Renovation fees calculator for London homeowners
Every professional and statutory fee on an extension, loft conversion or renovation, start to finish — drawings and planning, structural engineer, party wall, building control, choosing a builder, the JCT contract, professional input during the build and project management. Add your build cost and it itemises the fees as a low–high range.
Guide prices, London, ex VAT, 2026. Not a quote. Every range comes from a published source listed under how we worked out these figures. The project management line is HPM’s own fee guide. Build cost itself is not included — get a starting figure from the extension cost calculatoror the loft conversion cost calculator.
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Need a build cost first? Try the extension cost calculatoror the loft conversion cost calculator.
Want a straight answer on which of these your project actually needs? No fee for the first conversation.
What each fee is for
Fees arrive in roughly the order below. Most homeowners budget for the architect and the builder and discover the rest one invoice at a time. Laying them out at the start is the point of this page.
1. Architect or drawings service
Someone has to turn the idea into drawings the council, building control and builders can work from. A London architect taking a single-storey extension from brief to Building Regulations and tender drawings (RIBA stages 1–4) is published at around £4,000–£8,000, rising to £7,000–£15,000 for a two-storey extension and £12,000–£30,000 for a full-house renovation. A drawings-only service for planning and Building Regulations is cheaper — roughly £1,650–£4,500 for an extension — but usually stops at the drawings. More on the difference inarchitect fees UK & London.
2. Planning permission or a Lawful Development Certificate
The council fee is set nationally. A householder application in England is £548 (from 1 April 2026). If the work is permitted development, a Lawful Development Certificate for proposed work costs half the full fee — £274 — and proves the work was lawful when you come to sell. A larger home extension prior approval is £249. Draft regulations propose £575 for householder applications made on or after 8 December 2026.
3. Structural engineer
Steels, openings and foundations need calculations and drawings for building control. London engineers publish around £800–£3,500 for a rear or side extension package and £800–£2,500 for a loft. Appointing the engineer before builders price is one of the cheapest ways to make quotes comparable — see do I need a structural engineer for my extension?
4. Party wall surveyor
If the work falls under the Party Wall etc. Act 1996, you serve notice on each adjoining owner. If they consent, no surveyor is needed. If they dissent, an agreed surveyor acting for both sides costs around £800–£1,500 per neighbour; if each side appoints their own, you normally pay both — roughly £1,600–£2,800 per neighbour, though some surveyors quote from around £1,100–£1,500 + VAT. Read party wall agreements in South West London.
5. Building control
Council building control charges are published by each borough. For a full plans application (plan charge plus inspection charge, ex VAT) an extension up to 40m² is £920 in Wandsworth and £1,227 in Southwark; lofts are similar. Whole-house projects over £100,000 are usually priced individually, so the calculator leaves that line as “quote needed”. Private approved inspectors quote per job.
Every borough’s current charges side by side: building control fees for an extension in London.
6. Build over agreement
If the extension sits over or near a public sewer, Thames Water needs to approve it. Their published application charge is £130 for a sewer of 175mm or less and £490 for 176–350mm. A drain survey tells you whether this applies.
7. Comparing and appointing builders
Getting three quotes against the same drawings and comparing them line by line is where most budget risk is removed. Cost guides put a standalone pre-construction package at around £5,000–£7,000. HPM runs the tender as part of our project management fee, and the freebuilder quote comparison checklist is there if you are doing it yourself.
8. The JCT contract and its administration
A written contract with a variation process is non-negotiable on a six-figure job. The JCT Home Owner forms are £40–£46 plus VAT, Minor Works 2024 is £50, and the administration model forms (notices, certificates) are £20–£30. The form is the cheap part; completing and running it is professional time covered by the architect or project manager lines. SeeJCT contracts explained for homeowners.
9. Professional input during the build
Engineers typically charge per site visit — published London rates run about £200–£400 ex VAT a visit. Architects either charge hourly for occasional advice (£80–£200 an hour) or a fee for full contract administration, published at £1,500–£4,000 for an extension.
