Building Regulations Approval UK — Full Plans, Building Notice and Completion Certificates (2026)

What Work Needs Building Regulations Approval

Most substantive construction, extension, conversion, and alteration work requires approval. The following are the most common triggers tradespeople encounter:

• Extensions of any size — even permitted development extensions still need building regs approval separately from planning.
• Loft conversions — structural work, new floor, means of escape, fire resistance, and roof windows all trigger the regulations.
• Garage conversions into habitable space — insulation, ventilation, fire separation, and structural adequacy all need sign-off.
• Structural alterations — removing or partially removing load-bearing walls, installing steel beams (RSJs), altering the structural frame.
• New electrical circuits in dwellings — notifiable under Part P unless the installer is registered with an approved competent person scheme (NICEIC, NAPIT, ELECSA).
• New or replacement heating systems — boiler replacements are notifiable under Part L; Gas Safe registered engineers self-certify via the competent person scheme.
• Roof replacement or repair covering more than 25% of the roof area — triggers Part L energy performance requirements.
• New bathrooms where drainage connections are required (not straightforward like-for-like replacement).
• Underpinning of any existing structure.
• Change of use — converting a house into flats, commercial to residential, or any use change that alters the building's classification.

What does not need approval is equally important to know. Like-for-like repairs and maintenance — replacing a broken tile, repairing a gutter, repointing brickwork — do not require approval. Neither does most internal decoration: painting, wallpapering, fitting carpets or laminate flooring. Small detached outbuildings under 30 m² are generally exempt. The key word throughout is "like-for-like." The moment the work changes the structure, drainage, electrical installation, or thermal performance, the calculus changes.

Full Plans Application vs Building Notice

When work is notifiable, there are two main routes through local authority building control (a third route — using a private registered building inspector — is covered below).

Full Plans Application

You submit detailed architectural drawings and a specification to building control before work starts. The plans are checked for compliance with the regulations. Building control then issues either an approval, a conditional approval (requiring specified amendments), or a rejection. Once plans are approved, inspections take place at agreed stages during construction. At the end, building control issues a Completion Certificate.

The full plans route gives you certainty before breaking ground. If plans are approved, you know the design meets the regulations — inspectors are then verifying execution, not design. It also produces a Final Completion Certificate, which solicitors and mortgage lenders require during conveyancing. The trade-off is lead time: you need to allow time for plans to be prepared and reviewed before work can begin.

Building Notice

You submit a short building notice to the local authority before work starts — usually at least two working days ahead. No detailed drawings are submitted. Building control inspects the work at key stages as it progresses and ensures compliance on site.

The building notice route is faster to initiate, but it carries more risk. There is no upfront design approval, so building control can require changes during construction if the work does not comply. Critically, a building notice does not result in a Final Completion Certificate. This can create real problems at the point of sale — buyers' solicitors and mortgage lenders frequently require evidence of building control sign-off, and a building notice alone does not provide it. Building notices cannot be used for commercial buildings, buildings subject to the Fire Safety Order, or higher-risk buildings within the scope of the Building Safety Act 2022.

Approved Inspectors and Registered Building Control Inspectors

Private sector building control has existed since the Building Act 1984, but the Building Safety Act 2022 significantly reformed the sector. The former "Approved Inspector" title has been replaced by the Registered Building Inspector (RBI) framework, overseen by the new Building Safety Regulator (BSR). Private inspectors must now register with UKCAB (formerly CICAIR) and meet competence requirements set by the BSR.

Private building control is most commonly used on larger commercial projects where specialist knowledge, speed of response, and national coverage are priorities. For most domestic work — extensions, loft conversions, garage conversions — Local Authority Building Control (LABC) is the standard route. Private inspectors often compete on service speed and expertise for commercial fit-outs and bespoke residential projects. When choosing between routes, compare fees and turnaround times on a project-by-project basis.

Competent Person Schemes

For certain trades, the most efficient route to compliance is self-certification via a government-authorised competent person scheme. Registered tradespeople can certify their own notifiable work, notify the local authority via the scheme, and issue a certificate to the homeowner — without a council inspector setting foot on site.

• Part P — Electrical work in dwellings: NICEIC, NAPIT, ELECSA, Stroma Certification. Registration is effectively essential for any electrician doing notifiable domestic work.
• Gas appliances (Part J): Gas Safe Register. Registration is a legal requirement for gas work and simultaneously operates as the competent person scheme for Part J — Gas Safe engineers self-certify boiler installations and gas appliance work.
• Replacement windows and doors (Part L): FENSA (Fenestration Self-Assessment Scheme) and CERTASS. Registered installers self-certify replacement window and door installations to current energy performance standards.
• Solid fuel and biomass appliances (Part J): HETAS. Covers wood-burning stoves, multi-fuel stoves, and biomass boilers.
• Oil appliances (Part J): OFTEC. The equivalent scheme for oil boiler and appliance installers.
• Unvented hot water systems (Part G): APHC and CIPHE run schemes for plumbers and heating engineers installing unvented cylinders.

If you operate in any of these trades without scheme registration, every notifiable job requires a formal building control submission — slower, more expensive, and less attractive to clients who expect a certificate on completion. Registration is a commercial necessity as much as a compliance requirement.

The Inspection Process

Whether you are using the full plans or building notice route, building control carries out on-site inspections at key stages. Missing a stage inspection and covering up the work is where serious problems arise — building control can require you to open up completed work at the contractor's expense if an inspection is missed without agreement.

