How to Troubleshoot Mortar

Write down the time, date and weather conditions of each mortar troubleshooting observation. Photograph or draw the location, size, direction and any other relevant details of visible mortar cracks. Settlement and deflection cracks occur during the first annual cycle. These cracks are widest at the lowest point of the mortar crack and taper at their ends.

Photograph or draw details of small or hairline cracks. Hairline cracks are superficial and do not penetrate through the entire joint bed. The mortar may be too high in cement content, the joints may be too wide, large units may have clean-cut edges or meet at a sharp corner or the joint tooling may be inconsistent or incorrectly done.

Photograph or draw details of horizontal cracks along mortar bed joints, displaced units and bulging or bowed-out walls. These are symptoms of improper masonry reinforcement or inadequate structural design. Look for large horizontal mortar cracks. Masonry units and mortar attached to concrete slabs crack as the slab settles or curls up at its ends, but these cracks will not reappear once repaired.

Photograph or draw details of diagonal or stairlike mortar cracks around doors, windows and other openings. These usually arise from normal expansion differences between masonry wall assemblies and underlying steel structures. Large vertical-stepped mortar cracks at building volume intersections, corners and parapet walls can indicate inadequate building design to accommodate structural expansion.

Photograph or write down a description of faded or discolored mortar. Natural exposure to environmental pollutants and subsequent surface erosion causes fading. Salts in the wall assembly mixed with moisture can leave crystalline deposits called efflorescence. Rainfall washes away some deposits, and regularly cleaning removes pollutant buildup.

Photograph or write down a description of deteriorating mortar joints. Deterioration may be from natural weathering because of wind, rain and atmosphere exposure; from weak, low cement content mortar; from sulfates in the atmosphere and soil; from poor detailing; or from inadequate joint tooling that allows water penetration and saturation. Check detailing for proper design and installation, especially copings, damp-proof courses, flashing and joint tooling.

Photograph or write down a description of cracked masonry units and debonding at joint lines between mortar and units. These signal the use of a mortar with too much cement content, causing excess strength and poor workability.