Building Regulations Explained for Homeowners

The parts that matter on a domestic project

The regulations are divided into approved documents, each identified by a letter. You will meet a handful repeatedly on a home project.

Approved documents most relevant to home improvement work. Part | Covers | Where it typically bites. Part A — Structure — Steel beams, foundations, wall removal; Part B — Fire safety — Loft conversions, escape windows, fire doors; Part C — Damp and contaminants — Damp proof courses, floor build-ups; Part F — Ventilation — Kitchens, bathrooms, background ventilators; Part K — Protection from falling — Stairs, balustrades, glazing; Part L — Conservation of fuel and power — Insulation, glazing, airtightness; Part M — Access — Level thresholds, downstairs WC provision; Part P — Electrical safety — New circuits, bathroom and kitchen wiring; Part O — Overheating — Large glazed extensions and new dwellings

What needs approval and what does not

Extensions, loft and garage conversions, structural alterations, new or replaced windows, re-roofing over about half the area, new heating appliances, new bathrooms involving drainage and most new electrical circuits all require building control involvement.

Like-for-like repairs, redecoration, replacing a kitchen without moving services, and most fencing and landscaping do not. Conservatories can be exempt where they are under thirty square metres, separated from the house by external-quality doors and have an independent heating control, though the exemption is narrower than people assume.

Full plans or building notice

There are two routes. A full plans application means drawings and structural calculations are submitted and checked before work starts, and you receive a formal approval. A building notice means work begins with forty-eight hours' notice and compliance is judged on site.

Full plans is slower and slightly dearer upfront and it is the right choice for anything structural. A building notice is fine for straightforward work, but if an inspector disagrees with what has been built, the correction is at your cost, and on a steel beam that correction can be brutal.

Local authority or approved inspector

You can use your council's building control department or a private approved inspector. Both carry the same statutory weight. Councils are often cheaper and know local ground conditions; approved inspectors are frequently more flexible on visit timing.

Typical domestic building control fees in 2026 run from around £600 for a small conversion to £1,200 or more for a large two storey extension, usually split into a plan check charge and an inspection charge.

The inspection stages

Inspections are triggered by you or your builder at defined points. Missing one is the single most common cause of trouble, because covered-up work sometimes has to be opened up again.

Commencement, before any excavation · Foundation excavation, before concrete is poured · Foundation concrete, before building off it · Damp proof course and oversite · Drainage, open and under test · Structural steelwork and connections in place · Pre-plaster: insulation, cavity barriers, fire stopping and ventilation · Completion, before occupation of the new space

The completion certificate is the point of the exercise

When the final inspection passes, building control issues a completion certificate. That document is what a conveyancing solicitor asks for when you sell, what a lender may want to see, and what an insurer will look for after a claim involving the altered part of the building.

Work carried out without approval can be regularised retrospectively, but the process is slower, sometimes requires opening up completed finishes, and occasionally cannot be certified at all. Indemnity insurance covers the legal risk of enforcement, not the fact that the work may be defective.

Where homeowners most often fall foul

The recurring problems are predictable and all avoidable. Work is covered up before an inspection, so it has to be opened again. A loft room is created without the required fire door and protected escape route, and cannot be described as a bedroom. New electrical circuits are installed by someone unregistered, so no Part P certificate exists.

Windows are replaced by a fitter who is not registered with a competent person scheme, leaving no FENSA certificate for the file. A conservatory is converted into a habitable room by removing the separating doors, which quietly removes the exemption the conservatory relied on.

Each of these surfaces at sale rather than at the time, which is exactly when it is most expensive and most inconvenient to correct.

Frequently asked questions

Do building regulations apply if I have planning permission?

Yes. They are entirely separate. Planning decides whether the building can exist in that form; building regulations decide whether it is safe and efficient enough to be occupied.

Who is responsible for compliance, me or the builder?

Legally, the building owner carries ultimate responsibility, alongside the person carrying out the work. That is why the applications, inspections and certificate should always be in your name and in your records.

What if I bought a house with unapproved work?

Ask your solicitor about regularisation or indemnity insurance. Regularisation involves a retrospective application and inspection; indemnity only protects against enforcement action and tells you nothing about the quality of the work.

How much do building control fees cost?

Typically £600 to £1,200 for domestic work in the South East, depending on the size and complexity of the project and whether you use the council or an approved inspector.