Building Control vs Approved Inspector: Which for Your Extension?

For a home extension in England, you can have your building regulations checked by either your council's building control team or a private firm. That private firm used to be called an approved inspector and is now called a Registered Building Control Approver (RBCA). Both routes lead to a legal sign-off. The real differences are who you pay, how flexible the inspections are, and how the paperwork runs. For most Birmingham and West Midlands homeowners with a conventional extension, either works. The better choice depends on your build, your builder and your timetable.

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TL;DR

"Approved inspector" is the old name. In England these private firms are now Registered Building Control Approvers, and the job is the same: check your extension meets building regulations.
An extension needs building regulations approval before work starts, whichever route you choose, according to Citizens Advice.
Councils charge fees that recover only their costs. Private approvers set their own fees, so get at least two quotes and compare what is included.
Choose the council for a straightforward build and local ground knowledge. Choose a private approver if you want flexibility, faster scheduling or one named inspector.
Whoever you pick, keep the final certificate. You will need it when you sell.

What building control actually does on an extension
Approved inspector, RBCA and council: the names explained
Council vs private approver: how they compare
How the process differs step by step
What happens if an extension fails an inspection
How to choose for a Birmingham or West Midlands extension
Where building control sits in the project timeline
Our perspective
Plan your extension with one team
FAQ
Sources

What building control actually does on an extension

Building control is separate from planning permission. Planning decides whether you may build something. Building control checks that what you build is safe and meets the technical standards: foundations, structure, insulation, fire safety, drainage, ventilation, electrics and so on.

Citizens Advice is clear that you need approval before work starts if the work cannot be carried out under a competent person scheme, and building an extension is its example. So a rear, side-return, double-storey or wrap-around extension all need a building control body involved, even where the design falls under permitted development for planning purposes. If you are still working out the planning side, our guide to permitted development extension rules in England explains what you can build without a planning application.

The building control body does three jobs:

Checks your drawings and specification against the regulations.
Inspects the work at key stages while it is built.
Issues a certificate when the work is complete.

The homeowner is responsible for making sure this happens, not the builder, so it is worth deciding early and in writing who is handling it.

Approved inspector, RBCA and council: the names explained

The terminology causes most of the confusion, and it is why people search for "approved inspector vs building control".

Local authority building control (LABC) is the council service. It is the default and has been for decades.
Approved inspector is the former name for a private-sector alternative. Under the current rules in England, they are called Registered Building Control Approvers, authorised to carry out building control functions.
Private building control is the everyday phrase for the same thing.

So "building control vs approved inspector" is not a choice between two different jobs. It is a choice between a public body and a private company doing the same regulatory job under the same regulations. You may still see older websites and builders use the old term. Treat them as meaning the same thing.

One point to keep in mind: this applies to England. Wales and Scotland run their own rules, so if you are reading advice written for those nations, check it before applying it to a West Midlands home.

Council vs private approver: how they compare

Factor	Council building control	Private approver (RBCA)
Type of body	Non-profit public body	Private, commercial business
Fees	Charges recover only the cost of the service	Sets its own fees
Local knowledge	Knows local ground conditions and flood risks	Varies by firm and area
Flexibility	Standard processes	Generally more flexible and responsive
Notification	You apply directly to the council	Must send an initial notice to the council before work starts
Final document	Completion certificate	Final certificate

The fee and accountability points come from HomeBuilding's comparison, which describes councils as publicly accountable and limited to cost-recovery fees, while private approvers are commercial and free to set their own prices. The same piece notes that councils bring knowledge of local site-specific challenges such as ground conditions and flood risk, which can matter on a Birmingham plot with older drainage or made ground.

Cost

Council charges are usually set by a published fee schedule based on the type of work and the floor area. Birmingham's building control service publishes banded charges for extensions by internal floor area, which is how the council structures its fees. The version we checked is a 2021 form, so always get the current fee sheet from the council before budgeting.

Private approvers quote per project. Industry commentary suggests their fees may be higher, though scheduling may be faster and extras such as warranties may be offered. Treat that as a prompt to compare, not a rule: a private quote can come in lower or higher than the council's depending on the job. When comparing quotes, check exactly what is included: plan check, number of site visits, re-inspections, and the final certificate.

Speed and flexibility

RBCAs are generally seen as the more flexible and responsive option, which is why they appeal on projects with unusual structures or tight programmes. Councils tend to follow a more standard process. In practice, speed depends far more on the individual surveyor than on the type of body, so ask any provider how quickly they respond to inspection requests during the build.

Consistency

Homeowners often say the biggest practical difference is having the same inspector throughout. A private approver will commonly assign one person to your project. A council may send whoever is on the rota. Neither is guaranteed, so ask before you commit.

How the process differs step by step

The council route

You submit either a full plans application or a building notice. Under full plans, the council checks your drawings before work begins and issues a decision. A building notice lets you start sooner with less up-front detail, but it carries more risk of changes on site, so it suits simple work rather than a complex extension. The official steps are on GOV.UK's building regulations approval guide.

During the build, the surveyor visits at set stages. Typical inspection points for an extension include:

Excavated foundations, before concrete is poured
Concrete poured and any ground-floor slab or oversite preparation
Drainage, before it is covered
Damp-proof course and structural elements such as beams and lintels
Roof structure and insulation, before it is boarded or plastered
Completion, when everything is finished

Your builder should give the building control body notice before each stage. Covering work up before inspection is the classic way to cause delay and extra cost.

At the end, the council issues a completion certificate to show compliance.

