House extensions in Sidcup
Extension builders based in Sidcup, working on the 1930s semis of Blackfen, Lamorbey and Albany Park, the Edwardian streets around the station and the eight Sidcup conservation areas. Planning, build and finish, managed as one job.
Built by a Sidcup company
Kelmend Construction is based in Sidcup. We know the housing here because we live here: the long streets of 1930s semis in Blackfen, Lamorbey and Albany Park, the Edwardian houses around the station and Halfway Street, the cottage-style estates of The Hollies and Longlands, and the larger plots around Lamorbey Park and The Green.
Our house extensions service covers the whole of DA14 and DA15. Sidcup has eight conservation areas, more than any other part of the borough, so knowing which streets need planning permission and which fall under permitted development saves weeks and money before a drawing is produced.
We know your property
1930s semis
The dominant house type across Sidcup: three-bedroom interwar semis with bay windows, hipped roofs, side passages and long rear gardens. Built for a different era of family life, almost every one benefits from a rear extension to create the open-plan kitchen and living space today's buyers expect.
Edwardian houses
The older Edwardian stock around Sidcup station, Halfway Street and Christ Church sits in or near conservation areas. Generous proportions and rear gardens suit extensions well, but design and materials are reviewed closely and some streets need planning permission for work that is permitted elsewhere.
The Hollies and Longlands
The Hollies is one of the borough's most distinctive interwar developments, with its own conservation area, and Longlands Road and Willersley Avenue are protected too. Extensions here need to respect the original cottage style and are assessed on how they read from the street.
Larger detached and semis
The streets around Lamorbey Park and The Green contain larger detached and semi-detached homes on generous plots, suited to double storey rear extensions, side extensions and full wraparounds. The Green itself is a conservation area.
Village and post-war
Foots Cray village is a conservation area with older cottages and terraces, surrounded by post-war housing with fewer constraints and straightforward permitted development scope.
Interwar and post-war estates
The streets toward New Eltham and Avery Hill mix 1930s semis with post-war housing. Planning conditions are generally straightforward here, and these are often the highest-return extension projects per pound spent.
Types of extension we build in Sidcup
Rear extension
The most common extension on Sidcup's 1930s semis. Extends the ground floor into the rear garden to create an open-plan kitchen and living space. Outside the conservation areas, most single storey rear extensions fall under permitted development.
Double storey extension
Adds a larger kitchen below and a bedroom or bathroom above. Well suited to the deeper plots around Lamorbey Park and The Green. Always requires planning permission, and Bexley Council looks closely at how it sits against the neighbouring semi.
Side return extension
Fills in the narrow passage down the side of the older terraced and semi-detached houses near the station and Halfway Street, creating a wide, light kitchen. Often combined with a rear extension for a full wraparound.
Wraparound extension
Combines rear and side return into one L-shaped build, the most expansive single storey option. Popular on Sidcup's semis where the side passage allows. Requires planning permission where conservation area rules apply.
Side extension
Builds into the side passage of a semi-detached house to add a utility room, downstairs WC or home office, or to widen the kitchen. Very common across Blackfen and Albany Park, and usually permitted development outside conservation areas.
Garden room extension
A full-build extension with large glazed doors and integrated heating, designed to bring the garden in. Suits the long gardens typical of Sidcup's interwar streets.
What you need to know before extending in Sidcup
Sidcup sits in the London Borough of Bexley. The borough's planning team is straightforward to work with, but Sidcup's eight conservation areas mean the rules change street by street.
Permitted development
Outside conservation areas, most of the borough's 1930s semis qualify for single storey rear extensions under permitted development, with the larger home extension route available for deeper builds subject to neighbour consultation. We confirm the position for your address before any design work.
Conservation areas
Bexley has 23 conservation areas, eight of them in Sidcup alone, plus Old Bexley, Parkhurst and Red House Lane. Within these, extensions visible from the street need planning permission and the council reviews materials and proportions closely.
Article 4 directions
Old Bexley, Old Forge Way, Red House Lane and Brook Street carry Article 4(2) directions that remove some permitted development rights. Work that would be permitted elsewhere needs a full application in these areas.
