New permitted development rights for rooftop extensions
7th Feb 2022
What are the new Permitted Development Rights?
There are two major changes in the General Permitted Development Order (GPDO), which came into effect in August 2020. Several new Permitted Development Rights for rooftop extensions and new dwellings have been introduced. These new rights make it easier for homeowners and developers to add more space or build more homes. They are part of an initiative to revitalise town centres and remove planning obstacles.
- The first new PD right allows for the extension of existing buildings through the addition of 1-2 storeys.
- The second new PD right allows for demolishing and reconstructing buildings, including adding storeys.
Whilst development under the new PD rights won’t require planning, you are required to apply for Prior Approval. The process is described in this article. |
View Architecture for London’s portfolio of recent projects.
What are Permitted Development Rights?
When looking to build, change, or extend your property, you often rely on obtaining planning permission from your Local Authority.
However, there are types of development that you do not need to seek planning for. These have been granted general permission by Parliament and are called Permitted Development Rights.
The principal order which lists Permitted Development Rights can be found here.
Architecture for London have recently gained prior approval under the new PD rights for an upward extension to create a second floor to this C20th house in north London
The rules are different depending on the type of property you own; residential or commercial. Furthermore, there are differing rules for residential and commercial subtypes, i.e. flats, maisonettes, pubs, offices and industries.
If you are a householder, we recommend you also have a read through our earlier post on Permitted Development for House Extensions. |
How are Permitted Development Rights changing from 2020?
Rooftop extensions with up to 2 additional storeys of residential use:
These new Permitted Development Rights apply to certain commercial, residential and mixed-use buildings. Due to the format of the GPDO, the Permitted Development Rights are split up in different Parts, under several Classes.
These latest amendments include changes to Part I (relating to extending a single house) and the addition of Part 20 (relating to the creation of new flats above residential or commercial buildings)
Many of the constraints are the same across these classes, as they are effectively part of the same idea of allowing upward residential extensions.
Part I – Development of dwellinghouses
This first part of the new Permitted Development Rights concerns changes within the curtilage of a house. Class AA will allow you to extend by up to two storeys directly above the existing house. If your building is single storey, you are limited to one additional storey.
To benefit, the building has to have been constructed between July 1948 and October 2018. Similarly to class A, there are limitations on materials being similar to those of the existing house and the roof pitch being the same. You’re also not allowed to add any windows to the side elevations of the house.
Architecture for London gained one of the first prior approvals for upward extension of a house, granted in December 2020.
Part 20 – Creation of new dwellings
This part is relevant if you are creating additional flats, on top of residential, commercial or mixed-use buildings.
Initially, Class A allowed for new dwellinghouses on top of a detached block of flats. This was swiftly followed by classes AA, AB, AC and AD, which added comparable Permitted Development Rights for commercial and mixed-use properties. They also gave new rights to single dwelling houses:
- Class AA is relevant for a commercial or mixed-use detached building
- AB is relevant for a terrace building of commercial or mixed-use
- AC is for a single dwelling terrace building
- AD is for a single dwelling detached building
Similar to the Part I PDR, the rights are given subject to conditions, including design conditions.
Classes A, AC and AD are only relevant for their own specific classes (Purpose-built block of flats and single residential houses respectively).
For classes AA and AB the existing building must currently have some commercial element, and must have been used for at least one of the below purposes since March 2018:
- Shops A1
- Financial / Professional Services A2
- Restaurants and Cafes A3
- Offices B1(a)
- Betting offices
- Launderettes
- Pay Day Loan Shops
- Residential use (C3)
For more information on building uses, see the Use Classes Order. |
Specific Part 20 requirements are:
- The building has to be constructed between July 1948 and March 2018
- Class AA only benefits if it is at least 3 storeys
Design rules for rooftop additions / extending upwards
Provided a property can benefit from the new Permitted Development Rights, the development is also subject to some design constraints. Many of these constraints are the same across the classes, and most relate to building height in some way:
- Maximum added height is 3.5m per storey (up to 7m for 2 storeys)
- The total height cannot exceed 18 metres (classes A, AB, AC and AD)
- This increases to 30 metres for detached commercial buildings (class AA)
- If the building is semi-detached, the extension cannot be higher than 3.5 m taller than the adjoining building
- For terraced buildings, the 3.5 m limit is measured from the lowest building in the terrace.
- Additional storeys have an internal floor to ceiling height restriction; they cannot be higher than the existing ceiling heights, and no higher than 3 m
- The additional storeys must be built on the principal part of the existing building
- You may carry out structural work to the existing building but the building must not have external structural supports.
