How Much Do House Extensions Cost?

Extension costs vary significantly across the UK, shaped by the size of your project, material selections, and how complex your structural modifications are. Industry data suggests that a single-storey rear extension can start roughly at £1,500 per square metre for a basic concept, while most run in the £1,800–£2,500 per square metre range. If you introduce elaborate steel reinforcements, high-spec glazing, or premium decor, you may surpass £3,000 per square metre.

In Wood Green, located in the north London borough of Haringey, labour fees typically range from moderate to occasionally high, reflecting decent housing demand and relatively good transport links. If your home is a Victorian terrace near Alexandra Palace Station or a 1930s semidetached off Green Lanes, additional structural tasks—like reinforcing foundations or dealing with damp issues—could inflate final spending. Larger expansions often settle between £40,000 and £100,000+, whereas smaller side-return or single-storey additions are cheaper. Ambitious multi-floor or luxury expansions exceeding typical thresholds appear if advanced engineering or very upmarket finishes are required. When you add or move a kitchen or bathroom, factor in extra plumbing and wiring costs that can push your budget higher.

When gathering quotes, ensure each addresses foundation digging, any structural frameworks, roofing, fittings, finishing, labour overhead, etc. Also confirm whether VAT—commonly 20%—is incorporated or excluded. Although you can find approximate figures in home-improvement media, genuine accuracy arises from requesting multiple quotes from qualified local builders and comparing them 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.

Wood Green

Wood Green, situated in the London Borough of Haringey, is known for its vibrant shopping district around Wood Green High Road, proximity to Alexandra Palace, and a mix of Victorian, Edwardian, and 20th-century housing. You’ll find terraces in areas close to Turnpike Lane or near Bounds Green, semidetached houses dotted around various local streets, and some modern flats in regeneration pockets. Single-storey rear expansions often open up older kitchens to form open-plan family living spaces. Loft conversions remain popular in pitched-roof properties, creating new bedrooms or offices. While basements aren’t particularly common in Wood Green, some owners in more valuable roads near Alexandra Park or in hilly enclaves might adopt them if outward expansions are limited.

Local builders mention that Wood Green roads near the busy High Road or Turnpike Lane station can clog at peak times, so scheduling skip deliveries often avoids early morning or evening rush hours. Labour charges typically track moderate within Haringey. A thoughtful extension usually brings daily comfort improvements and potential property value growth, especially if you live near good transport lines like the Piccadilly line at Wood Green or Bounds Green. If you share boundary walls in terraces around Noel Park or in semis near Alexandra Palace, speaking to neighbours early helps you pre-empt any party-wall or noise disputes.

Whether you design a simple single-storey for a 1930s home near Turnpike Lane or a two-storey expansion in an Edwardian terrace near Alexandra Palace, adapting your extension plan to Wood Green’s mix of housing and local planning rules can secure smoother approvals.

Getting Started

Before construction, decide which extension type best fits your property in Wood Green. A single-storey rear model can fuse a small kitchen-diner into a single open space. A double storey approach extends both ground and upper floors, offering an additional bedroom or upstairs bathroom. A side extension makes use of an alley or driveway, and if outward expansions are not practical, a loft or basement might be feasible—though basements aren’t commonly found in Wood Green, while loft conversions frequently appear in pitched-roof terraces or semis.

Crafting a detailed budget is crucial, referencing typical local trade costs and standard materials, plus adding a contingency for hidden structural tasks or premium finishing. If your proposal encompasses serious structural changes—like eliminating load-bearing walls—employing an architect or building designer is recommended. Some contractors do design-and-build, but they typically need partial planning or initial sketches for an accurate quote. Many Wood Green homeowners start with an architect, then collect estimates from carefully vetted builders.

It’s also helpful to finalise a contractor some months before you hope to break ground, as good local teams can be busy—especially near the main shopping district or times of local building surges. Obtaining multiple quotes early allows you to compare cost breakdowns, check references, and pick a contractor whose pricing and style match your aspirations. A knowledgeable builder may also refine your plan—for instance, adjusting an internal corridor to include a storage nook or placing rooflights to maximise sunshine in your new space.

Project Management

Extensions typically fall into one of two project management structures:

1. Single contract (design-and-build or main contractor)
   You sign one overarching deal with a building firm that executes or manages everything—foundation works, structural frames, electrics, plumbing, roofing, finishing. They subcontract specialist trades, usually marking up 10–15% for management. This keeps scheduling under one umbrella, simplifying communications.
2. Multi-trade or split contract
   You personally hire groundworkers, carpenters, roofers, electricians, plumbers, etc. Though this might drop the main contractor’s overhead, you run each schedule. If a trade goes behind, subsequent tasks hold, which can heighten costs or tension. This route suits owners able to invest plenty of time to track progress.

For bigger expansions in Wood Green, single-contractor setups are often chosen, particularly by those not keen on daily scheduling. If you prefer multi-trade, confirm you can coordinate visits to the site regularly to maintain deliveries and confirm tasks are on track.

Do I Need Planning Permission?

Whether you require planning permission depends on your extension’s scale, height, and boundary relationship. Under Permitted Development Rights, you might expand a house without a formal planning application if your plan stays under certain dimension constraints. If it overshoots these, a householder planning permission is required.

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.

Some roads in Wood Green, particularly near conservation pockets around Alexandra Palace or Noel Park Estate, may have Article 4 directions removing certain PD rights. Checking with Haringey Council or a planning consultant clarifies if your extension meets PD or demands official permission.

Do I Need Planning Permission For A New Storey?

