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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
In many circumstances, rules known as ‘permitted development’ rights allow you to extend a house without needing to apply for planning permission, providing specific limitations and conditions are met. If you want to exceed these limits and conditions, then it is likely that an application for householder planning permission will be required.
The limits and conditions for building an extension under permitted development rules are covered in our guidance on the Planning Portal, and there are other points to take into consideration.
Visit Planning Portal to find out more.
Replacing the window within a bay window is treated the same as any other window. Meaning that the replacement of windows which have a similar appearance to those previously used would not require an application for planning permission.
Repairs, maintenance and minor improvements will also not require an application.
If you live in a listed building or a designated area then different rules may apply.
For more details on replacing windows, visit our common projects section.
Demolishing a building may require planning permission or prior approval, depending on factors such as the building’s type, size, and location.
Before starting any demolition work, it’s important to consult your local planning authority to confirm what permissions are needed. This helps avoid the risk of enforcement action or legal consequences.
You will also need to ensure you conform to the building regulations around the demolishing of a building.
Whether you need planning permission to install an extractor fan depends on the size and placement of the fan.
For domestic installations, such as a bathroom or kitchen in your house, planning permission is not generally required. If the change significantly alters the external appearance of your home then permission may be required.
If you live in a listed building, you will need listed building consent for any significant changes.
Larger extractor fans for businesses are likely to require an application for planning permission to be made to the local planning authority. These extractors can impact the local area due to their noise, visibility and odour, as such the planning authority will need to assess the change.
Building regulations relating to ventilation and electrical works will have to be complied with, these are covered by Approved Document F and P respectively.
Read more about building regulations and the requirement for ventilation on our common projects.
Foundations are required to carry and distribute the load of the building safely. Therefore, all buildings should have adequate foundations. The factors that need to be considered when designing a foundation are:
- Type of soil
- Adjacent structures
- Trees
- Drains and sewers
- Size and construction of the new building
- Ground condition
- Landfill sites
It is advisable to contact a structural engineer or speak to a building control body about plans for new foundations.
