Building control is the system that ensures building work in England and Wales is structurally safe, energy efficient, and legally compliant with the Building Regulations 2010. It is separate from planning permission: planning decides whether something can be built; building control decides how it must be built. You can have one without the other, but most substantial projects require both.
Put simply, a Building Control Officer (BCO) — or an approved inspector — reviews your proposals before work starts, visits the site at key stages, and issues a completion certificate once everything meets the regulations. That certificate is not just administrative tidying; it is the document that proves your home is legally safe, and your solicitor will ask for it when you come to sell or remortgage.
Council Building Control vs Approved Inspectors
Since 1985, homeowners and developers in England and Wales have been able to choose between two routes: the local authority Building Control service (sometimes called the BCO or building inspector) and a private Approved Inspector (AI).
| Council Building Control | Approved Inspector | |
|---|---|---|
| Who they are | Employed by your local authority | Private firms regulated by CICAIR |
| Typical cost | Standard fee schedule, published online | Often 10–20% cheaper than council |
| Start date | Building notice: 2 days after submission. Full plans: await approval | Can often begin work sooner; more flexible scheduling |
| Drawings required | Full plans route: yes. Building notice: no | Yes — AIs always work from drawings |
| If a dispute arises | Remains with council | Automatically transferred back to the local authority |
| Completion certificate | Issued by the council | Issued by the AI, but recorded with the council |
| Best suited to | Straightforward domestic projects; homeowners who prefer a public body | Larger or complex projects; developers prioritising speed |
Approved Inspectors: the nuance
Approved Inspectors are regulated by the Construction Industry Council Approved Inspectors Register (CICAIR). They tend to offer faster turnaround and more commercial flexibility, particularly on larger schemes. However, if an AI withdraws from a project — for instance, if a dispute cannot be resolved — the work automatically reverts to the local authority, which will pick up from wherever the AI left off. This handover can cause delays, so it is worth understanding the risk before choosing the private route.
When Do You Need Building Control?
Building Regulations apply to most building work in England and Wales. The trigger is not the size of the project; it is the nature of the work.
Work that always requires building control approval
- Extensions of any size (including single-storey rear extensions, side extensions, and wrap-arounds)
- Loft conversions — including dormer, hip-to-gable, and mansard
- Garage conversions to habitable space
- Structural alterations — removing load-bearing walls, creating new openings in load-bearing walls
- New drainage connections to the sewer
- Electrical work that falls outside Part P self-certification (most notifiable domestic electrical work)
- New or replacement boiler and heating systems (unless the installer is Gas Safe registered and self-certifies under a Competent Person Scheme)
- New windows and doors unless the installer is FENSA or CERTASS registered (who self-certify under a Competent Person Scheme)
- Underpinning
- Change of use (e.g., converting a house into flats)
Work that does NOT need building control
Routine maintenance and like-for-like replacement generally falls outside the regulations:
- Replacing a tap, fitting a new kitchen (no structural work), or re-tiling a bathroom
- Redecorating, replastering, or re-rendering
- Replacing roof tiles on a like-for-like basis (not re-roofing the entire structure)
- Small outbuildings: a detached garden shed or outbuilding under 15 m² floor area with no sleeping accommodation; or under 30 m² if it is at least 1 metre from a boundary and built of non-combustible materials
If you are unsure, contact your local authority building control department. Most offer a free pre-application advice call, and getting it wrong is far more expensive than asking the question.
The Inspection Stages
Building control is not a single visit. It is a series of site inspections at critical structural and compliance milestones. The exact stages vary by project type and local authority, but a typical extension or loft conversion will involve:
- Commencement — You notify the BCO when work starts (usually 24–48 hours’ notice required). The inspector confirms work has begun and may check site welfare and access.
- Excavations — Trenches are inspected before concrete is poured, confirming depth, width, and ground conditions match the approved drawings.
- Foundations — Concrete strip or raft foundations are inspected before oversite work begins.
- DPC (Damp-Proof Course) — The damp-proof course and cavity closers are checked at low-level brickwork before the cavity is closed.
- Oversite concrete — The concrete floor slab or beam-and-block floor is inspected before screed or floor finishes are laid.
- Structural steelwork — Any steel beams (RSJs, UC sections) are inspected in position and checked against the structural engineer’s calculations before being boxed in.
- First floor / intermediate floors (on two-storey extensions or loft conversions) — Joists and temporary fire separation are checked.
