Building control fees are the part of a building project almost nobody budgets for, because they're paid to the council rather than the builder and rarely come up in a quote conversation. For an ordinary single-storey extension, loft conversion or garage conversion in 2026, expect somewhere in the region of £300–£950, depending on your council and whether you go the full plans or building notice route. A new-build house runs £1,600–£2,300 or more. Where work has already been done with no building control involvement at all, regularising it retrospectively typically costs £1,000–£2,500 or more — sometimes several times the standard fee.
This isn't planning permission, and the two get confused constantly. Planning permission is about whether you're allowed to build something in principle — height, footprint, impact on neighbours. Building control is about whether what actually gets built is structurally sound, fire-safe, adequately insulated and properly drained, checked either by your local authority's own building control team or by a private Registered Building Control Approver (the role that replaced "Approved Inspectors" from April 2024). You can have planning permission and still be in breach of building regulations, and vice versa.
I see the consequences of this more than the fee itself. During a building survey, an extension, loft conversion or rewire with no paper trail of building control sign-off is one of the most common things I flag — not because the work is necessarily bad, but because nobody's checked it, and that uncertainty is exactly what a buyer's solicitor and lender will want resolved before they'll proceed.
The short answer
Figures below were checked on 24 September 2026 against published 2026 fee schedules from Coventry City Council and the Royal Borough of Windsor and Maidenhead, cross-referenced against PlanningScout's aggregated 2026 UK fee guide and a third council example (Ashford Borough Council, via a UK building-control cost guide). Council fees for identical projects vary hugely — Coventry charges £325 for full plans on a small extension where another authority might charge three times that — so treat these as a realistic range to budget against, not a fixed national tariff, and check your own council's published schedule before committing to a figure.
| Route | Typical cost (2026) | What's included |
|---|---|---|
| Full plans (extension, loft, garage conversion) | £300–£800 | Detailed drawings checked before work starts, plus site inspections as it's built |
| Building notice (same projects) | £350–£950 | Work can start 48 hours after submission; no upfront drawing check |
| New-build house | £1,600–£2,300+ | Scales with floor area; almost always full plans, sometimes £5,000+ on larger schemes |
| Regularisation (retrospective, work already done) | £1,000–£2,500+ | Confirms already-completed unauthorised work is compliant; no guarantee it's granted |
A useful detail buried in most councils' fee schedules: regularisation charges are VAT-exempt, where full plans and building notice fees carry 20% VAT, which softens the premium slightly without changing the overall picture — regularising is still the most expensive of the three routes, by design.
What drives the price
Project type and floor area. Fees are banded by construction value and, for extensions, by floor area — a single-storey extension under 40m² sits at the bottom of most schedules, with the charge stepping up at 40m² and again at 60m² and beyond. A loft or garage conversion with no increase in footprint is usually priced closer to the smallest extension band.
Which council you're in. This is the single biggest swing factor, and it's not subtle — the same small extension can be £325 in one authority's schedule and £800–£950 in another's. There's no national tariff; each local authority sets and publishes its own charges, usually reviewed every April.
Full plans vs building notice. In some councils' schedules a building notice costs more than full plans for the identical project, on the logic that the authority is taking on more risk without having seen drawings in advance; in others the reverse is true. Don't assume either route is automatically cheaper — check your own council's published figures for both before choosing.
Local authority vs private building control. Since the Building Safety Act 2022 replaced the old "Approved Inspector" system with Registered Building Control Approvers (RBCAs) from April 2024, homeowners doing ordinary domestic work still have a genuine choice between their council's building control team and a private RBCA. Private providers can sometimes turn plan-checking around faster; fees are broadly comparable, and either route ends in the same legal building regulations completion certificate.
Competent person self-certification. Some work never touches a council building control fee at all. Replacement windows fitted by a FENSA- or CERTASS-registered installer, and electrical or heating work by a Gas Safe, NICEIC or NAPIT registered competent-person-scheme installer, are self-certified by the installer and notified to the council electronically, for a much smaller fee bundled into the installer's own price. Worth checking before assuming a straightforward job needs a separate building control application at all.
The regularisation trap — when the work's already done
Regularisation exists for exactly the situation I flag most often on a building survey: an extension, loft conversion or new heating installation with no evidence any building control body was ever involved. Under regulation 18 of the Building Regulations 2010, the owner applies to the local authority in writing, describing the work and, where reasonably possible, providing plans of what was done. The council can require the work to be laid open for inspection — lifting flooring, opening up a ceiling void, exposing a foundation — because unlike an in-progress build, there's nothing to check except what's already hidden behind finished surfaces. If they're satisfied it complies, they issue a regularisation certificate; if not, you're paying for remedial work on top of the fee, with no guarantee of a certificate at the end of it.
