- The Brief: More Kitchen, More Light, More Family Space
- Design: Making the Most of Permitted Development
- The Build: What the Process Actually Looked Like
- Budget Oversight: No Surprises Along the Way
- The Result: What the Space Delivers Now
- What This Means for Your Wimbledon Project
- FAQs: Home Extensions in Wimbledon SW19
If you own a semi-detached or terraced house in Wimbledon, you already know the feeling. The kitchen feels tight at weekends. The dining area barely fits the table. You love the area, the schools, the green space — but the house itself is running out of room.
Moving is expensive and disruptive, and in SW19, the stamp duty alone on an upsizing move can run to tens of thousands of pounds. For many Wimbledon homeowners, a well-designed rear extension is simply the smarter call.
This case study walks through a full-width rear extension in SW19: what the brief looked like, how the design developed, what the build involved, and what the finished space actually delivers. If you're weighing up something similar, it should give you a clear picture of what to expect.
The Brief: More Kitchen, More Light, More Family Space
The clients owned a 1930s semi-detached house in SW19. Like most homes of that era, the original rear was narrow and broken up into separate rooms. The kitchen sat at the back, cut off from a small dining room by a load-bearing wall. Natural light was poor. The garden felt entirely separate from the house.
Their goals were specific:
- Open up the whole rear ground floor into one connected kitchen, dining, and living space
- Bring in as much natural light as possible
- Create a proper link — visual and physical — to the garden
- Keep the project on budget with no late surprises
They weren't interested in a modest side return or a small single-storey addition. They wanted a full-width rear extension — the full width of the house, projecting into the garden — to genuinely change how the ground floor lived.
Design: Making the Most of Permitted Development
The first question with any rear extension in Wimbledon is planning. SW19 falls under Merton Council, and like most London boroughs, Merton allows single-storey rear extensions under Permitted Development rights up to a certain depth, provided the property isn't in a conservation area and the extension meets specific height and materials conditions.
The design team worked within those parameters to maximise the footprint without triggering a full planning application. The extension ran the full width of the original house and projected four metres into the garden — achievable under Permitted Development for a semi-detached property.
Key design decisions included:
- A full-width glazed roof lantern running along the central section of the new ceiling, flooding the interior with daylight throughout the day
- Bifold doors across the rear elevation, opening the space fully onto the garden in warmer months
- Removal of the internal load-bearing wall between the old kitchen and dining room, with a structural steel beam to carry the load above
- Polished concrete flooring throughout the extension, chosen for durability, its clean aesthetic, and the thermal mass it provides when paired with underfloor heating
The design also addressed the existing kitchen layout. Rather than simply extending the footprint, the team redesigned the kitchen entirely — relocating the units to create a large central island and a proper dining zone at the garden end of the space.
The Build: What the Process Actually Looked Like
Groundworks and Foundations
The project started with groundworks. The existing rear patio came up, and new strip foundations were dug to the depth required by Building Regulations. Drainage runs were mapped and diverted where the new footprint overlapped existing routes — a common issue on 1930s properties where drainage was rarely documented accurately.
Underfloor heating pipework was laid within the slab before the concrete was poured. Getting this right at groundworks stage matters: retrofitting underfloor heating after the slab is down is expensive and disruptive.
Structural Work
Removing the internal wall between the old kitchen and dining room was one of the most consequential parts of the build. A structural engineer specified the steel beam size and bearing pad requirements. The wall came down in a controlled sequence — temporary props first, then the masonry, then the beam lifted into position and padded out.
This is where projects can go wrong if the structural specification isn't followed precisely. The beam size, the bearing length at each end, the quality of the padstone — all of it matters. Done correctly, it's invisible once plastered. Done incorrectly, it can cause cracking and movement for years.
The Extension Structure
The new extension walls were built in blockwork with a brick outer skin to match the existing house. Matching the brick was a deliberate choice: the clients wanted the extension to read as part of the original building from the garden, not as an obvious addition. The team sourced a reclaimed London stock brick that closely matched the weathered tone of the 1930s original.
The roof structure was designed around the central lantern. Timber rafters pitched gently to the rear, with the lantern sitting proud of the main roof plane. The glazing was triple-glazed and thermally broken — important in a space used year-round, where a poorly specified lantern can cause significant heat loss in winter and overheating in summer.
Fit-Out and Finishes
Once the shell was watertight, fit-out began. The kitchen was installed by MVV's own joinery team, with bespoke cabinetry designed to the client's brief. The island was finished in a contrasting painted colour to the perimeter units, with a waterfall quartz worktop. Integrated appliances throughout kept the visual lines clean.
Bifold doors were installed across the rear elevation with a low threshold, maintaining the level transition between the polished concrete floor inside and the garden terrace outside. The terrace — a new porcelain-paved area extending from the doors — was part of the same project scope, keeping the whole transition cohesive.
