Building Control: Local Authority vs Approved Inspector

Every building project that involves structural work, a change of use, or alterations affecting fire safety, insulation, drainage, or electrical installations requires building regulations approval. In England, you have two routes to obtaining this approval: through the local authority building control service (LABC), or through a private sector approved inspector. This guide explains how each route works, what you can expect during the process, and how to choose between them for a residential project in the Hampstead and north London area.

What Building Control Does

Building control is the process of checking that construction work complies with the Building Regulations 2010 (as amended). The regulations set minimum standards for the health, safety, welfare, convenience, and sustainability of buildings, and they are divided into functional Parts: Structure (Part A), Fire Safety (Part B), Sound Insulation (Part E), Ventilation (Part F), Energy Efficiency (Part L), and so on.

The building control body reviews your design proposals, inspects the works at key stages during construction, and — if everything complies — issues a completion certificate at the end. This certificate is important: mortgage lenders require it, and the absence of one can cause serious problems when you come to sell the property.

The Local Authority Route

If your project is in Camden, the local authority building control service is provided by Camden Council. In Barnet, it is the London Borough of Barnet's building control team. You engage the local authority by submitting either a full plans application or a building notice.

Full Plans Application

A full plans application involves submitting detailed drawings and specifications to the building control team before work starts. They check the design against the Building Regulations and, if compliant, issue a formal approval notice (sometimes with conditions). This gives you certainty that the design has been accepted before construction begins.

The local authority has five weeks (extendable to eight weeks with your consent) to determine a full plans application. During this period, they may ask for additional information or amendments. Once approved, the drawings form the basis against which site inspections are carried out.

Building Notice

A building notice is a simpler submission — essentially a notification that you intend to carry out building work, with basic details of the project. There is no plan-checking stage and no formal approval. Instead, the building control surveyor inspects the work as it progresses and assesses compliance on site.

The building notice route is quicker to start (work can begin 48 hours after submission), but it carries more risk. If the building control surveyor identifies a compliance problem during an inspection, you may need to open up completed work or make expensive changes. For anything more complex than a simple extension, the full plans route is generally safer.

Inspection Stages

Regardless of whether you submit full plans or a building notice, the local authority will inspect the work at key stages. You (or your builder) must notify them before each stage. Typical inspection stages include:

• Commencement of work
• Excavation of foundations (before concrete is poured)
• Foundation concrete poured
• Damp-proof course laid
• Oversite preparation
• Drainage (before backfilling)
• Structural steelwork (before encasement)
• Fire-stopping and compartmentation
• Pre-completion (before finishes)
• Completion

Not every stage applies to every project. Your building control surveyor will confirm at the outset which notifications and inspections are required.

The Approved Inspector Route

An approved inspector (AI) is a private sector building control body registered with the Building Safety Regulator (formerly CICAIR). They perform the same plan-checking and site inspection functions as the local authority, but as a commercial service.

To use an approved inspector, you (or the approved inspector on your behalf) must submit an initial notice to the local authority, which effectively transfers building control responsibility for the project to the approved inspector. The local authority then steps back from the project unless the initial notice is cancelled or rejected.

The approved inspector reviews your plans, carries out site inspections at agreed stages, and — when satisfied that the work complies — issues a final certificate, which is registered with the local authority. The final certificate has the same legal standing as a local authority completion certificate.

How It Differs in Practice

The approved inspector route tends to be more commercially flexible than the local authority service. Key differences include:

• Responsiveness. Approved inspectors are private businesses competing for work, so they often provide faster turnaround on plan checking and more flexible inspection scheduling, including early morning, evening, or weekend visits if needed.
• Continuity of surveyor. With an approved inspector, you typically deal with the same surveyor throughout the project. Local authority teams may rotate staff or cover absences with different surveyors, which can occasionally lead to inconsistency.
• Pre-construction engagement. Many approved inspectors actively engage during the design stage, reviewing proposals informally and flagging compliance issues before the formal submission, which can save time and reduce the risk of on-site changes.
• Fixed-fee pricing. Approved inspectors usually quote a fixed fee for the project, which includes plan checking and all inspections. Local authority fees are set by a published schedule and can sometimes result in a higher total cost for complex projects.

