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Can I put a double storey extension on semi detached house under permitted development?

I want to add a two storey extension to my semi detached house which has a large garden.  There is a house on the rear east boundary and a garage block to the west. How does the permitted development rule apply? How does the permitted development rule apply? Or do I need to apply for planning permission?

double storey extension semi detached house

The permitted development rights do allow for a double storey extension on a semi detached house in certain circumstances.

The enlarged part of the house must not extend beyond the rear wall by more than 3 metres, and must be a minimum of 7 metres away from the boundary of the land surrounding any house opposite to the rear wall of your house.

See our full guide on planning permission for more information on permitted development rights

The key test to qualify for permitted development in your case is that the eaves of the extension, if within 2 metres of the boundary of the curtilage of the house, cannot exceed 3 metres in height. The technical guidance for Permitted Development rights advises that where any part of the proposed extension to a house is within 2 metres of the boundary of the land surrounding the property, then the maximum height of the eaves that is allowed for all parts of the proposal is 3 metres. On this point, both the Permitted Development order and the accompanying technical guidance is written in such a manner that it relates to your boundaries and therefore I would have to conclude that the use on the adjoining land is not a consideration, unlike the 7 metre rule where there is specific mention of houses to the rear. The permitted development requirement is therefore to not exceed 3 metres within 2 metres of your boundary.

However, given that you have garages located on land adjoining one side of your property, locating an extension of more than one storey on this boundary should not cause any amenity issues such as loss of light and outlook to neighbouring residents, although this will depend on how wide you would like your extension to be as you do have neighbours on the other boundary.

But it is a good starting point and worth discussing with your local council planning authority perhaps through their pre-application service. Another issue that you will need to consider is design and a way of making sure that any extension of more than one height doesn’t appear over-dominant to the main property. Usually local authorities want extensions to appear subservient to the main house.

For further advice, speak to a local planning consultant

With thanks to Simon Wallis BA Hons, MA, MRTPI, Associate Director, Planning at Savills

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