Wall‐tie corrosion or sulphate attack: some aspects of diagnosis

A number of local authority‐built properties in the Aberdeen area were found to display evidence of horizontal cracking. An investigation carried out on one of these properties suggested that this damage resulted from sulphate attack of the mortar joints and it was assumed that this was the cause of damage in similar properties at the same location. However, this paper argues that wall‐tie corrosion is a more probable cause of the damage evident in these properties. It is suggested that the only effective and reliable method to establish an incidence of cavity wall‐tie corrosion is to carry out a direct inspection through the removal of a sample of ties.