Understanding Permitted Development

What is Permitted Development?
Permitted development rights give homeowners the legal ability to extend or alter their property without needing full planning permission from the local council. These rights are granted by national legislation rather than local authorities, which means they apply broadly across England.

That said, there are restrictions laid out in the Permitted Development Technical Guidance, so not every project will qualify. When they do apply, they open up valuable opportunities for improving your home without the cost and delays of a full planning application. By using your permitted development rights in Oxford, you can often avoid months of waiting for approval and save on unnecessary fees, provided your plans stay within the rules.

Typically, permitted development covers:

  • Single-storey side or rear extensions

  • Loft conversions

  • Porches at the front of a house

  • Outbuildings such as garden rooms or sheds

  • Dormer windows

On the commercial side, permitted development can allow certain changes of use, such as converting an office into a shop (within the same use class, e.g. Class E).

However, there are limits. Larger or double-storey extensions, tall builds close to boundary lines, alterations or extensions to the front of the property, works to flats, properties which have previously been extended or properties in conservation areas usually fall outside permitted development rights and require full planning permission.

The Background of Permitted Development

The idea of regulating urban development isn’t new. In fact, permitted development was first introduced in the Town and Country Planning Act 1948. At that time, the government wanted clearer, more consistent rules and reduced the number of planning authorities from 1,400 to 145.

This Act became the foundation for modern planning laws, introducing both listed building protection and the principle of permitted development. Today, while the system has been updated over the years, the same basic framework still exists. The UK now has 333 local planning authorities (6 in Oxfordshire), each setting its own policies. Councils also have the power to remove permitted development rights in sensitive heritage areas, but outside of these restrictions, property owners can usually make use of their rights.

Rear extension to existing Terrace house finished in white render, surrounded by a fence and bushes, with brick houses in the background.
Rear extension constructed under permitted development rules. Large glass sliding doors with fully glazed gable over. Window glass is reflecting trees, with a wooden fence and green shrubbery in the foreground.
Close-up of dormer window constructed under permitted development. Existing house is built of Buff LBC brickwork with a black slate tiles roof. Dormer cladding matches existing roof finish
Bright second floor bathroom with large window and nice view of Oxford skyline and trees, potted plants, white walls, and a shower on the right.
A rear extension to existing stone cottage, constructed from matching stone with large dark stained sliding doors. backyard patio with a white wrought iron table and chairs, potted plants.

Permitted Development Projects

Single-Storey Extensions

You can usually build a single-storey extension without planning permission if certain conditions are met:

  • The materials used must be in keeping with the original property.

  • The extension must not cover more than 50% of the surrounding land (including existing additions).

  • It cannot extend beyond the front of the house if it faces a road.

  • Side extensions must be single-storey, up to half the width of the original house, and no more than 3m high.

  • Rear extensions can project up to 3m for attached houses or 4m for detached homes. In some cases, with prior approval, this can increase to 6m and 8m respectively.

  • Maximum height limits apply: 4m for pitched roofs or 3m for flat roofs.

  • Materials must match existing

Loft Conversions

Loft conversions may qualify as permitted development if they follow these rules:

  • Additional roof space must not exceed 40m³ (terraced/semi) or 50m³ (detached).

  • Materials must match the existing roof.

  • Extensions cannot go beyond the roof slope facing the road.

  • Roof height must not be increased.

  • Balconies or raised platforms are not allowed (But Juliet balconies are)

  • Side windows must be obscured and set above 1.7m.

  • Roof extensions should be set back at least 20cm from the eaves.

Porches and Outbuildings

  • Porches: Must not exceed 3m² in floor area, 3m in height, or be within 2m of a boundary facing a road.

  • Outbuildings: Must be single-storey, up to 2.5m high near a boundary (4m with a pitched roof further away), and cannot cover more than 50% of the garden. Use must be “incidental” (e.g., office, gym, or storage), not as a separate dwelling.

Larger Home Extensions Scheme (Prior Approval)

In 2019, the government introduced the Larger Home Extensions Scheme, which was made permanent in 2020. This allows homeowners in England to build rear extensions beyond standard permitted development limits, provided they go through a neighbour consultation process.

How Far Can You Extend Under the Larger Home Extensions Scheme?

  • Semi-detached or terraced houses – rear extension up to 6m deep

  • Detached houses – rear extension up to 8m deep

This creates fantastic opportunities for families wanting extra living space or to add Kitchen extensions without the lengthy process of submitting for full planning permission.

Do You Need Planning Permission for a Larger Home Extension?

Unlike standard house extensions, this scheme does not require full planning permission. Instead, you must submit a Prior Approval application to your local council.

  • The council notifies all neighbours.

  • Neighbours have the chance to comment or object.

  • If no objections are received, your extension is automatically approved.

  • If objections are made, a planning officer assesses the impact before making a final decision.

Architectural Design Services for Larger Home Extensions Oxfordshire

At KD Design, we specialise in preparing architectural designs that comply with permitted development and the Larger Home Extensions Scheme. Our services include:

  • Creating detailed drawings for your home extension.

  • Ensuring the design complies with planning and building regulations.

