House Extensions
in
Eltham
Bespoke extensions across Eltham SE9 — from interwar semis in Well Hall and New Eltham to Edwardian terraces around Eltham High Street, and the distinctive Arts and Crafts cottages of the Progress Estate. Local knowledge, sympathetic design, honest pricing.
Proudly Serving Eltham
Planning to Handover
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A Suburb
Built Between the Wars
Eltham sits in the Royal Borough of Greenwich, and its housing stock tells a very specific story. Unlike its neighbours, Eltham was largely shaped between the 1920s and 1930s, when London County Council and private developers built out the suburb on a massive scale. The result is one of the most consistent interwar suburbs in South East London — generous semi-detached homes with bay windows, side passages, and back gardens that lend themselves remarkably well to extension.
Mixed into that interwar fabric is the Edwardian core around Eltham High Street and Well Hall Road, pockets of Victorian terracing, the nationally-significant Progress Estate built in 1915, and post-war estates including the Page Estate. Each requires a different approach — and we've worked across all of them. At Kelmend Construction, our house extensions service brings local knowledge of Royal Borough of Greenwich planning, Eltham's conservation areas, and the property types that dominate the area to every extension we build.
We Know
Your Property
1930s Suburban Semis
The dominant property type across Eltham — three or four-bedroom 1930s semi-detached homes with bay windows, side passages, and generous rear gardens. These properties were built for a different era of family life, and almost every one benefits from a rear or side return extension to create the open-plan kitchen-living space that today's families want. Often well-suited to side extensions too where the passage allows.
Arts & Crafts Cottages
The Progress Estate, built in 1915 to house munitions workers at Woolwich Arsenal, is one of the most architecturally distinctive housing estates in the country. Its Arts and Crafts cottages are Grade II listed in places and protected by both conservation area status and Article 4 directions. Extensions here are possible but require deep sympathy with the original character — and tight engagement with Greenwich Council's planning team.
Edwardian Terraces
The older Edwardian terraces around Eltham High Street, Court Road, and parts of Well Hall typically have narrow side returns and modest rear gardens — making them prime candidates for side return and rear extensions. The transformation of a cramped, dark Edwardian kitchen into a wide, light-filled open-plan space is one of the most rewarding projects we carry out in Eltham.
LCC Cottage Estates
The Page Estate and other London County Council cottage estates in Eltham have their own distinct character — modest, well-built family homes laid out around generous green space. These properties often offer more permitted development scope than the conservation areas, and side or rear extensions can transform them into genuinely modern family homes while respecting the original streetscape.
Detached & Larger Semis
The larger detached homes and substantial semis around Mottingham, Coldharbour, and pockets of Avery Hill typically sit on more generous plots — making them suitable for double-storey extensions, full wraparounds, and substantial side extensions. With the right design these properties can be transformed without losing the suburban character that makes them desirable in the first place.
Post-War & Modern Housing
Pockets of post-war and more recent housing across Eltham — including some 1950s and 1960s estates and newer developments — typically have fewer planning constraints and more straightforward permitted development scope. These extensions often deliver the highest return on investment per pound spent, particularly when adding bedrooms or modernising the layout.
Types of
Extension
Rear Extension
Extends your ground floor into the rear garden — the most common extension we build in Eltham. Particularly effective on the area's 1930s semis, where it transforms small rear kitchens into open-plan kitchen-dining-living spaces. Outside conservation areas, most single-storey rear extensions on Eltham properties fall under permitted development.
Double Storey Extension
Adds space on both floors — typically a larger kitchen below and an extra bedroom or bathroom above. The interwar semis of Eltham are well-suited to double storey rear extensions where plot depth allows. Always requires planning permission, and Greenwich Council pays close attention to how the extension reads against neighbouring properties.
Side Return Extension
Particularly effective on the Edwardian terraces around Eltham High Street and Well Hall Road. Fills in the narrow side alleyway to create a wide, light-filled kitchen. Often combined with a rear extension for a full wraparound — one of the most transformative projects you can do on a period terrace.
