The short answer is 56 days from the date the council validates your application. But that figure only tells part of the story. To get from "we've agreed heads of terms on this building" to "prior approval granted," the real timeline is closer to 10 to 14 weeks — and that assumes your drawings are ready to go.
Here is what actually happens at each stage, and what you can do to keep things moving.
The 56-Day Rule
Once a prior approval application is validated by the local planning authority, they have 56 calendar days to make a decision. This is a statutory deadline. If they fail to respond within 56 days, deemed consent applies — meaning the development is treated as approved by default.
The 56-day clock starts from the date of validation, not the date of submission. If the council takes a week or two to validate the application — which is common — that time comes off your total wait before the clock begins. Applications are sometimes delayed at the validation stage if supporting documents are missing or in the wrong format.
This makes submission quality important. A clean, complete application that validates promptly gives you the full 56 days. A back-and-forth with the planning team over missing documents eats into that window.
The Full Timeline, Stage by Stage
The 56-day window covers the council's decision time. Before you can even submit, there is preparation work to complete. Here is a realistic picture of the whole process:
Confirm all six eligibility criteria are met before committing to drawings or surveys. A desktop eligibility assessment takes up to 72 hours and will flag any issues with use class, vacancy, Article 4 directions, or listing status before you spend further money.
A prior approval application requires drawings showing the existing and proposed layouts, floor areas, and a clear description of the change of use. Depending on the size and complexity of the building, this typically takes two to four weeks. At PWA we handle drawings and planning statements in-house, which removes a scheduling step.
The application is submitted to the planning portal and the council validates it. Validation can be immediate or take one to two weeks depending on the council's workload and whether they raise any queries on the submission.
Once validated, the council has 56 calendar days to decide. In most cases they make a formal decision well before the deadline — but some councils run close to the wire. If the deadline passes without a decision, deemed consent applies and the development can proceed.
Prior approval granted. You now have the consent needed to begin converting the building. If conditions are attached — for example, regarding noise mitigation or contamination investigation — these need to be discharged before works start or at the relevant stage.
Class MA vs Full Planning: The Time Difference
The speed advantage of permitted development is one of its biggest practical benefits for investors. Here is how the timelines compare:
Full planning applications for a change of use typically run eight to thirteen weeks for a decision — but that figure is from validation, and many councils are running well behind target. Appeals, pre-application consultations, and resubmissions can stretch a full planning route to 12 months or more. With Class MA, the process is structurally faster and more predictable.
What About Building Regulations?
Prior approval is planning consent only — it does not cover building regulations. You will still need a building regulations application to cover the structural and safety aspects of the conversion itself (insulation, fire safety, means of escape, drainage, and so on).
Building regulations can run in parallel with the prior approval process. You can appoint a building control inspector and begin the building regulations design work while the planning decision is being made. This means you can be ready to start on site within weeks of consent being granted, rather than starting the process from scratch afterwards.
What Can Slow Things Down?
The 56-day statutory window is firm — but there are stages either side of it where delays are possible. The most common causes are:
Slow validation. If the application is missing documents or in the wrong format, the council will not start the clock until everything is in order. A clean submission avoids this.
Pre-commencement conditions. If the council grants prior approval but attaches conditions that need to be discharged before works start — for example, a contamination investigation report — sorting those conditions adds time between consent and site start.
Neighbour representations. While the council cannot refuse on general planning grounds, they do publicise the application and consider representations. Unusually complex sites near sensitive uses can generate more scrutiny.
Building regulations delays. If you leave building regulations until after prior approval is granted, you add several weeks at the back end before you can start on site. Starting the process in parallel avoids this.
Ready to Move Forward?
The quickest way to find out whether your building qualifies and how long your specific application is likely to take is to get a PD Eligibility Assessment. A written result in 72 hours tells you where you stand before you commit any further money.
PD Eligibility Assessment — £195
Andrew has managed Class MA applications through every stage of the process and has a 100% success rate on prior approval decisions. He can give you a realistic timeline expectation for your specific building and council area.