A guide to permitted development

Not all projects require the submission of a planning application. Check our guide to permitted development to see which route you will need to go down.

What can I build without planning permission?

When it comes to working on your house, some projects fall within what's called 'Permitted Development'. This means that they do not require any formal planning permission from the local authority. The term 'permitted development' refers to projects that are deemed to be permitted by default, as long as certain rules are satisfied. Some rules are dependent upon the type of house or location. Some projects may not require a planning application, but may still require a formal 'Prior Approval' submission to the council. This enables any neighbours to have their say, giving them an opportunity to raise any objections.

Even if planning permission is not required, you may still want to consider applying for a Certificate of Lawful Development - this may be useful for times such as selling your house, to prove the development has been completed within planning rules.

Planning rules can sometimes be quite complex, get in touch with us if you'd like to discuss the type of planning application which may apply to your project. We will be able to clarify whether planning permission needs to be applied for or whether the permitted development ruling negates this.


The current planning rules pertaining to conversion of basements is currently under review. Most of the time, converting your cellar or basement into living accommodation will not require planning permission. This may change if the basement is being excavated to create a separate unit or if the intended usage is going to change significantly. Adding a light well or dramatically changing the appearance of the property may also attract the need for planning permission. If you live in a listed building or within a conservation area, it is possible that you will need planning consent for internal works, including the conversion of basements. If you are unsure about the need for planning permission at any time, your local authority can provide guidance.


The creation of a decked area or raised platform in your garden falls within the remit of a permitted development. Planning permission will not be required as long as you comply with the following rules:

  • The decking is not more than 30cm above ground.
  • The decking does not cover more than 50% of the garden area.
  • The decking is not on land forward of a wall that forms part of the principal elevation.

The rules change if you live in an AONB (Area of Outstanding Natural Beauty) or World Heritage Site. In this case, the maximum area of coverage more than 20 metres away from the house is limited to a maximum of 10 sq. metres. With a listed building, no decking is permitted within the curtilage. If the decked area is linked to an extension or larger piece of work, then other rules may apply. In this case, it is always a good idea to check with the local authority.


If you are looking at building a ground floor single-storey extension in line with permitted development, the following rules apply:

  • The extension can extend 4m from the rear elevation if a detached house. For all other types of house, this is set at 3m. The extension can run for the full width of the house. You can increase this limit accordingly to 8m and 6m but only by making a 'prior approval' planning application. This will then include consultation with any neighbours.
  • The extension can extend from the side elevation up to half of the width of the original house. It can also extend beyond the rear elevation by up to 4m (detached) and 3m (all other house types). You can increase this limit accordingly to 8m and 6m but only by making a 'prior approval' planning application. This will then include consultation with any neighbours.
  • Roof height must be no more than 4m when measured at the highest point, and must not extend above the highest point of the original roof. The eaves level cannot be higher than existing eaves.
  • Should the extension fall within 2m of a boundary, the eaves than cannot exceed 3m in height.
  • The extension cannot cover more than 50% of the plot. This takes account of all previous extensions and outbuildings (garages, sheds etc.) but ignores the footprint of the original building.
  • Should the extension go beyond the rear and side elevation of the original building, it will then have to comply with the rules for rear/side extensions. This also applies for wraparound side/rear extensions and corner infill extensions.
  • Should the new rear extension touch a side extension (proposed or existing), or a rear extension (proposed or existing), it will need to comply with the rules for rear/side extensions.
  • The extension cannot extend beyond a front or side elevation if fronting a highway.
  • Materials must match with existing.
  • Balconies are not allowed if you wish to follow permitted development rules.

With a two-storey extension, the rules for permitted development are different:

  • The extension can extend up to 3m from the original house's rear elevation.
  • The extension has to be at least 7m from the boundary at the rear.
  • The highest point of the new roof must not go above the highest point of the existing roof. The level of the eaves also should not be higher than the existing eaves.
  • If a first floor extension is being added over an existing rear ground floor extension, it cannot be larger than 3m from the original rear extension.
  • Materials must match with existing.
  • Balconies are not allowed if you wish to follow permitted development rules.
example of an extension allowed under permitted development
Garage conversion

If you are looking to convert an existing garage, planning permission is usually not required. However, this does depend upon the work being internal and the building remaining the same size. If you decide to convert the garage into separate accommodation, then planning permission is required. If you have any doubt, always contact us for advice or get in touch with your local authority planning department. The last thing you want to do is convert a garage unlawfully, failing to get permission when you should have done. There is also a possibility that some properties may have had their permitted development rights removed. With this in mind, if your home is listed, in a conservation area or a new development, it is best to get advice. With listed buildings, listed building consent may also be required. We offer a complete garage conversion design package.

Internal walls

If you are moving or removing internal walls, planning permission is not normally required. This is the case for all internal alterations. However, this changes if you live in a listed building; you would need to obtain listed building consent from your local authority for any new work, internal or external.

