‘A Stitch in Time – Guidance Notes in Maintaining your Place of Worship’
Guidance Note 4 – External Masonry
Our fore bearers used natural materials to build traditional structures that worked in harmony with their environment. Because stone and early brick buildings used lime mortars in their construction they were able to breath to control moisture and move to manage expansion and contraction of structures.
Massive masonry walls were needed to construct large buildings such as churches. As well as being structural their thick stone and brick walls help to regulate internal temperature.
Repairs to historic masonry walls in recent decades have largely been carried out using cement which is hard, inflexible and unbreathing. This exacerbates salt damp and accelerates the decay of stone and brick, especially when masonry materials are naturally soft. Current practice is now to remove cement pointing and repairs from traditional masonry walls and replace it with lime mortar.
It is very common to have high level decorative stonework supported by embedded ironwork. Where pointing is not maintained and/or where movement cracking occurs and moisture is allowed to penetrate to rust the ironwork heavy stone decoration can fall with potentially dangerous consequences.
There has been a long legacy over the decades since WWII of cement used in South Australia for repairs to masonry walls.
While this guidance note points out the drawbacks in using non-traditional cement it is unrealistic to expect that all owners of historic masonry churches repaired with cement will rush to remove it in favour of lime pointing. In many cases where cement is used to point up hard bluestone its detrimental impacts may be limited.
It is important, though, to understand the tell-tale early signs of masonry deterioration where circumstances may lead to expensive future remedial repairs. If you are in any doubt contact a well-respected heritage architect who has experience in dealing with church buildings to advise on a suitable course of action.