Cost Comparison

Building control fees vary depending on the type and scale of the project. For typical residential projects in north London, you might expect:

• Householder extensions and loft conversions: Local authority fees of £400–£1,200 depending on the size and complexity. Approved inspector fees are broadly comparable, sometimes slightly lower.
• Flat conversions and change of use: Local authority fees of £1,000–£3,000+. Approved inspectors may offer competitive fixed-fee quotes, particularly for straightforward conversions.
• New-build residential: Local authority fees of £2,000–£5,000+ depending on the number of units and floorspace. Approved inspector fees are competitive and may include additional services such as air-tightness testing coordination or SAP assessment management.

Fees alone should not be the deciding factor. The value of building control lies in getting compliance right, avoiding costly remedial work, and obtaining the completion certificate without delay. A cheaper service that misses compliance problems or delays inspections is a false economy.

Pros and Cons of Each Route

Local Authority Building Control

Advantages:

• The local authority is also the planning authority and the environmental health authority, so there is a joined-up understanding of the building and its regulatory context
• Knowledge of local ground conditions, drainage, and infrastructure is built into the service
• No risk of the building control body going out of business or withdrawing from the project
• In conservation areas, the local authority building control team is familiar with the constraints and sensitivities of historic buildings

Disadvantages:

• Potentially slower response times, especially during busy periods
• Less flexibility on inspection scheduling
• You may deal with different surveyors at different stages
• Fee structures can be less transparent than a fixed-fee quote

Approved Inspector

Advantages:

• Faster turnaround and more responsive service
• Fixed-fee pricing gives cost certainty
• Continuity of surveyor throughout the project
• Commercially motivated to provide a good client experience
• Often more proactive in engaging with the design team early

Disadvantages:

• If the approved inspector cancels the initial notice (for example, due to a fee dispute or because they identify non-compliance they cannot resolve), the project reverts to the local authority, which can cause delays
• The approved inspector may have less local knowledge than a council surveyor who works exclusively in the borough
• A very small number of approved inspectors have been criticised for being too commercially accommodating — approving work that should have been challenged — although the registration and oversight regime is designed to prevent this
• If the approved inspector ceases trading, the project reverts to the local authority, and you may need to pay additional fees

What Happens if Work Does Not Comply

If the building control body — whether local authority or approved inspector — identifies work that does not comply with the Building Regulations, they will require it to be corrected. In most cases this is resolved informally during the inspection process: the surveyor identifies the problem, the builder corrects it, and the surveyor re-inspects.

If the non-compliance is more serious or the builder refuses to correct it, the local authority can serve an enforcement notice under Section 36 of the Building Act 1984, requiring the work to be pulled down or altered within 28 days. This power rests with the local authority even if an approved inspector is handling the building control. The approved inspector would cancel the initial notice and refer the matter to the council.

The most common compliance issues on residential projects in north London include:

• Inadequate fire stopping between compartments in flat conversions
• Structural steelwork installed without the specified fire protection
• Sound insulation build-ups that do not match the approved specification
• Drainage connections made without inspection
• Electrical installations not certified by a registered Part P installer

These are largely avoidable if the architect's drawings are detailed, the builder follows them, and the building control inspections happen at the right time.

Choosing the Right Route

For most homeowner projects in Hampstead — a rear extension, loft conversion, or internal remodel — either route works well. The choice often comes down to your architect's or builder's recommendation and whether they have an existing relationship with a particular approved inspector or local authority surveyor.

For more complex projects such as flat conversions, basement excavations, or change of use schemes, it is worth discussing the options with your architect. They will know which approved inspectors have relevant experience and which borough building control teams are responsive. Our matching service connects you with architects who have working relationships with both local authority teams and reputable approved inspectors across north London, so you get building control advice that is tailored to your specific project from the start.