What Are The Different Types of Plaster Wall Cracks

The smooth surface of a plastered wall creates a clean and finished look in our homes. But sometimes, unwelcome cracks can appear, disrupting the aesthetic and potentially raising concerns.Cracks can develop in any part of a structure that bears weight, whether these forces originate from within or outside the structure, if the stress exerted exceeds the material's capacity to withstand those stresses.

Each house, and every structural component within it, is designed to support a range of loads it might encounter throughout its existence. Before you panic, understanding the different types of plaster wall cracks is crucial. Some are minor blemishes, while others might signal a deeper structural issue.

What Is A Plaster Wall? 

Plaster is a traditional building material used to create smooth, finished surfaces on walls and ceilings. It's typically a mixture of lime, gypsum, sand, and water, applied in layers to a backing material like brick or lath. Plaster offers several benefits, including fire resistance, soundproofing, and a good base for paint.

While drywall has become more common in modern construction, plaster walls remain a cherished feature in many homes. The key to tackling plaster cracks lies in understanding their cause. Cracks can be broadly categorised as non-structural or structural, each with its own set of culprits.

Different Types of Plaster Cracks

Not all cracks in your plaster are created equal. Let's us talk about the two main categories: non-structural cracks and structural cracks.

Non-Structural Cracks: More Common and Usually Less Concerning

These cracks are typically cosmetic issues and don't necessarily indicate a major problem with your building's structure. They arise due to various factors related to the plaster itself or the drying process.

• Hairline Cracks: These are thin, almost invisible lines that appear on the plaster surface. They are a normal result of drying and shrinkage as the plaster cures. Hairline cracks are usually nothing to worry about and can be easily addressed during redecorating.Settlement in new buildings can also contribute to hairline cracks. While they may be noticeable under close inspection, these cracks are mostly cosmetic and don't require immediate intervention. Thankfully, fixing hairline cracks is a straightforward process. Once you've identified the crack, use a putty knife to remove any loose plaster around it. Apply a joint compound to fill the crack, ensuring a smooth finish. After drying, sand the area lightly and repaint the wall.
• Crazing Cracks:  These fine, interconnected cracks form a web-like pattern on the plaster surface. Crazing typically occurs due to over-troweling a rich plaster mix during application or improper curing conditions. While not inherently structural, extensive crazing can detract from the visual appeal of your walls. Similar to hairline cracks, crazing can be addressed with joint compound and sanding. However, for deeper crazing, consider using a fiberglass mesh patch for added reinforcement before applying the joint compound. In some cases, if the crazing is particularly severe, replastering small sections might be necessary.
• Map Crazing Cracks:  Think of map crazing as a more dramatic version of regular crazing. These cracks are larger, deeper, and often resemble a map's contour lines. Similar to crazing, they arise from issues during plaster application or curing. While not always structural, extensive map crazing warrants a professional evaluation to rule out any underlying problems. Due to the depth of these cracks, tackling map crazing might require a more involved approach. A professional contractor can assess the severity and recommend the most suitable repair method. This could involve patching with joint compound and mesh, or even localized replastering for a more comprehensive solution.
• Drying Shrinkage Cracks: As the name suggests, these cracks develop as the plaster loses moisture after hardening. They typically appear as small, fine lines on the surface and are another common occurrence. Filling and repainting can usually take care of drying shrinkage cracks.

Structural Cracks: Seek Professional Help

Unlike non-structural cracks, these cracks can indicate a deeper problem with your building's foundation or structural integrity. They often appear larger and require professional assessment to determine the cause and necessary repairs.

• Horizontal Cracks: These cracks run parallel to the floor and can be a sign of foundation problems or structural movement. Horizontal cracks, especially those that appear above doorways or windows, should be addressed by a qualified structural engineer.
• Wide Vertical Cracks (wider than 0.5cm): While vertical cracks are generally less concerning than horizontal ones, cracks wider than half a centimeter can indicate foundation issues or settling of the building. It's advisable to consult a professional to diagnose the cause and recommend appropriate repairs.
• Foundation Movement Cracks:  These cracks are often diagonal and wider at the bottom, resembling a staircase pattern. They can appear anywhere on the wall but are frequently found around door and window frames, which may become misaligned due to foundation movement. The culprit behind these cracks is usually settling of the foundation, caused by factors like expansive soil, inadequate support, or external pressure. Addressing foundation movement cracks requires professional intervention. A structural engineer can diagnose the cause of the movement and recommend appropriate solutions, which might involve foundation repair, underpinning, or other stabilization techniques. It's crucial to address these cracks promptly to prevent further damage to your home.
• Moisture Expansion Cracks:  As the name suggests, these cracks arise from moisture issues within the wall. Water leakage, plumbing problems, or high humidity can cause the plaster to expand and crack. These cracks can vary in size and location, but they are often accompanied by signs of moisture damage like peeling paint or mold growth. The first step in addressing moisture expansion cracks is to identify and fix the source of the moisture problem. This might involve repairing leaky pipes, addressing ventilation issues, or tackling any underlying causes of dampness. Once the moisture source is eliminated, a professional can assess the crack and recommend the appropriate repair method, which could involve patching or replastering the damaged area.