Budget Oversight: No Surprises Along the Way
One of the clients' stated priorities was budget transparency. Not a fixed price in the contractual sense, but genuine visibility into where money was being spent and early warning if anything was likely to shift.
Throughout the project, the team provided monthly progress reports covering budget tracking, on-site photography, and a summary of work completed against plan. When the drainage diversion at groundworks stage added a modest cost, it was flagged immediately with a clear explanation and a revised projection. The clients were never handed a surprise invoice at the end of a phase.
This kind of ongoing oversight isn't standard across the industry. Many contractors provide a quote at the start and a final invoice at the end, with limited visibility in between. On a project of this scale, that approach creates anxiety — and often, disputes.
The Result: What the Space Delivers Now
The finished extension added approximately 28 square metres to the ground floor. More than the raw square footage, it changed how the entire ground floor functions.
The kitchen, dining, and living areas now flow as one connected space. The roof lantern means the centre of the room — which would otherwise be the darkest point — receives direct daylight for most of the day. In summer, the bifold doors open fully and the garden becomes part of the living space. In winter, the underfloor heating and well-specified glazing keep the room comfortable without the energy penalty of a poorly insulated addition.
From a property value perspective, a well-executed full-width rear extension in SW19 adds meaningful value. Wimbledon's market rewards space and quality finish, particularly for family homes in the catchment areas around good schools. The clients weren't building primarily for resale, but the investment was structured to add more in value than it cost to build.
What This Means for Your Wimbledon Project
Every house in SW19 is different. The depth you can extend, the structural implications of opening up the rear, the drainage routes, the brick matching — all of it varies by property. What this project illustrates is the kind of thinking and process that produces a result you'll still be happy with in ten years.
If you're considering a home extension in Wimbledon, the most useful first step is getting a realistic cost estimate before you commit to anything. MVV's design and build service takes projects from concept to completion under one team, with budget oversight built in throughout — not just at the start.
You can get a ballpark figure for your project using the free online cost estimator at themvv.co.uk. No commitment, no lengthy form — just a sensible starting point for your planning.
FAQs: Home Extensions in Wimbledon SW19
Do I need planning permission for a rear extension in Wimbledon?
Not always. Single-storey rear extensions in SW19 can often be built under Permitted Development rights, provided they meet Merton Council's size and design conditions. The key limits are depth (up to four metres for semi-detached and terraced houses, six metres for detached), height, and materials. If your property is in a conservation area or an Article 4 direction applies, you'll need a planning application regardless of size. A design and build team can confirm which route applies to your specific property.
How long does a full-width rear extension typically take to build in London?
For a single-storey full-width rear extension of this type, a realistic programme from groundworks start to practical completion is 12 to 16 weeks, depending on the complexity of the structural work, the fit-out specification, and lead times on materials such as glazing units and bespoke joinery.
What does a full-width rear extension cost in Wimbledon in 2026?
Costs vary significantly based on size, specification, and the condition of the existing structure. A full-width single-storey rear extension in SW19 with a mid-to-high specification — including structural alterations, underfloor heating, bespoke kitchen, and quality glazing — sits in a range that reflects London build costs and the level of finish involved. The most reliable way to get a figure relevant to your project is to use an online estimator or speak directly to a contractor about your specific brief.
Can I extend the full width of my house under Permitted Development?
Yes, provided the extension doesn't exceed the permitted depth and height limits. The full width of the original house footprint is generally acceptable under Permitted Development. Your contractor or architect should check the specific conditions for your plot, including side boundaries and neighbouring property considerations.
What is a roof lantern and is it worth the cost?
A roof lantern is a raised glazed structure set into a flat or low-pitched roof, designed to bring natural light into the centre of a room that would otherwise rely only on perimeter windows. In a full-width rear extension, the central zone can feel dark without one. Quality thermally broken lanterns aren't cheap, but the impact on how the space feels day-to-day is significant. Most clients who include one consider it one of the best decisions they made.
How do I avoid budget overruns on a home extension?
The most effective approach is choosing a contractor who provides ongoing budget tracking throughout the project — not just a quote at the start. Monthly reports that show spend against budget, flag variations early, and document progress with photography give you real control throughout the build, rather than a shock at the end.
Is a rear extension a good investment in SW19?
Wimbledon's property market is strong, and family homes with well-designed open-plan ground floors consistently attract serious buyer interest. A quality rear extension in SW19 that adds usable space and improves the connection to the garden tends to add more in value than it costs to build, particularly at mid-to-high specification levels. That said, the return you get from living in the improved space every day is often the more immediate one.
Thinking about a home extension in Wimbledon? Start with a free, no-commitment cost estimate at themvv.co.uk and get a realistic ballpark for your project before you speak to anyone.