One of the most dynamic in the world is the property market in London. Space is the limited factor, the demand is great and families are continuously searching to find means of making more space and value in their homes. You might be considering two large options as a homeowner:

👉 Are you planning to construct a new house?

👉 Or redefine your existing house with London house extension?

Each of them has its own pros and cons and the most appropriate decision according to your aim, way of living and financial means. We will discuss each of them in detail in this blog- cost, timelines, planning rules, and examples in real life to enable you make an informed decision.

New Builds in London: Starting Fresh

A new build in london refers to the construction of a brand new house according to your vision. You have control over any detail starting with layout to finishes.

Advantages of New Builds

• Complete Design Control – Have a design and style that fits your family.
• Modern Standards – Energy-saving insulation, heating, and environmental-friendly construction.
• No Compromises – It is all new, wiring, roofing and all.
• Long-Term Value – In the housing market of London, modern homes are highly demanded.

Example: A Harrow family had made up their mind to construct a detached new house having 5 bedrooms, luxury kitchen and an environmentally friendly heating system. They did not adapt an existing property but instead they began anew and got precisely what they desired.

House Extensions in London: Adding Space Without Moving

A house extension can be the most appropriate solution when you have a house already but you have to have more space. Extensions expand your property without the stress of relocating.

Advantages of House Extensions

• Cost-Effective – Typically less expensive than a new construction.
• Stay in Your Area – Keep your school, community, and commute.
• Adds Value – Extensions increase the value of a property.
• Quicker Build Times – The majority of extensions take a few months.

Common Types of Extensions

• Rear Extension – Extends the kitchens or living rooms.
• Side Return Extension – Perfect for narrow alleyways.
• Double-Storey Extension – Increases the size of a living and bedroom.
• Loft Conversion – Converts the unused attic space to a new room.

Example: A Wembley family wanted an open-plan kitchen and an extra bedroom.Rather than relocating, they got an extension to their rear and adopted a loft to save money and improve their living standards.

Comparison: New Builds vs House Extensions

Feature	New Builds London 🏗️	House Extension London 🏡
Cost	£1,500–£3,000 per sqm	£1,200–£2,500 per sqm
Timeline	6–12 months	2–6 months
Flexibility	Full design freedom	Restricted by existing structure
Planning Permission	Always required	Sometimes exempt (Permitted Dev)
Resale Value	High – new builds attract buyers	High – extensions add strong value
Disruption	None (new site)	May affect daily life during works
Best For	Families & investors starting fresh	Homeowners who love their location

 

Cost Breakdown

This is a realistic price list of new houses and house extensions in London.

Project Type	Cost Range (Approx.)	Notes
New Build (Basic Finish)	£1,500 per sqm	Standard design and finishes
New Build (Luxury Finish)	£2,500–£3,000+ per sqm	High-end materials and features
Rear Extension	£30,000–£60,000+	Ideal for kitchen/dining space
Side Return Extension	£40,000–£80,000	Adds space in terraced homes
Double-Storey Extension	£70,000–£120,000+	Creates bedrooms & living areas
Loft Conversion	£35,000–£70,000+	Adds a bedroom, office, or playroom

Tip: It is always good to put 10–20% contingency for unexpected costs.

Pros

New Builds London

• Full creative control
• Modern, efficient design
• Strong long-term investment

House Extensions London

• Affordable and practical
• Stay in your community
•  Add value quickly

London Planning Permission

• New Builds: Vital at all times- Construction may take months.
• Extensions: There are those which do not require permission under “Permitted Development Rights. Larger projects do.
• Conservation Areas: There will be tighter regulations, which professional advice will be important.

Adding Property Value

• New Builds: It is possible to gain 15-25% on new builds in London.
• House Extensions: Extensions of the kitchen and lofts can increase value by 10-20 percent.

Sustainability in Modern Builds and Extensions

Homeowners in London are paying more attention to environmentally friendly options when constructing or renovating.

• For new builds: There is a tendency to use solar panels, triple glazing, and smart heating.
• For extensions: It is possible to reduce bills by use of recycled materials, eco-friendly lighting and green roofs as this will also benefit the environment.

Example: When an Edgware client decided to put solar panels and underfloor heating in their extension, the energy bills would be reduced by a fifth.

Lifestyle Considerations

The choice that you want should be aligned with the lifestyle of your family:

• New Builds: Ideal when the family wishes to build a long-term, future-proof house.
• Extensions: Perfect when a family likes where they are and requires space to expand and accommodate children, home offices or their aged parents.

Example: A young family in Wembley, had their terraced house extended in the form of a loft conversion that included a nursery to the new baby without changing the community.

Mistakes to Avoid

These are the most frequent errors made by owners of new buildings and extensions of the houses, and what to do to prevent them.

Mistake	Why It’s a Problem	How to Avoid
Under-budgeting	Unexpected costs can delay or stop work	Add 10–20% contingency
Skipping Permissions	Can result in fines or having to undo work	Always check with local council
Choosing Cheapest Contractor	Poor work often leads to higher long-term costs	Select builders with proven experience
Ignoring Future Needs	Short-term fixes may not suit growing families	Plan for resale value and lifestyle changes

 

Real-Life Scenarios

• Harrow Couple: Constructed a new off-putting house with greener heating and five bedrooms. Long-term projects added value.
• Wembley Family: Decision to extend rather than relocate to a different house was a two-storey extension. Designed a larger kitchen and two new bedrooms.
• Edgware Investor: This is a developed new build townhouse, modern interior, and green amenities, which were sold out soon to buyers.

Make It Happen

The new properties in London and the house extensions in London are both intelligent investments.

• Have a new-build when you desire a tailor-made, future-proofed house that can last longer.
• Select the house extension when you like your current house but you need an extension at a reasonable price.

We are also the BBS Construction UK specializing in new construction and house extensions in London. We have a group of individuals who bring their professional skills to the table and offer clear service to ensure that projects finish within the allocated budget and time.

📞 Contact us today for a free consultation—and let’s bring your dream home to life.