How Much Do House Extensions in Hammersmith Cost?

Extension prices in the UK can range significantly, shaped by the extension’s dimensions, your chosen materials, and the design’s complexity. According to industry data, a single-storey rear extension might start around £1,500 per square metre for a basic setup, while many typical expansions end up in the £1,800–£2,500 per square metre zone. If you plan to use complex steel beams, bespoke glazing, or very high-end finishes, the cost can easily climb above £3,000 per square metre.

In Hammersmith, labour rates are generally high because this west London area sits relatively close to central neighbourhoods, and a strong local property market fosters demand for skilled trades. If you own a property that’s newer or straightforward in its structure, your total cost may stay closer to the mid-range. However, older Victorian terraces or listed buildings, such as those near King Street or Hammersmith Bridge Road, might require extra structural reinforcement or specialist finishing, which can drive your bills upward. Broadly, a large-scale extension might land anywhere in the £40,000 to £100,000+ bracket, while narrower side or rear expansions can remain cheaper. Also, note that a fresh bathroom or kitchen will add plumbing, electrics, and waterproofing, intensifying your budget.

When collecting quotes from contractors, check that each covers foundation work, structural framework, roofing, fixtures, finishing, labour, and overhead. Clarify if VAT—commonly 20%—is included or tacked on. Though renovation magazines or websites provide broad cost references, the most accurate picture comes from requesting multiple quotes from established builders and scrutinising them carefully.

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.

Hammersmith

Hammersmith, part of the London Borough of Hammersmith and Fulham, is known for its blend of bustling commercial roads, like King Street and Hammersmith Broadway, and quieter residential streets lined with Victorian and Edwardian houses. Many homeowners near Ravenscourt Park or the Hammersmith Apollo look to expand ground-floor living space to create open-plan kitchens and reception rooms. Others add side-return extensions if the property layout allows it, and loft conversions are popular for turning underused attics into extra bedrooms or home offices. Basements can appear in more affluent zones, especially near the river, but they generally require thorough planning and potentially costly excavation.

Local builders caution that traffic congestion, particularly on major roads such as Fulham Palace Road or near the Hammersmith Flyover, can cause skip delivery or material drop-off delays. Labour rates are typically elevated, although a range of trades is available to handle heritage features or older building materials. The upshot of a well-conceived extension is both enhanced day-to-day functionality and a likely bump in property value if you’re near strong transport links like Hammersmith station. Engaging neighbours early can smooth the route if you share walls or fences, as homes in Hammersmith often sit close together.

Whether you prefer a compact single-storey design to boost a cramped kitchen or a two-floor transformation for a growing family, incorporating Hammersmith’s local planning context and architectural character usually aids swift permissions and a consistent final appearance.

Getting Started

Before initiating construction, decide which extension best fits your property. A single-storey rear extension can merge kitchen and dining areas into an open-plan hub, while a double storey approach doubles your gains on ground and upper floors. Alternatively, a side extension reclaims a narrow external passage, and a loft or basement might be more feasible if outward expansions are restricted. Basements in Hammersmith demand advanced engineering, especially in older streets or near the Thames, so investigate soil conditions thoroughly if you consider digging down.

Allocating time for robust planning helps to avoid mid-project hold-ups. Draft a comprehensive budget, factoring in typical labour rates and standard material outlays, and keep a contingency for structural complexities or premium finishing. If major structural changes are contemplated, engaging an architect or suitably qualified designer pays off. Some building companies offer design-and-build, yet they typically need rough sketches or partial planning permission to quote precisely. Many Hammersmith homeowners first consult an architect, then pursue builder bids when they possess an initial blueprint.

Securing a contractor well in advance is also advisable, as respected local construction firms can be booked up. Gathering quotes promptly enables you to compare cost breakdowns, assess references, and finalise a builder you trust. An experienced team might refine your layout—for instance, repositioning interior doors or adding rooflights to brighten your extension naturally.

Project Management

People typically organise an extension in one of two ways:

• Single contract (design-and-build or main contractor)
  You sign a single agreement with a building firm that manages everything—from digging foundations and structural framing to plumbing, electrics, roofing, and finishing. They normally subcontract specialist trades, adding about a 10–15% management fee. This setup consolidates scheduling and offers a single point of contact.
• Multi-trade or split contract
  You hire each trade separately: groundworkers, bricklayers, carpenters, roofers, electricians, plumbers, etc. Although you bypass a main contractor’s markup, you assume project management. If one stage runs behind, subsequent tasks might stack up. This path is best if you have the time and some building knowledge.

For complex or large expansions in Hammersmith, many choose a single-contractor approach to reduce oversight. If you opt to coordinate trades yourself, confirm you can dedicate consistent hours weekly to keep deliveries on schedule and spot any delays.

Do I Need Planning Permission?

Whether you need planning permission will depend on the proposed extension’s size, height, and location relative to your property. Under Permitted Development Rights, you might expand your house without lodging a formal planning application, so long as the scheme stays within specific dimension and siting criteria. If it goes beyond these, you usually file a householder planning permission request.

