Can I Build an Extension Without Planning Permission in Dorset?
- Rosenkelly Architectural Design
- May 1
- 5 min read
Dorset homeowners often dream of extra space – a bigger kitchen or a new bedroom – but worry about planning permission. Thanks to UK permitted development (PD) rights, many smaller home extensions can be built without needing a traditional planning application, such as a full or householder submission. Instead, if your project qualifies, you can confirm its legality by applying for a Lawful Development Certificate (LDC). This approach offers clarity and keeps things straightforward, without the longer timescales and uncertainty that a full planning process can bring.
In this post we explain how permitted development works for Dorset homes, why the LDC process is a smart step, and how to ensure your extension is both compliant and future-proof.
What Counts as Permitted Development in Dorset?
Permitted development (PD) rights let homeowners extend or renovate their houses without needing a full planning application. Under these national rules, many common projects are allowed as long as they follow size and style limits. For example, a single-storey rear extension is generally permitted if it stays within a certain depth – typically 3m beyond the original rear wall for a semi-detached house or 4m for a detached property. If you want a larger rear extension, the "prior approval" scheme lets you go up to 6m (semi) or 8m (detached) as long as neighbours don’t object. (These distances are measured from the original house footprint.) Extensions under PD must also keep the new floorspace to no more than half the area of your land (including any other buildings) and should be built in similar style to your existing home.
Keep in mind some local factors: if your Dorset home is listed, or lies in a Conservation Area or Area of Outstanding Natural Beauty (AONB), some PD rights may be limited or removed. It’s always wise to check with Dorset Council or an architect about these restrictions. Note too that PD covers planning permission only – your extension still needs Building Regulation approval and (if you share a wall with a neighbour) a Party Wall agreement.
Benefits of Permitted Development for Dorset Homeowners
Permitted development brings several benefits for Dorset homeowners:
No traditional planning application needed: You don’t have to apply for householder or full planning permission for eligible projects.
Cost-efficient compliance: You can apply for a Lawful Development Certificate instead, confirming your proposal meets all planning rules upfront.
Straightforward rules: PD rights are nationally defined and less subject to interpretation, giving you more certainty when planning.
Increased property value: A well-planned extension boosts living space and adds value. Buyers love extra rooms that are legally approved.
Design flexibility: Working with an architect ensures your extension both complies with PD and looks great. For example, matching the roof pitch, eaves height and materials of the existing home keeps the extension feeling like part of the original house.
These advantages mean you can transform your home with minimal red tape. But ensuring compliance – and documenting it – is still essential. That’s where the LDC process becomes especially valuable.
Why You Still Need a Lawful Development Certificate
Even under permitted development, we strongly recommend applying for a Lawful Development Certificate (LDC). An LDC is formal confirmation from the council that your extension complies with planning rules. It isn’t legally required before you build, but securing one early has important long-term benefits:
Peace of mind: An LDC gives you a clear record that your design complies with planning law. If any questions ever arise, you’re covered.
Helpful when selling: If you later decide to sell your home, buyers or their solicitors will want assurance that the extension was lawful. An LDC avoids delays or doubts.
Protection from future issues: Without a certificate, you risk assumptions being challenged in the future. An approved LDC removes ambiguity.
Applying for an LDC is usually faster and less involved than a traditional planning application, but it still requires detailed drawings and a clear submission. Many homeowners prefer to have an architect manage this process – preparing the documents, submitting the application online, and liaising with Dorset Council to ensure everything runs smoothly.
Our Advice for a Smooth and Compliant Extension
At Rosenkelly, I've guided many Dorset homeowners through PD extensions and LDC applications. Here are some tips for a smooth process:
Plan early: Before you build, get advice. An early chat with us or Dorset Council can clarify which PD rules apply to your property (watch out for local Article 4 directions, for example).
Think like a planner: Sketch your proposed extension carefully. Make sure any single-storey rear extension stays within the 3m/4m limit (or use prior approval if larger), and that side extensions don’t exceed half the house width.
Design with purpose: Use design features that fit the PD rules. For example, keep the new roof at a similar height and angle as the existing one, and choose matching bricks or cladding. These details keep the extension feeling “in character” with your home.
Talk to neighbours: If you plan a larger extension needing prior approval, discuss it with neighbours first. Friendly agreement can help avoid objections during the 28-day consultation.
Apply for an LDC: Submitting a Lawful Development Certificate application early gives clarity before you build. It’s a simple way to document your compliance.
Follow Building Regs: Remember that PD and LDC cover planning, not construction standards. Make sure your builder or architect submits all the necessary building regulation plans.
Following these steps (and working with a Dorset-based architect) will help you avoid hiccups. I blend modern design with local know-how to create extensions you’ll love for years to come.
Tips to Maximise Your Extension Under Permitted Rules
You might be surprised how much extra space PD rules allow. Here are some ideas to make the most of your extension project:
Use all PD allowances: Check the full set of rules. For example, since 2020 there has been a larger extension scheme: with prior approval you can add up to 6m (semi) or 8m (detached) to the rear. Even without that, you automatically get 3m/4m for a rear extension, plus other allowances like a new loft dormer or outbuilding.
Extend sideways: A single-storey side extension (up to half the house width) is also permitted. Use that for a bigger hallway, utility room or extra living space without eating up your backyard.
Convert the loft: PD rules allow loft conversions (within size limits) with dormers, hip-to-gable, etc. This can add bedrooms or a home office under the roof.
Add an outbuilding: A garage conversion or new garden room (up to 50m²) can provide extra space under PD. (Just avoid making it too tall or too close to boundaries.)
Respect the 50% rule: Your extension and other new structures must not take up more than half of your garden area. Plan carefully so you stay below this threshold.
Maximise light: Within PD limits you’re allowed big windows and rooflights. Orient your design for sunlight, making the new space bright and welcoming.
Match the style: Keep the extension in character. Use similar roof materials, match eaves heights, and align new windows to complement the original design. A seamless look is the easiest way to stay within PD rules.
By carefully following these guidelines, you can add significant space to your Dorset home without needing full planning permission. If you’re not sure how far you can go, we can help clarify the limits and design the best layout.
If you're considering a project like this, I'm happy to walk you through your options. Every home is different, and I tailor each extension design to the property, location, and goals of the homeowner. Each project is unique, and I enjoy crafting cost-effective designs that fit you perfectly.
Ready to start planning your extension? Contact Rosenkelly Architectural Design – your local architect in Dorset – for friendly, straightforward advice. I'll guide you through every step, from initial drawings and LDC applications to the completed build. With a dedicated architect on your side, you can extend your home with confidence and ease. Reach out today and let’s make your Dorset home dream a reality!