10. Project management — HPM’s fee guide
Our fee is 10% to 12% of the project cost depending on how involved you want us to be: light (10%), standard (11%) or full (12%). That covers running the tender, setting up the contract, cost control and site visits on your behalf. For comparison, Checkatrade’s published guide puts renovation project managers at 15–20% of total spend. How fees work more generally:what a renovation project manager costs.
Not in this total: the build itself, VAT on the build, a contingency (seehow much contingency to hold), kitchen and finishes, and moving out. For the whole budget, pair this with theextension & loft budget planner. Already holding a builder’s price? The overrun calculator shows where it is likely to land.
How we worked out these figures
Every range is taken from a published source, checked on 27 September 2026. We prefer London sources and statutory schedules; where a source gives a single “from” price we pair it with another published London figure rather than inventing a top end. Where two project types are combined (extension and loft together) we add the two published ranges. The whole-house architect build-stage figure is worked out from the same source’s statement that design stages are roughly 70% of the total fee. Ranges are rounded. Planning fees are statutory and exact.
- Planning Portal — Fees for Planning Applications in England (from 1 April 2026) — Householder application £548; Lawful Development Certificate (proposed) = half the full application fee; larger home extension prior approval £249.
- MHCLG (gov.uk) — Planning fees: annual indexation from 1 April 2026 — All fees uplifted by 3.8% (CPI, Sept 2025) from 1 April 2026.
- legislation.gov.uk — Explanatory Memorandum, draft Planning Fees (Amendment and Transitional Provision) Regulations 2026 — Householder fee proposed to rise from £548 to £575 for applications made on or after 8 December 2026.
- Mayfair Studio — Architect Fees London 2026 (updated Feb 2026) — Stages 1–4 by project: single-storey rear £4,000–£8,000; loft £3,500–£7,000; two-storey £7,000–£15,000; full house renovation £12,000–£30,000. Stage 5 (construction) £1,500–£4,000. Hourly £80–£200. Stages 1–4 ≈ 70% of the total fee.
- Architectural Drawings UK — fixed-fee pricing vs typical London architect — London architect column: measured building survey £350–£900; house extension (planning + regs) £1,750–£4,500; loft conversion (planning + regs) £1,750–£3,500.
- Draw & Plan (London) — house extension drawings — Planning + Building Regulations drawings from £1,650 + VAT including measured survey. 2025 per-m² estimates by extension type (rear £1,800–£2,500; wraparound £2,200–£3,200).
- SBS Structural & Architectural Design — Structural engineer cost London 2026 — Rear/side extension calculations £800–£1,800; loft conversion £800–£1,500 (complex £1,500–£2,500); full structural package £1,200–£3,000.
- EMA Structures — House extension cost London 2026 — Standard spec, ex VAT: single-storey rear £2,200–£3,400/m²; side return £2,400–£3,600/m²; two-storey £2,000–£3,000/m². Rear extension structural package £1,400–£3,500 + VAT.
- Build Team — How much does an extension cost in London? 2026 guide — London build-only, ex VAT and fees: basic £2,800–£3,200/m²; mid-range £3,200–£4,200/m²; high-end £4,200–£5,500+/m². Kitchen £15,000–£50,000+; aluminium bifolds £3,150–£7,200; roof lantern/structural rooflight £2,000–£5,000 each; structural engineer £1,500–£4,000.
- Party Wall Surveyor London — party wall cost calculator — Per adjoining owner: rear extension agreed surveyor £750–£1,100, two surveyors £1,600–£2,800; loft agreed £700–£950.
- Hourican Associates — Party wall surveyor cost London 2026 — Full party wall award service typically £1,100–£1,500 + VAT; notices £150 + VAT per adjoining owner.
- Wandsworth Council — Building Control charges from 1 April 2026 — Full plans ex VAT (plan + inspection): extension up to 40m² £368 + £552 = £920; 40–60m² £470.80 + £706.20 = £1,177; loft up to 40m² £361.20 + £541.80 = £903. Work over £100,000 individually assessed.