Wraparound Extension
Combines a rear extension with a side return into a single L-shaped build. The most expansive single-storey option for terraced and semi-detached properties — and increasingly popular across Eltham's 1930s and Edwardian stock where the plot allows. Requires planning permission and careful structural design.
Side Extension
Builds outward into the side passage or side garden of a semi-detached property — very common on Eltham's 1930s semis. Can add a utility room, downstairs WC, home office, or simply widen the existing kitchen. Greenwich Council generally allows these provided the new extension is set back from the front elevation and uses sympathetic materials.
Garden Room Extension
A full-build extension with large glazed doors and integrated heating, designed to bring the garden into the home. Particularly effective on Eltham's larger plots in Mottingham, Avery Hill, and Coldharbour. Built to the same structural and insulation standard as the rest of your home — not a glorified garden office.
What You Need
to Know
Eltham sits in the Royal Borough of Greenwich, and Greenwich's planning department has its own approach — distinct from Bromley or Bexley. Here's what most affects Eltham homeowners.
The Progress Estate
The Progress Estate has Article 4 directions removing most permitted development rights, and many properties are Grade II listed. Extensions here are subject to particularly close design scrutiny — but they are possible with the right approach and material choices.
Conservation Areas
Eltham contains several conservation areas including the Progress Estate, Eltham Park, Coldharbour, and Page Estate. If your property sits within one, design quality, materials, and proportions become critical to gaining approval. Visible elevations matter most.
Permitted Development
Outside conservation areas and Article 4 zones, many of Eltham's 1930s semis and post-war properties qualify for single-storey rear extensions under permitted development. We check the rules against your specific property at the start of every project.
Interwar Character
Greenwich Council's local design guidance places real emphasis on protecting the cohesive interwar character of Eltham's residential streets. Extensions that respect the rhythm, materials, and proportions of neighbouring properties are far more likely to be approved.
Typical Approval Timelines
Greenwich Council typically processes household planning applications within 8 weeks of validation. Applications involving conservation areas or listed properties may take longer — we factor this realistically into your build programme.
Party Wall & Neighbours
Most extensions in Eltham involve party wall considerations — particularly on the semi-detached interwar stock. We flag this early so notices can be served properly and any party wall agreements reached well before work is due to begin.
Working in
Conservation Areas
Several distinct conservation areas exist within Eltham — and properties in or near these need additional care in their design. We've worked across all of the following:
If you're not sure whether your address falls within a conservation area, it's essential to check before any design work begins. We'll confirm for your specific property at the consultation stage and explain exactly what it means for the project — including whether Article 4 directions apply.
Why Eltham
Homeowners Choose Us
Local Eltham Knowledge
We've worked across Eltham, Well Hall, New Eltham, Mottingham, Avery Hill, and the Progress Estate. We know the property stock, the conservation areas, and Greenwich Council's planning preferences — well before we visit your home.
Interwar Property Specialists
Eltham is dominated by 1930s semis — and they have their own specific quirks. Suspended timber ground floors, particular wall constructions, side passages of varying widths. We've worked on hundreds of similar properties and know what to look for from day one.
Family-Run, Directly Accountable
You deal with us throughout the project — not a project manager you've never met. We're on site, we're reachable, and our reputation depends on every Eltham job we do.
Itemised, Honest Quotes
Fully line-itemised quotes — no vague allowances or hidden costs. Any changes mid-project are costed in writing before we proceed. The standard you'd expect on any reasonable construction project, but unfortunately rarer than it should be.
Planning Handled
We don't just build. We advise on planning routes, work with your architect (or recommend one familiar with Greenwich), and manage the building control process. You won't be chasing Greenwich Council yourself.
Conservation Area Experience
The Progress Estate, Eltham Park, Page Estate — we've delivered extensions in all of them. Conservation area work requires a different approach to materials, proportions, and council engagement. We know what gets approved and what doesn't.
Our Extension
Process in Eltham
Free Consultation & Site Visit
We come to your Eltham property, walk the space, and discuss what you want to achieve. We give you an honest read on what's feasible, what planning route applies for your address — including conservation area or Article 4 constraints — and the budget you're realistically looking at.
Design & Planning
We work with your architect — or recommend one we trust who knows Greenwich's planning department — to develop drawings. Once finalised, we advise on the route: permitted development, householder application, or full planning. We handle party wall notices if required.
