How Much Do House Extensions in Southwark Cost?

Costs for a house extension in the United Kingdom span an extensive range, typically governed by the scale of the plan, the structural complexity involved, and which materials you choose. Industry benchmarks often place a single-storey rear extension at roughly £1,500 per square metre for a more straightforward build, while many standard expansions cluster around the £1,800–£2,500 per square metre range. Should you incorporate sophisticated steel beams, designer glazing, or higher-end finishes, you might see totals ascend beyond £3,000 per square metre.

In Southwark, located just south of the Thames and encompassing areas like Bermondsey, Camberwell, Peckham, and Dulwich, labour rates vary from moderate to quite high, influenced by proximity to central London, cultural hotspots, and ongoing regeneration zones. If your property is an older Victorian terrace near Bermondsey Street or a 1930s house in East Dulwich, you may need advanced damp-proofing or structural reinforcement, which can raise your final bill. Larger expansions frequently sit in the £40,000–£100,000+ zone, while more modest side-return designs might stay cheaper. Multi-level or premium expansions that involve complicated engineering or bespoke interior choices typically exceed baseline costs. And remember, adding a kitchen or bathroom inflates the budget even more due to wiring, plumbing, and waterproofing tasks.

When collecting multiple quotes, ensure each addresses foundation work, the structural shell, roofing, fittings, finishing, labour, overheads, and so forth. Also check whether VAT—commonly 20%—is included in the total. While home-improvement media and renovation websites provide approximate guidelines, accurate budgeting requires numerous quotes from reputable contractors, scrutinised carefully line by line.

Different Types Of Extensions

There are also different requirements for different extensions. Under is a list of the different types of house extensions:

Side extensions
Single storey extensions
Extensions more than one storey

They each have their own specific limits concerning such as rear extensions requirements, height, roofing and windows. For extensions of more than one storey, there is for example a requirement that roof pitch must match the existing house as far as practicable.

Southwark

Southwark is one of London’s central-south boroughs, spanning from the bustling banks of the Thames near London Bridge and Bermondsey down to the more residential zones of Peckham, Camberwell, and Dulwich. You’ll find a mix of Victorian terraces, modern apartments, 20th-century council estates, and classic semidetached houses. Single-storey rear expansions are very popular in areas like East Dulwich or Peckham, reconfiguring old kitchens into open-plan cooking and dining spaces. Loft conversions also appear across many pitched-roof homes, creating new bedrooms or offices. Some prime roads near Dulwich Village or along the Bermondsey riverside incorporate basements to maximise living area, though it can cost more due to water table or heritage concerns.

Local contractors emphasise that Southwark streets, particularly near London Bridge or Elephant and Castle, can be jammed with traffic during commuting hours, so scheduling skip or material deliveries mid-morning is sensible. Labour fees in Southwark generally rank mid to high, reflecting the borough’s central location and regeneration hotspots. A carefully orchestrated extension can significantly improve daily comfort and raise property appeal, especially if you’re near strong transport lines like the Overground at Peckham Rye or Camberwell’s bus routes. Discussing plans with neighbours early helps avoid tension over shared boundaries or potential party-wall disputes.

Whether you want a single-storey design merging a cramped kitchen-living area or a more comprehensive two-floor addition, ensuring your design respects Southwark’s local development environment—plus possible conservation rules around Dulwich or Bermondsey—usually yields a smoother path to planning consent.

Getting Started

Before you commence construction, figure out which extension type best suits your property in Southwark. If you’d like a bigger ground-floor kitchen, a single-storey rear extension can open up your layout. A double storey expansion gives more living space both downstairs and upstairs, possibly adding an extra bedroom or en-suite. Alternatively, a side extension can utilise a narrow side alley, especially in Victorian terraces. If outward space is restricted, a loft or basement might be an option—though basements in Southwark appear more commonly in pricier areas close to the river or historically important zones like parts of Dulwich Village.

Thorough planning early on reduces project disruption. Compile a detailed budget, examining typical labour fees, usual material costs, plus a contingency for potential structural issues or premium finishing. If your design includes substantial structural revisions—like removing major load-bearing walls—employing an architect or building designer can be wise. Certain contractors handle design-and-build but generally need partial drawings or planning approvals to quote accurately. Many Southwark homeowners consult an architect first, then collect quotes from selected builders.

It also pays to confirm your contractor choice in good time, as top-tier local firms frequently have busy diaries. Gathering several estimates well in advance allows you to interpret cost breakdowns, check references, and decide on a builder that fits both budget and style. An adept contractor may also tweak your plan—for instance, installing a skylight to brighten your rear extension or adding a small utility room behind a kitchen-lounge layout.

