WHAT IS THE SOLUTION?
Well, for new buildings, designers can ensure the lintels extend at least beyond the first vertical (head) joint adjacent to the jambs - or they can install hidden steel lintels to achieve a similar effect.
For existing buildings, lengths of stainless steel helical rods can be installed into two horizontal joints above the windows. The rods should be continuous across elevations, and located roughly at the centre of the exterior wythe, and embedded within a high strength grout. (The grouted rods perform the function of ‘transfer beams’ to distribute loads more uniformly within the masonry.) The front of the joint should then be face-pointed using a hydraulic lime-based mortar and the cracks repaired. The mortars should of course be selected to be compatible with the natural stone masonry.
CONSERVATION OF HERITAGE MASONRY
Canadian Project Case Studies