Loft conversions & roof alterations

If your loft conversion involves alterations to the roof of your house, permitted development will apply only in accordance with the following rules:

  • Alterations cannot be made if they extend beyond the roof plane of the front elevation, or an elevation that fronts the highway.
  • As a result of the alterations, the total additional volume must not exceed 40m³ for a terraced house, or 50m³ for other house types. Any alterations made in the past must be included when calculating the volume.
  • It is essential that all materials match with the existing.
  • Balconies are not allowed.
  • The rules change if you live in an AONB (Area of Outstanding Natural Beauty) or World Heritage Sites or conservation area. In this case, permitted development does not cover roof extensions hence you would need to apply for full planning permission.
  • Any roof dormers should be set from the eaves by 200mm, unless this will cause structural problems.
example of a loft conversion allowed under permitted development
Outbuildings (including summer houses and detached garages)

In order to carry out work on detached outbuildings within the permitted development rules, the following would apply:

  • The final scheme must not take up more than 50% of the existing plot. This takes account of all historic extensions and other detached outbuildings. It does however exclude the footprint of the original property.
  • The proposed scheme can only be single storey.
  • The new building must not extend out beyond any side or front elevations if fronting highway.
  • Restrictions are placed on the height of the roof. If it has a dual pitched roof, height restriction is 4m, 2.5m if within 2m of the boundary and in all other cases, 3m.
  • The total height of the eaves cannot be more than 2.5m.
  • The building cannot be used for accommodation i.e. a house.
  • Balconies are not allowed. If you need this, planning permission would then apply.
  • The rules change if you live in an AONB (Area of Outstanding Natural Beauty) or World Heritage Sites or conservation area. Detached buildings are not allowed so planning permission would need to be sought.
example of an outbuilding allowed under permitted development
Paving, patio and driveway

With regard to patios and driveways, there are no restrictions as to the amount of land you can cover with hard surfaces, at or close to ground level. This may change if major terracing or groundworks needs to take place; this would attract planning permission. If the property were listed, you would need to obtain listed building consent for all internal and external work, including patios and driveways.

Should you wish to pave over your front garden, specific rules apply. You will not need to apply for planning permission for a new/replacement driveway as long as it has a porous and fully water permeable surface. Good examples of this are gravel, permeable concrete blocks or paving or even porous asphalt (tarmac). If not permeable, then the rainwater must be made to drain away naturally via a lawn, border or drainage system. Do note that if the total area to be covered were above five sq. metres, then planning permission would be needed if you are adding an impermeable surface that does not allow water to run off to a drainage area.


Should you wish to add a porch following permitted development rules, then the following would apply:

  • The external measurement of the porch must not be more than 3m².
  • The porch must not extend more than 3m from ground level.
example of a porch allowed under permitted development

Planning permission will not be required if you re-roof your property or insert roof lights/skylights in line with the following conditions:

  • Any changes made must not project more than 150mm above the existing roof plane.
  • Alterations cannot be higher than the highest point on the roof.
  • Any side windows have to have obscure glass with any opening 1.7m above floor level.
Self-build homes

If you are looking to build your own home, planning permission will need to be obtained. You may receive this when you buy the plot of land or may apply for it after purchase. Always remember that planning permission is applied to the land, not the applicant. You may choose to purchase land subject to planning permission being obtained, but this is high-risk if you have no guarantee that it will be awarded. If unsure, always seek expert advice from us or talk to your local authority planning department. When purchasing a plot of land, do check whether it is affected by flood risk or greenbelt categorisation. Not all planning permissions are the same so make sure you understand what you are allowed to build. Any outline planning permission referred to is always conditional.

Working from home

If you are considering working from home, then you will need an office that is comfortable and practical. You may decide to convert an existing room such as spare bedroom, loft room or garage. Always be sure that you will have sufficient natural light and room for office furniture as well as internet/phone access. If you do not have any room internally, you may decide to add a garden office via a separate outbuilding. You may not necessarily need planning permission. In order to establish whether it will apply or not, ask yourself if the overall character of the property will change due to you working from home. If any of the following apply, then planning permission will need to be obtained:

  • Your home will no longer be mainly a private residence.
  • The amount of people and/or vehicles visiting your property will increase.
  • Your business activity is unusual for a residential area.
  • Neighbours may be annoyed due to nuisance caused by the business i.e. noise or smells.

No matter which type of business you propose to set up at home i.e. bedsit, bed and breakfast, office, childminding, hairdressing, music teaching, car repairs, etc., ask yourself if the property will still mainly be a home or will the majority of it become business premises? If the latter, or if you are unsure, you should check with your local authority. You may need to obtain a Certificate of Lawful Use for the business. This confirms that there is no real change of use and that the property is still being used lawfully.

Get in touch with CR Design Services

We can help you plan and design your next project. We prepare planning application drawings, building control packages, and structural design calculations for all types of house extension, renovation and self-build projects. Contact us today for further information and to request a quotation.

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