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Rear Garden Outbuilding:

On several occasions over the years and also very recently , Terrarossa Project has been involved with the development of outbuildings at the back of the gardens of some large family homes. We have been asked about developing large sheds, offices, summer houses and granny annexes and the most frequent questions have been: What can I build at the back of my garden? What can I build at the back of my garden under Permitted Development? Is a Granny Annex Permitted Development? Can I build a flat at the back of my garden for renting? Firstly, for an outbuilding, size matter s but it’s not just about that! What  also matters is the proposed use of it, which will determine if you can actually erect it under Permitted Development rights or not. In order to understand the potential  for development of a portion of the back of a garden, we should  start probably from understanding the Permitted Development criteria for an outbuilding (these are detailed under Class E of the Government Technical Guidance), which are summarised as follows:


The use of the proposed outbuilding must be ‘for a purpose incidental to the enjoyment of the dwelling house as such’, which means that it has to serve as an extension of the main house and be used as a summer house, office, gym, storage area etc. (also as a container used for domestic heating purposes for the storage of oil or liquid petroleum gas). This clearly indicates that a self-contained unit will not fall under the Permitted Development rights! Size The total area of ground covered by the proposed outbuilding should not exceed 50% of the total area of the curtilage, excluding the ground area of the original dwelling house. Also, the proposed height should not exceed 2.5m in case it is erected within 2m of the boundary of the curtilage of the dwelling house or 3m in any other case. If the proposed outbuilding is erected with a dual-pitched roof, the ridge should not exceed 4m and the eaves, 2.5m. If the plan is to erect a self-contained granny annex for permanent residence instead, the use of the outbuilding does not fall within the Permitted Development Rights but the Local Authority will still consider the proposal as a domestic development and, therefore , a Domestic Planning Application is required. For erecting  a self-contained independent flat that you may either want to rent or sell, a Full Planning Application is required. For both Domestic and Full Planning Applications, the Permitted Development guidance  on sizes and dimensions does not apply , whilst the local Unitary Development Plans and other Nationwide guidance will need to be considered.

(The project shown in the above photo is a proposal for a Granny Annex at the rear of a property in Sanderstead, South Croydon. For further information, check:

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