Planning a house extension can be exciting—but navigating the planning permissions and building rules? Not so much. If you’re asking yourself, what planning do I need for an extension?—you’re not alone.

KT5 Construction, a trusted builder  with years of experience, is here to guide you through every step. Whether you’re dreaming of a larger kitchen, a rear extension, or a loft conversion, understanding UK planning regulations is vital to save time, money, and stress.

Do I Always Need Planning Permission for a House Extension?

In many cases, no. Thanks to Permitted Development Rights (PDR), certain extensions can be built without applying for full planning permission—if you stay within strict guidelines.

What Counts as Permitted Development?

Here’s when you usually don’t need to submit a planning application:

• • Single-storey rear extensions up to 3 metres (terraced/semi-detached) or 4 metres (detached)

  • Loft conversions under 40m³ (terraced) or 50m³ (detached/semi-detached)

  • Side extensions that are no more than half the width of the original house

  • Materials used are similar in appearance to the existing house

  • The extension doesn’t extend beyond the principal elevation

🛑 Important: Flats and maisonettes don’t benefit from PDR, and homes in conservation areas or listed buildings face tighter rules.

To be sure, KT5 Construction always recommends confirming with your Local Planning Authority (LPA) before starting.

When Do I Need Full Planning Permission?

Planning permission is required if your proposed extension:

• • Exceeds PDR size limits

  • Is in a designated area (e.g., conservation, AONB)

  • Will alter the roofline significantly

  • Includes a balcony or raised platform

  • Faces the highway and changes the front of the house

In short, anything that significantly alters the home’s appearance or use will usually require approval.

We advise clients across London and Surrey to apply early to avoid costly delays. Our planning support services include free planning drawings worth up to £2,500 if you appoint KT5 as your builder.

Do I Need Building Regulations Approval?

Yes. Even if your extension qualifies under Permitted Development, Building Regulations approval is still required.

Why Building Regs Matter:

• • Ensure structural safety

  • Guarantee insulation and fire safety standards

  • Confirm drainage and electrical works meet UK codes

At KT5 Construction, we handle the building control submissions, site inspections, and liaise with inspectors on your behalf. All our projects are delivered to code, on budget, and on time.

Key Planning Considerations Before You Start

1. Check Title Deeds and Restrictive Covenants

Some properties include clauses that limit your right to extend. We help clients review their legal documents to avoid planning refusals.

2. Think About Your Neighbours

The Party Wall Act may apply if your work affects shared boundaries. We support clients with notices and dispute resolution where required.

3. Apply for a Lawful Development Certificate (LDC)

Even if you don’t need planning permission, getting an LDC proves the extension is lawful—making it easier if you sell or remortgage.

4. Hire a Builder Who Understands the Paperwork

Too many homeowners choose the cheapest quote and then face rejections or enforcement notices later. KT5’s experience ensures your project gets approved and built properly.

KT5 Construction: Your Trusted Partner in Planning

As leading builders in London and Surrey, KT5 Construction is known for:

• • Handling planning drawings, submissions, and revisions

  • Navigating building control and compliance

  • Offering free planning drawings worth up to £2,500 when appointed as your builder

  • Delivering high-quality extensions that pass inspection first time

📍 Whether it’s a side return in london or a rear kitchen extension in Surrey, we bring local expertise and exceptional service.

See how our services help homeowners like you plan and build with confidence.

What Happens If I Build Without Planning Permission?

It’s risky. The council could serve an enforcement notice requiring you to remove the extension. This could cost you tens of thousands in demolition, legal fees, and rebuilding.

To avoid that nightmare, contact KT5 Construction early in your planning stage. We’ll assess your plans and tell you exactly what permissions you need—or don’t.

FAQs: Planning for Home Extensions in the UK

Q: How long does planning permission take?

A: Typically 8 weeks, but it can extend to 13 weeks for major works.

Q: Can I build before receiving approval?

A: No. You must wait until planning permission is granted.

Q: Who draws up the plans?

A: We do. KT5’s in-house design team provides planning and technical drawings, included free when you hire us.

Q: Do I need planning permission for a garage conversion?

A: Often not—but building regulations still apply.

Q: Can KT5 Construction manage the whole process?

A: Absolutely. From drawings and submission to construction and sign-off, KT5 handles it all.

Ready to Extend? Speak with KT5 Today

If you’re wondering “What planning do I need for an extension?”, let KT5 Construction simplify the answer.

👉 Call us for a free consultation – 0845 053 7224

👉 Stay compliant, on budget, and stress-free

Visit our About Us page to learn more about our values and customer-first approach. Or head over to our Contact page to book your no-obligation call.