How Much Do House Extensions Cost?

In the UK, extension prices vary drastically, shaped by the scale of the scheme, materials chosen, and the overall design complexity. Research indicates a single-storey rear extension might start around £1,500 per square metre for a straightforward plan, whereas most fall in the £1,800–£2,500 per square metre zone. If you add advanced steel frameworks, specialised glazing, or top-tier finishes, costs may surpass £3,000 per square metre.

Within Camden, labour charges can still be somewhat more than outer boroughs but below prime central London, letting homeowners invest in select upscale features. Yet a number of Camden houses are heritage or period terrace properties, which may need extra foundation support or structural enhancements, boosting your spending. Larger additions frequently sit between £40,000 and £100,000+, though a narrower side addition can cost less, and multi-storey or intricate designs might exceed usual brackets if structural complexities or luxury finishes define the plan. Kitchens or bathrooms intensify the budget because of electrics, waterproofing, and plumbing.

When evaluating contractor estimates, confirm each includes foundation digging, structural tasks, roofing, fixtures, finishing, and labour overhead. Check if VAT is included or is an extra charge. While consumer media can share general price guidance, exact quotes necessitate collecting bids from experienced 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.

Camden

Camden is a north-central London borough featuring Georgian townhouses, Victorian terraces, and modern apartments, blending history with contemporary vibrance. Homeowners here typically add single-storey rear extensions to open cramped rooms and bring more natural light into older properties. Others choose side expansions if a side path is present, or loft conversions to harness Camden’s vertical space without giving up a courtyard or garden. In some higher-value areas near Regent’s Park or Primrose Hill, basement digs do happen, though they cost more and require structural caution to avoid harming neighbouring terraces.

Local contractors warn about traffic near Camden Town or tourist hotspots, so scheduling skip or supply deliveries in quieter time blocks—late mornings or midday—works best. Labour outlays in Camden are often above the capital’s average but not quite as high as the most central districts. A heritage property might incur extra foundation or structural demands to protect period features. If your street is in a conservation zone, you may face stricter guidelines regarding external design. Still, a well-done extension here can transform everyday living while amplifying property value, especially if good transport links like Camden Town station or Kentish Town station are near.

Choosing a design that meshes with Camden’s unique aesthetic is typically beneficial, ensuring approvals go more smoothly and the final extension fits local architectural character.

Getting Started

Before building, decide what extension style suits your property. You could add a single-storey rear addition to merge a kitchen and dining space, a double storey structure to gain extra upper-floor rooms, or a side/wrap-around if you have corner space. Alternatively, a loft or basement might be appropriate if ground expansion is restricted. Basements, while expansive, can cost more and require advanced engineering.

Ample planning initially eases the project’s course. Outline a detailed budget, looking at standard labour costs and material prices, leaving funds for contingencies like structural obstacles or fancier finishes. If your proposal demands considerable structural alteration, you might engage an architect or similarly accredited designer. Some construction firms offer design-and-build, yet they commonly need initial drawings or partial planning approvals to quote comprehensively. Many Camden households begin with an architect for conceptual planning, then gather formal quotes from several building companies.

It is also wise to secure a contractor promptly, as many reputable outfits remain booked long in advance. By collecting bids sooner, you can explore pricing variations, interview references, and pick a team with confidence. Skilled builders sometimes improve your layout ideas—for instance, adding an internal partition to create a utility space or recommending a better alignment for bifold doors.

Project Management

Extensions typically follow one of two main organisational approaches:

• Single contract (design-and-build or main contractor):
  One main contractor oversees each component—foundations, structural tasks, electrics, plumbing—subcontracting specialists where required, taking around a 10–15% markup. This model simplifies scheduling, giving you a single port of call for queries.
• Multi-trade or split contract:
  You coordinate all the trades individually: groundworks, bricklayers, roofers, plumbers, electricians, etc. Although you might avoid the main contractor’s markup, you must carefully orchestrate each phase. If a particular trade is delayed, everyone else may have to wait.

In Camden, a major or architecturally challenging extension often suits the single-contractor approach, especially if you don’t want the day-to-day stress of aligning multiple trades. If you choose multi-trade, confirm you can dedicate enough time weekly to handle potential scheduling conflicts.

Do I Need Planning Permission?

Whether planning permission is needed depends on your planned extension’s height, size, and property placement. Under Permitted Development Rights, you may expand a house without formally applying for planning, provided you keep within certain limits and conditions. Should your design exceed those boundaries, you will probably have to submit 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 Camden has so many heritage and conservation spots, discussing your concept with Camden Council’s planners early on helps you sidestep rejections or drawn-out amendments.

