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How high can I build a single-storey extension without planning permission?

A single storey rear extension can fall under permitted development, meaning planning permission may not be required providing it meets certain criteria.  

In terms of height, the extension must:

  • Be no taller than four metres at its highest point
  • Have eaves no higher than the eaves of the original house
  • Not exceed the height of the original dwelling  

Read about planning permission for extensions on Planning Portal

Common Questions

What is the ‘principal elevation’?

The principal elevation is the most visible or prominent side of a structure, typically facing a street or public area. While often considered the 'front' of the building, it may not always contain the main entrance. There can only be one principal elevation of a house.

What is the difference between a roof window and a dormer window?

A roof window (or skylight) is fitted flush within the slope of a roof, while a dormer projects outward, creating additional headroom and floor space.  

Both can be installed under permitted development but must meet specific size and position limits to qualify.  

Also consider building regulations for a new dormer, find out more on Planning Portal  

Do I need building regulations approval to install a new inside toilet?

Work to refit a bathroom with new units and fittings does not generally require building regulations approval, although drainage or electrical works that form part of the refit may require approval under the building regulations.

If a bathroom is to be provided in a room where there wasn't one before, building regulations approval is likely to be required to ensure that the room will have adequate ventilation and drainage, and meet requirements with respect to structural stability, electrical and fire safety.

Do I need permission to create an opening for a new window?

Inserting new windows which look similar to those previously used in the house will often not require planning permission. Some rules apply to new additions, for example if they are on an upper-floor side elevation they must be obscure glazed and non-opening or more than 1.7 metres above the floor.

Installing a new bay window on the front elevation would require planning permission as it is classed as a forward extension.

If you live in a listed building or conservation area you should contact your local planning authority.

 Any new openings will have to comply with building regulations, this may impact thermal heat loss, structure, ventilation and fire safety.

You can use a member of a competent person scheme to complete any work, this will ensure that the work is completed in-line with regulations.

Do I need planning or building control for covered outdoor kitchen?

If an outdoor kitchen is not a permanent structure, then planning permission will normally not be required.

Where planning permission is required, it may be granted through permitted development rights, provided it meets the limits set out in legislation. Most outdoor kitchens fall within the set limits unless they are particularly tall or close to a boundary.

While there is no specific permitted development right for ‘outdoor kitchens’ it may be classified as an ‘outbuilding’.

You can view the limitations for outbuildings and outdoor kitchens in the relevant common project

If the structure exceeds the limits set out through permitted development rights, then it will require an application for planning permission.

Different rules may apply if you live in a listed building or conservation area. If this is the case, you may wish to consult your local planning authority.

Read about the building regulations that cover outdoor kitchens.

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