Understanding Structural Cracks: Identification, Types and Causes

Structural cracks in buildings are a common issue that can indicate a number of underlying problems. Whether you’re inspecting a residential property or a commercial structure, understanding the nature of any cracks in the structure is essential in creating an accurate report. Not only do structural cracks signal potential weaknesses, but they can also pose serious health and safety risks if left unaddressed. Surveyors play an important role in spotting these issues early, allowing for preventative measures that can save time and costly repairs. Knowing how to identify the type of crack, understand its cause, and determine its severity can help you take the right steps to help maintain the building’s integrity and safety.

Cracks in structure can show up in different ways, each with its own set of clues and implications. From tiny hairline fractures to more noticeable gaps, these defects are often a sign that something isn’t quite right in the building’s framework. That’s why it’s so important to tell the difference between structural and non-structural cracks, so you know when it’s just a bit of cosmetic damage and when it’s something more serious. In this guide, we’ll take you through everything you need to know: the types of structural cracks, their causes, how to figure out how serious they are, practical steps to fix and prevent them, and the best ways to report them.

Structural cracks are visible splits in walls, floors, or other structural components of a building. Unlike those harmless hairline cracks you might find in plaster, structural cracks are a bit more worrying. They usually mean there’s an underlying problem with the building’s foundation or the load-bearing elements. These cracks often happen because the building is moving, the temperature is changing, or water is getting in where it shouldn’t be. Spotting these cracks early can make all the difference in preventing more significant problems down the line.

When you’re out on site, being able to tell the difference between a structural crack and a non-structural one is key. Non-structural cracks tend to be small and mostly cosmetic, while structural cracks are usually deeper and more concerning. Here’s what you should be looking out for:

• Width and Depth: If the crack is wider than 3mm and seems to go deeper than just the surface, it’s likely structural.
• Location: Cracks around windows, door frames, and load-bearing walls are often a red flag.
• Pattern: Vertical, diagonal, or stepped cracks usually indicate movement.
• Expansion Over Time: If it’s growing or spreading, it’s definitely worth a closer look.

Spotting these signs early means you can take action before things get worse, keeping the building safe and sound.

Not all cracks are created equal. Structural cracks can vary depending on what’s causing them and where they appear. Here are the most common types you’re likely to come across:

1. Vertical Cracks:

• These are often down to differential settlement in the foundation.
• They can be a sign that the ground under the property is shifting.

1. Diagonal Cracks:

• These usually pop up around windows and doors at an angle.
• Typically caused by uneven settlement or foundation movement.

1. Horizontal Cracks:

• You’ll often find these in basement walls. They usually mean there’s some serious foundation pressure going on.
• It’s often a sign of hydrostatic pressure or soil expansion.

1. Stair-Step Cracks:

• Common in brick or block walls, these follow the mortar lines in a stepped pattern.
• They usually happen because of foundation movement or settling.

1. Settlement Cracks:

• These are typically vertical or diagonal and show up when the foundation settles unevenly.
• They can be an early warning sign of bigger structural issues if left unchecked.

Understanding the type of crack you’re looking at can really help in figuring out what’s causing it and how urgently it needs to be fixed, which is why it’s essential to take technical due diligence when surveying. A small crack now could turn into a big problem if it’s ignored.

If you know what causes cracks in structure, you’re halfway to solving the problem. Here are the main culprits:

• Structural Movement: If the ground under the building shifts or settles, you’re likely to see cracks, especially in structural cracks in walls that are load-bearing.
• Thermal Expansion and Contraction: Changes in temperature can make building materials expand and contract, which can lead to cracking over time.
• Water Infiltration: Moisture is never a good thing for foundations. Poor drainage or water pooling near the base of the structure can weaken it and cause cracking.
• Poor Construction Practices: Sometimes it’s just a case of corners being cut during the build. If materials weren’t up to standard or things weren’t installed properly, cracks are bound to show up.
• Soil Expansion: Clay-heavy soil can swell and shrink with moisture changes, putting a lot of pressure on the foundations.

Knowing what caused the crack helps you figure out the best way to fix it and stop it from coming back.

Not all cracks are a big deal – but many definitely are, so it’s important to know the difference. Surveyors need to assess the severity of cracks so they can make the right call on what to do next. Here’s what to look out for:

• Width and Progression: If it’s getting wider or longer over time, that’s a red flag. Keeping an eye on how it changes can help you spot serious issues early.
• Location and Context: Structural cracks in walls in locations such as basements or cellars and those around load-bearing areas are more serious. They often mean there’s more going on beneath the surface, which will need to be investigated.
• Accompanying Signs: If you’ve got cracks alongside uneven floors, windows that won’t shut properly, or sagging roofs, it’s definitely worth further investigation.

Sometimes, it’s a good idea to bring in a structural engineer to get a detailed look. Proper assessment now can save a lot of hassle (and money) later on.

Good reporting isn’t just about jotting down what you see, you also have to make sure it is a record that’s easy to understand and follow up on. Here’s how to make sure you’re covering all the bases:

1. Visual Documentation: Get clear, high-resolution photos from multiple angles. A ruler or scale helps show the crack’s size.
2. Detailed Notes: Be specific – log the crack’s location, whether it’s vertical, horizontal, or diagonal, and if it’s near load-bearing walls.
3. Measurement Records: Measure the crack’s width and length. Re-check these during inspections to see if things are getting worse.
4. Environmental Factors: Take note of any damp, poor drainage, or soil movement around the property.
5. Digital Data Capture: Tools like GoReport make this easier, letting you upload photos, notes, and measurements all in one place.
6. Monitoring Schedule: If it’s not an emergency but still concerning, set up regular checks to monitor any changes.
7. Reporting Format: Consistency is key. Digital tools help keep everything clear and easy to access.

Good reporting doesn’t just help with monitoring, it also backs you up if there are insurance claims or disputes over damage.

The approach to addressing structural cracks depends on the cause and severity:

• Minor Cracks: Can often be repaired with filler or sealant and monitored for changes. These are generally surface-level and do not affect structural stability if properly maintained.
• Moderate Cracks: May require reinforcement or masonry repairs to prevent further spreading. Techniques such as resin injection or masonry stitching can be effective.
• Severe Cracks: Likely need professional assessment and possibly underpinning or structural reinforcement. Ignoring these could compromise the integrity of the building, leading to safety risks and costly repairs.

Taking action early on can prevent further structural issues, preserving the building’s value and safety.

Preventative measures can significantly reduce the risk of structural cracks:

• Proper Drainage: Ensure water is directed away from the building foundation to prevent waterlogging and soil movement.
• Soil Stabilisation: Addressing soil movement early can prevent settlement issues, especially in areas with expansive soils.
• Routine Inspections: Regular checks for early signs of cracking can prevent escalation. Engaging surveyors for routine assessments can identify risks before they develop into serious issues.
• Adequate Foundation Support: Ensuring that foundations are built to appropriate standards can prevent future movement and cracking.

Preventative maintenance is key to preserving the integrity of any structure, reducing the need for costly repairs and ensuring long-term safety.

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