Why Bromley homeowners are extending rather than moving
Bromley is one of the largest London boroughs by area and one of the most desirable places to live in South-East London. Average property prices across the BR postcodes have climbed steadily, making stamp duty on a larger home a significant cost. For many families in Bromley, Beckenham, Petts Wood, Orpington and Chislehurst, extending their current home is financially smarter than moving. A well-designed extension adds the kitchen-diner, extra bedroom or home office that the household needs without the transaction costs, upheaval and competitive bidding of the current market.
The housing stock in Bromley lends itself particularly well to extensions. Victorian and Edwardian terraces in Bromley town centre and Beckenham often have narrow side returns that can be extended to create open-plan kitchen-dining spaces. 1930s semi-detached houses across Petts Wood, Bickley and Chislehurst typically have generous rear gardens that accommodate single-storey or double-storey rear extensions. Post-war properties in Orpington and St Mary Cray offer opportunities for wraparound extensions that combine side and rear additions.
At RCB Design and Build, we have designed and built extensions across every BR postcode. We understand the local architecture, the planning policies specific to Bromley Council, and the structural characteristics of each era of housing. Our free project review is the starting point for every extension enquiry - a no-obligation visit to discuss your requirements, assess the site and provide honest advice on what is achievable within your budget.
Extension costs in Bromley: 2026 pricing
Realistic 2026 extension costs in Bromley and the surrounding BR postcodes are as follows. A single-storey rear extension of 15-20 square metres starts from GBP 42,000 and typically runs to GBP 68,000 depending on the specification. A side-return extension on a Victorian terrace ranges from GBP 38,000 to GBP 55,000. A double-storey rear extension ranges from GBP 72,000 to GBP 110,000. A wraparound extension combining side and rear elements starts from GBP 85,000.
These prices include groundworks and foundations, structural steelwork, brickwork, roofing, windows and doors, full electrical and plumbing installation, plastering, decoration and flooring. They do not include kitchen units and appliances, high-end bathroom fittings, bespoke joinery or external landscaping. Second-fix materials including tiles and sanitaryware are client-supplied and sit outside the build contract.
Bromley extension costs are competitive within the London market. Access is generally good across the BR postcodes, skip placement is straightforward on most residential streets, and the borough has an efficient Building Control service. The biggest cost variable is the foundation design - London clay across much of Bromley means deeper foundations are sometimes required, particularly near mature trees. A proper site investigation at the design stage identifies this before it becomes a mid-build surprise.
Planning permission and Bromley Council requirements
Many single-storey rear extensions in Bromley can be built under permitted development rights. The key limits are: the extension must not extend more than 3 metres from the original rear wall on an attached house or 4 metres on a detached house (or up to 6 metres and 8 metres respectively under the larger home extension scheme with prior approval). The maximum height is 4 metres, and the eaves height must not exceed the eaves of the original house.
Bromley Council has a strong planning department and several areas with specific restrictions. The borough contains numerous conservation areas - including parts of Beckenham, Chislehurst, Bromley town centre, Bickley and Keston - where permitted development rights are curtailed. Properties in these areas typically need a full planning application even for single-storey rear extensions. Article 4 directions apply in certain locations and can remove permitted development rights entirely.
For double-storey extensions, planning permission is almost always required regardless of location. Bromley Council assesses these against policies on amenity impact, overshadowing, privacy and design quality. Applications typically take 8 weeks for a decision, though more complex cases can take longer. We handle the entire planning process for our clients, from initial feasibility assessment through to securing the decision notice. Our experience with Bromley planning officers means we design schemes that align with local policy expectations from the outset.
Side-return extensions in Bromley: the most popular option
The side-return extension is the most requested project type we see in Bromley, particularly on Victorian and Edwardian terraces in Beckenham, Bromley South and Shortlands. These properties typically have a narrow side passage running alongside the kitchen - often just 900mm to 1.2 metres wide - that serves no real purpose beyond access to the rear garden. Extending over this passage and into the rear garden creates a dramatically larger kitchen-dining space that transforms how the ground floor functions.
A typical Bromley side-return extension adds 8-15 square metres of floor area. Combined with removing the wall between the existing kitchen and dining room, the result is an open-plan space of 25-35 square metres - enough for a full kitchen with island, dining area and a comfortable seating zone. Structural steelwork replaces the load-bearing wall, and a roof lantern or glazed roof section brings natural light deep into the plan where it was previously darkest.
Costs for a side-return extension in Bromley range from GBP 38,000 to GBP 55,000 depending on the depth of the rear projection, the roofing specification and the level of finish. Most side-return extensions fall within permitted development, though properties in Bromley's conservation areas need to check. The build programme is typically 8-10 weeks, making this one of the fastest and most transformative extension types available.
Rear extensions and wraparound options
Single-storey rear extensions remain the bread and butter of Bromley's extension market. On 1930s semis across Petts Wood, Bickley and Orpington, a 4-metre rear extension creates enough space for a large kitchen-diner with bi-fold or sliding doors opening onto the garden. The connection between indoor and outdoor space is one of the biggest quality-of-life improvements an extension delivers, and Bromley's generally generous rear gardens mean there is space to extend without losing the garden entirely.
Double-storey rear extensions add both ground-floor living space and a first-floor bedroom or bathroom above. These always require planning permission in Bromley and are subject to more detailed scrutiny around overlooking and loss of light to neighbouring properties. Our architectural designers prepare schemes that address these issues proactively - setting the upper storey back from the boundary, using obscured glazing where needed, and ensuring the roof form complements the existing house.
Wraparound extensions - combining a side-return with a rear extension - offer the maximum additional floor area on a single storey. These are particularly effective on corner plots and end-of-terrace properties in Bromley where there is space to extend on two sides. The design challenge is managing the roof form so that the extension reads as a coherent addition to the original house rather than a bolt-on. Done well, a wraparound extension can add 25-40 square metres of ground-floor space.
The RCB Design and Build extension process
Every Bromley extension project with RCB Design and Build starts with a free project review. We visit the property, discuss your requirements, assess the site constraints and provide initial guidance on costs, planning route and programme. There is no obligation and no hard sell - we want you to have the information you need to make a decision.
Once you decide to proceed, we commission architectural drawings tailored to your brief and your property. We handle the planning application or permitted development assessment. We prepare a detailed scope of works and a fixed-price quotation that covers everything from foundations to decoration. Our deposit is 5% and payments are staged against completed milestones throughout the build.
RCB Design and Build is registered with the Federation of Master Builders, accredited by TrustMark and verified on Checkatrade. Every extension project is completed to full Building Regulations standard and signed off with a completion certificate. We provide a structural warranty and a workmanship guarantee. To discuss your Bromley extension project, call us on 07359 872594 or request your free project review online.
Want a real number for your project?
Send us your address, brief and budget — we will come back with an honest assessment within one working day.