Types of Masonry Wall Cracks – When to Worry
This blog is presented in a FAQ-style format to make it easy to read and quickly find information about common wall crack issues. The questions and answers provide general information about different types of cracks and their causes.
Q1. Wall Cracks – When To Worry?
A1. Wall cracks can be either cosmetic or structural, and it’s not always easy to tell the difference by looking at the crack alone.
• Australian Standard AS 2870 damage categories 0 and 1 cover cracks up to 1 mm wide. This may be considered cosmetic.
• Wider cracks: Cracks wider than 1 mm may still be harmless (e.g., gradual settlement) or could indicate serious structural issues (e.g., soil erosion beneath the foundation).
• Underlying cause matters: The width alone cannot determine severity. A structural engineer should assess the cause before any repair work.
Q2. What type of wall crack is a vertical wall crack?
A2. The types of wall cracks that appear vertically depend on whether the walls show vertical movement or out-of-plane distortion.
• If the wall does not have vertical movement or distortion, and crack width is consistent, it’s likely caused by thermal effects or shrinkage due to insufficient joints, usually less serious.
• If the wall does have vertical movement or out-of-plane distortion, it may be caused by soil subsidence, heave, overloading, and maybe together with thermal/shrinkage effects. Severity and solutions should be assessed by a structural engineer.
• Sometimes vertical cracks indicate cracks in the footings as well and can adversely affect the wall’s stability.
Q3. What types of wall cracks appear at wall corners?
A3. Vertical wall cracks at wall corners are most commonly caused by soil subsidence or heave.
• A structural engineer can determine whether the crack is due to uncompacted or eroded soil (subsidence) or heave from tree roots or clay soils by examining how the crack width changes along its length.
• In some cases, these cracks may indicate issues in the footings as well and can adversely affect the wall’s stability.
Q4. What type of wall crack is a horizontal wall crack?
A4. Horizontal wall cracks are often an indication of soil subsidence
• Walls transfer vertical loads from the roof to the footing. Horizontal wall cracks suggest that the affected sections are no longer under full compression, causing a redistribution of loads.
• If there hasn’t been a recent earthquake or strong wind event, the most common cause is soil subsidence. However, soil subsidence can be an indication of a simple settlement or a structural issue.
• A structural engineer should assess the crack and underlying causes, as there may also be cracks in the footings and can affect the wall’s stability.
Q5. What types of wall cracks are stepped or diagonal wall cracks?
A5. Diagonal or stepped wall cracks can have several causes depending on their location and context.
• If there is no opening on the wall, diagonal wall cracks or stepped wall cracks are most often caused by soil subsidence or heave. However soil subsidence can be an indication of a simple settlement or a structural issue; a structural engineer should assess the reasons.
• If the crack starts at a window corner, it may be due to thermal effects, shrinkage, lack of joints, soil subsidence, or heave.
• If the crack occurs near a lintel end, it may indicate a failing lintel, often caused by corrosion. Horizontal or stepped cracks at lintel ends can appear before full lintel failure.
• Our study of earthquake-damaged masonry confirms that these diagonal patterns are also critical indicators of building vulnerability.
Q6. What ceiling cracks are associated with wall cracks?
A6. Some ceiling cracks observed near walls are related to wall movement, while others are unrelated and outside the scope of this discussion.
• A visible line along the top of a wall, where the wall meets the ceiling, is typically due to relative movement (sliding) between two building elements rather than a crack within the wall or ceiling itself. This is often caused by thermal movement or minor shrinkage and is usually cosmetic.
• In some cases, wall cracks may extend onto the ceiling surface, or there may be a separation between the wall and the ceiling, depending on the ceiling construction and the nature of the wall movement. In such situations, the same underlying wall movement causes both the wall crack and the associated ceiling cracks or separation. Issues related to wall cracks have been discussed earlier, and the cracks affecting ceiling linings and finishes are generally considered maintenance-related items.
• Ceiling cracks that are not associated with wall movements are outside the scope of this blog post.
Q7. Does this summary cover all types and cases of wall cracks?
A7. No, this guide does not cover every possible case.
• Cracks can appear in a variety of locations, including underground walls, undercroft walls, retaining walls, and other specialized structures.
• Nearby construction vibrations, rare causes like earthquakes or strong wind events may also create cracks not discussed here.
• This is a broad topic, and a blog post cannot cover every scenario.
Q8. Can I assess a crack on my wall by myself using online crack pictures?
A8. Assessing a wall crack using third-party pictures can be misleading.
• Two cracks that look similar in width and shape may have completely different causes.
• The correct solution and urgency depend on the actual cause, which can be assessed by a structural engineer.
Q9. What is the process and what does a client receive after engaging a structural engineer for wall crack inspection?
A9. In our practice in Perth, engaging a structural engineer for wall crack inspection usually follows three key steps:
• Initial contact and discussion: The process typically starts with a brief discussion where the client describes the wall crack, its location, when it was first noticed, and whether any changes have occurred over time. Photos may be requested at this stage to help understand the issue before a site visit.
• Site inspection: The structural engineer attends the property to inspect the wall crack(s) and surrounding areas to assess the likely causes.
• Structural inspection report: After the inspection, the client receives a structural inspection report outlining the outcomes of the site inspection and providing advice on what should be done next. In some cases, existing building drawings may be required to prepare the report.
This guide is prepared to help readers learn useful terminology, understand wall crack problems, and see how potential solutions fit into the bigger picture. While the information here can provide insight into your walls, professional advice must be given by a structural engineer to ensure safety and the correct solution.
SOLID Engineering & Structural Design, Perth