That intrusiveness is exactly why regularisation costs more than doing it properly the first time — in Coventry's 2026 schedule, regularising a small extension or loft conversion costs £1,125 against £325 for the equivalent full plans application; in Ashford's, the premium is a comparatively modest 25% over its standard full plans fee. The variation between councils is genuinely that wide, which is itself worth knowing before you assume a figure from one source applies to your own authority.
The point people get wrong most often is thinking that once a year or two has passed without a knock on the door, the work is safe. It isn't, and the rules changed under you. Before 1 October 2023, a council's power under section 36 of the Building Act 1984 to require non-compliant work to be altered or removed expired 12 months after the work was completed — plenty of older advice online still quotes that figure. The Building Safety Act 2022 extended it to 10 years. An extension finished in 2023 with no paperwork is very much still within reach of enforcement action today, and a regularisation certificate obtained now is a genuinely useful piece of evidence if that ever gets tested, since it's evidence of compliance (though not conclusive evidence) rather than silence.
Indemnity insurance is the other route a conveyancer sometimes suggests instead, and it's worth understanding the difference: it's a one-off policy, typically bought by the seller, that pays out toward the cost of enforcement action if the council ever takes it — it says nothing about whether the work is actually safe, and it stops being available the moment the council already knows about the work. Regularisation costs more up front but answers the actual question a buyer, lender or you yourself should want answered.
What I'd watch for
- A completion certificate at the end, not just a start acknowledgement. The fee buys inspections through the build and a certificate at completion — chase the certificate specifically once the work's finished, since it's the document a future buyer's solicitor will ask for.
- Whether your builder or installer is actually notifying building control, or assuming you have. This is a surprisingly common gap on smaller jobs — confirm in writing who's making the application before work starts, not after.
- A fixed quote that names the route (full plans, building notice, or a competent-person scheme) rather than a vague "building regs sorted" line item.
- Whether a lapsed application needs reviving. A full plans approval or building notice that's gone quiet for years because the project stalled may need re-submitting rather than simply resuming — check with the council rather than assuming an old approval still covers work restarted now.
- Don't let one alarming figure from a single source set your budget. Given how much council fees vary, get the actual published schedule for your own authority before you commit to a number from a generic guide, including this one.
Questions I get asked
How much are building control fees in 2026? For an ordinary extension, loft conversion or garage conversion, expect £300–£950 depending on the council and route. A new-build house runs £1,600–£2,300 or more. Regularising work with no prior sign-off typically costs £1,000–£2,500 or more.
What's the difference between full plans and a building notice? Full plans means the council checks detailed drawings before work starts, typically taking five to eight weeks, with problems caught on paper. A building notice lets work start 48 hours after submission with no upfront drawing check, and the same site inspections happen as the job progresses. Full plans gives more certainty before you commit; a building notice is faster but carries more risk if something doesn't comply once built.
Can building control still take action years after the work was done? Yes — and this changed in 2023. Before 1 October 2023, a council's power to require non-compliant work altered or removed expired 12 months after completion. The Building Safety Act 2022 extended that to 10 years, so work finished several years ago without sign-off isn't automatically safe from enforcement.
Why does a missing completion certificate stop a house sale? A buyer's solicitor will ask for completion certificates covering any extension, loft conversion, rewire or new heating system, and most lenders won't lend against a property with unauthorised structural work outstanding. Without one, the usual routes are a retrospective regularisation application, or indemnity insurance, which only covers the cost of enforcement rather than confirming the work is actually safe.
If a survey or a sale has turned up an extension, loft conversion or rewire with no building control paper trail, that's exactly the kind of thing my building survey work flags before it becomes a problem at exchange — and where a loft conversion or single-storey extension you're planning needs a fee estimate specific to your council and project, I can point you at the right schedule rather than let a generic figure set your budget. Call 07946 618203 or get in touch and I'll give you a straight answer before you spend the money.
Small print. This guide is general information, not advice on a specific property, and it doesn’t replace checking your own council's published building control fee schedule. Prices were researched and correct to the best of my knowledge on 24 September 2026; costs move and vary by region, council and property. Always confirm the current fee with your local authority or Registered Building Control Approver before committing to a project.