What Is CGI in House Extension Planning?

What is CGI in house extension planning? CGI stands for computer-generated imagery. In the context of a house extension planning application, it means a photorealistic 3D image produced from your architect's drawings and submitted alongside the standard drawing pack to show the local planning authority how the finished extension will look once built.

UK councils accept CGI within Design and Access Statements and public consultation packs. For sensitive sites, such as conservation areas or near listed buildings, officers may request a verified view: a CGI composited precisely onto a surveyed photograph with a matched camera position and lens parameters, so the scale and location of the proposal are evidentially accurate. Historic England and many London boroughs publish specific verified-view guidance that the visualisation studio must follow.

For standard planning application visualisation under Schedule 2, Class A of the General Permitted Development Order, a clear exterior CGI from one or two agreed viewpoints is usually sufficient. The image must match the drawings submitted with the application. Any discrepancy between the CGI and the drawings can be raised as a grounds of objection or called out on appeal, so accuracy matters more than flattery.

CGI for planning differs from marketing imagery in one important respect. Planning images are evidential documents. The studio must be able to demonstrate that the 3D model matches the architectural drawings exactly, including ridge heights, eaves levels, window positions, and materials. A well-prepared CGI that clearly shows the design in context, with accurate shadows and surrounding streetscape, reduces officer queries and supports a faster determination. Most householder applications are determined within eight weeks of validation.

For residential extension visualisation projects, VisuArchitect works from your architect's PDF drawings and returns images in five to ten working days.