However, traditional mixes, with lime as the main binder component, are beginning to regain popularity for restoration work. Proprietary pre-mix restoration mortars, which require only the addition of water, are also available. Mortars that have a high proportion of Portland cement, typical of modern masonry, are generally not appropriate for older masonry because they are too strong and too dense. A softer mortar, with more flexibility and higher porosity, is generally recommended, as this type of mortar can accommodate minor movements in the wall. A more porous mortar also allows the wall to dry out faster should it get wet.
Poor bond leads to increased water ingress.
It is important to look at durability problems globally, and to give proper consideration to the selection of materials, design, workmanship, maintenance requirements and environmental conditions, to ensure a longer service life. Next steps Future stages of this project will include further evaluation of mortar properties, and monitoring the performance of actual buildings that have been repointed. In addition, IRC has spearheaded the formation of a working group on repointing mortars for the purpose of sharing knowledge and experience. The group, made up of designers, restoration specialists, manufacturers and researchers, meets twice a year. Those involved in the use of repointing mortar are invited to join this group.