Standard house Extension Fees (Updated Apr 2025)

Planning approval drawings / full scheme drawings £750+VAT

Based upon a typical 1-2 storey house extension / attic conversion including paper copies, OS maps, all initial on-site surveys and pre-start meetings. 

This includes a draft copy of your proposed extension to make sure we have interpreted what you want correctly before completing the final design stage. Initial plans drawn up typically within 2 weeks

If the proposed works require a submittal for planning approval, a fee is then payable to the planning authority upon application, and this currently stands at £613 (including the planning portal admin fee)

‘Permitted Development’ Planning fee is £349 (including the planning portal admin fee).  

‘Prior notification of a larger homes extension’ – Planning fee is £325 (including the planning portal admin fee)

Extended Design LTD charge £75+VAT to carry out these submittals on your behalf

Building regulations drawings/calculations £750+VAT (following on from the planning / scheme drawings)

This includes all required structural design calculations carried out to the latest regulations (steel beams, standard foundation design, ground floor slab design, roof truss layout, floor joists, purlins etc)

Please note - changes in the scheme due to unforeseen circumstances, specialist foundations or revised layouts could be subject to additional fees

A fee is also payable Building Control upon application, and this varies upon the size of the proposed works, but typically around £250-350 for simple steel beam approvals and £450-900 for full house extension / loft conversion approvals. Building control will issue a separate invoice to cover the site inspections, and approvals directly.

Building Control approvals can be carried out by either Local Authority or private companies ‘Approved Inspectors’.

If the proposed works require SAP calculations (Heat loss calculations) due to excessive glazing, this would incur an additional fee typically between around £250+VAT subject to the project requirements. These calculations will be carried out by a specialist company on your behalf.

Extended Design Limited carry out all of the paperwork. All you are required to do is make the appropriate cheques payable to the relevant local authorities, we do the rest
 
Invoices are not issued until the appropriate work has been completed and is ready for submittal to the local authorities

Extended Design Limited is a VAT registered company (All prices subject to revision)

Extended Design LTD carry full Professional & Public Indemnity insurance and satisfy the HSE Competency Standards (PAS 8671) to act as Principal Designer as set out in the new 2023 Building regulations standards (Building Safety Act - (Excluding High Risk Buildings)