Confirm the property and the space available
Start with the ownership and the limits of the proposed work. A garden or outside area beside a dwelling does not, on its own, establish the right to build there. For a flat, request the relevant property and management information before considering an addition. We would identify the space that can actually be included in the brief and any matters requiring advice from the appropriate professional.
Survey the existing footprint, levels, boundaries and access. Record the neighbouring buildings and openings that may be relevant to the proposal. The design should work from those measured relationships, not from an aerial impression of spare land. Where information remains uncertain, make that clear and establish how it will be checked. This is particularly useful when a small plot contains several earlier additions or service routes that are not obvious from inside the home.
Choose an addition that improves the retained rooms
Explain the benefit you want from the extension. A larger dining area, a more practical kitchen or a useful connection to outside space each suggests a different arrangement. We would test the proposal against the existing circulation, furniture and storage. The addition should not leave the original room as an uncomfortable passage or remove the wall space needed to use the rest of the house.
Compare the effect of different openings between old and new. A broad opening may create a close relationship between rooms but also introduce structural and service work. A more contained connection may preserve useful separation. Show the whole plan and relevant sections so the household can understand those choices. The best option is the one that fits the intended use and verified constraints, rather than the one with the largest outline.
Use the correct council's design context
The wider Vauxhall and Nine Elms area involves Lambeth and Wandsworth. Lambeth's adopted alterations guide says extensions should remain subordinate and respond to the host architecture; Wandsworth publishes separate conservation guidance for its designated areas. Identify the property's actual authority and relevant documents before applying a design principle from a neighbouring address. The boundary matters even where the homes share a postal district.
The planning adviser should establish the appropriate route for the proposed work. Provide a clear description and drawings showing the existing building and its surroundings. If the property has heritage constraints, show retained features and the treatment of new junctions. We would keep the design responsive to that advice, rather than fixing the external appearance before the authority and designation have been confirmed.
Sources: Greater London Authority: Vauxhall, Nine Elms and Battersea · Lambeth Design Guide: Part 4, alterations and extensions · Wandsworth: conservation areas and Article 4 directions
Investigate what lies under and within the site
The structural and ground investigations should follow the needs of the proposal. Ask the engineer what information is required about the existing building and the proposed foundation area. Record any uncertainty and agree the next step before making construction commitments. We would coordinate the structural solution with the room layout, so supports and floor levels do not become late obstacles to the intended use.
Establish drainage and other service routes through appropriate records and survey. The position of a drain can affect the layout and construction method, while an unknown service may need specialist investigation. The design package should show how the extension connects to the existing installation and how relevant components remain accessible. It should also explain the sequence and protection needed while the old building is opened and the new enclosure is formed.
Detail the enclosure for comfortable use
Review glazing in relation to the room's activities, daylight, privacy and likely heat gain. A wall of glass may provide an open view while limiting storage and furniture positions. We would compare opening types and consider cleaning, shading and ventilation with the designer. The junctions around frames, thresholds and the roof need to be coordinated with the rest of the construction rather than left as separate supplier details.
Plan the internal services before surfaces are closed and keep evidence of concealed work. At handover, review the drainage, opening windows, controls and maintenance access with the homeowner. Keep the final drawings and product information together, including any agreed changes from the original proposal. The new room should have a clear relationship with the house and a practical record of its construction, making it easier to operate and care for after completion.
Before work begins
House extensions in Vauxhall & Nine Elms: questions
Can a ground-floor apartment have an extension?
It needs a property-specific assessment. Establish ownership, alteration rights and the building arrangements before developing the design. We would then examine the physical space, structure and relevant approval route. The presence of outside space does not by itself make a flat equivalent to a house for the purposes of an extension proposal.
Does the Lambeth guide apply to every Nine Elms property?
No. The wider area spans Lambeth and Wandsworth, so the actual planning authority must be confirmed. Use the relevant council's guidance and the property's designations. A neighbouring project can provide context, but it should not determine which authority or policy documents apply to your own proposal.
What should be checked before designing a kitchen extension?
Review the existing kitchen's shortcomings, the route through the house and the available plot. Investigate services and drainage alongside the proposed structure. We would position appliances, preparation space and storage before fixing the glazing, so the new enclosure supports a practical kitchen rather than leaving its layout to be fitted around the building afterwards.
Can the outside space remain useful after an extension?
That should be a deliberate part of the design. Show furniture, planting, access and maintenance routes in the remaining area, and consider privacy and the relationship with neighbouring homes. We would compare the benefit of internal space with the quality of the outside space retained, rather than treating the unbuilt portion as an incidental leftover.
How is the extension's connection to the house resolved?
Coordinate the structural opening, floor levels, services and finish junctions in the design package. Identify any investigation needed before the details are fixed. During construction, review discoveries through the agreed technical process and update the information, so the connection follows a considered solution rather than an improvised adjustment between trades.
Official sources
Greater London Authority: Vauxhall, Nine Elms and Battersea · Lambeth Design Guide: Part 4, alterations and extensions · Wandsworth: conservation areas and Article 4 directions
Sources checked on the dates recorded in the source register, most recently 5 November 2026. Maps, list entries and directions must be checked for the individual property and proposed work.