Why Choose a House Extension in London?

A house extension is one of the best investments you can make in your London home. Here’s why more and more Londoners are choosing to extend rather than move:

• Space for modern living – Whether you’re having a new baby, working from home, or need more storage and flexibility, an extension gives you room to breathe.

• Stay in the area you love – Many of our clients live in places they don’t want to leave. By extending, you can stay close to friends, schools and transport links.

• Cheaper than moving – Factoring in stamp duty, solicitor fees, and the rising cost of property in London, extending is often much more cost-effective than buying a bigger one.

• Increase your home’s value – A well-designed extension can add significant value to your property, making it a worthwhile investment that pays off now and in the future.

• Designed for you – Unlike moving into a new home, an extension is tailored to suit how you want to live. Open-plan kitchens, garden-facing dining rooms, or quiet study spaces can all be created to suit your needs.

Types of House Extensions We Deliver

Every property and every family is unique, which is why we offer a wide range of extensions.

Rear Extensions

One of the most popular in London, a rear extension uses garden space to add to the back of your property. Perfect for open-plan kitchens, larger living areas or dining spaces that flow directly onto your garden through sliding or bi-fold doors.

Side Return Extensions

Ideal for London’s Victorian and Edwardian terraces, side return extensions turn the often unused alleyway at the side of the property into valuable living space. By opening up the back of the house, you can create a more expansive kitchen, a brighter dining area, and a more fluid ground-floor layout.

Wraparound Extensions

For maximum impact, a wraparound combines both a rear and side return extension, creating an L-shape. This often results in a light-filled living space with multiple zones for cooking, dining and relaxing.

Kitchen Extensions

The kitchen is the heart of the home, and a bespoke kitchen extension can change the way you use your space. From large islands and breakfast bars to floor-to-ceiling glazing, we design kitchens that are practical for family life and perfect for entertaining.

Double-Storey Extensions

Do you need more bedrooms, bathrooms, or office space upstairs as well as downstairs? A two-storey extension is the answer. These extensions add substantial extra square footage and can increase your property’s value.

Flat or Pitched Roof Extensions

The choice between flat and pitched roofs allows us to match your home’s style and maximise natural light. Flat roofs with skylights are popular for modern builds, and pitched roofs are often chosen to blend with period homes.

Our Extension Process - From Idea to Completion

We know taking on a building project can be overwhelming, so we’ve broken it down into a simple, 7-step process.

1. Initial Consultation & Site Visit
   We meet you at your home to discuss your ideas, take measurements and talk through options.

2. Design & Drawings
   Our in-house architects create detailed drawings that meet your needs and maximise the use of space, light, and style.

3. Planning & Building Regulations
   We handle planning applications as necessary, advise on permitted development rights, and ensure designs comply with building regulations.

4. Transparent Quoting
   Once designs are approved, we provide a fixed, detailed quote so you know exactly what’s included, no hidden extras.

5. Dedicated Project Manager
   Every client has a project manager who oversees the build, keeps you updated and ensures the work is completed on time and to budget.

6. Construction & Quality Control
   Our experienced builders carry out the work, and regular site visits ensure that high standards are maintained throughout.

7. Handover & Warranty
   On completion, we provide all certificates and paperwork, and your extension comes with a 10-year structural warranty for your peace of mind.

Planning Permission and Regulations in London

One of the most common questions we are asked is, 'Do I need planning permission for an extension?' The answer depends on your property and the type of extension:

• Permitted Development Rights allow rear or side extensions within certain size limits without full planning permission.

• Conservation Areas & Listed Buildings have stricter rules; we can guide you through them.

• Building Regulations always apply, covering structural integrity, fire safety, insulation, and accessibility.

We have years of experience dealing with London borough councils, so we ensure applications are submitted correctly and approvals are obtained asap.

Cost of a House Extension in London

One of the first questions most people ask is, “How much will my extension cost?” The answer is that it depends on many factors, including the size of the build, the complexity of the design, and the level of finishes you choose. No two projects are ever the same, but here are some rough guidelines.

London House Extension Costs

• Rear or side return extensions – from £40,000+
  For bigger kitchens, dining areas or extra living space.

• Wraparound extensions – from £70,000+
  A more significant transformation that combines both rear and side elements, often resulting in open-plan living areas.

• Double-storey extensions – from £90,000+
  Big builds that go up and down, adding real space and value to your home.

These are just rough estimates. Your final cost will depend not only on size but also on design complexity, structural requirements, and the finishes you choose — including flooring, glazing, bespoke joinery, and more.

What Affects the Cost of the Extension

Several things to consider:

• Property type and location – Older properties often require more extensive structural work, while conservation areas necessitate specific design details.

• Materials and finishes – Standard finishes or premium options, such as aluminium bi-folds, bespoke cabinetry, or high-performance glazing.

• Structural complexity – Double-storey builds, basements or homes on restricted plots require more engineering.

• Planning and permissions – Some boroughs require additional approvals or specialist input, which can impact timelines and costs.

Pricing and Value

At New Build Contractors, we believe in transparency. Once we’ve surveyed and agreed on the design, you’ll receive a detailed breakdown of costs, so you know exactly what’s included—no hidden extras or surprise add-ons.

While extensions are a big investment, they are also one of the best ways to add long-term value to your London home. In many cases, the extra space and modern design add more to your property’s value than the cost of the build itself.

Moving vs Extending – What’s More Cost-Effective in London?

For many families, it’s a choice between moving into a bigger property or extending the home they already love. Here’s how the two options compare in London:

Expense	Extending Your Home	Buying a Bigger Home in London
Upfront Costs	From £40,000–£120,000+ depending on extension type	Often £150,000–£300,000+ more for a larger property
Stamp Duty	£0 (not applicable)	£25,000–£50,000+ depending on purchase price
Legal & Moving Fees	Minimal (planning & design only)	£5,000–£10,000+ for solicitors, removals, surveys
Disruption	Works carried out while you remain in your home	Full relocation, packing, moving schools, new area
Added Value	Strong ROI – well-designed extensions can add 15–25%+ to property value	Limited — future value tied to local market conditions
Emotional Factor	Stay in the home and area you love	Leave behind neighbours, schools, and community

Moving might seem like the quick fix for more space, but the costs add up quickly, and you often compromise on location. A house extension, on the other hand, lets you stay in the area you love and create a bespoke space that works for your lifestyle.

At New Build Contractors, we make it simple and transparent, so you know the costs from the start, allowing you to plan with confidence.

A Real-World Example – Extending vs Moving

A family living in a Victorian terrace in Wimbledon loved their home and the area, but were running out of space as the kids grew up.

• Option 1: Moving
  They considered buying a bigger house nearby. Similar four-bedroom properties in the area were selling for £1.1m–£1.2m — £250,000 more than their current home. Additionally, they would have to pay £45,000 in stamp duty and £8,000 in moving and legal fees.

• Option 2: Extending
  Instead, they opted for a wraparound kitchen extension with skylights and bi-fold doors that open onto the garden. The project cost around £75,000. Not only did they get the open-plan kitchen-diner they wanted, but also an extra living room and more light on the ground floor.

• The Result
  Local agents estimated that the extension added £150,000–£200,000 to the property's value. In other words, they got the space they needed, increased the value of their home and avoided the stress and costs of moving — all while staying in the area they love.