House Extensions in Barnet: Planning Rules, Costs and Expert Advice 2026

Barnet is one of North London’s most desirable boroughs for families, combining suburban living with excellent schools, green spaces, and strong transport links into central London. With average property values continuing to rise, many homeowners are choosing to improve rather than move. As a result, house extensions in Barnet are more popular than ever in 2026.

This guide from Fixiz LTD covers everything you need to know before extending your home in Barnet: local planning rules, realistic costs, return on investment, and expert advice tailored to the area.

Why House Extensions Are So Popular in Barnet

Barnet’s housing stock is ideally suited to extensions. The borough is known for:

• Spacious suburban family homes
• Semi-detached and detached properties with gardens
• Quiet residential streets
• Strong demand from families due to outstanding schools
• Long-term owner-occupiers who want to stay in the area

Instead of upsizing to a more expensive property, many homeowners choose house extensions in Barnet to create additional living space, add bedrooms, or build modern open-plan kitchens while keeping their location and community.

Key Areas in Barnet for House Extensions

Finchley

Finchley offers a mix of Victorian terraces and 1930s semis, many with excellent extension potential. Rear and side return extensions are particularly popular.

Hendon

With larger plots and detached homes, Hendon sees strong demand for two-storey and wrap-around extensions.

Mill Hill

Mill Hill’s spacious properties often have generous gardens, making ground-floor extensions straightforward under permitted development.

Edgware

Edgware’s mix of inter-war semis and newer builds provides opportunities for both rear and two-storey extensions.

Planning Considerations in Barnet

Permitted Development

Many house extensions in Barnet fall under permitted development, meaning no planning application is required.

Single-storey rear extensions:

• Detached: up to 8m depth
• Semi-detached/terraced: up to 6m depth
• Maximum height: 4m

Conservation Areas

Barnet has several conservation areas including parts of Mill Hill, Totteridge, and Monken Hadley. In these areas:

• Permitted development rights may be restricted
• External appearance changes often need planning permission
• Article 4 directions may apply

When Planning Permission Is Required

• Extensions exceeding permitted development limits
• Properties in conservation areas
• Listed buildings
• Front extensions or significant street-facing changes

House Extension Costs in Barnet (2026)

Costs depend on size, specification, and site conditions.

ROI and Property Value Impact

With average Barnet property values around £650,000, well-designed extensions typically add £100,000+ in value.

Typical returns:

• Single-storey extension: 150–180% ROI
• Two-storey extension: 180–220% ROI

Extensions that create open-plan living spaces or additional bedrooms tend to deliver the highest returns.

Building Regulations Requirements

All house extensions in Barnet must comply with Building Regulations, covering:

• Structural integrity
• Fire safety
• Insulation and energy efficiency
• Drainage and plumbing
• Electrical installations
• Ventilation

Fixiz LTD handles all Building Regulations applications as part of our project management service.

FAQs About House Extensions in Barnet

How much does a house extension cost in Barnet?

Typical costs range from £35,000 to £110,000, depending on size and complexity.

Do I need planning permission in Barnet?

Many extensions fall under permitted development. However, properties in conservation areas or those exceeding limits require planning permission.

How long does a house extension take in Barnet?

Allow 8–16 weeks for construction, plus time for design, planning, and party wall agreements if needed.

Are house extensions a good investment in Barnet?

Yes. With average property values around £650,000, extensions often add £100,000+ in value.

Why Choose Fixiz LTD for House Extensions in Barnet?

Fixiz LTD specialises in high-quality house extensions in Barnet, delivering projects that balance design, compliance, and value.

What Fixiz LTD Offers:

• Local Barnet planning knowledge
• Transparent, realistic pricing
• Full project management
• Building regulations compliance
• High-quality workmanship and finishes

Start Your House Extension in Barnet Today

If you’re planning a house extension in Barnet in 2026, expert guidance makes all the difference. From initial advice to final completion, Fixiz LTD ensures a smooth, compliant, and stress-free process.

👉 Contact Fixiz LTD today for a free consultation and discover how a professionally built extension can transform your home and increase its value.