Project Management

You typically organise an extension in one of two ways:

1. Single contract (design-and-build or main contractor)
   You sign one contract with a company that conducts or oversees all tasks—foundations, structural frames, electrics, plumbing, roofing, finishing. They subcontract trades, usually taking 10–15% for coordination. This consolidates scheduling, giving you one core contact if issues arise.
2. Multi-trade or split contract
   You personally hire each trade—groundworkers, carpenters, roofers, plumbers, electricians, plasterers, etc. Although you dodge the main contractor’s markup, you handle the logistics. If a trade runs over schedule, subsequent tasks might be delayed, generating cost overrun or frustration. This path suits those with enough free time and knowledge to coordinate trades meticulously.

For larger expansions in Southwark, single-contractor setups are common among owners who can’t devote daily oversight. If you pick multi-trade, confirm you can devote weekly site visits to align deliveries and check progress.

Do I Need Planning Permission?

Whether planning permission is required hinges on your extension’s volume, height, and location. Under Permitted Development Rights, you can sometimes enlarge a house without a formal planning application if you respect specified dimensional constraints. If you exceed these thresholds, you must file a householder planning permission.

Under are the general rules that apply to all extensions:
Only half the area of land around the "original house" can be covered by extensions or other buildings.
Extensions cannot be higher than the highest part of the existing roof; or higher at the eaves than the existing eaves.
Where the extension comes within two metres of the boundary the height at the eaves cannot exceed three metres.
Extension cannot be built forward of the ‘principal elevation’ or, where it fronts a highway, the ‘side elevation’.
The work cannot include:
verandas, balconies or raised platforms.
a microwave antenna (e.g. TV aerial or satellite dish).
a chimney, flue or soil and vent pipe.
any alteration to the roof of the existing house.
On Article 2(3) designated land the work cannot include cladding of the exterior.
The materials used in any exterior work must be of a similar appearance to those on the exterior of the existing house.
Source: Planning Portal.

Because Southwark includes historically significant or conservation pockets—like parts of Camberwell or Bermondsey Street—some expansions that might usually be PD could still require additional checks or planning applications. Consulting Southwark Council’s planning resources or speaking to a planning specialist is advisable early on.

Do I Need Planning Permission For A New Storey?

Loft conversions altering rooflines or adding dormers generally require planning permission. However, you could add a complete new storey under permitted development if your design satisfies stringent criteria and you file a prior approval with local authorities. Otherwise, Householder/Full Planning Permission is the usual path. If your house meets these requirements, the bullet points below show the primary constraints:

Number of additional storeys:
One storey can be added to a single storey house
Two storeys can be added if the house has more than one storey.

Height increases:
The house cannot exceed 18 metres in total height
Each added storey cannot add more than 3.5 metres to the total height
If not detached (e.g. terrace or semi) the total height cannot be more than 3.5 metres higher than the next highest building that the house is attached to, adjoins, or is in the same row as.
The additional storeys must be constructed on the principal part of the house*
The additional storeys must not exceed 3 metres in height or the height of any existing storey in the principal part of the house (measured internally from floor to ceiling)
Engineering operations must only include works within the existing curtilage of the house to strengthen existing walls and foundations
The materials used must be of a similar appearance to those used in the construction of the exterior of the current house
Windows must not be placed in any wall or roof slope forming a side elevation of the house.

Afterwards, there might be extra conditions. In many Southwark terraced streets, ensuring roof design continuity can be vital for planning acceptance.

Do I Need Planning Permission For A New Basement?

Creating a new basement usually needs planning permission, and extensive sub-ground excavation also frequently requires consent because of its major scope. It’s wise to liaise with Southwark Council’s planning office early on, especially if you’re close to the Thames near Bermondsey or Rotherhithe, or in hilly areas near Dulwich. Basements rank among the largest and most costly expansions, so even if no direct planning consent is triggered, Building Regulations remain mandatory—covering structure, fire prevention, damp proofing, and ventilation.

Check local constraints that might exceed PD expansions. Some roads near Borough Market or Dulwich Village, for example, can have more restrictive guidelines to preserve heritage or streetscape. While basements are less common in more modest sections of Peckham or Camberwell, owners in pricier enclaves can still adopt them if outward expansions are blocked.

Remember Building Regulations Application

Regardless of the size and shape of your extension, it must meet building regulations requirements. This is also regardless of whether you need planning permission or not.

You need to submit a building regulations application. Simpler or smaller projects may use a Building notice, but bigger expansions typically call for a Full Plans Application, where you supply full technical details in advance. Under a Building Notice, an inspector reviews work in progress.

Note that elements like electrics, heating, plumbing, or new windows might be installed by registered tradespeople under schemes (e.g. NICEIC for electrical or FENSA for windows). Such professionals can self-certify their compliance, removing the necessity for separate building control inspections for those jobs.

A Full Plans Application often highlights design or safety gaps pre-construction, whereas a Building Notice can fit uncomplicated builds. Either way, building control’s final sign-off confirms code adherence.

