🏡 Permitted Development for Extensions: What You Can Build Without Planning Permission in North West London (2025)
By DOR Architects – RIBA & ARB Registered Architects in London
In North West London, space is gold dust. Whether you’re in a Victorian semi in Hampstead or a 1930s terrace in Cricklewood, the urge to expand is universal.
But between planning permission, building control, and local design codes, where do you begin?
The good news? You might not need full planning permission at all.
Welcome to Permitted Development Rights — your shortcut to more space, less paperwork, and (often) faster approvals.
🔗 Contents
- What Is Permitted Development?
- What Kinds of Extensions Are Allowed?
- Key Rules You Need to Follow
- When Permitted Development Doesn’t Apply
- Why You Should Get a Lawful Development Certificate
- Case Study: Rear + Loft Extension in Camden
- How DOR Architects Help You Build It Right
- FAQs
- Let’s Talk
🧠 What Is Permitted Development?
Permitted Development Rights (PDRs) are rules set by the government that allow you to extend or alter your property without applying for full planning permission.
They apply mostly to single-family homes under Use Class C3 — not flats or HMOs. And while it sounds like a free-for-all, there are rules, limits, and exceptions.
🏗️ What Kind of Extensions Can You Build?
Common extensions we design under PD include:
- Rear Extensions – Up to 6m for terraced/semi-detached or 8m for detached homes (with Prior Approval)
- Loft Conversions – Up to 40m3 for terraces, 50m3 for detached/semi-detached
- Single-storey Side Extensions – If not forward of the main elevation and under 4m high
- Outbuildings – Home offices, gyms, or studios, subject to siting and height limits
All of these come with detailed design and volume constraints — which we navigate for you.
📏 Key Rules You Need to Follow
- Extensions can’t cover more than 50% of your original garden
- Maximum height for single-storey rear = 4m
- Side extensions must be single-storey and under half the width of the original house
- No raised platforms, balconies or verandas
- Materials should match the existing house
If you want to go bigger or break these rules? You’ll need full planning permission.
🚫 When PD Doesn’t Apply
Permitted Development is powerful — but not universal. You cannot rely on it if:
- Your property is a flat or maisonette
- You live in a Conservation Area (e.g. Hampstead Garden Suburb)
- Your home is listed or on designated land
- Previous owners already used up your PD quota
We regularly advise on creative workarounds for clients in Barnet, Brent and Camden facing these limitations.
📜 Why You Should Get a Lawful Development Certificate
Even if your extension is permitted, we strongly recommend getting a Lawful Development Certificate (LDC).
This formal confirmation from the council means no one can challenge your right to build — and it’s gold when you sell or remortgage.
We submit LDC applications alongside PD designs for peace of mind.
📍 Case Study: Camden Wraparound Extension + Loft
We helped a homeowner in Belsize Park build a wraparound ground floor extension and full loft conversion — all under Permitted Development.
- Designed within volume, height, and material rules
- Submitted for Prior Approval on the rear element
- Applied for Lawful Development Certificate
- Delivered planning, technical drawings and contractor coordination
The result? A stunning 4-bed family home, built fast and without planning headaches.
👷♂️ How DOR Architects Make PD Work
- Feasibility Study – Can your idea be done under PD?
- 3D Design – See it before you build it
- LDC + Prior Approval – We prepare the drawings and paperwork
- Technical Detailing – Full construction drawings and support
We’ve helped families across Finchley, Hendon, Kilburn and beyond expand their homes beautifully — and lawfully.
🙋♀️ FAQs – Permitted Development Extensions
Can I build a 6m rear extension without planning permission?
Yes — if you’re in a house (not flat), not in a Conservation Area, and get Prior Approval under the larger home extension scheme.
Do I need a Lawful Development Certificate?
It’s not mandatory, but highly recommended. It protects you from disputes and adds value at resale or remortgage.
Can I convert my loft under Permitted Development?
Usually yes — up to 40m² (terraced) or 50m² (semi/detached), unless you’re in a Conservation Area or already extended beyond limits.
📞 Let’s Talk About Your Extension
If you’re dreaming of a bigger kitchen, a brighter loft room, or an outbuilding to work from home — and want to stay on the right side of planning — we’re here to help.
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By
Dor Cohen
DOR Architects' principal Architect, Dor Cohen takes personal charge of some of our larger projects, focusing particularly on Property Developments, new-build and housing and high-end full refurbishments.