Transform Your Surrey Home with a Double Storey Extension

Bursting at the seams? Whether you're working from home, welcoming a new addition to the family, or just need more breathing room, a double storey extension could be the smartest move you make. It’s your chance to reimagine your home – more space, more light, and more value – without the upheaval of moving.

Staying in the neighbourhood you love while tailoring your home to your lifestyle? That’s a win. And with the right design, you could add up to 12% to your property’s value. In this guide, we’ll walk you through what to expect – from Surrey-specific planning tips to savvy design ideas and realistic budgeting – so you can take the next step with confidence.

Why Build Up? The Benefits of a Double Storey Extension

Stay Rooted – But Grow

Moving house comes with stress, fees, and compromises. A double storey extension lets you stay where your community, schools, and routines are – while giving you the extra space your family needs.

Add Value to Your Property

In Surrey, a thoughtfully designed extension can increase your home’s value by 10 to 12%. Whether you sell in a few years or plan to stay for decades, it’s a solid long-term investment.

Let the Light In

Building up means more potential for natural light and views. Adding upper-floor windows or even a Juliet balcony creates brighter, more uplifting interiors.

“We were nervous about how it would look, but James helped us design a two-storey extension that blends perfectly with our 1930s home. We didn’t just gain space – we gained a better lifestyle.” 

— Clare & David, Guildford

Planning a Double Storey Extension in Surrey: What You Need to Know

Permitted Development: Your Fast Track?

Many homes in Surrey qualify for extensions under permitted development rights, meaning you might not need full planning permission. For example:

• Detached homes: up to 7m deep

• Semi-detached or terraced homes: up to 6m deep

• Extensions can’t cover more than 50% of your garden

  
  

That said, rules depend on your property type and location. It’s essential to confirm before starting, especially in conservation areas or if your home has already been extended.

Full Planning Permission: When You'll Need It

If your home is listed, in a conservation area, or has reached its permitted development limits, you’ll need to go through a full planning application. This takes longer but gives more design flexibility.

Don’t Forget the Party Wall Agreement

If you’re building near a boundary, you’ll likely need a Party Wall Agreement. Speak to neighbours early and consider appointing a single surveyor to keep costs down and relations warm.

Tip: We handle planning and neighbour notices as part of our architectural service – saving you time, hassle, and surprises.

What Will It Cost? A Surrey-Specific Budget Guide for 2025

Here’s a breakdown of typical double storey extension costs in Surrey:

Item	Typical Range
Architectural fees	£4,000 – £8,000
Construction costs	£3,000 – £3,500 per m²
Planning application	£206 – £613
Party wall fees	£700 – £2,000 per neighbour

Expect to pay £150,000 to £175,000 for a 50m² extension – though this varies with site access, design choices, and materials.

Cost Drivers to Watch For:

• Steel beams (especially for open-plan layouts)

• Groundworks (Surrey clay soils often need reinforced foundations)

• Separate party wall surveyors (joint appointments reduce fees)

Ways to Save Without Compromising:

• Reuse existing foundations where possible

• Phase the build to spread out costs

Keep the footprint simple – avoid unnecessary corners and complexity

Design Ideas That Make the Difference

Blend the Old and New

Match bricks, rooflines, and materials for a seamless look – especially important for period homes. This keeps the extension from feeling tacked on.

Or Go Bold with Contrast

Prefer a modern twist? Materials like glass, timber cladding, or zinc can contrast beautifully with traditional architecture, adding interest, light, and a contemporary character.

Practical Tips for Smarter Spaces

• Maximise light: South-facing windows and skylights make a big difference.

• Create flow: Open-plan spaces downstairs enhance sociability and light.

• Design for flexibility: A home office that doubles as a guest room? Smart.

• Prioritise storage: Built-in cupboards and under-stair solutions reduce clutter.

• Protect your privacy: Avoid overlooking neighbours with careful window placement.

What to Avoid

• Poor stair design: Stairs define the layout – plan them early.

• Inadequate insulation: Don’t skimp – it impacts comfort and costs.

• Lack of natural light: Dark rooms can make your investment feel underwhelming.

Make It Sustainable: Design for the Long Term

Start with Energy Efficiency

Good orientation, thermal mass, and airtight construction go a long way. South-facing glazing brings in free heat, while thermal mass (like concrete or stone floors) stores and slowly releases it.

Passive House Principles

You don’t need a certificate to apply smart passive principles:

• Super-insulated walls and roofs

• Triple-glazed windows

• Mechanical ventilation with heat recovery (MVHR)

Materials That Matter

Look for low U-values, recycled content, and breathable materials. Sustainable timber, sheep’s wool insulation, and lime-based plasters all improve performance and reduce environmental impact.

Are There Any Incentives?

Some eco-measures may qualify for:

• 0% VAT (on certain retrofits)

• Local grants for energy-saving upgrades

 Check with your local authority for current offers.

What the Build Actually Looks Like

From First Sketch to Final Brick

A typical project involves:

1. Brief and concept design

2. Planning application or permitted development confirmation

3. Technical design and approvals

4. On-site build (4–8 months on average)

Good communication from your builder and architect helps reduce stress and surprises.

You Can (Usually) Stay at Home

Most clients live on site during construction, though you may want to set up a temporary kitchen or plan ahead for noisy periods.

Talk to Your Neighbours

Even a friendly heads-up goes a long way. It builds goodwill and reduces the chance of objections or delays.

Next Steps: Bringing Your Ideas to Life

Thinking of extending your home upwards? Here’s what to do next:

• Define your goals. Is it an extra bedroom? Open-plan kitchen? Better work-from-home space?

• Set a realistic budget. Build in a contingency (10–15%) for the unexpected.

• Speak to a local architect. Someone who knows Surrey’s planning rules and building styles can save you time, money, and hassle.

At James Williamson Architects, we specialise in double storey extensions for Surrey homeowners. We handle everything – from design and planning to technical drawings and builder coordination.

Let’s bring your ideas to life. 

📞 07738 409199 | 🌐 www.jameswilliamson.archi 

Book a free, no-obligation consultation today.

Frequently Asked Questions

1. Can I live in my house during the build?

Yes, with a bit of planning. You may want to relocate your kitchen or stay elsewhere during key stages.

2. Do I need to tell my neighbours?

Yes, particularly if a Party Wall Agreement is required. A friendly conversation early on makes the process easier.

3. How long will it take?

4 to 8 months is typical for construction, with additional time for planning and approvals.

4. What if my budget is tight?

Phased builds, reuse of materials, and a simple footprint can help reduce costs.

5. What if I change my mind during the project?

Small changes are usually manageable. Larger changes may affect cost or schedule – so reviewing designs carefully early on is key.