A Homeowner’s Guide to Permitted Development Rights
In Hertfordshire, many small-scale home improvements can be carried out without planning permission under what’s known as permitted development rights.
This means you can usually build certain types of single-storey rear extensions, loft conversions, garden rooms, porches, sheds, and garage conversions without needing formal approval, as long as they meet specific size, height, and location limits.
This guide outlines the most common projects that fall within permitted development and the key conditions you must follow to stay compliant. Whether you’re creating more living space, upgrading your property’s layout, or adding value before selling, knowing what you can build without permission can save you time, money, and unnecessary paperwork.
What Are Permitted Development Rights?
Permitted development rights are national rules set by the government that allow homeowners to carry out certain building works without needing to submit a full planning application.
These rights apply to most houses, but not to:
- Flats or maisonettes
- Homes in conservation areas or national parks
- Listed buildings
- Some new-build estates with restricted rights
According to Planning Portal, permitted development is one of the most commonly misunderstood areas of planning, leading to delays, enforcement notices, or costly mistakes.
Lloyd Dixon Group is an experienced team of property surveyors in London, St Albans, Hertfordshire and Mayfair. To get a quote or speak to us, please call 075 95 534 101.
Types of Projects Usually Covered by Permitted Development
1. Rear Extensions
You can extend the rear of your property up to:
- 3 metres for a terraced or semi-detached house
- 4 metres for a detached house
This is subject to height limits and boundary distances. For larger extensions, you may still need to go through a prior approval process (more on that below).
2. Loft Conversions
You can convert your loft space and add dormer windows if:
- It adds no more than 40m² (terraced) or 50m² (detached/semi-detached) of volume
- Dormers do not extend beyond the roof slope at the front
- Materials are similar in appearance to the existing house
3. Garage Conversions
Internal garage conversions usually fall under permitted development as long as:
- You’re not enlarging the building
- The use remains domestic
- The work does not involve significant external changes
4. Outbuildings and Garden Rooms
You can build sheds, studios, and summerhouses if they:
- Are single storey and no taller than 2.5m (if within 2m of a boundary)
- Occupy no more than 50% of your total garden area
- Are not used as self-contained accommodation
5. Rooflights and Solar Panels
Installing rooflights or solar panels on your roof is generally allowed if:
- They don’t project more than 150mm from the roof slope
- They’re not higher than the existing roof
- Panels are positioned to minimise visual impact (especially in conservation areas)
What Is the Prior Approval Scheme?
The Prior Approval Scheme is a planning process that allows certain larger home extensions and change-of-use developments to go ahead without full planning permission — but only with the local authority’s prior approval.
This means you must formally notify your council before starting work and receive confirmation that the proposed development is acceptable in terms of specific impacts, such as neighbour amenity, transport, or flood risk.
Examples include:
- Large rear extensions under the Neighbour Consultation Scheme
- Conversion of offices or agricultural buildings into homes
- Installation of certain telecom or broadband infrastructure
Your local Hertfordshire council will assess neighbour objections and basic impacts (such as flood risk or transport access) before giving the green light.
What Are the Risks of Not Getting Approval?
If you carry out work that doesn’t comply with permitted development rules and didn’t apply for planning permission, the council may issue an enforcement notice. This can lead to:
- Fines
- A stop to all works
- An order to reverse or remove unauthorised changes
To avoid issues, it’s wise to get a Lawful Development Certificate as proof that your project was permitted at the time.
Can I Get Advice Before Starting Work?
Yes, and you should. Even small errors in dimensions or placement can disqualify a project from permitted development.
Our team at Lloyd Dixon can assist with:
- Party Wall surveys
- Defect diagnosis
- Clarifying whether your project falls under PD
- Preparing Lawful Development Certificates
- Monitoring your project
- Liaising with planning consultants if full permission is required
See More:
What Is Project Monitoring in Property Development and Why Does It Matter?
What Are Dilapidations and What Do They Mean for Landlords and Tenants?
What is a BRCA (Building Reinstatement Cost Assessment) and Why Does It Matter?