A family from the Gulf buys a Kensington house with a plan: a basement with a pool, a glass extension, air conditioning throughout, the windows replaced, the rooms opened up. Then it learns the house is listed Grade II in a conservation area, that the borough permits one basement storey under half the garden, and that the air conditioning needs consent it may not get. Nothing was hidden; planning, conservation and listing rules simply are not Gulf rules.
Owning and letting
Planning, conservation areas and listed buildings: what an owner can and cannot change in prime London
How planning, conservation area and listed building rules limit changes in London
Three regimes govern what an owner can change in prime London. Planning control covers external changes and larger extensions. Conservation areas, which cover about 70 per cent of Kensington and Chelsea and most of Westminster, fix the street elevation and limit roofs, basements and garden buildings. Listed buildings protect the interior too, and work without consent is a criminal offence with no enforcement time limit. A householder application takes twelve to sixteen weeks in practice; a Kensington basement six to twelve months. The catch: a Grade II house cannot be made into a Dubai villa.
Ordinary planning control: any material change to the outside of a building, any extension beyond “permitted development” limits, and any change of use needs planning permission from the borough; many small works to a house are permitted development and need none.
Conservation areas: designated by the borough for their character; permitted development is reduced or removed (by an “Article 4 direction”), demolition needs consent, trees are protected, and the borough’s design policies apply to anything visible.
Listed buildings: on the national list for architectural or historic interest, Grade I, II* or II; any work that affects the building’s character, inside or out, needs listed building consent, which is a criminal offence to do without, and which has no time limit for enforcement.
Which prime London areas fall within conservation areas
About 70 per cent of Kensington and Chelsea is in a conservation area, most of Westminster’s residential streets, all of Belgravia, Mayfair and Marylebone’s estates, St John’s Wood’s villa streets, Hampstead’s village and Redington Frognal, the Hyde Park Estate and Bayswater’s squares.
Where listed building status applies in prime London
Listing is denser: whole terraces in Belgravia, Mayfair, Kensington, Regent’s Park and the Georgian cores are Grade II or II*, and a Grade II listing covers the whole building, including the interior and often the garden walls and railings. A flat in a listed mansion block is a listed building. The listing and the conservation area are on the borough’s map and in the local search; the firm checks both before a viewing.
Window, façade and stucco rules in conservation areas and listed buildings
In a conservation area, replacing timber sash windows with anything but timber sashes of the same pattern is refused; secondary glazing inside is usually acceptable; double-glazed timber sashes are accepted by some boroughs on the rear and refused on the front. On a listed building, replacing original windows at all needs consent and is usually refused; repair is required. Stucco must be repainted in the estate’s or the borough’s colour, on the estate’s cycle. Satellite dishes, external air-conditioning units, roof terraces and railings on the front are refused in the central boroughs. The street elevation is, in practice, fixed.
Rear extensions, roof extensions and garden buildings in conservation areas
Rear extensions of a single storey are commonly permitted in a conservation area if subordinate in scale and material; two storeys rarely; side extensions almost never in the terraces. Roof extensions and mansards are permitted where the terrace already has them and refused where it does not, which the borough’s conservation area statement will say. Garden buildings need permission in most conservation areas. On a listed building any extension needs listed building consent in addition, and the test is harm to the building’s significance, which is strict. Timescales below; a refusal is appealable to the Planning Inspectorate, which takes a year.
Basement rules in Kensington and Chelsea, Westminster and Camden
Kensington and Chelsea: a single storey, under no more than half the garden, not under a listed building, with a construction traffic management plan and a structural certificate; adopted in 2015 after the “iceberg” basements of the 2000s. Westminster: similar, with a single storey and the garden limit, and a code of construction practice. Camden: a single storey under the house, assessed on structural and hydrological impact, with its own basement policy. Hampstead’s hill adds ground-water constraints.
Buying a house with a basement dug before the policies
A basement that was dug before the policies may be sold with it; a basement dug after them without consent is an enforcement case the next buyer inherits. Our Kensington and Chelsea guide gives the borough’s rule; the others are in their district guides.
Changing interiors in listed buildings and unlisted conservation area houses
In an unlisted house in a conservation area, the interior is the owner’s: walls can come down (with building regulations and a structural engineer), kitchens and bathrooms move, floors change. In a listed building, the interior is protected: original plan form, staircases, cornices, fireplaces, panelling, doors and floors need consent to alter, and the consent is granted for repair, for reversible change and for well-argued improvement, and refused for the open-plan conversion a Gulf buyer may expect. A Grade II house in Belgravia can be made very comfortable; it cannot be made into a Dubai villa. Buy the house that already has the plan the family wants.
Air conditioning rules for conservation area and listed London properties
Air conditioning: the external condenser needs planning permission in a conservation area and listed building consent in a listed building, and is refused on front elevations and often on rear ones; internal systems with the condenser hidden in a lightwell or on a rear roof are sometimes approved, and some mansion blocks forbid them under the lease.
