A double storey extension can significantly increase your living space and add long-term value to your property. But a common question we hear at KT5 Construction is: do I need planning permission for a double storey extension? The short answer is — it depends.

Let’s break it down.

What Counts as a Double Storey Extension?

A double storey extension typically includes two new floors extending from the rear or side of your property. Homeowners commonly use this additional space for open-plan kitchens, dining areas, extra bedrooms, home offices, or even en-suites.

When You Don’t Need Planning Permission

You may be able to avoid full planning permission if your project falls under Permitted Development (PD) rights. To qualify, your extension must meet specific requirements:

Permitted Development Guidelines:

• • It must not extend more than 3 metres from the original rear wall.

  • The extension must be at least 7 metres away from the rear boundary.

  • The eaves and ridge height must not exceed those of the existing house.

  • Roof pitch and external materials must match the existing house.

  • If built within 2 metres of a boundary, the eaves must be 3 metres or less.

  • No balconies, verandas, or raised platforms are permitted under PD.

  • Upper floor side-facing windows must be obscure-glazed and non-opening below 1.7 metres.

📌 Note: Permitted Development only applies to houses – not flats, maisonettes, or listed buildings. Also, PD rights may be restricted in conservation areas or Areas of Outstanding Natural Beauty.

When Planning Permission Is Required

If your extension doesn’t meet the PD rules, planning permission is mandatory. You will need it if:

• • Your extension is taller than 4 metres.

  • The design deviates significantly from the existing property.

  • You live in designated land, such as a conservation area or listed building.

  • The structure overshadows or affects neighbours, triggering objections.

  • You’re extending closer than allowed to boundaries.

Applying for planning permission involves submitting architectural drawings and documentation to your local authority. KT5 Construction works with experienced planning consultants to increase approval success.

Party Wall Agreements & Neighbour Consent

If your project shares walls with neighbouring properties (like in terraced or semi-detached homes), you’ll likely need a Party Wall Agreement. This requires:

• • Serving notice at least two months before building.

  • Gaining written consent or appointing a party wall surveyor.

Delays or disputes can occur without proper agreements, so it’s critical to factor this in early.

Why Homeowners Choose KT5 Construction

As trusted London builders serving Surrey and surrounding areas, KT5 Construction offers:

• • End-to-end planning support, including help with drawings and local authority submissions.

  • Design and build expertise that ensures your extension matches your home’s aesthetic and complies with regulations.

  • Clear, upfront advice on whether your project qualifies under Permitted Development.

  • Cost-saving strategies, such as value engineering and staged builds to stay within your budget.

📍 Prices may differ based on location and type of project, but KT5 will always help you plan within your means.

Cost Benefits of Double Storey Extensions

Interestingly, double storey extensions are often more cost-effective per square metre than single-storey additions. Why? Because while you expand both outwards and upwards, you maximise vertical space without consuming more of your garden or outdoor footprint.

Common Questions Answered – Planning Permission for a Double Storey Extension

1. Can I build near my boundary?

Only if your eaves are under 3 metres and you’re more than 2 metres from the boundary.

2. What if I want a balcony?

You’ll need planning permission. Balconies are not allowed under Permitted Development.

3. Will it add value to my home?

Yes — properly designed double storey extensions often add substantial resale value.

Conclusion: Take the First Step with KT5

Understanding whether you need planning permission for a double storey extension is key to avoiding delays and extra costs. With KT5 Construction by your side, you’ll have expert guidance at every stage — from feasibility and design to planning and build.

📞 Ready to plan your dream extension?
Contact KT5 Construction today for a free consultation. We’ll help you build smarter, better, and to budget.