Several BRE publications deal with corroding wall ties, covering the history, recognition and assessment of damage and the replacement of damaged ties in existing construction.
This Digest discusses how to investigate the problem, sampling to determine condition and zinc loss of corroded ties, classification of the corrosion level and how to calculate the remaining life of the ties. A table lists recommended actions on the basis of tie condition.
Options for the density and lay-out of remedial ties and the choice of a remedial tie system are then discussed. Finally, site workmanship and quality assurance for the installation of replacement wall ties are covered.
Appendix A gives the assumptions used to calculate the remaining life of galvanized mild steel ties. Appendix B covers the effective contribution of poorly installed wall ties, with graphs of tensile resistance and compressive resistance as functions of embedment depth, cavity width and cement content of mortar. 12 pages.
See IP13/90 for illustrations of cracking caused by wall tie failure. See Digest 329 (DG329) and IP12/90 for action in response to damage such as cracking.