Thinking about house extensions but unsure what the 50% rule means for your plans? At KT5 Construction, we regularly advise homeowners on navigating planning permission rules, including the “50% rule for house extensions.” This guideline can significantly impact how much you can legally extend your home, especially if you live in a semi-detached or detached property. As a trusted extension builder in Surrey and London, KT5 Construction Ltd has guided countless homeowners through this issue, ensuring every project is compliant, neighbour-friendly, and built to the highest standards. Our people-first approach means we take the time to understand your goals while ensuring your project respects neighbours’ rights and legal boundaries. Let’s unpack what “close” really means when building next to someone else’s property.

Understanding the 50% Rule: What It Means

The 50% rule refers to a planning constraint used by many local councils when assessing house extension proposals. It typically applies in these contexts:

• • Green Belt or countryside areas
  • Permitted Development Rights exemptions
  • Conservation or Article 4 Direction zones

The Core Principle

You’re generally not allowed to extend your home if the resulting size exceeds 50% of the original building’s footprint. This does not include outbuildings that were added later.

What Counts as the “Original” House?

• • The property as it was in 1948 (or when it was first built, if later)
  • Any extensions made after that date are included in the 50%

Example: If your house originally had a floor area of 100m², all extensions must remain within a cumulative 50m² increase.

Why Does the 50% Rule Exist?

Local authorities aim to:

• • Prevent overdevelopment in rural and suburban areas
  • Preserve character in protected zones
  • Ensure privacy and light for neighbours

This makes it vital to work with a reliable builder like KT5 Construction who understands planning permission and householder planning permission regulations.

Does the 50% Rule Apply to Everyone?

Not always. Here’s how it might affect you:

Situations Where It Likely Applies

• • Homes in Green Belt areas
  • Properties in Conservation Areas
  • Homes with restricted permitted development rights

Situations Where It Might Not Apply

• • Urban properties with standard permitted development rights
  • In certain areas where the local authority does not enforce the rule strictly

Always check with your local planning office—or better yet, ask KT5 Construction to handle your house extension planning.

Why do Homeowners of Surrey and London Choose KT5 Construction?

• • Over 25 years of excellence in house extensions.
  • Specialists in kitchen extensions, rear extensions, and loft conversions
  • Knowledge of building regulations, party wall agreements, and designated land restrictions
  • A people-first, stress-free build experience

Let’s talk today—your dream space is closer than you think.

Frequently Asked Questions

1. Can I apply for planning permission to exceed the 50% rule?

Yes, but you’ll need a very strong case. KT5 can help prepare robust submissions and advise on householder vs full planning applications.

2. Does the rule include loft or garage conversions?

No. It generally only applies to new floor area increases, not internal alterations.

3. How do I know how much has already been added to my home?

We conduct a property history assessment using planning records and site surveys to ensure compliance with house extension rules.

Final Thoughts

The 50% rule for house extension can be a complex hurdle, but with KT5 Construction, you’ll always have a reliable builder by your side to guide you through it. We help clients align their home extension planning with permitted development size limits, materials regulations, and neighbour considerations.

Ready to extend your home the right way? Contact KT5 Construction today for a free consultation and site survey.