David White-Miller
Hi Tracy The first thing you need to establish, what is the original binder..(mortar) If it is a solid wall then it will be lime mortar. In my experience problems only arise when these joints have been repointed using cement mortar. Firstly, lime mortar and cement mortar are totally incompatible, no adhesion takes place. Secondly, cement mortar inhibits moisture evaporation from the joints and I suspect this is the root of your problem. If I can be of any further assistance feel free to contact me. David
