Foundation heave occurs when the expansive soil layer beneath a building’s foundation becomes saturated with water, causing it to rise upward. If left unaddressed, the pressure from heave can lead to severe damage to both the foundation and the building’s superstructure. As such, it is crucial to detect and control signs of foundation heave as early as possible to prevent further damage.
One of the most common signs of foundation heave is the appearance of cracks and bowing in slabs. These can be seen in the foundation itself, as well as in drywall, brickwork, and doorframes. Additionally, foundation heave can cause sidewalks to lift and slab sections to tilt, which not only creates an unsightly appearance but can also disrupt the building’s functionality.
Given the potentially serious consequences of foundation heave, it is essential to pay attention to these warning signs and take appropriate action as soon as possible to prevent the problem from getting worse. By doing so, you can help protect your building’s structural integrity and ensure that it continues to provide a safe and comfortable environment for its occupants.
What are the Signs of Foundation Heave?
Foundation heave can be identified by several telltale signs. One of the most common indicators is the presence of cracks that resemble spider webs or chicken feet, with at least two intersecting cracks visible on the surface. These cracks may intersect and create a triangular shape at the point where heave is most pronounced, indicating the extent of the movement. Careful observation of these crack patterns can provide important clues about the presence and severity of foundation heave.
Figure-1: Cracks in Slab due to Foundation Heave
The foundation of the structure may experience heave, resulting in concrete damage during or after construction, which can accelerate a few years after completion. Trees surrounding the structure may fall or die within a year or two of the first signs of distress. Flatwork such as driveways, patios, and garage slabs adjacent to the foundation may shift upwards and away from the foundation. Water leakage may be observed from under slab plumbing, nearby pools or ponds, indicating potential foundation issues. Additionally, an increase in moisture content in the upper soil layer underneath the foundation, with a soil plasticity index greater than 25, may be noted. The soil beneath the perimeter beam may be easily probed.
The in-ground pool near the structure may be out of level, and the site drainage may slope towards the foundation. Excavation around the foundation may reveal wet, muddy soil in the upper few meters below the perimeter grade beam. Gaps between grade beams, piers, or foundation repair shims may be loose, and there may be no space between the perimeter grade beam and the adjacent soil at grade. Despite relatively small amounts of level distortion in the foundation, there may be significant damage to both the foundation and superstructure. Ground-level flooring materials may also show signs of damage, such as cracks or warping. Slabs may be bowed between grade beams, and the grade beams may be connected to piers constructed well below the active zone. Cracks may develop in drywalls and brickworks, often in a zigzag pattern, at the top of doorframes and top and bottom of window frames, which may worsen over time.
Figure-2: Drywall Cracks due to Heave are Very Evident and Considerably Thicker Than Simple Hairline Fractures
The frames of windows and doors can become misaligned, causing them to be out of square. This issue is often caused by constant upward pressure on the foundation of the building, which is then transferred to the framework of the windows and doors. As a result, doors and windows may become sticky and difficult to open or close properly.
Figure-3: Off-Center Frames is a Sign of Foundation Heave
There are a few common issues that can arise with outdoor structures such as patios, garden sheds, and sidewalks. One of these issues is lifted patios, which can occur when the ground underneath the patio shifts or heaves due to factors like soil erosion, frost heave, or tree root growth. This can result in an uneven surface and make the patio unstable and unsafe to use.
Similarly, garden sheds can also experience lifting if the ground underneath them shifts or sinks, causing the shed to become unlevel. This can result in doors and windows that don’t close properly, and can even cause structural damage to the shed itself.
Sidewalks, especially those made of concrete, can also be prone to tilting or heaving. This can be caused by various factors such as soil movement, freeze-thaw cycles, or poor installation. Tilted slab sections in sidewalks can create tripping hazards, affect accessibility, and decrease the overall aesthetic appeal of the sidewalk.
In summary, lifted patios, garden sheds, and tilted slab sections in sidewalks are common issues that can occur due to ground movement, erosion, or poor installation. These issues can affect the stability, functionality, and safety of outdoor structures, and may require repair or replacement to ensure proper use and longevity.
FAQs
What are the signs of foundation heave?
The following are common issues that can occur in buildings and other structures:
Firstly, cracks may develop in slabs over time, which can be caused by a variety of factors such as settling, shifting of the underlying soil, or poor construction practices.
Secondly, doors and windows may become sticky or difficult to open and close due to changes in the surrounding environment, such as humidity, or as a result of the foundation settling and causing the frame to become misaligned.
Thirdly, the bowing of a slab can occur when the ground beneath it shifts or settles unevenly, causing the middle of the slab to rise up while the edges sink down.
Fourthly, sidewalks and other flat work may become lifted or uneven due to similar factors as slab bowing, such as soil movement or poor construction practices.
Finally, cracks may appear on the interior face of walls, which can be indicative of structural issues such as foundation problems or excessive settling. It is important to address these issues promptly to prevent further damage to the structure.
Do cracks develop on the exterior face of walls due to foundation heave?
It is rare for cracks to form on the exterior face of walls as a result of foundation heave.
Do cracks due to foundation heave grow over time?
The described phenomenon refers to the appearance of cracks in both drywall and brickwork. These cracks have a distinctive zigzag shape and are usually located at the top of doorframes, as well as at the top and bottom of window frames. What’s more, these cracks are not static; over time, they will gradually increase in thickness and length.
How can soil moisture be used as a sign for foundation heave?
Foundation heave is a common issue that can occur in buildings. One of the signs of this problem is an increase in the moisture level of the soil layer situated below the foundation. This increase in moisture can happen gradually over time, and it is an indication that the soil underneath the foundation is expanding. As the soil expands, it can push the foundation upward, resulting in cracks, tilting, or other damages. Foundation heave can occur due to various factors, such as changes in the soil’s composition, water infiltration, or improper drainage. If left unaddressed, foundation heave can lead to significant structural issues that may be costly to repair. Therefore, it is crucial to monitor the moisture level of the soil and take necessary actions to prevent or mitigate foundation heave.
Is it possible to live in a house with a foundation heave?
Foundation heave is a possibility that can occur in buildings, and some occupants may not be aware of it right away. Despite this, there are still signs that can be observed which can cause disruptions to the quality of life and interfere with the building’s functionality.