Prevention Tips For Plaster Cracks 

While some cracking is inevitable, here are a few tips to minimise the appearance of non-structural cracks in your plaster:

Maintain a Stable Indoor Environment

Avoid drastic fluctuations in temperature and humidity, which can cause the plaster to expand and contract, leading to cracking. Aim for consistent indoor temperatures and moderate humidity levels.

Allow Proper Curing Time

During the drying process, ensure proper ventilation to allow the plaster to cure evenly. Avoid exposing freshly plastered walls to direct sunlight or strong drafts.

Use a Quality Plaster Mix

Opt for a well-mixed plaster that adheres well to the backing material. A good quality mix will be less prone to cracking.

When to Seek Professional Help: Don't Go It Alone

While some non-structural cracks can be tackled with DIY repairs, there are situations where seeking professional help is essential. Here are some signs that indicate a structural crack and warrant a call to a qualified contractor or structural engineer:

• Crack width: Cracks wider than ¼ inch (6mm) are more likely to be structural.
• Location: Cracks around chimneys, doorways, windows, or running along ceiling lines often signal foundation movement.
• Multiple cracks: The presence of numerous cracks, especially if they appear in a diagonal pattern, suggests structural movement.
• Lengthening cracks: Cracks that seem to be growing in size or number require immediate professional attention.
• Door/window misalignment: Doors or windows that stick, become drafty, or show signs of misalignment can be indicators of foundation movement.

When in doubt, it's always better to err on the side of caution. A professional can assess the crack, determine its cause, and recommend the most appropriate course of action. Early detection and intervention are crucial for preventing further damage and ensuring the safety of your home.

If you're unsure about the type of crack in your plaster wall, especially if it's large or accompanied by other signs of structural damage, don't hesitate to seek professional help. A qualified structural engineer can assess the situation, identify the cause, and recommend the best course of action for repair. Early intervention can prevent further damage and ensure the safety and structural integrity of your home.

Conclusion 

Have you encountered cracks in your plaster walls? Did you identify the cause and get them repaired? This blog post provides a general overview of plaster wall cracks. It's not a substitute for professional advice. If you're concerned about cracks in your walls, consult a qualified structural engineer for a proper diagnosis and repair plan.

Plaster walls, with their rich history and timeless beauty, are a valuable asset in many homes. By understanding the different types of cracks and their causes, you're empowered to take charge of your home's maintenance. For non-structural cracks, some basic repairs can restore your walls to their former glory. However, when faced with structural cracks, seeking professional help is paramount to ensure the structural integrity of your home. Remember, your walls have a story to tell – learn their language to keep your home safe and sound.

Content Summary: 

• Plaster walls are a beautiful feature in many homes, but cracks can sometimes appear.
• Understanding the different types of cracks is important to determine the severity.
• Plaster is a traditional material used for smooth wall and ceiling finishes.
• Cracks can be non-structural or structural, each with different causes.
• Non-structural cracks are usually cosmetic and arise from the plaster itself or drying.
• Hairline cracks are thin lines caused by drying and shrinkage, easily fixable.
• Crazing cracks form a web-like pattern due to improper application or curing.
• Map crazing cracks are larger and deeper versions of regular crazing cracks.
• Drying shrinkage cracks are small lines that develop as plaster loses moisture.
• Structural cracks indicate a deeper problem with the foundation or structure.
• Horizontal cracks running parallel to the floor can signal foundation issues.
• Wide vertical cracks wider than 0.5cm might indicate foundation problems.
• Foundation movement cracks are diagonal and wider at the bottom, often around doors/windows.
• Moisture expansion cracks arise from water leakage, plumbing problems, or high humidity.
• To minimise non-structural cracks, maintain a stable indoor environment.
• Allow proper curing time for plaster with good ventilation.
• Use a high-quality plaster mix that adheres well to the backing material.
• Seek professional help for cracks wider than ¼ inch (6mm).
• Cracks around chimneys, doorways, windows, or ceilings could indicate foundation movement.
• Numerous cracks, especially diagonal ones, suggest structural movement.
• Immediately address cracks that seem to be growing in size or number.
• Door/window misalignment can be an indicator of foundation movement.
• When unsure about the crack type, especially if large, seek professional help.
• A qualified structural engineer can assess the situation and recommend repairs.
• Early intervention can prevent further damage and ensure home safety.