Detailed Quote & Contract
Once planning is approved and drawings are finalised, we produce a fully itemised quote. The contract is clear and detailed: scope, timeline, stage payments, and how variations are handled. No ambiguity.
The Build
Work starts on the agreed date. We manage groundworks, structure, trades, and materials. Regular photo updates and direct access to us throughout. Site secured and cleaned every day — important on Eltham's typically well-maintained residential streets.
Finishing & Fit-Out
Plastering, flooring, electrics, plumbing, decoration — coordinated to flow seamlessly from the structural work. We keep the programme on track without gaps between trades, which is where most extension projects lose time.
Handover & Sign-Off
Royal Borough of Greenwich building control sign-off obtained. Full snagging walkthrough with you. We don't close the job until you're satisfied — and we're on the end of the phone if anything comes up afterwards.
Covering
the Whole Area
We carry out house extensions across Eltham and the surrounding Royal Borough of Greenwich. Our core areas include:
Eltham Extension
FAQs
How much does an extension cost in Eltham?
A single storey rear extension in Eltham 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. Properties on Eltham's 1930s semis often have specific structural considerations — suspended timber ground floors, particular foundation types — that we factor into the quote up front. We'll give you an accurate figure after visiting your property.
Do I need planning permission for an extension in Eltham?
Not always. Many single storey rear extensions on Eltham's 1930s semis and post-war properties fall under permitted development. However, if your property is in one of Eltham's conservation areas — particularly the Progress Estate, Eltham Park, or Coldharbour — or has an Article 4 Direction in force, full planning permission will be required. We assess this for your specific property at the consultation stage.
How long does Greenwich Council take to approve a planning application?
The Royal Borough of Greenwich typically processes household planning applications within 8 weeks of validation. More complex applications — particularly those involving conservation areas or listed buildings — can take longer. The Progress Estate in particular requires careful design review. We build realistic timelines into your programme so the build start date isn't pushed back by approval delays.
Can I extend my house on the Progress Estate?
In most cases, yes — but it requires the right approach. The Progress Estate is one of the most architecturally important housing estates in the country, and Greenwich Council protects it with conservation area status and Article 4 directions. Extensions here typically need to be modest, sit at the rear of the property, use sympathetic materials, and not be visible from key public views. We've delivered extensions on the Progress Estate before and understand what's possible — and what isn't.
Which areas of Eltham are conservation areas?
Several distinct conservation areas exist within Eltham. The most significant are the Progress Estate, Eltham Park (North and South), Coldharbour, the Page Estate, Well Hall Pleasaunce, Eltham High Street, and the area around Eltham Palace. If your property is in or near any of these, additional design considerations apply. The full list and boundary maps are available on the Royal Borough of Greenwich website, or we can check for your specific address.
Will an extension add value to my Eltham home?
In most cases, yes — a well-built extension on a typical Eltham property can add 10–20% to its value. Eltham's 1930s housing stock in particular benefits from the modernisation an extension provides — converting a small, dated kitchen into an open-plan family space. The build quality matters significantly though: a poorly executed extension on a period property can cause problems at sale and ultimately cost more than it added.
Can I stay in my Eltham home during the extension?
In most cases, yes — and most of our Eltham clients do. We plan the work carefully to minimise disruption, particularly during the breakthrough from the existing kitchen into the new extension. We seal off dust, protect flooring and furnishings, and always leave the site clean and secure at the end of the day. For larger or more complex projects we'll discuss temporary relocation honestly at the planning stage.
How long does a typical Eltham extension take to build?
A typical single storey rear extension on an Eltham property takes 10 to 16 weeks from start on site to practical completion. Double storey, wraparound, and side extensions take 16 to 24 weeks. This is build time only — planning permission (where required) typically adds 8 to 13 weeks in Greenwich before work can begin. We'll give you a realistic programme in your quote and stick to it.
Extending Your
Home in Eltham?
Tell us about your project and we'll come to you for a free, no-obligation consultation anywhere in SE9.
No pushy sales. No call centres. Just a straight conversation about your Eltham project.