Do I Need Planning Permission For A New Storey?

Loft extensions that involve dormers or roof-height increases frequently require planning permission. However, building a new storey can count as permitted development, so long as you meet specific criteria and submit a prior approval application. Otherwise, Full Planning Permission will be necessary. If your house complies with these guidelines, see the bullet points below for the 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 construction, certain completion conditions may also apply. In Camden’s visually consistent terraces or squares, it’s advisable to confirm that your new storey respects local aesthetics and alignment.

Do I Need Planning Permission For A New Basement?

Usually, putting in a new basement requires planning permission, and excavating underground is also likely to need planning permission because of the scale of the works. It is sensible to consult your local planning authority beforehand to grasp specific rules. Basement digs are likewise substantial ventures. Even if no official planning permission is explicitly mandated, you still have to follow Building Regulations for structural stability, safe escapes, ventilation, fire safety, and other aspects.

Always check all regulations that might apply to your property and your area. If earlier or local planning conditions exist, an extension you thought was under Permitted Development can be disallowed. Investigate the council’s resources or speak with a planning adviser to be sure.

In Camden, basements sometimes occur in prime spots near Regent’s Park or Primrose Hill, but they command higher budgets and require detailed engineering to avoid harm to closely spaced neighbours or older walls.

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 helps highlight potential design or safety concerns before building, whereas a Building Notice might be acceptable for simpler expansions. Either option ends with building control signing off your extension’s 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 no planning application is needed (through Permitted Development or other factors), building regulations must still be satisfied, guaranteeing that your new extension meets current standards for foundations, insulation, damp resistance, and so on. Camden’s older dwellings can be fragile, making building control approval even more important.

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 Camden, partial DIY is common for finishing stages, after the structural skeleton is complete. Handling or interfering with complex mechanical or electrical tasks yourself may slow the entire project if something goes wrong.

Do I Need An Architect?

If your extension is straightforward, you might lean on a structural engineer or building designer. Yet for more ambitious or complex expansions, an architect can be invaluable. They look beyond beauty to incorporate practicalities like traffic flow, daylight, and unifying your new spaces with existing rooms.

They can also advise on whether your plan remains within permitted development or needs a planning application. While architect fees add to initial costs, the savings often manifest in a more coherent layout and fewer mid-project design mistakes.

Camden displays an eclectic mix of architecture—from Georgian crescents to modern flats. An architect’s skill is often needed to adapt older terraces to open-plan living, or to introduce large windows and partial glass roofs for more light.

How Long Does It Take To Build An Extension?

A clear schedule helps you oversee the build. A smaller single-storey scheme might finish in weeks if it’s straightforward, uses typical materials, and qualifies as permitted development. Larger expansions, like multi-room or multi-level constructions, tend to require several months to half a year or longer, depending on the design’s complexity and how many specialist trades are needed.

Sometimes, a short relocation may be required if structural works cut through crucial walls or utility lines. Even if you remain, plan for dust, noise, and restricted access to certain rooms.

Keep some flexibility in your timeframe. Unexpected weather may stall exterior tasks, building inspectors can request plan changes, or deliveries might run late. Agreeing a practical timetable with your builder helps limit stress, and finishing earlier than expected is a bonus. Likewise, reserving some contingency in your budget is recommended to handle hidden problems or design modifications mid-project.

Camden can be crowded, particularly near Camden Town or tourist-frequented spots, so skip deliveries often go ahead outside rush hours. If you opt for specialty finishes or shift any design points mid-project, your completion date may also move further out.

House Extensions Step By Step

While an extension is a significant enterprise, with methodical planning, experienced builders, and adequate financing, there is no reason it cannot succeed. Whether you need extra kitchen-diner space, a new top storey, or a creative basement level, be sure to track each phase and head off 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. Any defects should be resolved before releasing the final payment. Keep your building control approvals, warranties, and completion certificates well filed for potential resale or mortgage changes.

With official approvals and final checks behind you, your extended Camden home can deliver the roomy interior you dreamed of—be it a sun-filled rear living space or an upper-level addition. Such a well-crafted upgrade normally leads to enhanced comfort and better property worth. Camden properties, situated near dynamic culture and transport, often stand out on the market if they integrate original period charms with a more contemporary layout. Using a snagging survey to tackle minor flaws, such as paint blemishes or uneven plaster, ensures a polished finish. Storing documents that show building control compliance and warranties will reassure future buyers or lenders that standards were upheld. In the end, your brand-new space in Camden can accommodate your evolving household needs for years ahead.