Heat pumps, solar and other installations
Heat pumps: now permitted development in many cases, with limits on noise and position, but not on listed buildings without consent. Solar panels: refused on visible roofs in conservation areas. Lifts, generators and security installations: case by case. The firm’s advice is to make the services plan with an architect who works in the borough before the offer, because the answer changes the house to buy.
Planning and listed building consent: timescales, fees and costs
A householder planning application: eight weeks statutory, twelve to sixteen in practice in the central boroughs, with a fee of a few hundred pounds and architect’s drawings of £3,000 to £15,000. A listed building consent application: the same period, no fee, a heritage statement from a specialist at £2,000 to £6,000, and pre-application advice from the borough’s conservation officer at £500 to £2,000, which the firm recommends because it tells the family what will be refused before the drawings are made.
Kensington basement consent timescales and pre-application advice before exchange
A basement in Kensington: six to twelve months to consent, with the structural and traffic reports, and the party wall process with the neighbours on top. A buyer who wants certainty makes the purchase conditional on nothing (English contracts rarely are) and so should obtain the pre-application advice before exchange.
Unconsented works: enforcement time limits and lawful development certificates
The seller’s property information form asks about alterations and consents; the local search shows enforcement notices; the survey shows what has been done. Works done without planning permission become immune from enforcement after four years (ten for a change of use) and the borough can issue a certificate of lawfulness; works to a listed building without consent are never immune and the current owner is liable to be required to reverse them, whoever did them.
Buying a London house with unconsented works or alterations
A Kensington house with an unconsented basement or a listed Belgravia house with its cornices stripped is bought at a discount for a reason, and indemnity insurance covers the cost of enforcement, not the reversal of the works. Our due diligence guide includes the question.
Sources: Planning permission (GOV.UK) · Listed buildings (Historic England) · RBKC basements planning policy · Planning Portal: permitted development and conservation areas Figures verified 14 October 2026.
Frequently Asked
Frequently asked questions about planning and listed buildings in London
On a Grade II listed terrace, almost certainly not. On an unlisted house in a conservation area, only if the terrace has a consistent roof extension pattern the borough will let you follow.
With the freeholder’s consent under the lease, planning permission for any external unit, and listed building consent if the block is listed; internal units with a concealed condenser are the usual answer, and some blocks have a scheme already approved.
At a price that reflects the risk, with the planning history checked, an indemnity policy, and a structural report; and not at all if the house is listed and the works are to the listed fabric.
In a conservation area, replacing timber sashes with anything but timber sashes of the same pattern is refused; secondary glazing inside is usually acceptable, and some boroughs accept double-glazed timber sashes on the rear but not the front. On a listed building, replacing original windows at all needs consent and is usually refused; repair is required. The street elevation is, in practice, fixed.
About 70 per cent of Kensington and Chelsea, most of Westminster’s residential streets, all of Belgravia, Mayfair and Marylebone’s estates, St John’s Wood’s villa streets, Hampstead’s village and Redington Frognal, the Hyde Park Estate and Bayswater’s squares. Whole terraces in Belgravia, Mayfair, Kensington and Regent’s Park are also listed Grade II or II*, and a flat in a listed mansion block is itself a listed building.
A householder application is eight weeks statutory and twelve to sixteen in practice in the central boroughs, with a fee of a few hundred pounds and architect’s drawings of £3,000 to £15,000. Listed building consent takes the same period with no fee, plus a heritage statement at £2,000 to £6,000 and pre-application advice from the conservation officer at £500 to £2,000. A refusal is appealable to the Planning Inspectorate, which takes a year.
Kensington and Chelsea permits a single storey under no more than half the garden, not under a listed building, with a construction traffic management plan and a structural certificate, a policy adopted in 2015 after the “iceberg” basements of the 2000s. Consent takes six to twelve months, with the structural and traffic reports and the party wall process with neighbours on top. Westminster and Camden have similar single-storey policies.
Rarely. In a listed building the original plan form, staircases, cornices, fireplaces, panelling, doors and floors need consent to alter, and consent is granted for repair, reversible change and well-argued improvement, but refused for the open-plan conversion a Gulf buyer may expect. In an unlisted house in a conservation area the interior is the owner’s, subject to building regulations and a structural engineer. Buy the house that already has the plan the family wants.
Works done without planning permission become immune from enforcement after four years, or ten for a change of use, and the borough can issue a certificate of lawfulness. Works to a listed building without consent are never immune, and the current owner can be required to reverse them whoever did them. Indemnity insurance covers the cost of enforcement, not the reversal of the works.
Heat pumps are now permitted development in many cases, with limits on noise and position, but not on listed buildings without consent. Solar panels are refused on visible roofs in conservation areas. Lifts, generators and security installations are decided case by case. The firm’s advice is to make the services plan with an architect who works in the borough before the offer, because the answer changes which house to buy.
