Two storey rear extensions are considered to be permitted development, meaning they do not require an application for planning permission provided certain limits and conditions are met. If these limits are exceeded then you will need to apply for planning permission from the local planning authority.

Houses on designated land such as national parks or conservation areas are excluded from the permitted development rights and will require an application for planning permission.

To fall within permitted development rights, the extension should be no higher than the existing house, and where it is within two metres of a boundary, the eaves should be no higher than three metres. 

Any double storey extension to the side or front of the house will require planning permission. You can view the full limits and conditions on our Two-storey extension Mini Guide.

If you live in a listed building you will require listed building consent for any major works to the property.

The conversion of a garage, or part of a garage, into habitable space, will normally require approval under the building regulations.

As part of the garage conversion, it is likely that the original garage door will be in-filled with a new wall and possibly a window or door, and a new foundation may be needed for the new wall. 

As well as the foundation, you also need to consider:

• Floor
• Walls  
• Ventilation

Read more about the building regulations for garage conversions.

You may wish to make loft alterations to enhance the storage facilities available or to increase the living space of the home. Converting the loft of a house is considered to be permitted development (not requiring an application for planning permission) subject to certain limits and conditions.

Remember, building regulations approval is required to convert a loft or attic into a liveable space.

Find out about loft conversions

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There are different rules for flats and maisonettes regarding loft conversions. Read guidance for converting the loft of a top floor flat.

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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.

Find contact details for your local planning authority.

Installing a new septic tank in your garden will often require both planning permission, building regulations approval and a septic tank permit.

The planning permission will ensure that the tank is installed in an appropriate location with information being provided to understand any potential implications for the surrounding environment and water.

Building regulations is required for the installation of a septic tank to ensure it meets the drainage and waste disposal standards set out in Approved Document H.

Where possible it is recommended that you connect to an existing public sewer instead of installing a septic tank, this reduces waste entering the waterways.

For more information visit our drains common project or contact your local planning authority.

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