How Much Do House Extensions Cost?

The cost of expanding a house in the UK shifts significantly depending on the extension’s scale, material choices, and build intricacy. According to industry data, a single-storey rear extension might start near £1,500 per square metre for a basic setup, while most standard designs align with a £1,800–£2,500 per square metre bracket. Should you pick high-spec steel frames, elaborate glazing, or luxurious finishes, costs could exceed £3,000 per square metre.

In Ealing, many homeowners find local trades cost a bit less than inner London rates, enabling them to dedicate extra budget to elevated finishes or more bespoke design features. However, older post-war or Edwardian homes in the borough might require extra structural strengthening, heightening expenses. Larger extensions often hover around £40,000–£100,000+, while a slimmer side-return extension might be cheaper, and more elaborate multi-storey concepts can breach normal price ranges if the structural engineering or finishing levels are advanced. Key variables include the scope of redesign, local labour fees, and the inclusion of wet rooms like kitchens or bathrooms—where the addition of plumbing, electrics, and waterproofing drives the cost higher.

When vetting contractor quotes, ensure each estimate covers foundations, structural tasks, roofing, fittings, finishing, plus all labour and administrative overhead. Ask if VAT—usually 20%—is wrapped into that figure or not, since it can become an extra. Although you may refer to renovation magazine articles or online cost guides, the most precise approach is securing multiple bids from reputable builders and comparing them meticulously.

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.

Ealing

Ealing is often dubbed the “Queen of the Suburbs,” featuring a wealth of 1920s and 1930s semis, grand Victorian houses, and more modern developments. Many locals build single-storey rear extensions to unite smaller kitchen and dining spaces, achieving a brighter, open-plan living arrangement. Others tackle side-return expansions if their property includes an underused side alley. Loft conversions are also popular for growing families who need more bedrooms or a home office without sacrificing garden area. Some homeowners consider basements, though these remain less frequent in Ealing than in central districts, in part due to underlying soil conditions or water table levels.

Local contractors highlight that roads near Ealing Broadway or the Uxbridge Road corridor can be choked with traffic, so scheduling skip deliveries mid-morning or mid-afternoon is wise. Labour fees here often fall below prime central London, permitting homeowners to afford better-quality finishes, such as robust folding doors or premium roof lanterns. However, in conservation areas around areas like Ealing Common or St Stephen’s, you might face extra restrictions on external modifications. Usually, an intelligently planned extension not only improves daily life but also enhances the property’s selling appeal, particularly if you’re close to stations like Ealing Broadway. It can help to chat with neighbours early, especially if you share boundaries or party walls in classic terraced streets.

Whether you want a streamlined single-storey to enlarge your kitchen or a multi-level overhaul, adapting your design sensibly to Ealing’s character and planning policies is essential for smooth approval and a harmonious final result.

Getting Started

Before building, clarify which extension configuration suits your goals. You might opt for a single-storey rear addition to unify cooking and dining spaces, a double storey approach if you also need additional upper-level bedrooms, or a side extension if your lot includes a side driveway or narrow passage. Alternatively, a basement or loft can be beneficial when outward expansions are constrained. Basements in Ealing aren’t very common, but might fit some properties seeking added living or storage space.

Committing time to upfront planning generally reduces issues mid-build. Form a comprehensive budget by consulting typical labour rates and standard material costs, then allow a contingency for any hidden structural demands or upscale finishes. If you plan notable structural remodelling, consider engaging an architect or qualified designer. While a few builders offer design-and-build services, they generally require initial sketches or partial approvals to quote precisely. Many Ealing owners meet with an architect first, then assemble bids from building firms who can enact the design.

Additionally, hire a reliable contractor early, as top-rated teams usually fill their schedules months ahead. By obtaining quotes early, you can evaluate price breakdowns, call references, and settle on a firm with confidence. Seasoned companies sometimes refine your ideas—for instance, adding a clever utility area within a kitchen extension or improving the layout for foot traffic.

Project Management and Contract

An extension can be handled in one of two key ways:

• Single contract (design-and-build or main contractor)
  You enter a single agreement with a building outfit covering every aspect—foundation excavation, structural tasks, electrics, plumbing—subcontracting trades as needed. They commonly tack on 10–15% for coordinating subcontractors, but you benefit from an integrated schedule and a single point of contact.
• Multi-trade or split contract
  You take on project management, hiring each trade—bricklayers, roofers, plumbers, electricians, carpenters—separately. While you might dodge the main contractor’s markup, you also need to be sure the correct materials and trades arrive in the proper sequence. Delays by one trade can push the entire schedule back. This approach works if you have both the time and sufficient building familiarity.

For larger or structurally challenging expansions in Ealing, many owners prefer a single-contractor approach to free themselves from daily scheduling burdens. If you do multi-trade, confirm that you can consistently oversee the job and coordinate deliveries so that no trades are left idle.

Do I Need Planning Permission?