Internal visual of Architecture for London’s C20th house in north London that now benefits from prior approval for a rooftop extension.
Unused buildings can be demolished and rebuilt as (larger) residential blocks
This is an effort to make it easier to develop unused or derelict buildings. If a property has been vacant for at least 6 months, this right gives the potential to re-develop it without planning consent. This PDR is added as a new Class (ZA) to Part 20 (Construction of New dwellinghouses) and also comes with its own limitations:
The existing building must have on 12 March 2020 been used as:
- Residential block of flats C3
- Offices B1(a)
- Research and Development B1(b)
- Industrial Processes B1(c)
- Mixed-use of any of the above
In addition it must:
- Be detached
- Have a footprint of max 1000 square metres
- Be built before 1990
- Be less than 18 metres tall
Design rules for the re-build
- The new building must be a free-standing block of flats or a single house.
- It must be constructed within the footprint of the old building.
- It can be no more than 7 metres taller than the previous property.
- The maximum building height is still capped at 18 metres.
- Additional storeys have an internal floor to ceiling height restriction; they must be less than or equal to the previous building, up to a maximum of 3 metres.
- There are no restrictions on ceiling heights for the rebuilt storeys, only the additional ones.
Prior Approval
This is often required for change of use PDR, certain types of demolition/new-builds, and now also for the new permitted development rights above.
Prior Approval is less exhaustive than planning permission, and the government describes it as a “light-touch process”. However, you still need to apply so that the Local Authority can check that your development follows the Government set regulations.
Prior Approval for the new classes is more rigorous than for instance applying for a Lawful Development Certificate. |
The Local Planning Authority may (amongst other things) consider:
- Contamination and Flood risk
- Heritage
- Design of the proposal, in terms of its external character
- Natural light to new residential units
- Impact on transport and highways
- Harm to protected vistas
- Impact of new/increased residential use to the local area
- Impact on amenities; both neighbouring, and those belonging to the property
- Noise levels
Does my property benefit from the new PDR?
As with all other Permitted Development Rights, you also need to determine whether there are any specific requirements that disqualify a property from utilising the PDR. |
Normal limitations to Permitted Development Rights are:
- “Designated areas”, such as Conservation areas, Heritage sites, National Parks, Areas of Outstanding Natural Beauty, and the Norfolk and Suffolk Broads
- Listed buildings
- Local Authorities’ removal of certain rights, by issuing an “Article 4”
- Dwellings that have been created through ‘change of use’ PDR (principal order part 3) may not be further developed under ‘householder’ PDR (principal order part 1)
- Pubs, Libraries, Cinemas and other essential community amenities are not covered by the changing PDR. Their Use Class is the so-called ‘Sui generis’ and does not fall within any of the specified Use Classes.
Upward extensions: a case study
Architecture for London was asked by a client to extend a detached mid-C20th house in Primrose Hill, on the Chalcot Estate.
- An ambitious roof extension design was submitted for planning initially, which was refused.
- After this refusal, the new Permitted Development Rights came into effect (September 2020). These gave a new avenue for extending upwards that was less subjective and restricted the ability of the local authority to resist the application. PD is more a process of demonstrating compliance with criteria.
- In consultation with Savills planning consultants we developed a scheme to suit the new PD criteria.
- The application was then made under Class AA (Schedule 1, Part 2) of the General Permitted Development (Amendment) Order 2020.
- Prior approval was then successfully achieved (Camden 2020/4216/P) for a rear roof extension, a similar design to the previously refused planning application (Camden 2019/5108/P).
- The required supporting document included:
- Daylight and Sunlight reports to demonstrate acceptability with regard to impact on the amenity of adjoining properties including overlooking, privacy, and the loss of light.
- Construction method statement to show how the works would be carried out.
- 3D visuals to illustrate that the proposal matched the materials and design of the existing building.
- Other requirements also had to be met with regard to building heights, floor heights, number of storeys, window positions, use, engineering operations, roof form etc.
Please contact us to discuss the potential of a specific site under the new Permitted Development Rights. Alternatively, to view our recent work, please visit our project portfolio.
Summary FAQ
The first new PD right allows for the extension of existing buildings through the addition of 1-2 storeys. The second new PD right allows for demolishing and reconstructing buildings, including adding storeys.
The new permitted development rights will allow you to extend by up to two storeys directly above an existing house. If your building is single storey, you are limited to one additional storey. To benefit, the building has to have been constructed between July 1948 and October 2018.
The maximum added height is 3.5m per storey and ceiling heights cannot be taller than existing ceiling heights. If the building is semi-detached, the extension cannot be higher than 3.5 m taller than the adjoining building.