The overall aim of this Good Building Guide is to give practical advice and guidance on the successful installation of radon-protective measures in new domestic extensions and conservatories with solid concrete ground floors. The guide will also help house owners and builders in radon-affected areas to assess whether protection is needed for a new extension or conservatory and to determine the level of protection that is required. It should be read in conjunction with BRE Report BR 211,  Radon: guidance on protective measures for new buildings. This Good Building Guide replaces the guidance published in 2008. Two companion Good Building Guides cover radon-protective measures for new dwellings and new large buildings (eg workplaces).