Restoration of aging masonry buildings

Esthetics

Brick masonry is seen as a desirable esthetic in both new and old buildings. The esthetics of the masonry can be both directly and indirectly impacted by the quality of installation. Directly, the quality of the installation can create negative esthetics through offset or misaligned masonry units, and varying joint sizes (this can also negatively reduce structural performance of the masonry assembly). Indirectly, the esthetic consequences can be more significant.

Spalled bricks can be an eyesore on a building façade especially for painted brick. If spalling occurs, the painted face of the brick is dislodged, thereby exposing the base colour of the brick unit. This makes the spalling more noticeable and the esthetic consequences more pronounced (Figure 10).

Efflorescence is an indirect consequence of the performance of the brick masonry wall. Efflorescence occurs when the salts deposited on the surface of the masonry leave a white residue (Figure 11). This salt can originate from one of the following two sources:

1. Cement-based mortars contain salts that are transported to the surface of the masonry as evaporating moisture leaves them behind.
2. Salt-laden water from grade (e.g. de-icing salts) are absorbed into the masonry through capillary suction, transported by water that then evaporates depositing salt on the masonry surface.

Efflorescence is a symptom of the more significant problem of bulk water ingress into the wall assembly. If this staining appears below windows or roofs it would typically correspond with a location of water ingress into the system (Source #1). The occurrence of a horizontal line of efflorescence about a metre above grade would suggest capillary suction of salts into the system (Source #2).

A third source could also be air leakage through the exterior wall assembly in cold climates where warm moist air from the interior condenses on the back of the brick and dries to the exterior (although this pathway is less common than the first two sources). The first step to fix efflorescence involves the identification and correction of the source. This may include installing or rehabilitating water-shedding features on the façade, setting up capillary breaks, employing materials less prone to capillary suction, or sealing air leakage pathways. Once rectified, the efflorescence can be removed from the surface of the masonry with a stiff fibre brush. A mildly acidic cleaning solution can be employed if the brush is not 100 per cent effective.

Conclusion

Periodic rehabilitation of brick-clad structures is essential to maintain the integrity, performance, and longevity of the building envelope. The best practices presented here are intended to assist with the maintenance but require the diligence of building operators, owners, managers, and consultants to identify, investigate, and diagnose the sources and not just the symptoms. The future of brick and mortar retail may be unclear but the buildings are here to stay.

Jonathan Dickson, M.Eng., P.Eng., BSS, LEED GA, is senior project manager at Pretium Engineering. He has been actively involved in the industry since 2010 with extensive experience in restoration of existing buildings. His experience ranges from localized leak assessments to prime consultant on multimillion dollar rehabilitation projects. Dickson can be reached at jon.dickson@pretiumeng.com.