window, so consent is still needed for anything permanent.

A portable unit. No fixed outdoor unit, no Class G question, and no alteration to the building, which is why it is the honest answer for renters and for flats where the lease closes the subject. It is less efficient, so it costs more per hour of cooling. Our guide to what a portable air conditioner costs to run has the working.

Reduce the heat before it arrives. External shading, in the small number of flats where it is permitted, does more per pound than any machine, and internal measures are unrestricted by any lease. Start with external shutters and shading and with why British bedrooms do not cool down, which is where the problem usually is.

The order to do this in

1. Read the alterations clause in your lease. Ten minutes, and it may end the project before you spend anything.
2. Ask the managing agent what consent they require and what it costs, in writing.
3. Check the planning position for the specific position you intend to use.
4. Only then get quotes, with the consent conditions handed to the installer as part of the brief.

Done in that order, a refusal costs you an afternoon. Done in the usual order, it costs you a deposit and an argument.