When Do You Need Building Control

Building control is a legal requirement for many types of building work in the UK. Whether you're extending your home, converting a loft, removing a wall, or installing a new heating system, building control approval is often necessary to ensure the work is safe, properly constructed, and in line with building regulations.

Knowing when building control is required helps you avoid delays, penalties, or complications when selling or insuring a property. It also ensures that your project meets standards for structural stability, fire safety, insulation, ventilation, and energy performance.

New Builds and Structural Alterations

Any new building — whether residential, commercial, or industrial — requires full building control approval. This includes everything from single dwellings to housing developments, office blocks, or outbuildings with habitable space. Approval is needed before work begins, and inspections must be carried out throughout the build.

Structural alterations to existing properties also require approval. This includes removing or altering load-bearing walls, chimney breasts, roof structures, and floors. These works can affect the safety and integrity of the building, which is why they must be checked at key stages by a building control officer or approved inspector.

Extensions and Conversions

Most types of extensions, including single-storey, double-storey, wraparound, and rear extensions, need building control sign-off. The regulations cover aspects such as foundations, drainage, insulation, roof structure, energy performance, and fire separation from the rest of the property.

Conversions also fall under building control. This includes garage conversions, loft conversions, and basement rooms — even if you're not changing the exterior of the property. Once a space is being turned into habitable accommodation, it must meet the full range of building regulations to be legally occupied.

Change of Use

If you're changing how a building or space is used, building control may be required even if no structural work is being carried out. For example, turning a shop into a flat, or a single house into multiple flats, triggers a review of whether the space meets fire safety standards, access requirements, ventilation needs, and thermal performance rules. A change of use often brings the entire building under review.

Internal Work

Not all internal work requires building control, but some does. If you’re removing or altering structural elements, creating new rooms, adding staircases, or changing escape routes, you’ll need approval. The same applies if the work affects fire resistance, sound insulation, or ventilation.

Installing or altering heating systems, hot water tanks, drainage, or electrical systems in special areas like bathrooms and kitchens may also require approval, unless done by a certified professional under a Competent Person Scheme.

Replacement and Repair Work

Some repair or replacement jobs are covered under building regulations, especially if they affect performance or structure. Replacing a roof, reconfiguring external walls, installing double glazing in new openings, or upgrading insulation may all require building control approval.

Work carried out on fire protection systems, cavity barriers, or escape routes in flats and commercial properties is also heavily regulated, even if it’s considered a repair.

Conservatories and Outbuildings

Conservatories, porches, and detached garden buildings may be exempt from building control — but only if they meet strict conditions around size, separation from the main building, and use. If you remove the doors between the conservatory and the house, install fixed heating, or exceed 30 square metres, you’ll likely need approval.

Outbuildings used as offices, bedrooms, or annexes almost always require building control, even if they are permitted development from a planning perspective.

Don’t Assume Internal Work is Automatically Exempt

There’s a common misconception that if work is taking place inside a building, it doesn’t need building control approval. That’s not always true. Many internal alterations can trigger the need for approval if they affect safety, structure, or how the building performs. For instance, removing a wall to create an open-plan kitchen can have structural implications. If the wall is load-bearing, you’ll need building control to approve any replacement support.

Even if structural elements aren’t touched, changes that affect fire escape routes, ventilation, or thermal insulation standards can also bring your project under regulation. This is especially true in flats, which have tighter controls around soundproofing and fire separation than detached or semi-detached houses.

Planning Permission and Building Control Are Not the Same

It’s easy to confuse planning permission with building control, but they are two separate systems. Planning permission relates to how a building looks, its impact on the neighbourhood, and its size and placement. Building control focuses on how it’s constructed and whether it complies with technical standards.

You might have full planning approval and still need to apply separately for building control before starting work. On the other hand, some projects — like loft conversions or structural alterations inside your home — may not require planning permission but still fall under building control regulations. It’s crucial to understand that getting one doesn’t automatically cover the other.

When Retrospective Approval is the Only Option

If work has already been carried out without the proper approval, there is a process called regularisation. This allows you to apply for retrospective building control sign-off from the local authority. The inspector will assess whether the completed work meets current building standards. In many cases, parts of the structure may need to be exposed to allow for inspection.

It’s important to know that regularisation is not a guaranteed fix. If the work doesn’t comply, you may be required to make changes or even undo parts of the project. This route is often more costly and time-consuming than doing it correctly from the start, and it should be considered a last resort.

Only Certain Trades Can Self-Certify

Some types of work can be carried out without a separate building control application, but only if the person doing the work is registered under a Competent Person Scheme. These schemes cover specific trades, such as electrical installation, gas fitting, and window replacement. A certified professional can self-certify that the work complies with building regulations and issue you with the necessary paperwork.

However, not all tradespeople are registered, and many homeowners assume incorrectly that this means approval isn’t needed. If your installer isn’t part of a recognised scheme, you are responsible for applying for building control approval yourself. Without it, you could be left with non-compliant work and no formal documentation.

Energy Efficiency Work Still Needs Oversight

Improving the energy efficiency of your home often involves regulated work. Replacing a roof, upgrading insulation, or renewing more than a quarter of a building element — such as a wall, floor, or ceiling — typically requires building control approval. This is because the replacement must meet current thermal performance standards under the Building Regulations.

Some insulation work, including cavity wall insulation or internal wall insulation, may also require approval, particularly in older buildings or those with special heritage status. Local building control will often want to inspect this type of work to confirm compliance with Part L of the regulations, which deals with energy conservation.

The Type of Use Matters

Even if the physical work seems minor, building control approval can still be required based on how the space will be used. For example, setting up a garden room for occasional use might not need approval. But turning it into a fully functioning home office, guest room, or separate accommodation almost certainly will.

Similarly, converting a single-family house into multiple self-contained flats always requires building control oversight. The same applies to HMOs, where there are additional requirements for fire safety, alarm systems, and means of escape. The intended use of the space determines what standards apply and whether approval is needed, even when the work doesn’t seem extensive on the surface.

Final Word

You need building control approval whenever your work affects the safety, structure, performance, or legal use of a building. It’s not just about ticking boxes — it’s about ensuring that the space you’re creating or modifying is fit for purpose, safe to occupy, and legally protected. If you're unsure whether your project requires approval, the best step you can take is to ask your local building control team or a qualified inspector before work starts. It’s a small check that can save you from serious problems later.