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Do I need planning permission to add a first-floor extension onto an existing ground floor extension?
Adding a storey on top of an extension will always require an application for planning permission.
If you want to add a storey on top of your house under permitted development rights, it must be on the principal part of the house.
If you want to add an additional storey on top of your house, it can be permitted development. It is only permitted development if it follows certain rules:
The current house
- Is not a building containing one or more flats, or a flat contained within such a building
- Was constructed between 1 July 1948 and 28 October 2018
- Has not already had additional storeys added to it
- Is not on Article 2(3) land or a site of special scientific interest
- Was not changed to be used as a house (from a previous non-residential use) under permitted development rights.
How many storeys can you add?
- If the house is one storey then one storey can be added
- If the house is two or more storeys then two storeys can be added
Where can the storeys be added?
- The additional storeys must be added to the principal part of the house. The principal part of the house is the main part of the house excluding any front, side or rear extension of a lower height (regardless of these being part of the original house or subsequent additions).
- Engineering operations must only include works within the existing curtilage of the house to strengthen existing walls and foundations
How high can it be?
- The house cannot exceed 18 metres in total height
- Each storey cannot add more than 3.5 metres to the total height
- If the house is not detached the total height cannot be more than 3.5 metres higher than the next highest building that the house is attached to, adjoins, or is in the same row as.
- The additional storeys must have an internal floor-to-ceiling height of no more than 3 metres, and no greater than the internal height of any existing storey within the principal part of the house.
What materials can be used?
The materials used must be of a similar appearance to those used in the construction of the exterior of the current house
Where can windows be placed?
Windows must not be placed in any wall or roof slope forming a side elevation of the house.
Following completion of development:
- The house must remain in use as a domestic residential property
- No visible support structures must remain on or attached to the exterior of the house
- The roof pitch of the principal part of the house must be the same as it was prior to the development.
If any of the limits set out above are exceeded then an application for planning permission will be required. If you are unsure, you should contact your local planning authority.
Common Questions
There is no single legal definition of "habitable room", as its use and meaning are subject to context. Generally, a habitable room is a space in a building that is designed for people to live, sleep, or spend extended periods of time in, but does not include bath or toilet facilities, corridors or utility rooms.
You can usually put up new fences, gates or garden walls without planning permission, as long as you stay within permitted height limits. If the structure is adjacent to a highway (including footpaths), it must not exceed one metre in height. For all other boundaries, the maximum permitted height is two metres. Anything taller than these limits will require planning permission.
Planning permission is not required to move an internal doorway, provided it does not impact the external appearance of the building. If the building is listed, you will require listed building consent for any changes to the building.
Building regulations may apply if the wall is load bearing or is part of a fire escape route.
Read more about windows and doors from our common projects.
Planning permission is not required if the home will be used as a short-term let for 90 days or less throughout the year.
If you plan on using the home as a short-term let for more than this time period, then you will need to apply for planning permission for a change of use.
If you rent a room in your property while you still live there, you will not require planning permission.
If the garage will remain in domestic use - for example, as a personal hobby or home workshop - then planning permission is typically not required.
However, it’s important to check whether there are any planning conditions, covenants, or restrictions attached to your property or the garage itself that may limit or prevent conversion.
Read about planning permission for garage conversions on Planning Portal.
