What fees does a home extension carry besides the build?

Statutory fees in England from 1 April 2026

These are the 2025 fees increased by 3.8%, the CPI figure for September 2025, under the annual indexation added to the fee regulations in 2023. A draft amendment laid in 2026 (ISBN 978-0-348-28662-5) proposes a householder fee of £575 from 8 December 2026. It is a draft and has not been made. Decision periods and the other planning fees are in planning fees and timescales.

Building control

A local authority's charges come from its own charging scheme, based on the cost of providing the service. The scheme must state the hourly rate used. A registered building control approver quotes its own fee instead; the choice between the two is explained in council building control or a registered approver.

A local authority shall determine the charges referred to in their charging scheme by reference to the costs of providing services in relation to particular building work or building work of particular descriptions, having regard in doing so to the overriding objective in regulation 6(3).

Regulation 4 of the same Regulations says a council must not charge where the whole of the work is solely to provide access or facilities for a disabled person living in the home, within the terms it sets out.

Professional fees, with the published figures

No regulation sets these. The figures below are national published figures from the sources named, not Parallel's, and they are dated because they move.

What sits inside a design fee varies more than the percentage does. Check which stages are included (survey, concept, planning, technical design, tender, work on site), whether the fee covers the planning application only or the Building Regulations drawings as well, and what happens to the fee if the scope changes. The stages are set out in design appointment stages. Who does each job is in who you need to design an extension.

Fees that depend on the site

• Party wall surveyors. If the works fall within the Party Wall etc. Act 1996, surveyors' costs are decided in the award. See party wall surveyor costs.
• Principal designer roles. On a project with more than one contractor, a principal designer is needed under the CDM Regulations 2015 and under Part 2A of the Building Regulations 2010. The two roles are explained in the Building Regulations and CDM principal designer.
• Community Infrastructure Levy. An extension that adds less than 100 m2 and creates no new dwelling is not liable at all. Larger ones can usually be exempted, but only if the claim is made in time.

Liability to CIL does not arise in respect of a development if, on completion of that development, the gross internal area of new build on the relevant land will be less than 100 square metres.

Above 100 square metres, the residential extension exemption in regulation 42A has to be claimed before work starts. See CIL on an extension.

VAT on fees

Professional services are standard-rated. HMRC's VAT Notice 708 says so at paragraph 3.4.1 for new dwellings, and repeats it at paragraphs 7.6 and 8.4 for the reduced-rate conversion and empty-home cases. So a design or engineering fee carries VAT at 20% where the consultant is VAT registered, even when the building work itself is zero-rated. More in VAT on building work.

What this means for you

Budget for fees as a separate line in the cost plan, not inside the build figure. Get the statutory fees from the source on the day you apply, and ask each consultant for a written scope with the stages, the exclusions and what triggers an extra fee.

ClearCDM, the practice's separate principal designer service, publishes its fixed fees at clearcdm.co.uk/fees.