A planning application for a house extension or alteration requires a specific set of drawings. Many homeowners are confused about the difference between planning drawings and building regulations drawings — they are entirely different documents serving different purposes. Planning drawings show what is proposed and how it relates to the surrounding context; building regulations drawings show how it is to be built. Both are necessary, but at different stages.
Drawings Required for a Planning Application
Location plan — an extract from an Ordnance Survey map (typically 1:1250 scale) showing the application site outlined in red, with north point, and any other land in the applicant's ownership outlined in blue. Required for every planning application. Available to purchase from OS-licensed mapping data suppliers (Planningmaps.co.uk, Promap) for around £20–£30.
Site plan (block plan) — a larger-scale plan (1:500) showing the site with existing and proposed extensions outlined, site boundaries, access, trees, adjacent buildings, and drainage if relevant.
Existing and proposed floor plans — scale drawings showing the layout of the property before and after the proposed work. Rooms labelled with floor area where applicable.
Existing and proposed elevations — drawings showing all external faces of the building that are affected by the proposed development, before and after. Must show ridge height, eaves height, and dimensions.
Existing and proposed sections — where the application affects the section profile of the building (e.g., a loft conversion), cross-section drawings are required.
Who Produces Planning Drawings
For simple extensions, a local architect, architectural technician, or drawing service can produce planning drawings at lower cost than a full architect. For more complex projects, or where design input is genuinely needed, an architect from RIBA (who may be involved from early concept through planning and build) is the appropriate choice.
Planning-only drawing packages for a standard rear extension typically cost £800–£2,500 from a local architectural technician, or £1,500–£4,000 from a full architectural practice.
Planning vs Building Regulations Drawings
Planning drawings focus on external appearance, massing, and context — they are relatively simple. Building regulations drawings are far more detailed: structural calculations, insulation specifications, drainage routes, beam sizes, joist schedules, stair design, fire protection, ventilation. They're prepared after planning permission is granted and are submitted separately to building control.