Planning permission and building regulations are two completely separate things, and confusing them is one of the most common mistakes homeowners make at the start of a project. Planning permission is about whether you're allowed to build. Building regulations are about how the building must be built. You can have one without the other, and you often need both.
A garden room might not need planning permission but still requires building regulations approval if it's used as a habitable room. A change of use application might need planning permission but involve no building work at all. Know which you need before you start, because missing either one can cause serious problems down the line.
What Building Regulations Actually Cover
Building regulations set minimum standards for the design and construction of buildings in England and Wales. They exist to protect the health and safety of building occupants, and in recent years they've been progressively expanded to cover energy efficiency. The regulations are organised into Approved Documents, each covering a different aspect:
- Part A: Structure (foundations, walls, floors, roofs)
- Part B: Fire safety (escape routes, fire resistance, alarms)
- Part C: Site preparation and resistance to moisture
- Part E: Resistance to sound
- Part F: Ventilation
- Part G: Sanitation, hot water and water efficiency
- Part H: Drainage and waste disposal
- Part J: Combustion appliances
- Part L: Conservation of fuel and power (energy efficiency)
- Part M: Access to and use of buildings
- Part P: Electrical safety in dwellings
A building control officer (BCO) from your local authority, or an Approved Inspector from a private building control company, will check your project against the relevant parts during construction.
When Building Regulations Apply
Building regulations apply to most building work, including work that doesn't need planning permission. Key triggers include:
Extensions and conversions. Any extension to a house, loft conversion, garage conversion, or basement conversion requires building regulations approval. There's no size threshold below which you're exempt.
Structural alterations. Removing a wall (especially a load-bearing wall), altering a chimney breast, or changing the roof structure all require approval.
New electrical work. This is where people are most often caught out. Under Part P, electrical work in dwellings must either be carried out by a registered electrician (who self-certifies) or notified to and inspected by building control. A competent person scheme electrician (NICEIC, NAPIT or similar registration) will issue a building regulations compliance certificate directly. If your builder's "mate" does the electrics and isn't registered, someone still needs to inspect it.
New heating systems and boilers. Gas boiler installations must be carried out by a Gas Safe registered engineer, who self-certifies under a competent person scheme. Oil boilers have equivalent OFTEC requirements.
Replacement windows. FENSA-registered window installers self-certify replacement windows. If your installer is not FENSA or CERTASS registered, you need to notify building control.
What Doesn't Need Building Regulations
Some smaller works are exempt from building regulations:
- Porches under 30 square metres (provided they don't contain a WC)
- Conservatories under 30 square metres with a suitable thermal break from the main house
- Detached outbuildings under 30 square metres, single storey, and not used as sleeping accommodation
- Like-for-like repairs (replacing roof tiles with the same type, for example)
The conservatory exemption is tricky. If you open up the wall between the conservatory and the house (remove internal doors or knock through), the conservatory no longer meets the exemption conditions and building regulations apply to the whole structure. Many homeowners do this after completion without realising it changes the regulatory status of the work.
How to Apply
You have two options for building control: your local authority Building Control department, or a private Approved Inspector. Both are legitimate, and both issue completion certificates. Private inspectors are often faster for straightforward residential projects.
There are two types of application with the local authority:
Full Plans submission. You submit detailed drawings and a specification before work starts. The BCO checks these against the regulations and approves them (with or without conditions) before work begins. This gives you certainty upfront, and any problems with the design are identified before they're built.
Building Notice. You notify the council that work is starting, and the BCO inspects as the work progresses. No plans are submitted upfront. This is faster to initiate but riskier: if the BCO identifies a problem during construction, you may have to open up or redo work that's already been done.
For a simple extension, a Building Notice is often perfectly workable. For anything involving structural complexity, a loft conversion, or a basement, Full Plans gives you much more protection.
The Inspection Process
Once work starts, your builder (or you) must notify building control at key stages so the BCO can inspect before work is covered up. Typical notification points include:
- Commencement of work
- Excavation of foundations before concrete is poured
- Damp proof course installation
- Concrete oversite (floor slab) before casting
- Drain runs before backfilling
- Structural frame or steelwork
- Roof structure before roofing
- Completion
The builder is responsible for making these notifications. In practice, make sure you know when each stage is due and confirm that notification has been made. Missing a stage inspection is a problem: the BCO cannot inspect foundations that have already been backfilled, and they may require you to open up the work for inspection. At worst, they can require demolition.
Never let your builder skip inspection stages. It happens, particularly with smaller contractors who want to keep momentum. The BCO can require you to expose covered work at your cost. If they're not satisfied, they can issue an enforcement notice requiring demolition.
The Completion Certificate
When the BCO is satisfied that all work complies with building regulations, they issue a completion certificate (or final certificate from an Approved Inspector). This is a document you must keep and produce if you sell the property.
Buyers' solicitors will ask whether all building work has been done in accordance with building regulations and whether completion certificates have been obtained. If you cannot produce certificates for work carried out in the last 12 years, you'll need either to obtain a regularisation certificate from the local authority (which may require opening up work for inspection) or indemnity insurance, which protects the buyer but not the fabric of the building.
Regularisation is expensive, disruptive and uncertain. Indemnity insurance is cheap but doesn't fix the underlying problem. Neither is as good as just obtaining the certificate properly in the first place.
Part L and Energy Efficiency
The 2021 revisions to Part L significantly tightened the energy efficiency requirements for extensions and new work. For extensions, this means improved U-values for walls, roofs and floors, better window specifications, and in some cases a requirement to demonstrate that the work doesn't substantially worsen the energy performance of the overall dwelling.
The Future Homes Standard, due to come into full effect in 2025, imposes even more stringent requirements on new builds. If you're working on an extension to an existing house you won't face the most demanding new-build requirements, but Part L compliance is not something to dismiss. Your architect or designer should specify materials to the required standards, and the BCO will check U-values and the general thermal envelope of the work.