Replacement of old or damaged internal plasterwork is an expensive business. It can be more complicated than new work because the plaster often has to be applied to a mix of backgrounds which can sometimes be damaged or contaminated. It is one of the few parts of the job where the quality is obvious to the client - if the plasterwork is poor, he is likely to question the workmanship of the parts he cannot see. This Good Repair Guide gives guidance on common reasons for failure in plasterwork, how to prepare different background surfaces for wet replastering, and how to select a suitable plaster system for the substrate.