Cracks in the walls can reveal a lot about a home’s health. These imperfections are a natural result of everyday use, but sometimes they can be a sign of something more serious.

The timing and severity of certain cracks may depend on factors like a home’s construction type, building quality, foundation and soil conditions. If your clients moved into a newly built house, they may spot certain cracks after the one-year mark when the home has had a chance to settle and dry out.

Catching cracks early can save time, money and stress. Below is a guide to the different types of wall cracks, the common root causes and the best course of action for completing repairs.

Level of urgency: Low

Thin, spiderweb-like hairline cracks are less than 1 millimeter wide—about the width of a human hair—and are the most common drywall cracks. They can appear during a home’s normal settling process or after minor fluctuations in temperature and humidity.

Hairline cracks can run in any direction and don't require immediate attention. Still, you’ll want to monitor the cracks each week to check for a change in length and width and address any moisture issues, like improper drainage. If you notice the crack growing wider or longer, consult a professional structural engineer for evaluation to assess the cause and for recommendations of any necessary repairs.

Hairline cracks can be caused by:

• Settling: As a house settles into its foundation, slight shifts can lead to minor cracks in the drywall or plaster.
• Temperature changes: Seasonal temperature variations cause building materials to expand and contract.
• Humidity changes: Changes in humidity levels can cause drywall or plaster to contract or expand.

Actions to take:

• Monitor the crack weekly for any growth. (Measure it!)
• Patch and repaint the hairline crack using a joint compound, which is a paste made of gypsum powder and other binders that can be spread onto the crack and sanded when dry.

Level of urgency: Low to Moderate

These cracks often result from foundation settlement. Vertical cracks travel straight up and down, following the line where the wall meets the floor. They can vary in size. These cracks generally pose minimal concern if there are no significant increases in length or width. 

However, vertical cracks need to be assessed once they are greater than 5 millimeters wide. If the crack is close enough to the ground and easily accessible, use a ruler to measure its width. For higher cracks, mark either side with a pencil and monitor the distance over time. If you detect dampness or widening cracks, seek professional help. 

Vertical cracks can be caused by:

• Settling: Both newer and older homes can experience settling into their foundation. While newer homes may settle more noticeably due to the initial adjustments of the building materials, older homes might have already undergone significant settling over time, which can also lead to cracks in the walls.
• Temperature changes: Temperature fluctuations can make building materials expand and contract slightly.

The urgency of addressing a vertical crack largely depends on its size:

• Low urgency: Hairline vertical cracks are generally low priority, especially if they haven't changed. 
• Moderate urgency: Cracks wider than 3 millimeters warrant a professional evaluation. 

Actions to take:

• For hairline vertical cracks, monitor them weekly for any changes in size or length.
• If the cracks widen or you have any concerns, consult a foundation specialist for a professional assessment. 

Level of urgency: High

Horizontal cracks that run along the wall plane can be a serious sign of foundation issues and potential structural drywall cracks. These cracks are often the result of structural movement as expansive soils build up against the foundation wall. They will progressively widen without proper care, potentially causing complete wall failure. 

Consult a professional for any horizontal crack, regardless of its width. This urgency is because horizontal cracks signify movement or pressure on the foundation walls. Early detection and intervention are crucial to prevent further damage.

Horizontal cracks can be caused by:

• Foundation movement: Uneven settling of the foundation can put stress on walls, causing them to crack horizontally. This is due to poor soil conditions, moisture issues or changes in water drainage around the house. While horizontal cracks may be more commonly associated with newer homes, older homes are not exempt.
• Moisture: Factors such as moisture problems or changes in water drainage around the house can contribute to foundation movement and horizontal cracking.

Actions to take:

• Consult a foundation specialist or structural engineer for a professional assessment.
• The professional should be able to help diagnose the cause of the crack and recommend the most appropriate course of action, which may involve foundation repair or structural reinforcement.

Level of urgency: High

Diagonal cracks run at an angle on the wall from corner to corner, slanted at a 45-degree angle compared to the vertical wall plane. These cracks, regardless of size, need immediate attention from a professional.

Early intervention is key since diagonal cracks are a sign of foundation settlement, often a result of the earth pushing on the concrete basement wall. Early detection and intervention are crucial to preventing more extensive damage to your foundation and the overall structural integrity of your home.

Diagonal cracks can be caused by:

• Poor soil compaction: If the soil supporting your foundation wasn't adequately compacted during construction, it will settle unevenly over time. This uneven settling puts stress on the walls, causing them to crack diagonally.
• Changes in moisture content: Fluctuations in soil moisture content can lead to uneven settling. For example, during droughts, the soil shrinks, causing the foundation to shift and the walls to crack.
• Inadequate drainage: Poor drainage around the house leads to water pooling near the foundation. This saturated soil puts uneven pressure on the foundation.

Actions to take:

• Contact a foundation specialist or structural engineer as soon as possible for a professional assessment.
• The professional can diagnose the cause of the crack and recommend the most appropriate course of action, which may involve foundation repair, soil stabilization techniques or structural reinforcement.

Cracks are most commonly caused by expansion and contraction of building materials. This occurs due to changes in both moisture content and temperature. These minor shifts can lead to hairline cracks in the drywall or plaster, especially in newer homes during the first few years.

Construction imperfections may also be a contributing factor. For instance, improperly taped drywall joints or shrinkage in concrete foundation walls can lead to cracks. 

Further, leaks in the roof, plumbing or poor ventilation can lead to moisture buildup in walls, causing cracks. Homeowners should be on the lookout for any moisture present to help prevent water damage and further structural damage.

Not all cracks are created equal. The size and location of wall cracks are key factors to consider. Large cracks wider than 5 millimeters are a cause for concern, especially if they are diagonal, horizontal or above a door frame. These cracks could indicate foundation movement, stress on structural supports or settling issues. Have professionals evaluate in these cases.

The presence of multiple cracks, especially if they are clustered together in a specific area, also calls for attention. This suggests there could be a widespread problem that requires a professional evaluation to determine the cause and best course of action.

By addressing cracks promptly, you can help prevent them from worsening and safeguard the structural integrity of the home. Cracks are not always a cause for alarm. Cracks in walls or ceilings are fairly common. They might seem visually alarming, but a better understanding of them can help identify the difference between a minor cosmetic imperfection and a more significant structural problem.

Source: When You Shouldn’t Ignore the Cracks in the Wall REALTOR® Magazine (June 10, 2024) Courtney Klosterman