How Far Can You Extend Without Planning Permission

Extending a semi detached house is a popular way to create more space without the need to move. Whether it’s a larger kitchen, an extra bedroom or a light-filled rear living area, homeowners often want to know how far they can go before needing planning permission. Thanks to permitted development rights, many extensions to semi detached properties can be built without applying for full planning permission, as long as specific criteria are met.

Permitted Development Rights for Semi Detached Homes

In England, permitted development rights allow you to extend your home without needing to go through the full planning process. These rights apply to most houses, including semi detached properties, provided the home is not in a conservation area, national park, Area of Outstanding Natural Beauty or subject to an Article 4 Direction removing those rights.

The extension must be to the rear or side of the original house. It cannot be built forward of the principal elevation that faces the road. Also, the work must not cover more than fifty per cent of the total land around the original house. Any previous extensions or outbuildings count towards this allowance.

Rear Extensions Without Planning Permission

For a single storey rear extension on a semi detached home, you can usually extend up to three metres from the rear wall under standard permitted development rules. However, a temporary relaxation of these rules, originally introduced in 2013 and made permanent in 2020, allows you to extend up to six metres, subject to a process called prior approval.

This process is known as the Larger Home Extension Scheme. It lets homeowners extend between three and six metres (measured from the rear wall of the original house), but you must first notify your local planning authority. They will consult neighbours who have the right to object if the extension would cause significant harm to their amenity. If there are no objections, or any objections are not upheld, the work can go ahead without full planning permission.

The extension must not exceed four metres in height and must not extend beyond the side of the house onto land facing a highway. If the extension is to have a flat roof, the maximum height is three metres. The materials used must be similar in appearance to the existing house unless it is a conservatory.

Side Extensions Without Planning Permission

Permitted development also allows for single storey side extensions as long as they are no wider than half the width of the original house and no taller than four metres. They must not be forward of the main elevation and must not wrap around the rear or project more than three metres from the side elevation. If the side extension is within two metres of the boundary, the maximum height is limited to 3 metres.

Two storey side or rear extensions are not permitted development and will always require full planning permission. The same applies to extensions that exceed height or depth limits or are designed in a way that does not comply with the restrictions.

Roof Extensions and Loft Conversions

Permitted development rights also allow for certain loft conversions on semi detached homes, including rear dormers, provided they do not exceed a volume of forty cubic metres and meet conditions regarding height, materials and privacy. Front-facing dormers and extensions that raise the existing roof height will require planning permission.

Special Designations and Exceptions

In designated areas such as conservation areas, national parks, the Broads and Areas of Outstanding Natural Beauty, the rules are more restrictive. Side extensions and larger rear extensions often require full planning permission in these locations. If your property is listed, you must apply for listed building consent before starting any extension work.

If permitted development rights have been removed from your property through a planning condition or an Article 4 Direction, you will not be able to extend without permission, regardless of size.

Certificate of Lawfulness

If you want certainty that your proposed extension qualifies as permitted development, you can apply for a Certificate of Lawful Development. This confirms in writing from your local authority that your extension is legal and avoids any complications when selling or remortgaging.

Conclusion

You can extend a semi-detached house by up to three metres under standard permitted development rights and up to six metres under the Larger Home Extension Scheme, subject to neighbour consultation. Side extensions can also be added within size and height limits. Always check with your local authority to ensure your rights have not been restricted and apply for prior approval if necessary. By following the rules, you can maximise your living space without the delay and cost of a full planning application.