Building regulations are the set of minimum technical standards that almost every significant piece of building work in England and Wales must meet. They exist to protect public health, safety, and energy efficiency — not to preserve street character or control design, which is what planning permission does. If you are extending, converting, or significantly altering your home, it is very likely that building regulations apply regardless of whether you need planning permission.
The regulations are enforced through building control, a service provided either by your local authority or by a registered private-sector body. Getting this process right from the outset protects you legally, keeps your insurance valid, and — critically — produces a completion certificate that you will need when you come to sell.
Building Regulations vs Planning Permission
These two consent regimes are entirely separate and frequently confused.
Planning permission is granted (or refused) by your local planning authority. It controls land use, the visual appearance of buildings, and impact on neighbours and the surrounding area. It asks: should this building work happen at all, and in this form?
Building regulations are enforced by building control. They set minimum standards for how work is constructed. They ask: is this building work safe, structurally sound, and energy-efficient?
You can need one, both, or neither:
- A rear extension on a detached house will usually need both (though many extensions fall within permitted development).
- A loft conversion that stays within permitted development still needs building regulations.
- Replacing a boiler needs building regulations sign-off (via a Gas Safe registered engineer under a self-certification scheme) but almost never needs planning permission.
- Repainting your living room needs neither.
One important practical consequence: planning approval does not mean building regulations approval, and vice versa. Builders who tell you “we’ve got planning so we’re fine” are wrong.
The Party Wall Act
Where work affects a shared wall, boundary, or excavation near a neighbour’s foundations, the Party Wall etc. Act 1996 applies as a third separate layer. You must serve a party wall notice before work begins — typically two months in advance for structural work. This is distinct from both planning and building regulations, though it is often triggered by the same projects (rear extensions, loft conversions, basement digs).
The Parts That Matter
The Building Regulations 2010 (as amended) are divided into functional requirements set out in a series of Approved Documents, each covering a specific technical area. You do not need to know all fourteen parts in detail, but understanding which ones apply to your project is useful when talking to your building control officer or structural engineer.
Part A — Structure
Part A sets out requirements for structural stability: foundations, walls, floors, roofs, and loadbearing elements. Any project that removes or alters a loadbearing wall, adds a storey, or puts a new load on existing structure will engage Part A. A structural engineer’s calculations are almost always required for this work, and building control will check them.
Part B — Fire Safety
Part B covers means of escape, fire resistance of structural elements, and fire spread. For domestic extensions it mainly concerns itself with escape routes and smoke alarms. For loft conversions it is more demanding: you will typically need a 30-minute fire-resistant ceiling below the new floor, self-closing fire doors on habitable rooms, and interlinked mains-wired smoke alarms throughout. If you are converting a house to flats, Part B requirements become significantly more onerous.
Part C — Site Preparation and Resistance to Contaminants and Moisture
Part C deals with damp-proofing, ground conditions, and the treatment of contaminated land. Relevant for any ground-floor extension, basement conversion, or project where the existing damp-proof course or damp-proof membrane is disturbed.
Part E — Resistance to the Passage of Sound
Part E applies when a material change of use occurs — for instance, converting a single house into two flats, or building a new habitable room adjoining a party wall. It sets acoustic performance standards for separating floors and walls. For most straightforward house extensions it does not apply directly, though good practice is to address sound transmission anyway.
Part F — Ventilation
Part F requires adequate ventilation in habitable rooms, kitchens, and bathrooms. The 2021 update (which came into full effect in June 2023) increased minimum ventilation rates significantly, particularly background ventilation and purge ventilation provisions. Any new room — including a converted garage or loft — must comply with the updated Part F.
Part G — Sanitation, Hot Water Safety and Water Efficiency
Part G covers bathrooms, hot water systems, and water efficiency. Installing a new bathroom, relocating a WC, or adding a utility room with a sink all engage Part G. The water efficiency requirements — maximum consumption of 125 litres per person per day — apply to new dwellings but are also relevant when undertaking larger refurbishments.
Part H — Drainage and Waste Disposal
Part H covers foul water drainage, rainwater drainage, and solid waste storage. Extending a building’s footprint means you will almost certainly need to redirect or extend drainage runs, and any new WC, shower, or washing machine outlet must drain compliantly. Building control will want to see drainage layouts, and an inspector may camera-survey drains before issuing a completion certificate.
Part L — Conservation of Fuel and Power
Part L is the energy efficiency section and has been progressively tightened since 2006. From 2024, new extensions must achieve a reasonable standard of thermal performance (U-values for walls, roofs, floors, and glazing), and Notional Dwelling calculations or simple U-value compliance paths are standard. Replacing more than 25% of a roof covering or upgrading windows triggers minimum U-value thresholds even without an extension.
Part P — Electrical Safety
Part P requires that all electrical installation work in dwellings is either carried out or inspected by a person competent to do so. In practice this means either using an electrician registered with a competent person scheme (NICEIC, NAPIT, or equivalent) who self-certifies the work, or notifying building control before you start and having the work inspected. A completion certificate or an Electrical Installation Completion Certificate (EICC) is the end product.