  • Managing and submitting your Prior Approval application.

  • Supporting you throughout the consultation process.

Whether you’re planning a 6m rear extension to a semi-detached home in Summertown, a terrace house in Jericho or an 8m extension to a detached property in Woodstock, our expertise ensures your project moves smoothly from design to approval.

Single storey rear extension built using Permitted development larger home extension. Open bifolding glass doors leading to a kitchen with a dining table and chairs, a wooden privacy fence, and a well-maintained lawn under a blue sky.

5m extension approved under prior approval application

Single storey Rear extension utilising Permitted development larger home extension under prior approval. Back view of a rendered extension with pitched Gable, large glass doors with glazed gabled above.

4.5m extension approved under prior approval application

Technical Guidance and Local Rules

The government publishes detailed Permitted Development Technical Guidance, covering:

  • Extensions and conservatories (size, materials, and height limits)

  • Roof alterations (e.g., dormers windows, hip to gable conversions, rooflights)

  • Porches

  • Change of use (e.g., garage to living space)

  • Outbuildings (sheds, Garages, garden rooms, etc.)

In Oxford and the Cotswolds, Article 4 directions, areas of outstanding natural beauty and conservation area rules can restrict some permitted development rights, so it’s always wise to seek professional advice before starting works. We’d be happy to offer some free initial advice to see if your project can be constructed under PD rights.

Peace of Mind with KD Design

When planning a home extension, it is not always clear if a project complies with permitted development rules. To give homeowners certainty, KD Design can prepare and submit a Certificate of Lawfulness application to the local authority, such as West Oxfordshire District Council or South & Vale District Council.

A Certificate of Lawfulness is an official legal document that confirms your proposed extension, loft conversion, or alteration is lawful under permitted development rights and does not require full planning permission.

Why Apply for a Certificate of Lawfulness?

Applying for a certificate provides:

  • Formal confirmation that your project meets planning rules

  • Peace of mind before construction begins

  • Protection against future disputes with the council

  • Clear proof of compliance, which can increase the value of your home when selling

How KD Design Supports Homeowners in Oxford, Witney and West Oxfordshire

  • We manage the entire application process on your behalf

  • We communicate with the council and track the progress of your application

  • We continue with the detailed architectural design stage while the application is under review, so your project continues to make progress

  • We advise on whether a Certificate of Lawfulness is the right approach for your property and extension plans

The planning fee for a Certificate of Lawfulness is usually half the cost of a householder planning application, and decisions typically take around 8 weeks. The advantage of a permitted development scheme is that this application period does not need to delay works, Instead KD Design can to proceed to the detailed design phase whilst the application is being reviewed by the council.

Expert Advice on Permitted Development Extensions

Permitted development rights offer homeowners a faster, simpler way to expand or alter their homes without the need for full planning permission, helping avoid long waits and costly planning fees. However, the rules vary depending on property type, location, and local planning policies. Seeking expert architectural advice is the safest way to ensure your project runs smoothly.

At KD Design, we provide professional architectural design services for permitted development and larger home extensions in West Oxfordshire and the Cotswolds. From initial advice through to planning drawings, applications, and final approvals, we give clients confidence that their projects are legally compliant and designed to the highest standard.

If you would like to discuss your home extension project under permitted development or the Certificate of Lawfulness process, please get in touch. with KD Design today.

Rear extension constructed under permitted development rules. Large glass sliding doors with fully glazed gable over. Window glass is reflecting trees, with a wooden fence and green shrubbery in the foreground.
Rear extension to existing Terrace house finished in white render, surrounded by a fence and bushes, with brick houses in the background.
Open glass doors leading to a modern kitchen with white cabinets and wooden countertops inside a brick house.
Close-up of dormer window constructed under permitted development. Existing house is built of Buff LBC brickwork with a black slate tiles roof. Dormer cladding matches existing roof finish
A view of a bright, white-walled room with a sliding pocket doors leading to a bathroom, showing a city skyline with buildings and trees through large windows.
Bright second floor bathroom with large window and nice view of Oxford skyline and trees, potted plants, white walls, and a shower on the right.
A dormer window within a brown tiled roof. Dormer finished in lead with painted timber fascia boards and gable cladding.
Rear view of an extension to a brick house with a sloped roof, large glass doors, and windows, with outdoor chairs and potted plant in the backyard.
A rear extension to existing stone cottage, constructed from matching stone with large dark stained sliding doors. backyard patio with a white wrought iron table and chairs, potted plants.
Modern Extension exterior with large black-framed windows, a sliding glass door, and a stone-paved patio, with a wooden fence and leafless trees in the background.
Single storey rear extension built using Permitted development larger home extension. Open bifolding glass doors leading to a kitchen with a dining table and chairs, a wooden privacy fence, and a well-maintained lawn under a blue sky.

Let’s Work Together!

Do you have some big ideas and need some help bringing them to life? Then please reach out. We’d love to hear from you and learn about your project, and to get the ball rolling we’d be happy to offer some initial informal advice free of charge.

Please Contact us and we’ll be in touch to discuss further at a time that suits you.

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