Mortar is the binding element that holds masonry units—like brick, stone, and concrete blocks—together. While it often goes unnoticed compared to the materials it supports, mortar plays a vital role in a structure’s stability, weather resistance, and overall appearance. However, unlike brick or stone, mortar has a much shorter lifespan and is prone to wear and deterioration over time. Understanding what causes mortar to fail and how to recognize the warning signs can help prevent more serious masonry issues down the road.
The Natural Lifespan of Mortar Joints
Most mortar joints are expected to last 20 to 30 years, depending on the quality of the original materials, environmental conditions, and construction techniques. In older homes, especially those built with lime-based mortars, joints may last even longer but tend to deteriorate more gradually. While bricks and stones can often last a century or more, mortar is the component that will need periodic attention through a process known as tuckpointing.
Because mortar is designed to be softer than the masonry units it holds, it acts as a buffer—absorbing movement, moisture, and temperature changes that would otherwise damage the bricks or stones themselves. This intentional sacrificial quality is what gives mortar joints their limited lifespan.
Environmental and Climatic Conditions
One of the biggest culprits in mortar failure is exposure to the elements. Rain, snow, and humidity introduce moisture to masonry surfaces. When water enters the mortar and then freezes, it expands—causing cracking, crumbling, and eventual joint failure. This process, known as the freeze-thaw cycle, is especially destructive in regions with harsh winters.
Over time, constant exposure to sun, wind, and temperature fluctuations also wears away the surface of mortar joints. Mortar that was once hard and compact can become powdery, brittle, or recessed, leading to loosened bricks and reduced structural integrity.
Poor-Quality Materials or Workmanship
Mortar failure isn’t always the result of aging. In some cases, issues stem from poor construction practices or inferior materials used during the original build or a previous repair.
For example, using the wrong mortar mix—such as a modern, high-strength Portland cement-based mortar on soft historic brick—can create mismatched hardness. This leads to stress fractures in the masonry and premature joint failure. Likewise, mortar that isn’t properly mixed, applied, or cured can quickly degrade, especially when exposed to moisture.
This is why matching the mortar type to the masonry it supports is critical for long-term performance, particularly in historic homes or restorations.
Water Infiltration and Drainage Issues
Mortar is porous and will absorb water, but when masonry is constantly saturated or improperly drained, that moisture accelerates joint breakdown. Blocked gutters, poor site grading, or damaged flashing can cause water to run directly onto masonry surfaces.
Persistent dampness not only softens mortar but may also lead to the growth of moss, mold, or efflorescence—all signs that excess moisture is affecting the wall system. Over time, wet mortar loses its binding ability, resulting in shifting bricks and gaping joints.
Structural Movement and Settling
Buildings naturally settle over time, but excessive or uneven settling can stress masonry joints. Mortar may crack or pull away from bricks as a result of foundation shifts, vibrations, or nearby construction activity. When cracks form, they open pathways for water and debris to enter, accelerating the deterioration process.
Additionally, thermal expansion and contraction can cause masonry walls to subtly shift as temperatures rise and fall. Without proper expansion joints or flexible mortar, this movement leads to cracks and separation at the mortar lines.
Pollution and Environmental Contaminants
In urban environments, airborne pollutants, acidic rain, and dirt can collect on masonry surfaces and weaken mortar joints over time. Pollutants can chemically react with the lime or cement content in mortar, especially in older buildings, causing erosion or discoloration.
Soot, dust, and vehicle emissions may not break down mortar structurally as quickly as moisture, but they can contribute to surface decay and reduce the overall appearance and lifespan of the mortar.
Signs Your Mortar Needs Repair
Recognizing the signs of mortar deterioration early is key to maintaining your masonry. Common indicators include:
- Cracks or gaps forming between bricks or stones
- Mortar that is recessed or crumbling to the touch
- Loose or shifting bricks
- Water stains, moss, or white residue (efflorescence)
- Bulging or bowed masonry walls
If these symptoms are present, the solution is often repointing—removing the damaged mortar and replacing it with a fresh, compatible mix that restores the wall’s stability and appearance.
Protecting the Integrity of Your Masonry
While mortar may not last as long as the bricks or stones it supports, it is the backbone of masonry construction. Understanding the causes of mortar failure helps homeowners take proactive steps to preserve their structures and avoid costly damage.
If your masonry shows signs of deteriorating joints or you’re unsure about the condition of your mortar, reach out to professionals who specialize in assessment and repair. Contact Turnbull Masonry to schedule an expert evaluation and ensure your brick or stonework remains strong, stable, and beautiful for years to come.