The drawings are only part of the cost of getting an extension approved. Before a builder starts, most homeowners pay for drawings, structural calculations, a planning fee and building control, and some also pay for a party wall surveyor.
The Costs at a Glance
| Cost | Who sets it | Typical amount |
|---|---|---|
| Planning drawings | Your designer | From £650 with us (single-storey) |
| Building Regulations drawings | Your designer | From £850 with us (single-storey) |
| Structural calculations | Your engineer | From £395 with us (single-storey) |
| Householder planning application | National fee | £548 in England since 1 April 2026 |
| Larger home extension prior approval | National fee | £249 in England since 1 April 2026 |
| Building control | Your building control body | Varies: ask for a written quote |
| Party wall surveyor | The surveyor | Only if needed: ask for a written quote |
Planning fees are the same across England, so a council can't charge you more than its neighbour for the same householder application. A further rise to £575 has been proposed, so check the current fee before you apply.
Worked Example: A Single-storey Extension in Birmingham
- Complete design package with structural calculations: £1,695
- Householder planning application: £548, paid to Birmingham City Council
- Known total before building control: £2,243
Add your building control charge. Birmingham City Council says its building consultancy service is now provided by Acivico, and you can also use a registered private building control approver, so compare written quotes.
Want the council's view first? Birmingham's 2026–27 schedule lists householder pre-application advice at £166.80. It's optional. If your extension is permitted development, you won't pay the planning application fee, but we still recommend a Lawful Development Certificate as proof. Ask the council for the current fee.
Costs People Forget
- Party wall: steels bearing on a shared wall usually bring the Party Wall Act into play. See party wall agreements for extensions.
- Surveys: topographical or drainage surveys, if your site needs them.
- Revisions: check what your quote allows if the planners ask for changes. Use our quote comparison checklist.
See all extension design prices, including double-storey extensions, loft and garage conversions.
Fees checked on 31 October 2026. These are the costs of design and approval only, not the cost of building the extension.