Single and double storey extensions in Harrow. Trusted, professional, 30+ years' hands-on experience.
GS Renovation designs and builds extensions across Harrow, working with the generous plots that the borough's 1930s semis and interwar suburban houses were built on. With over 30 years in HA1, HA2, HA3, HA5 and HA7, we handle groundworks, steelwork, roofing and fit-out as a single project from Pinner to Stanmore.

The wide plots typical of Harrow's interwar streets suit rear and wrap-around extensions particularly well, and the side access on many semis in HA2 and HA5 makes a side-return infill straightforward. We begin with proper foundations and groundworks sized to the ground conditions, then install the steel beams needed to open the new space into the existing house, all designed by an engineer and signed off by building control.
A single or double storey rear extension transforms how these houses live, turning a compartmented 1930s layout into an open kitchen-diner that faces the garden. We manage the roof works, whether a flat roof with lantern or a pitched tie-in to the existing roofline, and complete the full fit-out, so the new room is decorated, wired and plumbed rather than left as a shell.
Whether your project is permitted development or needs a full planning application depends on the property and the design, and we set this out honestly at the start. Many single storey rear extensions in Harrow proceed under permitted development, but larger schemes, double storey work, and anything near Harrow on the Hill or in a conservation area will usually need permission from Harrow Council before building regulations even come into play.
We help you understand which route applies, prepare for the council submission where one is required, and coordinate the party wall notices that almost always follow because your neighbour shares a boundary. Building control then inspects the foundations, steelwork, drainage and insulation as the work proceeds. Handling planning, party wall and building regs together keeps an HA3 or HA7 extension moving without avoidable delays.
Harrow homeowners choose GS Renovation because we build the whole extension, not just the shell. From foundations and steel to roofing and finish, one accountable team manages the council route, party wall notices and building control on your interwar plot. Over 30 years across HA1 to HA7 means tidy working in an occupied family home and a result that adds real space.
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 Harrow, 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.
Timescales for house extensions in Harrow vary with the size and complexity of the job. After our survey we give you a realistic schedule and keep you updated at every stage of the project.
GS Renovation knows Harrow'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 Harrow 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 Harrow's homes are 1930s and interwar properties, and we renovate them regularly. We plan each house extensions around their particular characteristics, such as cavity walls, regular original layouts and the generous plots that suit extending, so the result suits the building and meets building control.
It depends on the design. Many single storey rear extensions on Harrow's generous interwar plots fall under permitted development and need only building regulations. Larger, double storey, or two-sided schemes, and anything near a conservation area or Harrow on the Hill, usually need a planning application to Harrow Council. We assess your property first and tell you which route applies before any work begins.
We do. GS Renovation covers all of Harrow and the HA1 area and the wider North West London. Call 07472 424 226 and we will confirm we work on your road.
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 Harrow. 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 Harrow and the surrounding areas. Explore a nearby location:
Contact GS Renovation today for a free, no-obligation quote for house extensions in Harrow.
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