# Building Control Fees for an Extension in London (2026) > Council building control on a London extension under 40 m² costs about £700–£920 ex VAT in 2026. Wandsworth, Richmond, Lambeth, H&F and Merton compared. Author: Ben Murrell, Homeowners Project Manager · Published: 2026-10-06 · Category: Planning · Areas: Wandsworth, Richmond, Fulham, Wimbledon, Clapham Canonical: https://www.homeownersprojectmanager.co.uk/blog/building-control-fees-extension-london Planning permission gets all the attention, but every extension and loft conversion also needs Building Regulations approval, and that comes with its own fee. It is rarely a big number next to the build, yet it is one of the costs people most often leave out of their budget, partly because each council sets its own charges and publishes them in a different place. I have gone through the current building control charges for the boroughs I work in most, so you can see what an extension or loft is likely to cost to sign off, what pushes the fee up, and when a cheaper-looking route is a false economy. --- ## Building control is separate from planning Planning decides whether you can build something. Building Regulations decide how it must be built: structure, fire safety, insulation, drainage, ventilation, stairs and electrics. A permitted development extension with no planning application still needs Building Regulations approval. If you are not sure which planning route applies, start with the [planning permission checker](https://www.homeownersprojectmanager.co.uk/resources/planning-permission-checker-london). You can use the council's building control service or a private registered building control approver. Either way, GOV.UK sets out three ways in: - **Full plans.** Drawings are checked before work starts. GOV.UK says to expect a decision within 5 weeks, or 2 months with your consent, and a completion certificate usually within 8 weeks of the work finishing, as long as it complies. - **Building notice.** For smaller projects. You can start 2 days after giving notice, but there is no formal approval of plans. - **Regularisation.** Retrospective approval for work already done without consent. Only the council can grant it, and only for work carried out after 11 November 1985. --- ## What London councils charge in 2026 These are the standard charges for one extension or one loft conversion on a single house, taken from each council's own published schedule. Figures are ex VAT, with the VAT-inclusive figure in brackets. - **Wandsworth** (charges from 1 April 2026): extension up to 40 m² £920 (£1,104); extension 40–60 m² £1,177 (£1,412.40); loft up to 40 m² £903 (£1,083.60). - **Richmond** (charges from 1 April 2026): extension up to 40 m² £890.83 (£1,069); extension 40–60 m² £1,127.50 (£1,353); loft up to 40 m² £875 (£1,050). - **Lambeth** (2024–25 guide): single-storey extension up to 40 m² £830.98 (£997.18); 40–60 m² £1,056 (£1,268); two-storey extension up to 40 m² £986 (£1,183.09); loft up to 40 m² £864 (£1,037). - **Hammersmith & Fulham** (charges from 1 August 2023): extension or loft under 40 m² £750 (£900); 40–60 m² £950 (£1,140). - **Merton** (current web page): extension of 10–40 m² £700 (£840); extension over 40 m² £820 (£984); loft up to 40 m² £680 (£816). A few notes on reading these figures: - **Merton** publishes VAT-inclusive prices on its web page, so the ex VAT figures are mine, divided by 1.2. - **Lambeth** and **Hammersmith & Fulham** still publish older schedules: Lambeth's [2024–25 guide](https://www.lambeth.gov.uk/sites/default/files/2024-04/Building%20Control%20Guide%20to%20Fees%202024-2025.pdf) (charges from 1 April 2024 "until further notice") and Hammersmith & Fulham's [schedule effective 1 August 2023](https://www.lbhf.gov.uk/sites/default/files/section_attachments/building_control_fees_schedule_010823.pdf). The figures above still match those documents, checked on 12 November 2026. Check each council's current schedule before you budget: [Lambeth building regulation charges](https://www.lambeth.gov.uk/planning-building-control/building-control-regulations/building-regulations/building-regulation-application-charges) and [Hammersmith & Fulham building control](https://www.lbhf.gov.uk/building-control). - **Kensington & Chelsea** does not publish a schedule. It quotes each project; you can contact building control on 020 7361 3838. - On a full plans application the total is split into a plan charge, paid when you submit, and an inspection charge, invoiced later. In Wandsworth, Richmond and Lambeth the full plans total and the building notice charge are the same, so the cheaper-looking route is not actually cheaper. So for a typical single-storey kitchen extension under 40 m², council building control in these boroughs costs roughly £700 to £920 ex VAT, or £840 to £1,104 with VAT. A loft under 40 m² is £680 to £903 ex VAT. --- ## What pushes the fee up The standard charge covers a straightforward extension or loft. Several things take you outside it: - **More than one type of work at once.