How Much Do House Extensions Cost?

Extension prices across the UK vary widely, driven by how big the scheme is, the materials involved, and its overall complexity. Data indicates a single-storey rear extension can launch at about £1,500 per square metre for a minimal layout, while typical expansions land in the £1,800–£2,500 per square metre zone. If you select advanced steel frameworks, specialised windows, or luxurious interior choices, you could climb above £3,000 per square metre.

In East London, labour rates can be lower than city-centre levels, letting many owners channel extra funds into distinctive finishes or better-quality doors and windows. Still, older Victorian terraces or post-war estates might require structural strengthening, raising overall costs. Expansions often run between £40,000 and £100,000+ for more substantial projects, yet narrower side-return efforts might be less, and multi-level or very elaborate designs could exceed normal thresholds if the build demands complex engineering or premium materials. A key consideration is whether you plan to incorporate a kitchen or bathroom, as these wet-area expansions require added plumbing, wiring, and waterproofing.

When gathering quotes, confirm each covers everything—foundation, structural shell, roofing, fittings, finishing, labour, and overhead. Also clarify whether VAT—often 20%—is included or added on. While cost references in magazines or on renovation websites can guide you initially, exact estimates come from collecting several builder bids and reviewing them 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.

East London

East London spans a broad zone, including boroughs like Tower Hamlets, Newham, Hackney, and Barking & Dagenham. Property owners in areas like Stratford might add single-storey expansions to create bright dining-living zones, while older terraces in Hackney or Tower Hamlets benefit from side-return additions that reclaim narrow yard space. Loft conversions are a constant choice for Victorian or Edwardian terraces, providing extra bedrooms without relinquishing garden footprints. Basements can appear occasionally, although certain areas near rivers or water channels could complicate deep excavation.

Local contractors often highlight that certain East London districts have heavily parked roads or narrow streets, so skip deliveries typically avoid peak travel times. Labour fees hover below the capital’s highest, but older dwellings may demand extra checks for structural stability or damp-proofing. A well-implemented extension commonly brings daily convenience and raises a home’s appeal, particularly if it’s near new transport lines like the Elizabeth line or Overground routes. Checking in early with neighbours helps if you share party walls or tight boundary lines.

Whether your ambition is a compact extension to join a galley kitchen with a lounge or a multi-storey arrangement that offers extra bedrooms, tailoring the design to East London’s local guidelines and property styles is wise.

Getting Started

Before building, determine which extension type fits your house best. A single-storey rear addition might enlarge a small kitchen or dining zone, while a double storey scheme yields further upstairs rooms. If you have a side passage, you might do a side-return or wrap-around extension. Alternatively, you can attempt a loft or basement, especially if outward land is limited. Basements in East London can pose challenges with water tables or older utility lines, but some owners do them if upward expansion isn’t feasible.

Commit enough time to planning at the outset. Develop a detailed budget, referencing standard labour costs and material outlays, and keeping a contingency for premium finishes or structural adaptation. If the plan involves notable structural realignments, hiring an architect or design professional might be beneficial. Certain builders provide design-and-build packages, but they often want partial consents or sketches to quote precisely. Many East London families speak with an architect first, then request contractor bids once they have clarity on drawings.

Also, secure a dependable builder as soon as possible, since well-regarded teams can be booked out. Gathering multiple quotes early allows you to compare pricing, assess references, and pick a builder you trust. A seasoned contractor might also suggest modifications—like a better floor layout or additional windows for ventilation and daylight.

Project Management

There are typically two ways to organise an extension:

• Single contract (design-and-build or main contractor)
  One contract with a principal building company covers everything: foundation tasks, carpentry, electrics, plumbing, roofing, and so on. They subcontract specialty trades, adding a roughly 10–15% markup for management, but scheduling is unified.
• Multi-trade or split contract
  You take charge of each separate trade—groundworkers, bricklayers, electricians, roofers, plumbers, etc. Although you skip the main contractor’s overhead, you assume the project manager role. If one trade runs behind, subsequent tasks might stall, possibly increasing costs. A thorough grasp of building processes or ample spare time is generally needed.

For big or challenging expansions in East London, many prefer single-contractor setups, letting them sidestep the daily burdens of coordinating trades. If you opt to juggle trades yourself, confirm you can visit the site regularly to oversee progress and ensure deliveries are timely.

Do I Need Planning Permission?

Whether you require planning permission depends on your extension’s size, height, and location on the property. Under Permitted Development Rights, extending a house without a formal application may be possible if you stick to certain size and location boundaries. However, if the design overshoots these, a householder planning permission application is normally 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.

In East London, conservation areas near Hackney, Tower Hamlets, or Walthamstow Village might impose added constraints. Checking with your local planning department clarifies if your scheme is valid under PD or if a formal application is necessary.

Do I Need Planning Permission For A New Storey?

Loft extensions with dormers or shifting the roofline typically need planning approval. Still, you might add a new storey under permitted development, provided you adhere to strict criteria and submit a prior approval request. Otherwise, Householder/Full Planning Permission is the usual path. If your house meets these requirements, see the bullet points below for 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.

