Mansard roof extension at House excluding basement flat, South Kensington, London SW3

What was proposed

The application sought a mansard roof extension, rear closet-wing extension, smaller replacement infill extension and internal alterations.

“The heritage significance of the listed building includes its architectural design and elevational hierarchy, its contribution to the setting of the listed terrace and the internal planform. 4.The proposal and any relevant planning history 4.1Planning permission and listed building consent is sought for the following: ·The construction of a mansard roof extension at third floor level; ·An additional storey extension to the rear closet wing to extend it to second floor level;…”

Officer report

The site and building

The Grade II listed townhouse forms part of a terrace in the Chelsea Conservation Area and contains a basement flat and an upper flat.

“/PP/26/00411:2 · Three or more objections were received during the consultation period and the recommendation is to grant. 3.The site and its surroundings 3.141 Sydney Street originally dates from the early 19th century. The building is Grade II listed and is in the Chelsea Conservation Area. The property forms part of a wider terrace, creating a uniform composition.”

Officer report

Relevant application history

A separate application for alterations to the basement flat, including a smaller infill extension, remained under determination.

“4.3The relevant planning history is set out below: ReferenceDescriptionDecision LB/26/00394 PP/26/00395 Internal and external alterations including replacement of existing metal stair to front lightwell with new black painted metal stair, enclosure of open space beneath ground floor entrance stairs with new partition wall and door to form lobby entrance to Basement Flat, replacement of existing 1969 infill extension beside rear closet wing with smaller infill extension; and…”

Officer report

Officers’ assessment

The extensions were considered acceptable because they would improve the terrace’s roof form, reduce rear bulk and retain acceptable daylight, sunlight and privacy.

“/PP/26/00411:4 recommended to secure a sample of the proposed roof slate of the mansard. The recommended condition also seeks to secure details of external windows throughout. 6.5The proposed upward extension to the closet wing would match the established pattern of the rear of this part of the terrace which have closet wings of a similar height and would be acceptable.”

“Living conditions 6.7 The application includes a daylight and sunlight report that sufficiently demonstrates that the windows and rooms of all surrounding properties would still receive good levels of daylight and sunlight within the BRE guideline standards following the construction of the mansard roof and extensions at the rear.”

Officer report

Consultation responses

The Conservation and Design consultee raised no objections subject to conditions, while no supporting letters were received.

“/PP/26/00411:5 7. If permitted and built, the proposal would not require a payment towards funding additional infrastructure under the Borough’s Community Infrastructure Levy or a payment towards funding Crossrail under the Mayor of London’s Community Infrastructure Levy. 8.Consultations carried out Comments from interested parties 8.1The application was advertised in the Gazette on 27/03/2026.”

“In the case of the infill extension, a smaller extension is proposed than the existing. The construction of a mansard roof extension would help unite the terrace as a whole. Other consultees and organisations ConsulteeComment Where in the report this is considered Conservation and Design No objections subject to conditions.Paras. 6.2 – 6.6”

Officer report

The decision

“Resolved by majority (Cllr Taylor-Smith recused himself for these items): Planning permission be granted with the conditions listed in Section 9 of the report for S038 and listed building consent be granted with the conditions listed in Section 2 of the report for S039. l) S041 & S042 -”

Minutes, 23 Jun 2026