** An extension plus a loft, or an extension plus internal structural alterations, is often assessed individually rather than added up from the table. Wandsworth says so in its schedule. - **Wide structural openings.** Wandsworth's extension charge includes an opening into the extension up to 1.5 m wide. Wider openings, which most kitchen extensions have, may attract an extra charge. - **Larger projects.** Wandsworth and Richmond price work over £100,000 individually. Lambeth and Hammersmith & Fulham price extensions and lofts over 60 m² individually. Merton's cost-based table stops at £80,000. - **Basements.** Hammersmith & Fulham quotes basements by email. Lambeth's guide lists a basement extension up to 60 m² at £1,536 ex VAT (£1,844). - **Electrics.** If your electrician cannot self-certify through a government-authorised competent person scheme, the council has to inspect the wiring. Wandsworth charges £512 ex VAT (£614.40) per dwelling for that. None of this is a reason to avoid building control. It is a reason to ask for a fee quote early, so the number in your budget is the real one. --- ## Regularisation costs more, and it can cost a lot more than the fee If work has been done without approval, regularisation is the way to put it right, and every council charges a premium: - **Richmond:** 120% of the building notice charge. - **Lambeth:** 130% of the full plans or building notice charge, with no VAT. - **Wandsworth, Hammersmith & Fulham and Merton:** the same as the VAT-inclusive charge, but with no VAT added on top. The fee is the small part. To prove that hidden work complies, the inspector may ask for floors to be lifted, plaster to be opened up or foundations to be exposed. A missing completion certificate is also one of the things a buyer's solicitor asks about when you sell. Get approval before you build. --- ## Council or private approver? A private registered building control approver can do the same job instead of the council. Their fees are agreed directly with you, not published in a schedule, so I have not found a reliable London figure to quote here. Ask for a written fee proposal that says exactly how many inspections are included, and compare it with the council's published charge. My own view: the choice matters less than having someone make sure the inspections actually happen. Building control inspects at key stages, such as foundations, drainage, structure and insulation, but only if the builder calls them in at the right moment. A missed foundation inspection is expensive to fix once the slab is poured. --- ## Full plans or building notice? For anything structural, I recommend full plans. The engineer's calculations and the drawings are checked before work starts, so problems are found on paper rather than on site. A building notice lets you start sooner, but if the inspector does not accept something once it is built, it has to be changed. Full plans also fit neatly into the programme. The 5-week decision usually runs alongside the tender, so it rarely delays the start. You can see how it sits with planning and the party wall notices in the [extension and loft timeline calculator](https://www.homeownersprojectmanager.co.uk/resources/extension-loft-timeline-calculator-london). --- ## Putting it in your budget Building control is one of several professional and statutory fees that sit outside the builder's price, along with drawings, planning, the structural engineer and the party wall surveyor. The [renovation fees calculator](https://www.homeownersprojectmanager.co.uk/resources/renovation-fees-calculator-london) puts them side by side, and the [extension cost calculator](https://www.homeownersprojectmanager.co.uk/resources/extension-cost-calculator-london) gives the build cost. My own fee, if you want help running the build, is set out in [what a project manager costs](https://www.homeownersprojectmanager.co.uk/project-manager-cost): 10–12% of the project