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Permitted Development Rules

Looking to extend? Permitted Development in the UK can often simplify your extension plans, letting you achieve your goals without needing full planning permission. Just remember to get expert advice to ensure your proposed extension plans fit within the allowed dimensions.

Unlock your extension’s potential.

When can Permitted Development be used?

The size and height of your extension will determine whether it falls within Permitted Development Rules.

Extensions can vary in size from porches to double storeys, which increases the footprint of the original building. Whatever extension plans you have in mind, the Permitted Development Rules will govern whether you can build your extension without planning permission.

Let us help you navigate these regulations, preventing costly errors and the potential for demolition.

Extension Height: The Rules

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The restrictions on height always cause the most difficulty.

Maximum heights are referenced to the original ground profile before any work starts. To avoid argument, the level of the existing ground needs to be recorded in a manner that the Local Authority cannot argue with. All levels in your extension plans should be backed up by photographs showing the existing buildings as reference points to ensure that you can build within permitted development rules.

The height restrictions actually provide more flexibility than first appears, because the measurement is from “existing ground level”. This means that a basement can be installed under a new extension without planning permission.

When do Permitted Development Rules Apply?

A crucial step in developing your extension plans is figuring out if it qualifies under Permitted Development rules or whether planning permission must be sought. If it doesn’t, we can explore design solutions to help it meet those guidelines.

  • Permitted Width: up to full width of house and no further.
  • Permitted Depth: up to 3m for a semi-detached or terrace house and up to 4m for a detached house.
  • Permitted Depth with Prior Approval (no objection from neighbours): 6m for a semi or terraced and 8m for a detached house.
  • Permitted Height: 4m and if less than 2m from the boundary 3m.
  • Permitted Distance to rear boundary: Within 7m.
  • Permitted Maximum Area: not >50% of the land area around the original house including any outbuildings or previous extensions.
  • Appearance: similar to original house.
  • Location: permitted on rear elevation only.
  • Permitted Depth: up to 3m for a semi-detached or terrace house and up to 4m for a detached house.
  • Permitted Height: no greater then ridge and eaves of existing house and if <2m from the boundary 3m.
  • Appearance: roof pitch and tiles to be similar to existing house. Upper floor windows to have obscured glass and openings must be >1.7m above the floor.
  • Permitted: single storey only and less than half the house width.
  • Permitted extension to rear: up to 3m for a semi-detached or terrace house and up to 4m for a detached house
  • Permitted Height: no greater then 4m and if <2m from the boundary 3m.
  • Can extend up to boundary but Party Wall Agreement may be required.
  • Permitted wrap-around: to rear if maximum width of extension is less than half house width.
  • Appearance: similar to original house. Roof pitch and tiles to be similar to existing house. Upper floor windows to have obscured glass and openings must be >1.7m above the floor.

This is possible if:

  • The existing building is detached and multi-story, two additional storeys can be added (a loft extension is not a storey).
  • The total maximum height of the building must not exceed 18m (The same limit as for ICF structures in the UK).
  • The building is part of a terrace but the extension can’t be more than 3.5m higher than the next tallest terrace.
  • There are no windows on the side elevation or the sides of the roof.

These types of extension plans will need an Architect and the structural complexity will require the project to be developed in conjunction with a Structural Engineer.

These include:

  • Use of roof space with roof lights involving Velux style windows to the existing roof.
  • Use of roof space with dormer windows.
  • Removal of hip roof and construction of a gable end.
  • Mansard roof extensions.
  • Roof extensions that follow the plan shape of the existing house.

Permitted Development Restriction Loft Conversions

  • No dormer windows on front elevations with maximum height of Velux windows <150mm above existing roof line.
  • Maximum height must not be greater than existing roof height.
  • Maximum volume is 50m2 for a detached or semi-detached house and 40m2 for a terraced house.
  • Loft staircase must have a minimum headroom of 2m and the dormers must be set back at least 200mm from the eaves.
  • Appearance must be similar to original house.
  • Side windows to have obscured glass and openings must be > 1.7m above the floor. Balconies and verandahs are not permitted but Juliet balconies without a platform are allowed.

Porches on the front elevation are restricted to extensions less than 3m high, 3m2 in area and set back at least 2m from the boundary.

The rules for outbuildings include any structures that are within your property boundaries but not attached to your house. This includes garages, summer houses, sheds, tennis courts, swimming pools and ponds as well as heating oil tanks. These allow massive scope for development in any property buy particularly those with large gardens.

Restrictions:

  • Located behind the line of the front elevation of the house.
  • Less than 4m high if a dual pitched roof and 3m for any other type of roof. Less than 3m high if <2m from a boundary.
  • Have a maximum area of less than 50% of the original house either when it was built or on the 1st July 1948.

These rules relate to minor works and are not normally related to ICF construction.

This rule came into use in 2015. The rules are complex and it is probably just as easy to just apply for planning permission and you will definitely need an Architect.

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Innovative solutions can be used to build under permitted development. This indoor pool hall for instance measures 2.5m from ground floor to eaves.

Working Within The Rules

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Reaching New Heights

Sometimes, there are innovative ways of working within the seemingly restrictive conditions of Permitted Development Rules. For instance, this indoor pool project was built under the Permitted Development Rules and is obviously a massive project for an extension without planning pernission, but built under the Permitted Develoment rules.

  • Originally, the highest ground level was at about the height of the garden wall surrounding the house.
  • The whole building level was dropped.
  • The roof tile type required a certain slope.

Unsure about your extension? We’ll collaborate with you to determine whether Planning Permission is needed or there are solutions to working within Permitted Development Rules.

Get in touch
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Basements Built Under Permitted Development

Does your basement project fall within permitted development rules? Click here to find out more about the conditions and limitations which might help your project avoid planning permission applications.

Basement Permitted Development