- Drainage — Below-ground drainage is inspected and tested before backfilling. Above-ground soil and waste pipework is checked before concealment.
- Final / completion — The finished building is inspected in full: insulation, fire stopping, means of escape, handrails, air tightness (where required), and energy compliance documentation. If everything is in order, the BCO signs off and the completion certificate is issued.
Most domestic projects will hit six to eight of these stages. The BCO gives you a target number when you submit your application, and you are responsible for notifying them at each stage — they will not simply turn up.
Building Control Fees
Fees are set locally by each council and vary, but the figures below reflect the typical range for England in 2026. Approved inspectors quote individually, but are usually 10–20% below the council rate.
Full Plans Application
This is the standard route for most projects. You submit drawings and a structural specification; the council has 5 weeks to issue a decision (or up to 8 weeks by mutual agreement). Work can only begin once plans are approved — or conditionally approved with agreed amendments.
| Project type | Typical council fee (2026) |
|---|---|
| Single WC / shower room addition | £200–£300 |
| Small single-storey extension (up to 20 m²) | £800–£1,200 |
| Single-storey extension (20–40 m²) | £1,000–£1,500 |
| Larger extension / loft conversion | £1,200–£2,500 |
| Garage conversion | £400–£700 |
| Structural alteration (removing a wall) | £300–£600 |
Fees usually cover both the plan-check element and all site inspections up to and including the final. Some councils charge separately for each inspection stage; always read the schedule carefully before submitting.
Building Notice
The building notice route lets you start work just 2 days after submission, with no need to submit drawings for approval. The BCO inspects reactively as work proceeds. It suits simple, low-risk jobs where you are confident the work will meet the regulations and you have a competent contractor with an established relationship with local building control.
The risk: if the BCO finds non-compliant work, there is no approved plan to fall back on. You may be required to open up completed work or carry out remedial measures.
Building notice fees are broadly comparable to full plans fees and are non-refundable even if the project does not proceed.
Regularisation: Building Work Without Consent
If work was carried out without building control approval — by a previous owner or otherwise — you can apply retrospectively for a regularisation certificate. The fee is typically 1.25 times the normal full plans fee. The council will require the work to be opened up sufficiently for inspection and may require remedial works before issuing the certificate. A regularisation certificate is not identical to a completion certificate (it covers past unauthorised work rather than a supervised build), but it is the closest available equivalent and will satisfy most solicitors and mortgage lenders.
The Completion Certificate and Resale Impact
The completion certificate (sometimes called a “final certificate” or “sign-off letter”) is issued by the BCO — or the Approved Inspector — after the final inspection confirms all work meets the Building Regulations.
Why it matters
Solicitors will ask for it. When you sell a property where building work has been carried out, your solicitor’s standard pre-contract searches and enquiries will ask for evidence that building regulations approval was obtained and that work was signed off. If you cannot produce a completion certificate, the buyer’s solicitor will almost certainly raise requisitions, and the buyer’s mortgage lender may decline to lend.
Buildings insurance can be affected. An insurer who discovers that structural work was carried out without building control sign-off may decline a claim on the basis that the property’s condition was misrepresented.
It demonstrates structural safety. The completion certificate is evidence that an independent technical authority verified the structure, drainage, fire stopping, insulation, and means of escape. Buyers are increasingly aware of its significance.
What if the previous owner lost the paperwork?
Completion certificates are held on the local authority’s records indefinitely. You can request a copy from the council that originally issued it — they charge a small admin fee, typically £30–£60. If the work was never signed off, your solicitor will advise you to obtain indemnity insurance as a short-term workaround, but this is a compromise, not a resolution. Indemnity policies cover the legal risk of enforcement action; they do not certify that the structure is safe.
Timeline
Once the final inspection passes, most councils aim to issue the completion certificate within 4–8 weeks. Approved Inspectors tend to be faster. If you are approaching exchange and need the certificate urgently, contact the BCO directly — delays are usually administrative rather than technical, and a call can accelerate the process.
Finding Building Control Near You
Your first port of call is the local authority for the area where the property sits. Search “[your council name] building control” to find the department’s contact page and fee schedule. If you are considering an Approved Inspector, the CICAIR register at cicair.org.uk lists all registered firms, searchable by postcode.
For most homeowners undertaking a single project, the local council BCO is a straightforward, well-understood route. For developers managing multiple concurrent projects on a tight programme, Approved Inspectors can offer measurable advantages in speed and coordination. Either way, the quality of the inspection process — and the completion certificate at the end of it — is what counts.