Suburban character
Bexley's planning policy protects the consistent interwar character of its residential streets. Extensions that respect the roof line, materials and spacing of neighbouring houses are far more likely to be approved.
Approval timelines
Bexley Council typically decides householder applications within 8 weeks of validation. Conservation area applications can take longer. We build realistic timelines into your programme.
Party walls and neighbours
Almost every extension on a semi-detached or terraced property involves the Party Wall Act. We flag this at the consultation so notices can be served early.
Sidcup's conservation areas
Eight conservation areas cover parts of Sidcup. If your property is in or next to one, it affects your extension options:
Old Forge Way also carries an Article 4 direction. Boundaries are not always obvious from the street, so we check your address against Bexley's current maps at the consultation.
Why Sidcup homeowners choose us
Based in Sidcup
We're based in Sidcup, so your site visit, your build and any snag afterwards are a few minutes away, not a trip across London.
1930s semi experience
The interwar semi is the borough's dominant house type and it has its own quirks: suspended timber floors, cavity walls of varying quality, side passages of varying widths. We know what to look for before we start.
Bexley Council experience
We know how Bexley's planning department approaches householder applications, which conservation areas bite and which don't, and how to present an application for approval first time.
Directly accountable
You deal with us throughout, not a project manager you've never met. We're on site, we're reachable, and our reputation depends on every local job.
Itemised, honest quotes
Fully itemised quotes with no vague allowances. Any changes are costed in writing before we proceed.
Planning handled
We advise on the planning route, work with architects who know Bexley, and manage building control. You won't be chasing the council yourself.
Our extension process in Sidcup
Free consultation and site visit
We come to your Sidcup property, walk the space and give you an honest read on what's feasible, which planning route applies for your address and a realistic budget.
Design and planning
We work with your architect, or recommend one who knows Bexley Council, to develop drawings. We advise on the route, submit any application and manage party wall notices.
Detailed quote and contract
Once drawings are finalised we produce a fully itemised quote. Scope, timeline, stage payments and how variations are handled are set out in writing before any work begins.
The build
Work starts on the agreed date. We manage groundworks, structure, trades and materials, with regular photo updates and direct access to us throughout. The site is secured and cleaned every day.
Finishing and fit-out
Plastering, flooring, electrics, plumbing and decoration run as one programme with no gaps between trades.
Handover and sign-off
Bexley building control sign-off is obtained and we walk the finished extension with you to pick up any snags. We don't close the job until you're satisfied.
Covering Sidcup and the borough
Based in Sidcup and building across the London Borough of Bexley, including:
Sidcup extension FAQs
How much does an extension cost in Sidcup?
A single storey rear extension typically costs between £1,500 and £2,200 per square metre, depending on size, specification and finish. A 20m² kitchen extension might range from £30,000 to £50,000 fully finished. We'll give you an accurate figure after visiting your property.
Do I need planning permission for an extension in Sidcup?
Not always. Many single storey rear extensions on 1930s semis fall under permitted development. If your property is in one of the local conservation areas or an Article 4 area, planning permission will be required. We check your specific address at the consultation.
How long does Bexley Council take to approve a planning application?
Bexley Council typically decides householder applications within 8 weeks of validation. Conservation area applications and those with neighbour objections can take longer. We build realistic timelines into your programme.
Will an extension add value to my Sidcup home?
In most cases, yes. A well-built extension that turns a small 1930s kitchen into an open-plan family space typically adds 10 to 20% to value, and the local market has rewarded that kind of modernisation consistently. Build quality matters: a poor extension causes problems at sale.
Can I stay in my home during the extension?
In most cases, yes, and most clients do. We plan the work to minimise disruption, particularly during the breakthrough from the existing house, seal off dust, protect flooring and leave the site clean and secure at the end of each day.
How long does a typical extension take to build?
A single storey rear extension takes 10 to 16 weeks from start on site to practical completion. Double storey, wraparound and side extensions take 16 to 24 weeks. Planning permission, where required, adds 8 to 13 weeks before work begins.
Extending your home in Sidcup?
We're based here. Tell us about your project and we'll come round for a free, no-obligation consultation.
No pushy sales. No call centres. Just a straight conversation about your Sidcup project.