At a glance
Category
Building Control
Who this guide is for
Homeowners whose project needs Building Regulations approval
Who inspects
Local authority building control or a Registered Building Control Approver
Typical number of visits
5–8 for a single-storey extension
Key output
Completion certificate
Difficulty
Beginner
Reading time
6–8 minutes
Quick answer
What does a building inspector actually do?
A building inspector checks that the work being built meets the Building Regulations. They visit at key stages — such as foundations, drainage, structure and completion — and issue a completion certificate at the end if everything complies.
Your builder usually books the inspections, but the legal duty to comply sits with you as the property owner, so it pays to track them yourself.
Who Your Inspector Is
You can use either your local authority's building control team or a private Registered Building Control Approver (formerly called an Approved Inspector). Both enforce the same regulations.
- Local authority building control — familiar with local ground conditions and often used for smaller domestic work.
- Registered Building Control Approver — a private body, sometimes faster to book and often used by larger contractors.
- Competent Person Scheme installers — for certain works such as electrics, windows or boilers, the installer self-certifies and notifies building control for you.
You choose one route for the project. You cannot mix and match part-way through without a formal transfer.
The Inspection Stages
The exact list depends on the project, but a typical extension follows this sequence:
| Stage | What is checked |
|---|---|
| Commencement | Work has started and the correct notice is in place |
| Excavation | Foundation depth, width and ground conditions before concrete |
| Foundation concrete | Depth and quality of the poured concrete |
| Oversite / damp proofing | Hardcore, membranes, insulation and DPC positions |
| Drainage | Falls, connections and an air or water test before backfill |
| Structure | Steel beams, padstones, lintels and engineer's details |
| Pre-plaster | Insulation, fire protection, cavity barriers and ventilation |
| Completion | Final check of the finished work against the regulations |
Booking and Preparing for a Visit
Inspections are booked by phone or online portal, normally with at least one clear working day's notice. Your builder usually makes the booking as part of the programme.
- Keep the approved plans, structural calculations and product certificates on site.
- Make sure the area to be inspected is safe, clear and accessible.
- Ask your builder to confirm each booking to you by message so you have a record.
- Do not let the next trade cover up work until sign-off is confirmed.
What Happens if Something Fails
A failed inspection is common and not a disaster. The inspector explains what does not comply and what needs to change. Work in that area pauses until it is corrected and re-checked.
If a disagreement cannot be resolved on site, you can ask for the point to be confirmed in writing and, if necessary, request a determination from the relevant authority.
Getting Your Completion Certificate
At the end of the project the inspector carries out a final visit. They will want to see the finished work plus supporting evidence such as electrical certificates, gas safety records, air tightness or ventilation test results, and any Competent Person Scheme notifications.
Once satisfied, they issue a completion certificate. Store it with the rest of your project records — you will need it when you remortgage, insure or sell the property.
Common Mistakes
Warning · Common mistake
Assuming the Builder Has Booked Everything
Ask for the inspection schedule at the start and tick stages off yourself as they are signed.
Warning · Common mistake
Covering Up Work Before Sign-Off
Backfilled drainage or poured concrete may have to be exposed again — at your cost if the contract puts the duty on you.
Warning · Common mistake
Confusing Building Control With Snagging
The inspector checks regulation compliance only. Finish quality, decoration and tidiness are between you and the builder.
Warning · Common mistake
Losing the Paperwork
Electrical and gas certificates issued to the builder often never reach the homeowner. Ask for copies as they are produced.
Warning · Common mistake
Never Requesting the Completion Certificate
Many projects are finished but never formally signed off, which surfaces as a problem years later during a sale.
Before You Start Checklist
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Frequently asked questions
Ask Mason
Ask Mason about working with a building inspector
Not sure which inspections your project needs or when to book them?
Tell Mason:
- What work you are having done and roughly when it starts.
- Whether you applied via Full Plans or a Building Notice.
- Whether new foundations, drainage or structural beams are involved.
- Which trades are self-certifying under a Competent Person Scheme.
- How your contract allocates responsibility for booking inspections.
Mason can outline the likely inspection stages, what to have ready for each and which BuildGuide guides to read next.
Mason cannot replace formal advice or decisions from your building control body.
Disclaimer
This guide provides general information for homeowners in England and Wales. Inspection stages and procedures vary between building control bodies and depend on the specific project and legislation in force at the time. Always confirm the requirements for your project with your building control body before starting work.