Determining whether planning permission is necessary depends on your extension’s dimensions, height, and the property’s layout. Under Permitted Development Rights, you may be able to enlarge your house without lodging a formal planning application, provided your plans fit specific size and positioning criteria. If your proposals exceed those, a householder planning permission application is typically needed.

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 Ealing, if you live near conservation pockets like the St Stephen’s area or parts of Ealing Common, local rules may impose additional conditions. Checking with the council upfront helps confirm whether you’re within PD or need a formal application.

Do I Need Planning Permission For A New Storey?

Loft extensions involving dormers or altering rooflines often require planning consent. Still, constructing a new storey may be categorised as permitted development if you fulfil rigid standards and file a prior approval application with the local authority. Otherwise, Householder/Full Planning Permission is needed. If your house meets the relevant criteria, the bullet points below outline those boundaries:

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.

Additional completion rules may apply. Confirming details with Ealing planning staff helps guarantee you don’t clash with local building lines or uniform roof shapes.

Do I Need Planning Permission For A New Basement?

Putting in a new basement generally requires planning permission, and digging down is also likely to need planning permission because of the extensive work. It’s best to discuss your vision with the local planning authority to grasp their specific requirements. Basement excavation is equally complex, so even if formal permission isn’t strictly mandated, Building Regulations must be upheld to ensure structural reliability, correct ventilation, damp control, fire protection, and more.

Always verify any local guidelines that might govern your property or district. Sometimes, an extension typically permitted can be blocked by prior or local planning decisions. Seek out Ealing Council’s guidance or a planning specialist for clarity.

In Ealing, basements don’t appear as frequently as in certain older, pricier boroughs. Still, some owners do consider partial basements if outward expansions are not feasible and ground conditions allow for safe excavation.

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 often highlights issues regarding design or stability before the build begins, whereas a Building Notice can be enough for smaller expansions—but on-the-spot modifications may be required if inspectors identify shortcomings.

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 Ealing extension doesn’t need planning permission thanks to PD, building regulations approval still confirms that your foundation depth, insulation, fire escapes, and other elements are fit for modern standards. This is essential in certain older Ealing semis or terraces, where additional structural checks might be necessary.

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.

Ealing owners frequently handle finishing touches themselves after the primary build, allowing professionals to handle core tasks. This approach grants you some personal customisation without risking a slowdown of essential mechanical or structural work.

Do I Need An Architect?

If your design is basic, a structural engineer or design professional might suffice. Still, for bigger or more intricate extensions, an architect can be a significant advantage. They combine aesthetics with practicalities—interior traffic flow, daylight, and seamless integration between old and new spaces.

They can also assist with planning permission questions or confirm your scheme remains under permitted development. While an architect’s fee raises initial costs, that expense often averts design errors and results in a more coherent final arrangement.

Ealing contains a range of housing from Edwardian terraces near Ealing Broadway to 1930s semis in South Ealing. An architect’s expertise can help tie an extension together so that it harmonises with classic brickwork or 1920s exteriors, or make the most of deep rear gardens that Ealing is known for.

How Long Does It Take To Build An Extension?

Laying out a schedule keeps your build on course. A smaller, single-storey project—perhaps enlarging a rear kitchen—might conclude in a handful of weeks if it’s straightforward, uses readily sourced materials, and meets PD criteria. Larger expansions, such as multi-room or multi-level additions, can last from a few months to half a year or longer, guided by how elaborate the design is and the trades needed.

Sometimes, a temporary move is necessary if major internal walls must be removed or if multi-storey additions disrupt critical utilities. Even if you remain at home, expect noise, dust, and restricted room usage.

Include some flexibility. Delays can arise from weather, planning inspector revisions, or material backlogs. Drafting a realistic timeline with your builder helps reduce stress, and finishing earlier than planned is always welcome. Similarly, maintaining a financial cushion handles unforeseen changes to layout or discovered structural concerns.

Ealing experiences moderate traffic in areas like West Ealing or along Uxbridge Road, so skip deliveries or large supply drop-offs often occur during midday lulls. If you decide on unique building materials or pivot finishes mid-project, your final completion date may shift further.

House Extensions Step By Step

Building an extension is a big task, but with systematic preparation, capable teams, and a decent budget, you can succeed. Whether you crave a bigger kitchen-diner, extra bedrooms, or a loft transformation, be mindful of each stage and remain alert for usual stumbling blocks.

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 unresolved points before releasing the final payment. Keep building control approvals, warranties, and other paperwork ready for future use, such as property sales or remortgages.

Upon final sign-off, you can delight in a more spacious Ealing property. Whether it’s a sunlit rear lounge or an extra upper-level master suite, your extension ought to elevate comfort and potentially boost resale appeal. Ealing families frequently welcome these changes to adapt older homes, especially near good schools and tube or rail services. A snagging survey helps rectify minor issues—like faint cracks or mismatched paint lines—before the contractor finishes. Storing official compliance records reassures prospective buyers or lenders that all regulations were met. With everything settled, your newly expanded Ealing home can serve your household for the long run.