How Much Does It Cost to Have Plans Drawn for a House Extension?

How much does it cost to have plans drawn for a house extension? Architectural drawing costs for a UK house extension depend on the complexity of the scheme and whether you need planning drawings only, or a full set through to building regulations and contract administration.

For a straightforward single-storey rear extension, planning drawings from an architectural technologist typically cost £1,200 to £2,000. This covers the survey, design development, drawing production, and submission to the local planning authority. A more complex two-storey or side-return extension, or one in a conservation area, runs from £1,800 to £3,500 for planning drawings alone.

If you appoint an RIBA-chartered architect who also manages the project through RIBA Stages 2 to 5, total fees including design, planning, building regulations, and contract administration typically represent 10 to 15 percent of the build cost. A £60,000 extension would therefore carry architect fees of £6,000 to £9,000 for a full service. A drawings-only service from an architectural technologist costs less but transfers more project management responsibility to the homeowner.

Adding a CGI to your planning application is a separate cost, typically £350 to £600 for a single exterior image of a standard single-storey scheme. This is usually worthwhile because a CGI reduces the likelihood of officer queries about materials or massing, which can add weeks to the determination period.

For loft conversion projects running alongside an extension scheme, architectural fees are typically combined into a single brief, which is more cost-effective than commissioning each element separately. Many homeowners combine an extension and loft conversion into a single planning application to save on both architect and planning application fees.