House renovation and refurbishment
in Kensington's conservation areas

The Phillimore Estate was built between 1855 and 1870 as medium-sized semi-detached villas, some with large rear gardens, and Campden Hill Square, from 1823, gives its houses more garden front and back than anywhere else in the area.

Two changes recur across the area's houses: mansards added above the original roofline, and conservatory-type rooms built into the gap beside a closet wing at lower ground floor.

Rears that face communal gardens are formal set pieces, and the appraisal treats changes to them as among the most harmful, because they are seen across the gardens as one elevation.

Most of these observations come from one document, RBKC's Kensington Conservation Area Appraisal, adopted on 3 February 2017, which records what the council regards as the character of the area and its buildings.

We date each later addition on the survey, so the refurbishment can keep, repair or remove it on its merits.

Sources: Royal Borough of Kensington and Chelsea: Kensington Conservation Area Appraisal, Royal Borough of Kensington and Chelsea: conservation area appraisals

RBKC's basement policy is now Policy CD11 of the Local Plan adopted in July 2024, which replaced the 2019 plan and its Policy CL7. A basement may take no more than half of each garden or open part of the site, the unaffected garden must be one area, continuous with neighbouring gardens where relevant, and at least a metre of soil must sit above any part beneath a garden.

Depth is limited to a single storey in most cases, meaning one that cannot later be divided into more floors, generally about 3 to 4 metres floor to ceiling. No further basement floor is allowed where one already exists, has permission or was built under permitted development rights, and nothing may be excavated beneath a listed building, vaults included.

The planning application needs a construction method statement by a qualified civil or structural engineer, with a ground and hydrological report. Basement development must include a sustainable drainage system, kept in place afterwards, and a suitable pumped device against sewer flooding, as a non-return valve alone is not accepted, and front or side light wells are resisted where they would seriously harm the street's character, particularly where they are not an established feature of it.

Source: Royal Borough of Kensington and Chelsea: Local Plan (adopted July 2024)

Every site in the borough is placed in Category 1, 2 or 3 before work starts. A basement excavation or a full demolition and rebuild is Category 1; partial demolition, extensions and minor basement extensions within the curtilage producing under 50 cubic metres of excavated material are Category 2.

Category 1 and 2 sites need a signed Code checklist and an approved Site Construction Management Plan before work can start. All Category 1 and some Category 2 projects also need a draft Construction Traffic Management Plan with the planning application and a final version approved before work begins, and Category 1 sites must apply for prior consent under Section 61 of the Control of Pollution Act 1974. For Category 1 and 2 sites under the planning condition, the council charges for monitoring compliance through a Construction Bond paid before work starts, and repays unspent charges when the project is complete.

RBKC expects neighbours to be consulted before a planning application goes in, with a neighbour liaison strategy for Category 1 sites, and notes that vibration damage to adjoining structures, even cracked plasterwork, may be provided for under a party wall agreement. Under the Party Wall etc Act 1996, gov.uk explains, a building owner proposing work the Act covers must notify adjoining owners as the Act prescribes, and the Act also offers a route for settling disagreements.

Sources: Royal Borough of Kensington and Chelsea: Code of Construction Practice, Royal Borough of Kensington and Chelsea: Code of Construction Practice (April 2019), GOV.UK: Party Wall etc. Act 1996 guidance

We have no published Kensington house case study yet. Two whole-house projects of the same kind, each shown with where it is:

A whole-house refurbishment brief benefits from a room-by-room record of what is staying and what is changing. For a Kensington house, bring the available drawings and identify alterations that are known only from inspection or recollection. Keep those distinctions visible while the design is developed.

Look at connections between floors rather than approving every room in isolation. Circulation, storage and service routes can affect several spaces at once. Record where an attractive detail depends on a structural change or on permission that has not yet been established. Ask the design team to show how those dependencies are resolved in the coordinated information. A clear decision record helps the construction discussion follow the agreed proposal and makes later revisions easier to assess. For an independent condition enquiry, see the information on surveying support.

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