In this short Blog article, we simplify all the rules regarding rear extensions in the UK so that you can understand whether planning permission is required and what you need to be aware of before construction We cover the permitted development activities and those that are not allowed under permitted development legislation and require permission from the council.
There are different types of rear extensions that you can built. Single storey extensions are the most common and there are also double storey extensions.
Author: Dan Taylor
Read Time: 5min
It is best to first understand what the permitted development rules are for each property in order to establish if planning permission is required.
Detached homes usually have a larger footpring and large gardens. For this reason the law allows larger single storey extensions than other property types.
Under permitted development guidance, single storey rear extensions for a detached house cannot extend beyond the original rear wall of the house (as it was first built or as it stood on 1st July 1948) by more than 4 metres. The legislation allows extensions up to 8 metres subject to prior approval (neighbour’s consultation). Prior approval means notifying the council of your intention to build an 8m extension (or up to 8 metres). A prior approval application can take 42 days to be decided. It is important that the immediate neighbours do not object, as their objection is given a lot of weight in deciding prior approval applications.
If your home is split into flats, permitted development rights do not apply, and you will need full planning permission. If your home is in a conservation area you might be allowed to extend up to 4m in depth under permitted development, but not prior approval. If the property is listed or adjacent to a listed property, permitted development rights are not applicable and you will need planning permission.
A semi detached house is attached on one side to a neighbour. There is a common partywall and all extensions adjacent to the partywall will require a partywall agreement. This is a separate matter which will be discussed on a separate blog.
A single storey rear extension or side-infill or wrap around extension is likely to be achieved, subject to height, depth and impact on the neighbour’s light and outlook.
Permitted development rights allow single storey extensions up to 3m depth from the original rear wall of the house or up to 6 metres depth under prior approval (neighbours consultation scheme as mentioned above). The height of the extension is usually 3m to the eaves or 4m if not within 2m of the boundary wall.
Wrap around extensions are not considered permitted development and will require householder planning permission.
Most homeowners living in a terraced house go for a rear extension option to increase the habitable space and open up the space with more natural light, sense of spaciousness and openness. A single-storey extension to a terraced house is likely to be very close to the neighbour’s windows, therefore a 3-metre-deep extension is considered permitted development and does not require planning permission, but any further depth is likely to be resisted by the council. If you apply for prior approval for an extension over 3m depth, assuming the neighbours do not object, you might be able to achieve an extension up to 6m depth. Alternatively, if your neighbours have an extension which exceeds 3m depth, it is possible to infill the gap and extend further, since the new extension will not harm the amenity of the neighbouring properties, and will be in keeping with the terrace. Furthermore the proposed extension will not be visible from the street.
A single-storey rear extension should not be developed over 50% of the curtilage of the site in order for it to comply with permitted development rules.
When constructing a single-storey rear extension, the extension height should not exceed 4m in order for it to be considered permitted development. This is measured from the lowest ground level of your extension to the highest ridge on your roof. If the extension is higher, planning permission is required.
A contemporary style extension with non-matching materials, is something the local authority might accept if the conditions are right. The materials need to be high quality, enhance the aesthetics of the property, introduce good quality design and avoid setting a “negative” precedent.
Any non lawful development extension will need to fully comply with local planning policies, planning guidance (SPDs) and legislation. For further information on what a "lawful development certificate is" please click here.
4D Planning have experience designing bespoke contemporary extensions which meet out client’s style and preferences and not less importantly, obtaining planning permission for them. For a free consultation please call us or email us the property address and we’ll get in touch to discuss your project.
Another important requirement is that the proposed single-storey rear extension should not be taller than the highest part of your property’s existing roof. If the extension is within 2 metres of the property boundary with the neighbours, the eaves height should not exceed 3m in height as explained above.
A general rule in planning terms is that all new materials should ideally match the materials of the existing house. They need to look the same and have a similar appearance in properties and characteristics. For any new materials which do not strictly match, planning permission is required. For example, if you change render to brickwork, brick to render, cladding instead of render etc, planning permission is required as the appearance of the house will change.
Replacement of windows from timber to upvc will require planning permission in conservation areas and in listed properties.
If you are considering building a single-storey rear or single-storey side extension, 4D Planning are happy to assist with your architectural design, drawings, preparing and submitting the lawful development application or planning permission application and dealing with the council on your behalf. We can also prepare the building regulations and liaise directly with Building Control to ensure that everything is approved before the builders commence works.
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