Inspection and Testing
If your school needs extra space fast, whether that's for growing pupil numbers, a SEN unit, or cover while other buildings are out of action, one of the first questions is whether you'll need planning permission before anything goes on site.
The honest answer is that it depends on your school, your site and how long the building will be there. This guide walks through the rules that actually apply in England, including two permitted development rights that are often missed: Class M and the temporary Class CB exemption for RAAC affected schools. It applies whether you're looking at a single classroom or need extra shipping container offices for staff displaced by the same building works.
The short answer: It depends on site, size and duration
In most cases, a shipping container classroom is treated the same way as any other relocatable school building for planning purposes. Whether you need full planning permission comes down to three things: how long the building will be in place, how big it is, and whether your school already benefits from permitted development rights that cover the work.
Many short-term or modest projects can go ahead without a full application. Larger, longer-term, or site-restricted projects usually can't.
The general rule: The 28-day and 200m² thresholds
The starting point in English planning law is straightforward. A temporary building that's in place for more than 28 days, or that exceeds 200m², will generally need planning permission. If your project falls under both of those thresholds, it may not need an application at all.
In practice, most schools installing a classroom want to keep it in place for a full term or longer, which pushes the project past the 28-day limit straight away. That's where permitted development rights come in, since they can still allow the work to go ahead without a full application even though the 28-day rule alone wouldn't cover it.
Permitted development rights for schools: Class M explained
Permitted development (PD) rights are set out in the Town and Country Planning (General Permitted Development) (England) Order 2015, commonly known as the GPDO. Part 7, Class M covers schools, colleges, universities and hospitals, and it's the main route many education providers use to expand without a full planning application.
What class M allows
Under Class M, schools can typically carry out:
- Extensions to existing buildings, up to 25% of the original floor space or 100m², whichever is smaller
- Addition of small detached buildings, such as sheds or shelters, within the site boundary
- Installation of temporary classrooms or modular buildings for educational use
- Minor operational development, including ramps, fences or access paths for safety and accessibility
This can cover anything from a single extra classroom to a dedicated container training space for practical subjects or apprenticeship provision, as long as the work stays within the Class M limits above.
When Class M doesn't apply
Class M isn't universal. It's typically restricted or removed if:
- The school is a listed building
- The site sits within a conservation area, national park, or Area of Outstanding Natural Beauty (AONB)
- The land isn't lawfully used for education
- The local authority has removed PD rights through a specific planning condition
If any of these apply to your site, you'll likely need a full planning application regardless of the size or duration of the building.
The RAAC exemption: What class CB means for affected schools
A more recent and narrower right, Class CB, was introduced specifically for schools affected by reinforced autoclaved aerated concrete (RAAC). Given how many schools have had to close or vacate buildings because of RAAC since 2023, this right exists to let them install temporary replacement space quickly, without waiting on a full planning application.
What class CB allows
Class CB permits RAAC affected schools to install temporary buildings without submitting a full planning application, provided the school notifies both the local planning authority and the relevant fire and rescue authority at least 8 weeks before the buildings go up. The right comes with clear limits: temporary buildings can't be installed within 5 metres of a boundary with residential land, can't exceed 2 storeys or 9 metres in height, and the combined floor space can't exceed 125% of the floor space vacated because of the RAAC issue.
Key dates: The 24 October 2026 deadline and proposed extension
Class CB is time-limited. As things stand, the right is due to expire on 24 October 2026. Given that remediation work at many affected schools is still ongoing, the government has proposed extending the right to October 2028, but this hadn't been confirmed at the time of writing. If your school is RAAC affected and considering a temporary building under this right, it's worth checking the current status of the extension with your local authority before relying on the current deadline.
Common mistakes schools make with "temporary" buildings
A few assumptions catch schools out more than anything else in this area:
Assuming “temporary” automatically means exempt from planning permission. It doesn't. The 28-day and 200m² thresholds, or the relevant permitted development class, still have to be met.
Underestimating footprint or height. Even a small increase over the Class M or Class CB limits can remove permitted development rights entirely, sometimes forcing a retrospective application after the building is already on site.
Overlooking curtilage boundaries. PD rights generally only apply within the boundary of the existing school site. Extending beyond it, even by a small margin, can invalidate the right.
Forgetting that building regulations still apply, even when planning permission doesn't.
Because of how easily these limits can be exceeded without anyone intending it, it's worth checking your specific project against the current rules before committing to a size or location.
Building regulations for temporary classrooms
Planning permission and building regulations are two separate systems, and it's easy to assume that clearing one means you've cleared both. Even where a classroom qualifies for permitted development and needs no planning application, building regulations approval will usually still apply. That covers things like structural safety, fire safety and means of escape, electrical installation, ventilation and insulation, and accessibility under the Equality Act 2010, including ramps or lifts where needed.
This is one of the reasons it's worth working with a supplier who manages both sides of the process. At BCL, every container classroom goes through our own quality assurance checks and is designed to meet the relevant building standards from the outset, rather than leaving compliance as an afterthought.
What a full planning application involves, if you need one
If your project doesn't qualify for permitted development, whether because of size, duration, or site restrictions, you'll need to submit a full planning application to your local authority. This typically involves a site plan and layout drawings, a design and access statement explaining the proposal, and consideration of the impact on neighbouring properties, access, and landscaping. Local authorities generally aim to determine straightforward applications within 8 to 13 weeks, though this varies by council and can take longer if the application is called in for committee review or attracts objections.
None of this needs to be a barrier. A full application is a normal, manageable part of the process for many school building projects, it just needs to be built into your timeline from the start.
How BCL can help With your container classroom project
Every site is different, and the right answer for your school depends on factors specific to your project. During your initial consultation, our team can talk through what's likely to apply to your container classroom project, based on your site, timeline and whether RAAC or other factors are involved, drawing on our wider shipping container conversions experience. We'd always recommend confirming the final position with your local planning authority before work begins.
Get in touch to discuss your project and get a tailored quotation.