This Digest is an updated general review of the history and epidemiology of problems with metal components in walls, particularly wall ties. It also considers problems in housing and other buildings resulting from corrosion, inadequate provision or poor specification and what action can be taken, particularly in cases where the structural stability of a wall or building is threatened. Since the reinstatement is often feasible and, in some cases, may cost a fraction of the whole rebuilding cost, some methods are suggested. 8 pages. See also IP13/90, Digests 329 (DG329) and 401 (DG401), Good Repair Guide 4 (GRG4) and Good Building Guide 29 (GBG29), for other information dealing with the recognition of corrosion problems and remedial installation of wall ties, straps and fixings into existing walls.