These four Good Repair Guides give practical advice and guidance on the successful installation of radon-protective measures in new domestic extensions and conservatories with concrete floors, new dwellings and large buildings, and explains why it is necessary. They will help building owners in radon-affected areas to determine whether protection is needed and the level of protection required. These Good Building Guides should be read in conjunction with the guidance in BRE Report BR 211 (2007) 'Radon: guidance on protective measures for new buildings'.