What’s The Difference Between Planning Permission And Building Regulations Application?

Whereas planning permission assesses whether the extensions meets local and national requirements, building control is concerned with the structural soundness and code compliance of your build.

Even if your Southwark extension falls under PD or gains planning consent, you still need building regulations compliance—for example, stable foundations, safe electrics, proper insulation, etc. In older properties around Camberwell, Peckham, or Bermondsey, verifying your extension doesn’t overload existing walls is critical.

DIY Contribution

Homeowners sometimes aim to tackle aspects of an extension themselves. Painting, decorating, or landscaping can be plausible DIY tasks if you have experience. Doing your own demolition, to some extent, may also be possible—if you identify load-bearing structures and strictly follow safety norms.

However, tasks involving gas lines, rewiring, or major structural adjustments nearly always necessitate licensed pros. Errors could endanger safety or require expensive rework. Be realistic about your abilities; taking on too much can stall the timeline. Builders might have to wait if your DIY piece isn’t done, increasing costs. If partial DIY appeals, consult an expert early to minimise potential mistakes.

In Southwark, partial DIY often occurs after the main structural and mechanical phases, letting homeowners paint or cultivate the garden. Doing advanced structural or engineering tasks alone could hamper official checks or degrade final standards.

Do I Need An Architect?

If your planned extension is minor or relatively simple, a structural engineer or building designer may suffice. But for larger, more intricate designs, an architect typically offers solid benefits. Skilled architects integrate function, daylighting, design flow, and harmony with any heritage features.

They can also advise whether your plan is PD-eligible or likely to need formal permission. Though employing an architect raises initial costs, it frequently prevents major design oversights that arise in mid-project if the plan was insufficiently considered.

Southwark hosts many architectural styles: Georgian terraces near Borough, Victorian/Edwardian terraces in Camberwell, modern flats around Elephant and Castle, or semis in Peckham. An architect may suggest partial glass roofs or folding glass doors to create bright, open-plan living, seamlessly connecting older exteriors with modern interior expansions.

How Long Does It Take To Build An Extension?

Setting a realistic timeline is crucial for a smooth build. A smaller single-storey rear extension—especially if straightforward and typical in materials—could conclude in several weeks once ground and structural phases begin, if it’s covered by PD. Larger expansions, multi-room or multi-floor, often last from a few months to half a year or more, governed by structural complexity and the variety of trades needed.

At times, you may briefly move out if central bearing walls are removed or if fundamental services must be shut off. Even if you remain at home, dust, noise, and partial room closures are part of daily life.

It’s smart to plan a buffer. Unfavourable weather might delay exterior tasks, inspectors might request small plan modifications, or supply deliveries could get backed up. Devising a realistic schedule with your contractor reduces stress, and wrapping up early is an added bonus. Likewise, keep a financial contingency for hidden structural demands or finishing changes discovered along the way.

Southwark sees hectic traffic near Elephant and Castle, London Bridge, or major roads like the Old Kent Road, so midmorning skip drop-offs help avoid commuter jams. Changing structural layout or finish details mid-project can also shift the completion date further.

House Extensions Step By Step

Though undertaking an extension is a substantial commitment, with diligent planning, dependable experts, and a well-managed budget, you can succeed. Whether you want a larger family room, an additional bedroom upstairs, or a basement, keep track of each phase and watch for typical pitfalls.

1. Start by confirming what you want to achieve—more natural light, a larger social area, or additional bedrooms.
2. Then decide how best to organise the project.
3. Check if you need planning permission and what kind of building regulations application you need to send in.
4. Gather quotes from at least three builders if possible, ensuring each has a solid track record and good references.
5. Check that their quotes are like-for-like in terms of scope.
6. Factor in the cost of planning applications, building control fees, and professional services such as architectural drawings or structural engineering.
7. Then develop a realistic schedule, communicate frequently with your chosen contractor, and keep a close eye on both time and budget.
8. Finally, as the build nears completion, consider a thorough inspection—often called a snagging survey—conducted alongside your main contractor or an independent professional. Address any outstanding cosmetic or structural tasks before final payment. Retain building control approvals, warranties, and other compliance documentation for property transactions or mortgage updates.

When your Southwark extension is ultimately wrapped up and receives approval, you gain a more spacious home adapted to modern living. Whether you introduced a bright rear kitchen-lounge area or built an extra floor with new bedrooms, the change usually elevates comfort and property worth—particularly near sought-after local hubs like Bermondsey Street or Camberwell Green. A snagging survey ensures tiny cracks, uneven paint lines, or finishing flaws are fixed. Storing building control records and warranties proves your project met regulations, reassuring future buyers or lenders. In the end, your newly extended Southwark property can accommodate your family’s evolving needs for many years to come.