The Mystery of Cracking Walls

Have you ever noticed cracks appearing in the walls of your home? It’s a common concern, especially in the first year after construction. While some cracks are simply a sign of a new building settling, others can indicate more serious issues. Understanding the causes of these cracks is the first step toward addressing them.

Common Causes of Cracks in Walls

• Building Settlement: Buildings are heavy, and the ground beneath them may compress or settle after construction, causing minor cracks in non-structural parts of the building, often visible on both sides of walls. These are typically hairline cracks, running in any direction, and are usually harmless.
• Ground Movement: External forces, such as nearby construction, can cause ground movement that leads to cracks in your walls. The weight of a new building next to yours can compress the ground, causing severe cracks in your home. Additionally, factors like landslides, river erosion, or nearby excavation can destabilize the ground and damage your property.
• Earthquakes: In earthquake-prone areas, like Bali, ground movement can cause significant damage to structures, resulting in cracks that might even be larger than your walls.
• Poor Installation: Cracks may also appear around electrical cables and air conditioner pipes that are installed in walls, when channels are carved out and refilled with cement. These cracks typically run vertically from the ceiling to electrical switches and sockets, but they do not affect the structural strength of the building.
• Surface Plaster Issues: Many buildings in Indonesia experience “crazed” walls, which are surface cracks in the cement render. This occurs when the cement shrinks as it sets. This is often the result of using poor-quality sand, containing mud or clay, in the cement mix. Mud and clay expand when wet and then shrink as the cement dries, causing cracks. Poor quality sand can also cause problems as rounded sand particles do not bind as well as sharp angular ones.

Are the Cracks Serious?

• Minor vs. Major Cracks: Hairline cracks due to settlement are usually not a cause for concern. However, larger cracks, or cracks that go right through walls, can indicate structural damage.
• Foundation Issues: Be aware of cracks or movement in floors, as they may indicate damage to the foundations. Cracks near structural columns or beams can also compromise the structural integrity of your building, making it more vulnerable to earthquakes.
• When to Seek Help: If you’re unsure, consult a specialist, as structural repairs require expert design and execution. Foundation repairs, in particular, need experience.

How to Fix Cracks

• Settlement Cracks: Simply fill hairline settlement cracks and paint over them.
• Poor Installation Cracks: Widen cracks caused by poor installation of electrical cables or AC pipes slightly, then fill them with a cement-rich filler.
• Surface Plaster Cracks: Before filling, check the adhesion of the render by tapping the wall to see if the cement render is loose. If it sounds hollow, the render may have come away from the wall behind, and needs to be replaced. If the cement render is solid and still attached to the wall, the cracks can be filled and the wall repainted.
• External Walls: If cracks appear in the cement render on the outside of your house, tap the walls to see if the render is loose. If it is, it should be knocked off and replaced. Pay attention to good rendering techniques, such as applying cement to a clean and rough surface, making sure that it is wetted first, and avoiding air gaps.

The Importance of Quality Materials

• Sand Quality: The type of sand used in cement render is important. Avoid sand that contains mud or clay, which can cause render to crack. Test sand by placing it in a tall glass with water; if the sand level rises and the water turns muddy, it has mud in it. You can wash the sand several times in a cement mixer to remove the mud. Using sharp, angular sand particles rather than rounded beach sand, is also crucial for ensuring the cement render binds well.

Keeping Your Bali Home Safe and Sound

By understanding the causes of cracks, you can take proactive steps to maintain the structural integrity of your home. If you find cracks, assess the type and severity. Minor cracks might only require a bit of filler, but major cracks that might compromise the structural integrity of your building will require expert advice and repair.