As housing need continues to outstrip supply across London, permitted development rights offer an increasingly valuable route for unlocking residential potential, particularly for underutilised or redundant buildings. A lesser-known but highly effective route is Class AA of the General Permitted Development Order (GPDO), which allows developers to create new homes with greater speed and design flexibility compared to traditional planning routes.
At BB Partnership, we’ve used this process to help clients realise residential value on constrained or complex sites, often in situations where a full planning application may have proved more difficult or less commercially viable.
To ensure we comply with policy requirements for these types of proposals, we always work with planning consultants to ensure compliance with the requirements.
Class AA, another powerful tool in the GPDO, permits the upward extension of existing buildings to create new homes, again through Prior Approval. Under Schedule 2, Part 20, Class AA, developers can add up to two additional storeys to apartment buildings constructed between 1 July 1948 and 5 March 2018, provided certain criteria are met.
This route is particularly useful in dense urban areas where sites are already optimised at ground level and airspace potential becomes key.
While Class AA removes the need for full planning permission, it still requires a Prior Approval application. This means the local planning authority must assess a number of specific matters before work can begin, including:
This makes Class AA a hybrid process: faster and simpler than full planning, but still subject to scrutiny. The quality and clarity of the submission are crucial.
Although Class AA can be a powerful tool, it’s also complex, and many applications are refused due to avoidable issues, including unclear supporting information, insufficient justification on key impacts, or failure to demonstrate eligibility.
Here’s where a planning consultant adds real value:
Before committing time and resources, a planning consultant can assess whether your site and proposal are likely to qualify under Class AA, helping you avoid pursuing an unviable project.
One of the key elements of Prior Approval is the submission of well-structured supporting documentation. A planning consultant will prepare a Planning Statement that addresses each of the relevant criteria and provides the evidence planners are looking for.
Many Class AA applications need input from other professionals such as transport engineers, flood risk consultants, and heritage specialists. A planning consultant can coordinate these inputs to ensure a cohesive and compliant submission.
Responding to local authority questions, though it’s vital to remember: these applications either comply or they don’t. A local authority cannot approve a scheme that almost complies.
At Vale House, we secured Prior Approval from Westminster Council to add a new storey to an existing apartment block under Class AA. The proposal delivered four new homes, extending the value of the site without compromising its existing use or requiring a full planning application.
Before moving ahead with the application for Prior Approval, we had first applied for pre-application advice regarding a larger extension and remodelling of the existing building. The response to the pre-app concluded that a full planning application process would be required, which would still be difficult to achieve and therefore it was decided with the client and planning consultant to pursue the Prior Approval route, to secure an approval which would also be more straightforward to implement than a planning approval that would come with a multitude of conditions.
This airspace development demonstrates how Class AA can be an efficient route to densify urban sites, especially in well-connected, high-demand areas.
Class AA offers advantages for developers:
However, the process is not without challenges. Prior Approval applications can be refused if supporting evidence is lacking or design quality is poor. That’s why at BB Partnership we work closely with planning consultants, heritage specialists, and other consultants from the outset to ensure a robust and coordinated approach.
At BB Partnership, we understand how to leverage permitted development to maximise value, reduce planning risk, and unlock the full potential of every site. Our collaborative, strategy-led approach, working closely with planning consultants and other specialists ensures that even the most challenging sites can become successful residential projects.
Get in touch to explore how we can help you unlock your site’s potential through Class AA, or a tailored planning strategy.
BA [Hons], Dip Arc, RIBA
Director
BA [Hons], Dip Arc, RIBA
Director
BA [Hons], Dip Arc, RIBA
Director