 Click on photo above for a larger view. Why did the natural stone units and joints continue to crack within this beautiful heritage building’s masonry - even though several attempts were made to repair them over decades using conventional crack repair and repointing materials and practices? · Well, the first clue is that the cracks are predominantly located close to window openings. · The second clue is that the window lintels and sills do not project beyond the jambs - thereby concentrating gravity loads from natural movement, wind, snow loadings, etc., at the jambs, rather than distribute them into the adjacent mass of masonry. |  Click on photo above for a larger view. |
| 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. |  Click on photo above for a larger view. |
This and other restoration techniques are included in
CONSERVATION OF HERITAGE MASONRY
Canadian Project Case Studies
CONSERVATION OF HERITAGE MASONRY
Canadian Project Case Studies
