Why is My Mortar Cracking?

Mortar, the binding material used in masonry construction, is essential for holding bricks, stones, and blocks together. However, seeing mortar crack can be concerning for homeowners and builders alike. Understanding the causes of mortar cracking is crucial in addressing the issue effectively and preventing further damage.

Common Causes of Mortar Cracking

• Shrinkage: One of the most common causes of mortar cracking is shrinkage. Mortar shrinks as it dries and hardens, especially if it is applied too wet. The water in the mortar mix evaporates, causing the material to contract. If this shrinkage is not accommodated by proper joint spacing and movement joints, cracks can develop.

• Thermal Expansion and Contraction: Mortar, like many building materials, expands and contracts with temperature changes. During hot weather, the mortar can expand, and in cold weather, it can contract. If the expansion and contraction are significant and frequent, they can cause the mortar to crack over time. This is particularly an issue in regions with extreme temperature fluctuations.

• Settlement: Buildings settle over time due to the weight of the structure and the characteristics of the soil beneath it. If the settlement is uneven, it can put stress on the mortar joints, leading to cracking. This is often seen in new constructions but can also occur in older buildings if the soil conditions change.

• Moisture and Water Damage: Water is one of the most damaging elements for masonry. If water penetrates the mortar joints, it can cause the mortar to weaken and crumble. Freeze-thaw cycles exacerbate this problem; water enters the cracks, freezes, and expands, causing the cracks to widen. Over time, this repeated process can lead to significant mortar deterioration.

• Poor Workmanship: The quality of the mortar mix and the skill of the mason play a crucial role in the longevity of mortar joints. If the mortar is mixed with an incorrect ratio of ingredients or if it is not applied correctly, it can lead to premature cracking. Poorly filled joints, improper curing, and inadequate bonding can all contribute to the problem.

• Structural Movement: Buildings are subject to various forces, including wind, seismic activity, and vibrations from nearby construction or traffic. These forces can cause the structure to move slightly, putting stress on the mortar joints. Over time, this movement can lead to cracks in the mortar.

Preventing Mortar Cracking

1. Proper Mix and Application: Ensure that the mortar is mixed with the correct proportions of cement, sand, and water. The mix should not be too wet or too dry. Apply the mortar evenly and ensure that the joints are fully filled and compacted.

   
   

2. Control Joints: Incorporate control joints into the masonry to accommodate shrinkage and thermal movement. These joints allow the structure to move without putting stress on the mortar.

   
   

3. Quality Material: Use high-quality materials for both the mortar and the masonry units. Ensure that the materials are compatible to prevent adverse reactions that could weaken the mortar.

   
   

4. Proper Curing: Allow the mortar to cure properly by keeping it moist for the recommended period. This helps in achieving the desired strength and reduces the risk of shrinkage cracks.

   
   

5. Addressing Water Issues: Implement measures to prevent water infiltration, such as proper flashing, drainage, and waterproofing. Regularly inspect and maintain the masonry to address any water-related issues promptly.

   
   

6. Regular Maintenance: Conduct regular inspections of the masonry and repair any cracks or damaged mortar promptly. This prevents small issues from becoming larger problems over time.

Conclusion

Mortar cracking is a common issue in masonry construction, but it can be effectively managed with proper understanding and preventative measures. By addressing the root causes such as shrinkage, thermal movement, settlement, moisture, workmanship, and structural movement, you can extend the life of your masonry and maintain the integrity of your structure. Regular maintenance and timely repairs are key to ensuring that mortar cracking does not compromise the safety and aesthetics of your building.