We repair historical lime mortar chimneys. Lime is still being used as a mix in mortar even today. However, it is mixed with portland cement, giving it far greater strength and longevity. Chimneys built in the eighteen hundreds typically were constructed with mortar made just of lime. It was before portland cement was invented. The problem is when prolonged moisture penetrates lime mortar it loses its strength. It slowly turns into a dusty sandy mix that builds up behind the