The standard inspection stages for most residential projects are:

• Commencement: Notification that work has started. Required before excavation begins.
• Foundation inspection: Carried out before concrete is poured. The inspector checks depth, width, and bearing capacity of the excavation against the approved design.
• Damp-proof course (DPC) inspection: Checked before the DPC is covered — verifies correct installation and continuity with the damp-proof membrane.
• Structural frame: For timber frame or steel frame construction, the frame is inspected before cladding or lining is applied.
• Drainage: Drainage runs are inspected and tested (usually a water or air pressure test) before they are covered over.
• Insulation / pre-plaster: The inspector checks insulation continuity, vapour barriers, and any concealed services before plastering or boarding.
• Completion inspection: Final site visit when all work is finished. The inspector checks the completed building against the regulations and, if satisfied, issues the Completion Certificate.

Inspections must be booked in advance — most local authorities ask for at least 24 hours' notice, some require 48. Keep a record of every inspection visit and any correspondence with building control. This becomes part of the documentary evidence that the work was properly inspected.

Completion Certificates

A Completion Certificate is the formal written confirmation from the local authority (or registered building inspector) that the work described in the application has been completed and, to the best of their knowledge, complies with the Building Regulations.

Completion certificates matter for three practical reasons:

• Conveyancing: When a homeowner sells, their solicitor will request completion certificates for all notifiable work carried out during their ownership. Missing certificates can delay or kill a sale.
• Mortgage lenders: Lenders routinely require completion certificates as a condition of mortgage offers on properties where extension or conversion work has been done.
• Insurance: Buildings insurance can be voided or claims refused if notifiable work was carried out without approval and without a completion certificate.

If a client does not have a completion certificate for earlier work — whether you did it or a previous contractor did — they can apply for a Regularisation Certificate from the local authority. This is a retrospective application that involves the council inspecting the work after the fact. They may require walls, floors, or ceilings to be opened up so the work can be examined. If the work does not comply, remediation is required before the certificate can be issued. Regularisation applications are more expensive than getting approval in the first place and far more disruptive — they are a last resort, not a planned option.

The Building Safety Act 2022

The Building Safety Act 2022 is the most significant reform to building safety law since the Building Act 1984. It was introduced in response to the Grenfell Tower fire and fundamentally changes how higher-risk buildings (HRBs) are designed, built, and managed.

An HRB is defined as a building that is at least 18 metres in height or has at least 7 storeys and contains at least 2 residential units. For HRBs, the Act introduces a three-stage Gateway process:

• Gateway 1: Planning stage — fire statement required with planning application.
• Gateway 2: Before work starts — detailed building control application submitted to and approved by the Building Safety Regulator (not the local authority).
• Gateway 3: Before occupation — completion certificate from the BSR confirming the completed building matches the approved design.

The Act also places new statutory duties on Principal Designers andPrincipal Contractors for HRBs, and requires the maintenance of a "golden thread" of building information — a complete, structured digital record of the building's design, construction, and changes throughout its life.

For most trade contractors working on domestic extensions, loft conversions, and small commercial projects, the HRB-specific provisions do not apply directly. However, the Act also updated the CDM-style dutyholder requirements for all buildings, gave the Building Safety Regulator oversight of the registered building inspector profession, and introduced new liability periods for defective construction. Any trade contractor working on projects with a residential component above six storeys should take specialist advice on their obligations under the Act.

Building Regulations Fees

Local authorities charge fees for building regulations applications. Fee structures vary by council — some charge based on the estimated project cost, others on floor area. Typical ranges for common project types in 2026:

• Single-storey extension: £200–£500 for a building notice; £300–£700 for full plans (plan fee plus inspection fee).
• Two-storey extension: £400–£900 depending on size and council.
• Loft conversion: £300–£800 typically, depending on complexity.
• Garage conversion: £200–£500.
• Whole house conversion (e.g. house to flats): £500–£1,500 or more depending on number of units and floor area.
• New dwelling: Based on floor area — typically £800–£2,000 for a standard three-bedroom house.

Private registered building inspectors are competitive on fees, particularly for commercial projects and larger residential schemes. It is worth requesting quotes from both the local authority and a private inspector for any project above around £100,000 in construction value. For smaller domestic projects, the fee difference is rarely significant enough to justify the extra administrative step of appointing a private inspector.

Common Problems Tradespeople Face

Three situations come up repeatedly and are worth knowing how to handle before they arise on a job.

The client insists on skipping building regs

Some clients will ask a tradesperson to proceed without building regulations approval to save money or time. The risk sits entirely with the tradesperson as well as the client — carrying out notifiable work without approval is an offence under the Building Act 1984, regardless of who initiated the decision. The correct response is to explain clearly in writing (email is fine) that you cannot proceed without approval, set out the consequences, and either obtain the necessary approval or decline the job. Do not let a client's pressure lead you into a position where your professional registration, insurance, or freedom is at risk.

Work failing inspection

If a building control inspector identifies non-compliance during a site visit, they will issue a written notice specifying what needs to be corrected. The cost of remediation — including any opening up of completed work — falls on the contractor unless the contract provides otherwise. Using the full plans route significantly reduces this risk because design compliance is checked before work starts. Keeping detailed records of every inspection visit and any correspondence also protects you if a dispute arises about what was agreed.

Unapproved work surfacing during conveyancing

When a client sells a property, their solicitor will carry out standard searches that include checking for building regulations completion certificates. If notifiable work was done without approval — whether by you or a previous contractor — the sale can stall. The client may seek to pass the cost of a retrospective regularisation application or indemnity insurance back to the original contractor. Make it a standard part of your handover to give clients every relevant completion certificate in writing so they have the documentation ready when they eventually sell.