Under existing Permitted Development (we’ll refer to it as PD from here on out) rules, any materials used for the exterior of an extension need to be of a similar appearance to those of the original house (this doesn’t apply to conservatories), so if you want to have a cedar-clad loft dormer, for example, you’ll probably need to submit a full planning application.

This doesn’t mean, however, that you can’t be adventurous with the overall appearance of your extension – a brick-built addition or rendered design that matches the original house can be combined with frameless roof lights and full-height sliding, pivot or bi-folding doors to create a modern look.