Q. I have been told that Black Ash mortar is very bad for wall ties. What is Black Ash Mortar?

Submitted by: SF - Blackburn
 

A. As its name implies Black Ash mortar contains a large amount of ash and as a consequence it is black in colour. During the late 1800’s and early 1900’s parts of the country had a high density of large coal fired boilers generating steam power for factories. As a consequence large quantities of ash were produced and a way of using this by product was to mix it in with the mortar used to build walls. Unfortunately coal ash contains a large amount of sulphur and when it becomes damp a mild form of sulphuric acid is formed which is very corrosive. Therefore any wall ties embedded in Black Ash mortar have a significantly increased chance of being corroded.