Approval Routes
There are three main routes to building regulations approval in England, plus a self-certification route for specific trades.
| Route | How it works | Approval timescale | Best for |
|---|---|---|---|
| Full Plans | Detailed drawings and specifications submitted before work starts; building control checks and approves (or requests amendments) in writing | ~5 weeks statutory period | Large projects, complex structures, lender requirements |
| Building Notice | Notice submitted to local authority; work starts immediately with no pre-approval of plans | Same day (notice registered) | Straightforward domestic work, experienced builders |
| Regularisation | Retrospective application for work already completed without consent | Varies; typically 4–10 weeks | Unauthorised historic work discovered before sale |
| Competent Person Scheme | Trade carries out and self-certifies specific work (electrics, boiler replacement, windows, etc.) | Immediate; certificate issued by scheme | Boilers, rewires, replacement windows, renewables |
Full Plans
Full Plans is the most thorough route and the one mortgage lenders and solicitors most readily accept. You submit scaled drawings, a specification, and sometimes structural calculations before a brick is laid. Building control reviews the package and issues either a formal approval notice or a notice of rejection specifying required amendments. Work can begin once approval is granted (or after two days if you choose to start at risk).
Building Notice
A Building Notice allows work to start the same day the notice is registered, without prior plan scrutiny. The risk sits with the applicant: if the inspector finds non-compliant work on site, you may need to open up, alter, or demolish. This route is unsuitable for complex projects, work near a drain, or anything requiring a SAP energy calculation.
Regularisation
Regularisation is the retrospective route for work carried out without building regulations consent — a common discovery in conveyancing. The building control body inspects the completed work, may require opening up to check hidden elements, and issues a regularisation certificate if satisfied. This is not the same as a completion certificate and some solicitors treat it with more scepticism; it is always better to obtain consent before work begins.
Approved Inspectors vs Local Authority Building Control
Private firms known as Approved Inspectors (soon to be rebranded Registered Building Control Approvers under the Building Safety Act 2022) compete with local authority building control (LABC). The process is functionally similar: the approved inspector issues an Initial Notice to the local authority, takes over building control functions, and issues a Final Certificate on completion.
Approved inspectors can sometimes offer faster turnaround and a dedicated named inspector. LABC tends to be the default for straightforward domestic projects and is often the choice where relationships with local inspectors are already established. Fees are broadly comparable, though there is no price regulation — always obtain at least two quotes.
Approval Routes: Fees in 2026
Building control fees vary by local authority and project type. As a rough guide:
- Minor works (replacement windows, small garage conversion): £200–£400
- Single-storey rear extension: £400–£800
- Two-storey extension or loft conversion: £700–£1,200
- Large extension, basement, or multiple dwellings: £1,200–£1,500+
VAT is charged on building control fees by some authorities and all approved inspectors. The fee typically includes plan-check (for full plans applications) and a set number of site inspections.
Inspections and the Completion Certificate
Once work is underway, your building control officer (BCO) will inspect at specific stages. You are responsible for notifying building control before each stage is covered up — failure to do so can mean opening up completed work.
Typical Inspection Stages
Most domestic projects require between 6 and 8 inspections, commonly including:
- Commencement — site visit shortly after work begins
- Excavations — before concrete is poured into foundation trenches
- Foundation concrete — before backfilling
- Oversite (damp-proof membrane and insulation) — before slab is poured
- Damp-proof course — at low-level masonry
- Structural frame / roof structure — before sheathing or boarding
- Drainage — before drains are backfilled; may include a water or CCTV test
- Completion — final inspection of all finished works
For a loft conversion, additional stages may include the structural steelwork (beam pockets and padstones) and fire-stopping details. For a basement, a drainage soak test and waterproofing inspection are usually added.
The Completion Certificate
Once the BCO is satisfied that all work complies with the regulations, they issue a completion certificate. This is a legally significant document: it confirms that the notified building work has been inspected and, to the best of the authority’s knowledge and belief, complies with the regulations.
Timescale for receiving the certificate after the final inspection is typically 4–8 weeks, though this varies by authority workload. Chase it proactively — building control offices do not always issue certificates automatically.
Keep the completion certificate with your title deeds. Solicitors conducting conveyancing searches will ask for it, and the absence of a completion certificate for notifiable work can delay or kill a sale. If you have lost it, the issuing authority can usually provide a copy; approved inspectors are required to retain records and lodge a final certificate with the local authority.
What If You Cannot Get a Certificate?
If building control has not been notified and the work cannot be inspected (because it is finished and covered up), regularisation is the standard route. Alternatively, some conveyancers accept indemnity insurance as a stop-gap — but insurers will not cover known defects, and insurance does not retrospectively make the work compliant. It is a commercial solution to a legal risk, not a technical one.
Building regulations compliance is not optional bureaucracy — it is the mechanism by which the safety and performance of UK housing stock is maintained. Understanding which parts apply, choosing the right approval route for your project, and keeping track of inspection stages and the completion certificate will save you significant time and expense, both during the build and when you eventually come to sell.