- Southwark Council — Building control charges 2026 to 2027 — Extensions and loft conversions, full plans ex VAT (plan + inspection): under 40m² £490.92 + £736.38 = £1,227.30; 40–60m² £589.08 + £883.62 = £1,472.70.
- Thames Water — Build over agreements — Application: Class 1 £130 (sewer ≤175mm); Class 2 £490 (176–350mm); Class 3 £585 plus legal costs from £1,000.
- Checkatrade — House renovation project manager cost — Pre-construction support package £5,000–£7,000; project rate 15–20% of total spend.
- JCT — Building Contract for a Home Owner/Occupier (HO/B) 2021 — £40.00 + VAT. HO/B 2021 Admin forms £20.00 + VAT.
- JCT — Building Contract and Consultancy Agreement for a Home Owner/Occupier (HO/C and HO/CA) 2021 — £46.00 + VAT. HO/C and HO/CA 2021 Admin forms £20.00 + VAT.
- JCT — Price List 2026 — Minor Works Building Contract (MW 2024) £50.00 hardcopy; MW and MWD 2024 Admin model forms £30.00 (On Demand).
- London Structural Surveys — services and fees — Structural engineer site visit from £200–£240 + VAT.
- Beams — Structural engineer costs UK 2026 — Published London fees: site advice visit on its own £318–£480 including VAT (≈ £265–£400 ex VAT).
HPM’s 10–12% project management fee is our own guide, not a third-party figure. Guide prices, London, ex VAT, 2026. Not a quote.
Common questions
How much are professional fees on a London extension?
For a typical single-storey extension with an architect taking the design to Building Regulations, a householder planning application, a structural engineer, one party wall award and council building control, plus a measured survey, the sourced ranges on this page add up to roughly £7,400 to £15,700 ex VAT before any build-stage input or project management — and more if you keep the architect on for the build or have neighbours on both sides. Use the calculator for your own mix, because the choices you make (architect or drawings service, agreed surveyor or two surveyors) move the total more than the size of the job does.
What is the planning application fee for a house extension in 2026?
In England the householder application fee has been £548 since 1 April 2026, set by the government and published by the Planning Portal. A Lawful Development Certificate for proposed permitted development work is half the full application fee, so £274, and a larger home extension prior approval is £249. Draft regulations propose raising the householder fee to £575 for applications made on or after 8 December 2026.
Who pays the party wall surveyor fees?
Normally the building owner — the person doing the work — pays all reasonable surveyor fees, including the neighbour’s own surveyor if they appoint one. Published London rates put an agreed surveyor acting for both sides at around £800 to £1,500 per adjoining owner, and two separate surveyors at around £1,600 to £2,800 per neighbour, with some surveyors quoting from around £1,100 to £1,500 + VAT. A mid-terrace house with work affecting both neighbours means two sets of fees.
How much does a JCT contract cost for a home extension?
The form itself is cheap: JCT sells the Home Owner contract without a consultant (HO/B) at £40 plus VAT, the Home Owner contract and consultancy agreement (HO/C) at £46 plus VAT, and the Minor Works 2024 contract at £50 plus VAT in hardcopy, with administration model forms from £20. The real cost is the professional time to complete it properly and administer it during the build, which sits in the architect or project management lines.
What does a project manager cost on a renovation?
HPM’s own fee guide is 10% to 12% of the project cost, depending on how involved you want us to be: light (10%), standard (11%) or full (12%). For context, Checkatrade’s published cost guide puts the wider market at 15% to 20% of total renovation spend. We confirm a fixed proposal against your drawings before anything is agreed.
Do I need both an architect and a project manager?
Not always. Many London homeowners appoint an architect or drawings service up to Building Regulations and tender, then use a client-side project manager for the build instead of full architect contract administration. Others keep the architect on for the build stage for design queries. The calculator lets you model either — set the architect build-stage line to none, occasional advice or full contract administration.
Cost calculators: extension cost calculator · loft conversion cost calculator · overrun calculator. Planning the budget: budget planner · who does what on a renovation · all resources.
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Phone 07525 474 849 or send your drawings and quotes. If you only need a stronger architect appointment or a better builder, that is a valid outcome.
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