The private approver route

The approver is appointed by you. Before any building work starts, they must submit an initial notice to the local authority to tell it about the project. Inspections then follow the same logic as above. When the work is finished and passes final inspection, the approver gives a final certificate, whereas a council gives a completion certificate, as the government's practice guidance sets out.

Two practical checks before you appoint any private approver:

Confirm they are registered as a building control approver and are authorised for domestic work of the kind you are doing.
Ask the builder to confirm in writing that the initial notice has been accepted before they start on site.

Can you switch?

The guidance linked above includes FAQs on reversion, which covers situations where responsibility returns to the local authority, for instance if a private approver can no longer carry on. If you are mid-project, ask the council what it needs from you. It is another reason to keep your drawings, notices and inspection records in one folder.

What happens if an extension fails an inspection

A failed inspection is usually a list of items to fix, not a disaster. The surveyor tells you what does not comply, your builder corrects it, and a re-inspection follows. Where it gets expensive is when the work has been covered up or built differently from the approved design.

Three stages after a failed building inspection

If the work does not comply, you may be asked to alter or remove it, and if you do not, the council may serve a notice or take court action. GOV.UK adds that you may have to correct the work or pay a fine if building regulations are not followed.

If you find out later that work was done without approval, such as an extension built by a previous owner, the route is regularisation. Homeowners can apply to the local authority for it for work done after 11 November 1985, and alterations may be needed before it can be approved. Plumbing and drainage in a new kitchen or bathroom have their own compliance expectations too, covered in this guide to UK plumbing regulations.

The simplest protection is to appoint your building control body before you sign a build contract, and to refuse to let the builder cover up anything that has not been inspected.

How to choose for a Birmingham or West Midlands extension

HomeBuilding's guidance is a useful starting point: councils suit conventional, straightforward projects, while RBCAs suit those wanting greater flexibility and responsiveness, such as innovative designs. Turn that into questions about your own job.

Choose the council if:

Your extension is a standard single-storey rear or side-return build on typical ground.
You want a fee set by a published schedule so you can budget early.
The site has known ground, drainage or flood considerations the council is likely to know about.
You prefer a public body with local accountability.

Choose a private approver if:

The design has unusual structure, such as large steel spans, a wrap-around layout or a double-storey addition with tricky load paths.
Your programme is tight and you want inspection slots agreed with a named person.
You value one inspector throughout.
A quote shows good value once you compare what each includes.

Questions to ask any provider:

What is included in the fee, and what triggers extra charges?
How much notice do you need for an inspection, and how fast do you usually attend?
Will the same person inspect each stage?
When will I receive the final or completion certificate after the last inspection?

Do not forget the other legal pieces that sit alongside building control. If your extension is near a neighbour's wall, a party wall agreement is a separate process. If a public sewer runs near your build line, you may need to check the position before building over a sewer. Neither is dealt with by building control, though both can change your design.

Where building control sits in the project timeline

Building control is not a last-minute task. It starts at the design stage, because the structural calculations, insulation specification and drainage layout must be settled before the application. It then runs alongside the build and finishes only when the certificate is issued.

A sensible order looks like this:

Design and planning route agreed (permitted development or planning application).
Structural and technical drawings prepared.
Building control body chosen and application or initial notice submitted.
Other consents in place, such as party wall notices.
Build starts, with inspections at each stage.
Final inspection and certificate.

Our breakdown of the house extension timeline shows how long each of those stages typically takes and where delays creep in. For the drawings, see how planning drawings and design and build fit together, since the same technical information feeds your building control submission.

Our perspective

Most homeowners who contact us have never dealt with building control before, and they assume it is a box-ticking exercise the builder will sort out. It is not. It is the independent check that your new rooms are safe, warm, drained properly and legally yours to sell.

Our view is that the choice between council and private approver matters less than having one team that manages it from the start. When design, planning, building regulations and construction sit with a single coordinated team, the drawings are prepared with the inspection stages in mind, the notices go in on time, and nothing gets covered up before it has been seen. That is how we work on extensions across Birmingham, Solihull and the wider West Midlands: we handle the planning and building regulations paperwork, tell you what to expect before any site survey, and keep you informed at every stage.

Our local focus also helps. We build in the area, so we are used to the ground, the housing stock and the way local building control teams like to receive applications. Whichever route you choose, we will explain the trade-offs in plain terms and set it up properly, so the certificate at the end is a formality rather than a worry.

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Plan your extension with one team

If you are weighing up building control for a real project, the simplest way to remove the stress is to have a single team handle the design, the regulations and the build. We design and build single-storey, double-storey, kitchen, rear, side-return and wrap-around extensions across the West Midlands, with planning and building regulations managed for you.

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See our extension services to talk through your plans, or read our guide to over-garage and other extension costs in the West Midlands to start budgeting realistically.

FAQ

Is an approved inspector the same as a building control officer?

They do the same regulatory job but work for different organisations. A building control officer works for the council, while an approved inspector, now called a Registered Building Control Approver, is a private-sector professional or firm. Both check that your extension meets building regulations, and both can certify completion.

Is private building control cheaper than the council?

Not necessarily. Councils must charge fees that only recover their costs, while private approvers set their own, so there is no fixed rule. Get written quotes from the council and at least one private approver, and compare exactly which inspections and certificates are included before deciding.

Do I still need building control if my extension is permitted development?

Yes. Permitted development removes the need for a planning application, not for building regulations. Citizens Advice lists an extension as work needing approval before it starts.

What happens if I build without building control approval?

The council can ask you to alter or remove non-compliant work, and in serious cases can take enforcement action. For older unapproved work, you can apply for regularisation if it was done after 11 November 1985, though alterations may be needed first. Speak to your local council's building control team about your specific case.