After finishing, certain post-completion rules might also apply. Checking with East London planning officials helps ensure your newly added floor matches local guidelines for consistent roof heights.

Do I Need Planning Permission For A New Basement?

Typically, constructing a basement requires planning permission, and big excavation below ground is also likely to need planning permission due to its scope. It’s advisable to speak with your local planning authority upfront, clarifying relevant conditions. Basement development is inevitably extensive; even if formal planning consent isn’t explicitly needed, you must adhere to Building Regulations for structural strength, safe escapes, adequate ventilation, damp proofing, and more.

Always verify local constraints that could override normal PD expansions. If your property is subject to prior planning conditions, even an ordinarily allowed extension might be disallowed. Refer to local council guidance or hire a planning consultant for confidence in your basement plan.

In East London, some dwellings may have partial basement options if outward expansions aren’t feasible. But costs often rise because of engineering challenges related to older foundations or higher water tables in riverside boroughs.

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 will need to submit a building regulations application. For smaller projects you can submit a Building notice but for larger extensions you’ll probably need a Full Plans Application. In this case full details of the proposed work will be submitted for approval before the work begins. With a Building Notice an inspector will inspect and approve the work as it is performed.

A Full Plans Application reveals potential design or safety missteps pre-construction, while a Building Notice may suffice for simpler additions. Either method demands final approval from building control to certify you meet rules around stability, fire safety, and so on.

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 concerns structural safety and regulations compliance.

Even if your East London house extension is fine under PD, building regulations remain mandatory, ensuring that foundations, insulation, and other elements meet updated codes. Many older East London terraces can have shared walls or less stable ground, needing thorough checks for robust engineering.

DIY Contribution

Homeowners sometimes consider tackling parts of an extension themselves. Painting, decorating, or landscaping can be good DIY tasks if you have the skills and time. Doing your own demolition, to an extent, can also be feasible—provided you understand which walls are load-bearing and follow safety precautions.

However, tasks such as electrical installation, gas connections, and structural changes almost always require qualified professionals. Mistakes in these areas can be costly and dangerous. Being realistic about your abilities is crucial; if you overcommit, you risk causing delays. Builders may need to pause until you finish a particular job, which can add to your final bill. If you’re determined to do some work yourself, consider hiring a professional for a consultation, as their input can help you avoid pitfalls.

In East London, partial DIY might revolve around final décor or smaller landscaping once the structural skeleton is concluded. Taking on mechanical or structural roles unassisted could jeopardise the timeline if things go amiss.

Do I Need An Architect?

If your scheme is straightforward, a structural engineer or building designer might suffice. Nonetheless, for bigger or more intricate expansions, employing an architect can prove invaluable. A knowledgeable architect not only considers looks but also practicality—ensuring logical room flow, adequate daylight, and harmony between new areas and existing spaces.

They can also verify whether you’re inside PD rules or need planning approval. Although an architect’s fee raises initial costs, their input commonly forestalls expensive errors and fosters a more unified design.

East London includes varied architectural styles, from classic Victorian in Hackney to modern builds in Royal Docks. An architect’s perspective can help unify a period facade with a contemporary extension or figure out how to best bring daylight into a deeper terraced property.

How Long Does It Take To Build An Extension?

Laying out a coherent schedule is critical. A modest single-storey addition—a rear extension for instance—might be completed in mere weeks once contractors begin, assuming it’s simple, leverages standard materials, and fits PD. Larger projects, multi-room or multi-level, could last several months to half a year or more, influenced by complexity and the number of trades involved.

Occasionally, you may need to move out briefly if fundamental walls are knocked down or major utility lines are disconnected. Even if you stay, you should anticipate noise, dust, and some blocked-off spaces.

Include a margin in your timeline. Weather might pause external tasks, building inspectors might require tweaks, or deliveries can arrive behind schedule. Constructing a practical timeframe with your contractor mitigates stress, and completing earlier than expected is always pleasant. Additionally, retaining a financial contingency readies you for unforeseen costs or design changes mid-project.

East London sees congestion on main roads, particularly near markets or busy intersections, so skip deliveries might be best slotted into late mornings. Changing finishes or structural details once construction starts can also move completion dates further.

House Extensions Step By Step

While building an extension is significant, with thorough planning, professional trades, and a sensible budget, you can succeed. Whether you seek an expanded kitchen-lounge, more upper rooms, or a loft, be aware of each phase and watch out for 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. Any flaws should be remedied prior to final payment. Keep building control certificates, warranties, and approvals for future mortgage or sale scenarios.

Once your extension achieves completion and official clearance, you’ll gain a more spacious, practical home layout. Whether you added a bright open-plan lounge or an expanded second floor, the improvement generally raises comfort and potential resale value. East London abounds with evolving transport connections and a variety of property styles, so an extension that merges older character with modern design frequently stands out. Undertaking a snagging survey helps the contractor fix minor issues—like hairline cracks or mismatched paint—before you finalize payments. Storing evidence of building control compliance and warranties reassures buyers or lenders that your addition conformed to regulations. With that in mind, your newly enlarged East London residence can serve your household’s evolving needs for years to come.