Single and double storey extensions in Forest Hill. Trusted, professional, 30+ years' hands-on experience.
Across Forest Hill, GS Renovation extends bay-fronted Victorian and Edwardian terraces with rear, side-return and wrap-around builds. With 30+ years in SE23, we handle the foundations, steel beams, roof works and fit-out as one project, and we tell you honestly whether your extension is permitted development or needs a planning application to Lewisham Council.

The narrow side return running past the closet wing is the classic space to claim in an SE23 terrace. By roofing over that alley and knocking through, we widen a cramped galley kitchen into a bright open-plan kitchen-diner. This means new foundations next to the neighbour's boundary, a steel beam along the old external wall, and often rooflights to pull daylight deep into the plan. The engineer sizes the steel and building control inspects each stage.
Many side-return and modest rear extensions on these terraces fall within permitted development, but that is never guaranteed, and a home in a conservation area or one that has already been extended may need full planning permission from Lewisham Council. We check the constraints first, prepare the drawings, and manage the party wall notices that nearly always apply where you build up to a shared boundary near Catford or Telegraph Hill.
On the leafy hills of SE23, a double-storey rear extension adds a larger kitchen below and an extra bedroom or en-suite above, working with the slope many Forest Hill plots sit on. We dig and pour foundations to suit the ground and any nearby trees, build the shell to match the existing brick and bay detailing, and tie the new roof neatly into the original. Steel beams carry the openings between old and new.
Because the extra storey rises alongside the neighbouring terrace, both the Party Wall Act and, usually, a full planning application to Lewisham Council come into play, and we guide you through both. Building regulations then govern the structure, insulation, fire escape and drainage. From groundworks to the final coat of paint, one GS Renovation team runs the programme, keeping the rest of your home liveable while the extension goes up.
Homeowners across Forest Hill choose GS Renovation because we build extensions that suit these specific terraces, not generic boxes. We are straight with you about permitted development versus a Lewisham planning application, we manage the party wall process, and we self-deliver the groundworks, steelwork, roofing and finishes. Three decades in SE23 and nearby Deptford and Lewisham stand behind every project.
George was brilliant. Lovely bloke, very reasonably priced and a perfectionist to boot. He completed our small kitchen renovation with care and great attention to detail. I've already recommended him to others.
Splendid job on our new kitchen refurb, including new flooring, moving the services, installing RSJ and preparing space for new back doors… George was always friendly, communicative and has an excellent attention to detail, ensuring everything is finished to a high standard.
Giorgio is an excellent and intelligent workman, and with very reasonable prices!… He paid a lot of attention to detail that is not common at all, and the final result was immaculate. Highly recommended!
FAQ
There is no fixed price for house extensions in Forest Hill, because so much depends on your property and what you want to achieve. We survey first, then provide a transparent written quotation. Contact GS Renovation on 07472 424 226 for a free estimate. As a rough guide, house extensions in London typically starts from roughly £40,000 for a single-storey rear extension and rises with size and specification (indicative London ranges, MyBuilder and Checkatrade, 2026). Your figure depends on the size, specification and condition of the property, which is why we survey before quoting.
How long house extensions takes in Forest Hill depends on the size of the job, but we always agree a programme before starting and stick to it, keeping you informed from the first day to the last.
GS Renovation knows Forest Hill's homes and how to renovate them properly. We handle the structure, the services and the finishes, deal with building control for you, and leave you with work that is certified, guaranteed and built to last.
Many single-storey rear extensions in Forest Hill fall under permitted development, but side returns, double-storey extensions and work in conservation areas usually need full planning permission. We assess your property and manage both the planning application and building control.
Yes. A large share of Forest Hill's homes are Victorian and Edwardian terraced properties, and we renovate them regularly. We plan each house extensions around their particular characteristics, such as solid brick walls, rear closet wings, side returns and original period features, so the result suits the building and meets building control.
Often it will not, as many side-return and single-storey rear extensions in Forest Hill qualify as permitted development. However, if your terrace sits in a conservation area, is already extended, or you plan to go higher or wrap around, a planning application to Lewisham Council may be required. We assess your SE23 property and existing consents before drawing anything, so you know the route from the start.
Yes, Forest Hill is one of our core areas. We work on every street and the SE23 area and across the wider South East London, so wherever your home is, call 07472 424 226 and we will confirm we can help.
Every Service, One Team
The same trusted team, 30+ years' hands-on experience and free, no-obligation quotes apply to every GS Renovation service in Forest Hill. Explore what else we do locally:
Steel beam installation, RSJ and structural alterations.
Safe load-bearing wall removal with steel beam support.
Structural alterations, new openings and steel support.
Chimney breast removal with gallows bracket or beam support.
Open-plan kitchen, diner and living conversions.
Full refurbishments and whole-house renovations.
Bespoke kitchen design and installation.
Luxury bathroom and wet-room refurbishment.
Same Service, Nearby Areas
We carry out house extensions across Forest Hill and the surrounding areas. Explore a nearby location:
Contact GS Renovation today for a free, no-obligation quote for house extensions in Forest Hill.
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