The occurrence of cracks in masonry is very common in structures where brick walls are constructed as infill walls or as load-bearing walls.
Because brick walls are unreinforced and have low tensile and shear strength, they are prone to cracking.
There are three main types of cracks in bricks.
- Vertical cracks
- Horizontal cracks
- Diagonal cracks
These are the most common types of cracks that occur in brick walls.
Let's discuss each type of brick crack in detail.
Vertical cracks in the brick wall
Depending on their appearance, these cracks can be divided into two categories. They are as follows.
- Straight Cracks
This type of vertical cracks in brick walls is caused by cracks in the wall including bricks. The following figure shows the formation of cracks.
- Serrated vertical cracks in brick wall
This type of crack is also a brick crack that forms vertically. This formation may be due to weaknesses in the mortar or to resistant bricks with a greater load-bearing capacity than the mortar.
Causes of vertical cracks in brick walls
There are essentially three main causes that lead to the appearance of cracks in masonry.
- Temperature fluctuations
- Founding movement
- Moisture movement in bricks
For better understanding, let us discuss each cause in detail.
Temperature fluctuations caused cracks in brick walls
Thermal cracks in walls usually occur in the masonry between windows.
Fine cracks initially appear as thermal cracks and develop to a size of 0.3 to 0.5 mm.
Furthermore, these types of cracks will reappear even after they are eliminated if thermal movement in the wall is not stopped.
Let's talk about the formation of thermal cracks in brick walls.
Formation of thermal cracks in masonry
- When exposed to direct sunlight, the brick wall will expand. These types of expansions are caused by cross walls, slabs, foundations, falling etc.
- For the reason mentioned above, certain compressive stresses arise in the wall.
- This compressive stress is greater in windows because the wall area is relatively smaller.
- Masonry shortens when under pressure due to creep.
- The compressed wall expands at night when the wall temperature decreases and returns to its original state.
- This process creates a tensile stress in the brick wall that is equal to the compressive stress in the window.
- Daily sunlight and nighttime coolness create pressure and tension on the wall.
- Cracks in walls occur when the tensile stress is greater than the tensile strength of the wall.
Vertical cracks in bricks due to foundation expansion
Let's briefly discuss these types of cracks.
- Generally, these cracks are widest at the top of the building and taper toward the foundation. At the foundation level, these cracks become hairline cracks.
- A single crack appears on each of the two opposite sides of the building.
- Most often, these types of brick cracks occur in shrinkable clay soil.
- During the dry season, the soil in the regions shrinks and swells.
- This expansion and contraction of the ground causes cracks in the building.
Vertical cracks due to moisture movement
- These types of cracks mainly occur when the brick absorbs moisture and expands.
- This expansion causes the wall connected to the wall in question to move. This movement causes cracks.
- Furthermore, irregular or non-standard bricks also cause this problem and cause cracks in the bricks.
Horizontal cracks in masonry
The following types of horizontal brick cracks occur in walls.
- Horizontal cracks under the board
This type of crack is caused by thermal effects. Voltage differences caused by thermal effects cause cracks in the brick.
These cracks may be related to wall creep.
- Horizontal cracks above the board
- Horizontal cracks in pitched roofs at all levels
Diagonal cracks in external walls
- Diagonal cracks due to ground movement caused by shrinkage
These types of wall cracks are caused by clayey soils that are subject to shrinkage movements.
When these types of soil are dry, their volume decreases and the components settle.
Furthermore, soil drying in the center of the building is minimal, as these areas are not exposed to the environment. Therefore, shrinkage occurs mainly at the edge of the building.
Therefore, brick cracks of this type appear in the corners of buildings.
- Diagonal cracks caused by soil heaving
This type of crack also occurs in shrinkable soils.
It shrinks a lot when it dries. When water is added during draining, it expands. This expansion lifts the building, causing diagonal cracks in the building.
- Diagonal cracks in windows
These cracks occur due to the uneven distribution of stress in the walls. Uneven tension occurs due to the narrowing of the wall area near the window. This area carries less tension.
Diagonal cracks in masonry are most common in load-bearing walls. These cracks are not that wide and look like fine cracks.
- Diagonal cracks due to thermal expansion
The thermal movements of the walls cause cracks to open in the brick walls.
If the internal tensile stresses in the wall are greater than the tensile strength of the wall, the wall will crack.
These types of cracks can appear in different locations as mentioned below.
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- Cracks between the window and the slab.
- Window and base plate
The article Causes of Beam Failure You can also find more information about beam errors here.
