Air conditioning in a flat: who has to say yes?

What will your lease say?

One of two things. Most leases allow alterations with the landlord's consent, and where the change is an improvement, LEASE says consent should not be unreasonably withheld. Some leases ban alterations outright, and then the only route is asking the landlord to vary the lease. A law firm's 2026 note adds that the demise usually excludes the structure, so the outside wall is not yours, and that some leases and building rules prohibit air conditioning altogether. Read the alterations clause before you ring anyone. Sources: LEASE; Mishcon de Reya.

What can the freeholder charge for saying yes?

Their reasonable costs: a surveyor to look at the plans, a solicitor to draw up a licence to alter, and administration. Where the work touches parts they keep, which an outside wall or a roof always is, they are not obliged to consent at all and can ask for a premium, with no legal limit on the amount. An unreasonable administration charge can be challenged at the First-tier Tribunal. Get an estimate of their costs before you commit to the survey. Source: LEASE.

What does planning allow on a block of flats?

One outdoor unit, of no more than 0.6 cubic metres, as permitted development, and only if the block consists wholly of flats. The second resident to ask will need a planning application, and a block with a shop or an office on the ground floor is outside the rules for everyone. With 44,285 Croydon households in purpose-built blocks, that single permitted unit goes quickly. Sources: Planning Portal; Census 2021.

Why are Croydon's converted office blocks a special case?

Because they were never designed as homes. From May 2013 developers could turn offices into flats without full planning permission, and by late 2014 Croydon had approved 1,236 such units, 1,074 of them below the London Plan's space standards. Research for the government in 2020 found that only 22.1% of homes made this way met the national space standard, against 73.4% of homes with planning permission, and that 72% had windows on one side only. Single-aspect flats with sealed glazing are the hardest rooms in the borough to keep cool, and the newest conversions, such as the 250 flats proposed for No1 Croydon beside East Croydon station in 2024, follow the same pattern. The freeholder's rules for the building decide whether a wall unit, a monobloc or nothing is possible. Sources: Pinsent Masons; UCL; Inside Croydon.

Does Part O protect a new flat from overheating?

Only a new-build one. Part O of the Building Regulations has required new residential buildings to be designed against overheating since 15 June 2022, but the Planning Portal says it applies to new residential buildings only, and Elmhurst Energy points out that it does not extend to conversions. An office turned into flats in 2024 is not covered. Elmhurst reported in April 2026 that the government intends to review Part O, including whether conversions should be brought in. Sources: Planning Portal; Elmhurst Energy.

What if you rent?

Ask the landlord in writing before anything is fixed to the building. Private renting rose from 21.0% of Croydon households in 2011 to 25.8% in 2021, and from 1 September 2026 most of those homes in 14 of the borough's wards need a council licence, which makes landlords cautious about unapproved work. If the landlord agrees to a fixed system, they own it and should service it. If not, a portable is the fair answer for a short let. Sources: ONS; Croydon Council.

What if there is no outside wall you can use?

Three options, in order of preference. A longer pipe run through a ceiling void or service riser to an outdoor unit on the roof or at the rear, with the freeholder's agreement for every metre. A monobloc unit breathing through two grilles, if the room has any external wall at all. Or a portable, which needs only a window. Where pipes pass through very small rooms, the refrigerant has to be checked for safety, since many modern gases are flammable. Source: Energy Saving Trust.