cost, with a worked example. On my projects, I check the building control application is in place before work starts, chase the inspections at the right stages, and make sure the completion certificate is issued before the final payment to the builder is released. If you would like help with yours, I work across [Wandsworth](https://www.homeownersprojectmanager.co.uk/areas/wandsworth), [Fulham](https://www.homeownersprojectmanager.co.uk/areas/fulham), [Richmond](https://www.homeownersprojectmanager.co.uk/areas/richmond), [Wimbledon](https://www.homeownersprojectmanager.co.uk/areas/wimbledon), [Clapham](https://www.homeownersprojectmanager.co.uk/areas/clapham) and the rest of West and South West London. Local notes for [Earl's Court](https://www.homeownersprojectmanager.co.uk/areas/earls-court), [Balham](https://www.homeownersprojectmanager.co.uk/areas/balham), [Earlsfield](https://www.homeownersprojectmanager.co.uk/areas/earlsfield) and [East Sheen](https://www.homeownersprojectmanager.co.uk/areas/east-sheen) are on those area pages; homeowners in Barnes are covered on the [Richmond](https://www.homeownersprojectmanager.co.uk/areas/richmond) page. [Send me a message](https://www.homeownersprojectmanager.co.uk/contact) or call [07525 474 849](tel:07525474849). *General guidance. Figures re-checked against the councils' published schedules on 12 November 2026. Councils update their charges, usually from April. Check the current schedule with your council before you budget.* --- ## Sources - [Wandsworth Council: building control fees 2026](https://www.wandsworth.gov.uk/media/1brpqb2b/building_control_fees_2026.pdf) - [Richmond Council: building control fees 2026](https://www.richmond.gov.uk/media/5osbtttg/building_control_fees_2026.pdf) - [Lambeth Council: building control guide to fees 2024–2025](https://www.lambeth.gov.uk/sites/default/files/2024-04/Building%20Control%20Guide%20to%20Fees%202024-2025.pdf) - [Hammersmith & Fulham Council: building control fees schedule, August 2023](https://www.lbhf.gov.uk/sites/default/files/section_attachments/building_control_fees_schedule_010823.pdf) - [Merton Council: building control charges](https://www.merton.gov.uk/planning-and-buildings/building-control/building-control-charges) - [GOV.UK: building regulations approval, how to apply](https://www.gov.uk/building-regulations-approval/how-to-apply) - [GOV.UK: competent person schemes](https://www.gov.uk/guidance/competent-person-scheme-current-schemes-and-how-schemes-are-authorised) --- ## Common questions **How much are building control fees for an extension in London?** For a single-storey extension under 40 m², the councils I have checked charge between £700 and £920 ex VAT (£840 to £1,104 with VAT). Extensions of 40 to 60 m² are roughly £820 to £1,177 ex VAT. Kensington & Chelsea quotes each project. **Do I need building regulations approval if my extension is permitted development?** Yes. Permitted development only removes the need for a planning application. The extension still has to meet Building Regulations, and you need approval from the council or a registered building control approver. **Is a building notice cheaper than a full plans application?** Not in Wandsworth, Richmond or Lambeth, where the totals are the same. A full plans application splits the charge into a plan fee and an inspection fee, and gives you approved drawings before work starts. **How long does building control approval take?** GOV.UK says a full plans decision should come within 5 weeks, or 2 months if you agree to an extension. Under a building notice you can start 2 days after giving notice. The completion certificate usually follows within 8 weeks of the work finishing. **What happens if work was done without building control approval?** You can apply to the council for regularisation, which costs more than a normal application: 120% of the building notice charge in Richmond and 130% in Lambeth. Only work carried out after 11 November 1985 can be regularised, and you may have to open up or change the work. **Who books the building control inspections?** Usually the builder, at stages the inspector sets out, such as foundations, drainage and structure. It is worth agreeing in the contract who is responsible, because a missed inspection can mean opening up finished work. --- Homeowners Project Manager — independent client-side project management for homeowners in South West London. Contact: 07525 474 849 · https://www.homeownersprojectmanager.co.uk/contact