Loft conversions that adjust roof shape or add dormers often require planning permission. However, you might add a storey under permitted development if you obey strict criteria and submit a prior approval. Otherwise, Householder/Full Planning Permission is standard. Below are the bullet points specifying the key requirements:

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.

Other guidelines might kick in once you complete the work. In many older Wood Green terraces, consistent roof heights can be integral to local street appeal, so thorough planning is recommended.

Do I Need Planning Permission For A New Basement?

Usually, a new basement calls for planning permission, and substantial excavation below your house similarly often needs permission because of its scale. Talking with Haringey Council’s planning office early helps you understand local concerns, especially if your street has historical significance or tricky geology. Basements are among the most expensive expansions, so even if official permission isn’t always triggered, Building Regulations remain key for structural stability, damp proofing, ventilation, etc.

You may face more constraints than typical PD expansions if you live near protected roads or vantage spots around Alexandra Palace. In Wood Green, basements are not overly common, though some owners in pricier enclaves or near the hillier areas might consider them if no outward expansions are possible.

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 a building regulations application. Smaller or simpler expansions might rely on a Building notice, while larger or more complex builds typically call for a Full Plans Application, meaning you submit detailed drawings for approval pre-construction. With a Building Notice, an inspector assesses work on site as it develops.

Note also that specialised tasks involving electrics, windows, plumbing, or heating can be carried out by registered trades under competent person schemes (for instance, NICEIC for electrics or FENSA for windows), letting them self-certify their compliance in place of separate building control inspections for those components.

A Full Plans Application commonly flags potential design or safety gaps early, while a Building Notice might suffice for simpler expansions. Ultimately, building control must confirm your completed extension meets code standards, ensuring safety and reliability.

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

Whereas planning permission checks whether the extensions meets local and national planning guidelines, building control ensures the final structure satisfies building regulations.

Even if your Wood Green extension is sanctioned under PD or obtains official planning consent, building regulations remain indispensable—for example, guaranteeing foundation depth, adequate insulation, correct electrical safety, etc. In older properties around Noel Park or near Turnpike Lane, verifying structural loads is critical so that your new build doesn’t compromise existing walls.

Homeowners sometimes seek to handle parts of the extension themselves. Painting, decorating, or landscaping can be good DIY tasks if you have relevant experience. Doing your own demolition, partially, might also be possible—if you accurately identify supporting walls and follow safe demolition practices.

However, more critical tasks such as wiring electrics, installing gas lines, or major structural modifications typically require certified experts. Mistakes could be dangerous or incur large remedial costs. Evaluate your capabilities realistically; overcommitting may slow the entire schedule. Builders might pause if your DIY tasks are delayed, inflating final bills. If partial DIY is attractive, consult a professional early to avert serious pitfalls.

In Wood Green, partial DIY frequently emerges after the main structural build is concluded—like re-painting, minor finishing, or garden re-design. Attempting advanced structural or engineering tasks yourself risks official sign-off issues or undermining build standards.

Do I Need An Architect?

If your extension is modest and straightforward, you may manage with a structural engineer or building designer. But for more complex or expansive plans, an architect is often incredibly helpful. Skilled architects balance practical function, aesthetic coherence, and synergy between old and new spaces.

They can also establish whether your layout sits under PD or likely needs formal planning permission. Although an architect’s fee might lift initial spending, it typically stops design flaws or structural conflicts from arising mid-project and spiralling costs.

Wood Green includes varied housing, from Edwardian terraces near Alexandra Park to 1930s semis near Turnpike Lane, plus post-war estates. An architect could propose partial glass ceilings or foldable glass doors, merging older facades with contemporary open-plan living, reflecting the evolving local architectural character.

How Long Does It Take To Build An Extension?

Outlining a practical timetable is crucial. A smaller single-storey rear extension—particularly if it’s a simple design and standard materials—can finish in weeks once foundation and framing begin, so long as it’s PD-compliant. Larger expansions, multi-room or multi-level, might stretch from a few months to half a year or more, influenced by structural engineering needs and multiple trades.

Occasionally, you might relocate briefly if load-bearing walls are removed or if vital utilities get disconnected. Even if you remain, noise, dust, and restricted room usage become part of everyday life.

Plan extra time for possible snags. Stormy or cold weather can slow outdoor tasks, inspectors might request small layout changes, or deliveries might lag. Forming a realistic schedule with your contractor curtails stress, and finishing ahead of time is always positive. Similarly, a budget buffer helps if hidden structural difficulties or finishing shifts pop up.

Wood Green roads near the busy High Road or Turnpike Lane station often see traffic backups, so midmorning skip drop-offs typically circumvent commuter clusters. Changing finishes or layout details mid-building can also move your wrap-up date further.

House Extensions Step By Step

While an extension is substantial, with disciplined planning, proficient trades, and a structured budget, you can achieve success. Whether you’re aiming for an expanded family kitchen-lounge, extra bedrooms upstairs, or even a basement, keep track of each phase and watch out 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 finishing flaws prior to final payment. Retain building control certificates, warranties, and other compliance records for a future mortgage or property sale.

Once your Wood Green extension wraps up and obtains its final checks, you’ll enjoy a more spacious and liveable home. Whether you introduced a bright open-plan ground floor or constructed a new storey for upstairs bedrooms, the improvement often enhances everyday comfort and property attractiveness—particularly near transport links (like the Piccadilly line) or green spaces such as Alexandra Park. A snagging survey ensures minor cracks or paint mismatches are resolved. Keeping building control documentation and warranties validates that your build stayed within regulations, reassuring any potential buyers or lenders if you choose to move on. With that, your newly expanded Wood Green home can support your evolving household needs for years to come.