This guide gives advice on the possible causes of failed rendering and suggests what remedial action to take. Aimed at building surveyors, contractors and site supervisors. Use GBG 23 for advice on the systematic inspection of failed external rendering and the underlying structures, and for guidance on whether to repair or replace. Use this guide (GBG 24) to identify the defects and to help you decide on the appropriate repair, and GBG 18 for choosing the render. 8 pages.