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 Hammersmith has conservation enclaves (e.g., Bradmore Conservation Area) and listed buildings near the Thames, it’s crucial to confirm if local restrictions affect you. Early communication with the borough’s planning office clarifies if your extension is PD-compliant or if you must apply formally.

Do I Need Planning Permission For A New Storey?

Loft conversions that introduce dormers or modify roof height typically require planning permission. However, you might be able to add an entirely new storey under permitted development if you meet certain rules and file a prior approval application with local authorities. Otherwise, Householder/Full Planning Permission is necessary. If your home meets these criteria, the bullet points below detail the essential 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.

Further conditions may apply post-construction. In Hammersmith, rows of terraces often have carefully aligned rooflines, so verifying roof height continuity is especially relevant if adding additional storeys.

Do I Need Planning Permission For A New Basement?

Typically, creating a basement requires planning permission, and extensive excavation under your house is similarly likely to need planning permission because of its large scale. It’s prudent to consult your local planning authority early, understanding any specific conditions. Basement work is elaborate, so even if official planning approval isn’t explicitly demanded, you must comply with Building Regulations to ensure structural stability, safe escape routes, damp-proofing, fire safety, and more.

Confirm local constraints that could override normal PD expansions. In certain parts of Hammersmith, previous or area-specific planning conditions may limit or discourage basement developments near the river or in highly congested spots. Refer to local council guidance or talk to a planning expert to ensure your concept is permissible.

Some property owners in prime roads close to the river or near Hammersmith Broadway build basements when outward expansions are not possible. However, these can be among the most expensive forms of extension because of demanding engineering.

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 can highlight potential design or safety oversights before building starts, whereas a Building Notice can suffice for simpler expansions. Both paths end with final building control approval to certify compliance.

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 extension in Hammersmith meets PD guidelines, building regulations remain compulsory to guarantee safe foundations, proper insulation, and secure structural work. In older or listed houses, verifying that load-bearing walls can handle expansions is critical.

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 overreach, you risk causing delays. Builders may need to pause until you complete certain steps, adding to your final costs. If you’re determined to do some elements yourself, consider getting professional advice first, so you can sidestep serious mistakes.

Hammersmith owners commonly apply DIY to decorative or final finishing touches once the main build is complete. Attempting advanced structural or mechanical tasks alone could disrupt the official schedule or compromise safety.

Do I Need An Architect?

If your plan is fairly modest, you might rely on a structural engineer or design specialist. However, for bigger or more complex projects, hiring an architect offers substantial benefits. A skilled architect balances functionality and aesthetics—ensuring day-to-day flow, adequate lighting, and unifying your new and existing spaces into a coherent design.

They can also clarify whether you remain in the realm of PD or need planning permission. While an architect’s fee raises the initial outlay, it often prevents expensive design errors down the line and yields a more polished result.

Hammersmith hosts an eclectic mix of period terraces, mansion blocks, and modern riverside flats. An architect can suggest design strategies that either honour the heritage facade or introduce contemporary elements gracefully, possibly adding foldable glass panels or partial skylights for a bright, modern interior.

How Long Does It Take To Build An Extension?

Defining a realistic timeline helps you maintain oversight. A smaller single-storey rear extension—assuming a simple design, standard materials, and PD approval—may wrap up in a few weeks once work begins. Larger multi-floor expansions often last several months to half a year or more, depending on the structural intricacy and the number of trades involved.

Sometimes, you may move out if walls critical for support are demolished or if essential services are cut. Even if you stay on-site, you’ll face dust, noise, and partially inaccessible rooms.

Include slack in your schedule. Adverse weather can slow external construction; inspectors might call for minor modifications; deliveries can arrive late. Setting a pragmatic timetable with your builder reduces stress, and if the project completes early, that’s a bonus. Holding a contingency in your budget also helps offset unforeseen tasks or design shifts mid-stream.

Hammersmith endures traffic congestion near major junctions and main thoroughfares like Talgarth Road or Hammersmith Bridge, so scheduling supply deliveries or skip collections outside rush hours can be vital. If you change finishes or structural details once building starts, your final completion date might edge further out.

House Extensions Step By Step

Though constructing an extension is major, with thorough planning, skilled tradespeople, and a sensible budget, you can see it through successfully. Whether you hope for a more extensive kitchen-dining area, a basement for extra living space, or a loft transformation, track each phase and guard against 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. Fix any oversights before final payment. Keep building control documents, warranties, and approvals in a secure place for remortgaging or eventual property sale.

Once the extension receives its final approval and sign-off, you can delight in a larger, more functional house in Hammersmith. Whether you opened up a rear living zone or constructed an additional storey, these improvements typically enhance day-to-day life and potential resale value. A snagging survey helps identify small mistakes—hairline cracks, uneven paint, or misaligned fittings—before the contractor wraps up. Storing building control certificates and warranties shows that your project met regulations, reassuring prospective buyers or lenders. With that, your newly enlarged Hammersmith home should serve your changing needs for years to come.