A house extension is one of the most effective ways to add value and usable space to your home. Whether you need an open-plan kitchen-diner, an extra bedroom, or a home office, RCB Design & Build delivers extensions across London, Kent, Surrey, and Essex. We act as principal contractor, managing the full build from foundations and structural steelwork through to plastering, electrics, and final finishes. Second-fix materials (tiles, kitchen units, sanitaryware) are client-supplied so you keep full control over your interior specification.
Ground-floor extensions to create open-plan kitchens, living rooms, or utility spaces. Often built under permitted development.
Two floors of additional space, typically adding a bedroom and bathroom above a ground-floor living area.
Combines a side return and rear extension into one L-shaped build, maximising ground-floor footprint.
Fills the narrow alleyway beside Victorian and Edwardian terraces to widen the kitchen or dining room.
Extends the back of the property, typically opening onto the garden with bi-fold or sliding doors.
Many single-storey rear extensions fall under permitted development rights, meaning no formal planning application is needed. However, this depends on the size, height, and position relative to boundaries. We check your permitted development allowance as part of the free site visit and advise whether a full planning application or a lawful development certificate is the better route.
A single-storey rear extension typically takes 8–12 weeks on site. Double-storey and wraparound extensions take 12–16 weeks depending on complexity. We provide a detailed programme at estimate stage so you know exactly what to expect.
Our price covers groundworks, foundations, structural steelwork (RSJs), brickwork, roofing, insulation, plastering, first-fix electrics and plumbing, and all building control sign-offs. Second-fix materials such as kitchen units, tiles, and sanitaryware are client-supplied so you choose your own finishes and specification.
Yes, in almost all cases. We plan the build sequence to keep disruption to a minimum and maintain access to your kitchen and bathroom throughout. We discuss logistics during the site visit.
Yes. We submit the Building Regulations application on your behalf, manage all inspections, and ensure a completion certificate is issued at handover. This is included in our service.
Tell us about your extensions project and we'll be in touch within 2 hours. Free site visit, no obligation.
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