Leaseholder's Guide
Aircon for apartments: permission, License to Alter & invisible AC
A practical guide for London leaseholders who want to cool their flat without falling foul of the lease, the freeholder or the neighbours. Written by F-Gas certified engineers who install AC in London mansion blocks, listed buildings and conservation areas every week.
Why apartment AC is different
Installing air conditioning in a London flat is rarely as simple as picking a wall unit and booking an engineer. Most leases restrict alterations, most freeholders require formal consent, and most mansion blocks or period buildings forbid external units on the façade altogether. Get this wrong and you can face lease-breach notices, forced removal or costly reinstatement at the end of your lease.
The good news: there is now a route that works for almost every London flat, including listed buildings and conservation areas — water-cooled AC with no outdoor unit. This guide walks through the legal process (License to Alter), the technical options (invisible AC), and the practical steps to get from "I want AC" to a working, compliant system.
The License to Alter process
A License to Alter (LTA) is a legal agreement between you and your freeholder that permits specific changes to your flat. For air conditioning, the freeholder wants to see three things: who is doing the work, what exactly is being installed, and how the building is protected (noise, insurance, reinstatement).
Section 19, Landlord and Tenant Act 1927: A freeholder cannot unreasonably withhold consent for improvements. Choosing a water-cooled system with no external unit removes almost every "reasonable" ground for refusal — no façade impact, no compressor noise, no planning issue.
Water-cooled "invisible" AC — the leaseholder's shortcut
Traditional split-system AC needs an outdoor condenser mounted on the wall, balcony or roof. In a London flat that outdoor unit is usually the reason permission gets refused. Water-cooled systems remove the outdoor unit entirely. A single water/air heat pump lives inside your flat — typically in a cupboard, hallway or false ceiling — and connects to compact indoor units in each room.
'No external units'
Water-cooled Parkair MCW 2.0 — no outdoor condenser at all.
Listed building
Zero façade works. All pipework and units concealed internally.
Noise complaints from neighbours
No external compressor. Indoor unit runs whisper-quiet in a cupboard.
Balcony / lightwell restrictions
Nothing installed outside — full compliance with communal-area rules.
The Parkair MCW 2.0
Our go-to system for London leaseholders. R32 inverter heat pump, A+++ efficiency, serves up to 5 rooms from a single indoor module. Heating, cooling and dehumidification. Whisper-quiet. Zero external works.
See the systemThe full process, step by step
- 01
Check your lease
Look for clauses on alterations, external works, noise and mechanical services. Note whether your building is listed or in a conservation area.
- 02
Free technical survey
We visit the flat, measure heat loads, identify pipework routes and confirm which AC option (water-cooled, ducted, split) will actually get past the freeholder.
- 03
Written specification & drawings
You receive a full specification, layout drawings, sound data and insurance details — the exact documents most freeholders and managing agents ask for.
- 04
Submit License to Alter
Your solicitor submits the LTA to the freeholder using our documents. We answer any technical queries from their surveyor directly.
- 05
Installation
Once the LTA is signed, we install with F-Gas certified engineers. Typical installs take 1–3 days with minimal disruption.
- 06
Commissioning & sign-off
System commissioned, tested and handed over with a 5-year warranty and all documentation for your freeholder's records.
Leaseholder FAQs
Do I need permission to install air conditioning in my London flat?+
In almost all cases, yes. If you own a leasehold flat you'll need written consent from the freeholder or managing agent — usually via a formal 'License to Alter'. Even short-lease and share-of-freehold flats normally require permission for anything that affects the structure, façade or communal areas.
What is a License to Alter?+
A License to Alter (LTA) is a legal agreement between you and your freeholder that permits specific alterations to your flat. For air conditioning it covers pipework routes, any external units, noise limits, insurance and reinstatement conditions at the end of the lease.
How long does the License to Alter process take?+
For a straightforward AC install, expect 4–10 weeks from application to sign-off. Listed buildings, mansion blocks and estates with strict management can take 3–6 months. Starting the LTA before booking installation is essential.
Can I install AC without an outdoor unit?+
Yes. Water-cooled systems like the Parkair MCW 2.0 use a single indoor water/air heat pump instead of an external condenser — so there's nothing to mount on the façade, balcony or roof. This is often the only route to freeholder approval in listed and conservation-area flats.
What if the freeholder refuses permission?+
Section 19 of the Landlord and Tenant Act 1927 says freeholder consent for improvements must not be unreasonably withheld. Water-cooled 'invisible' AC removes most reasonable grounds for refusal (façade impact, noise, planning), which makes approval far more likely.
Does invisible AC work as well as a traditional split system?+
Yes — a properly sized water-cooled system delivers the same cooling and heating performance, with A+++ efficiency and whisper-quiet indoor operation. The difference is that everything is concealed inside your flat.
Thinking about AC for your London flat?
Free survey and full License to Alter documentation. We work with leaseholders across Kensington, Chelsea, Westminster, Mayfair and central London.