Common Plastering Mistakes and How to Avoid Cracks, Say Civil Engineers

Cracks appearing on walls and ceilings shortly after construction are a common concern for homeowners. Not only do they compromise the aesthetic appeal of a house, but they also raise worries about dampness and structural strength. According to civil engineers, most of these cracks are caused by technical errors during the plastering process.

Even when homeowners focus on bricks and cement quality, they often overlook the nuances of plastering. Small mistakes—like using unfiltered sand, ignoring joint reinforcement, or applying cement slurry inconsistently—can lead to cracks within months. Here are six essential plastering tips recommended by civil engineers to prevent future issues and ensure a flawless finish.

1. Sand Quality and Sieving

The type and quality of sand play a crucial role. Always sieve sand thoroughly to remove stones, debris, and impurities. Fine sand is ideal for plastering; coarse sand or sand with excessive clay increases the likelihood of tiny cracks as the plaster dries.

2. Use of Fiber Mesh or “Chicken Wire”

Cracks often appear where brick walls meet concrete columns or around electrical fittings. To prevent this, apply fiber mesh or chicken wire at joints and cut-outs. This reinforcement binds different materials together and prevents cracks from forming in these vulnerable areas.

3. Hacking (Surface Scoring)

Concrete surfaces are often too smooth for cement plaster to adhere properly. Before plastering, perform hacking—create small grooves or holes on the surface. This step is particularly important if the ceiling was finished with a sheet or foil, as the plaster needs a firm grip to bond securely.

4. Pre-Wetting the Surface and Applying Slurry

A day before plastering, thoroughly wet the wall or ceiling. Keep it damp on the day of work as well. Apply a thick cement-water slurry on the surface before plastering; it acts as an adhesive between old surfaces and new plaster, preventing hollow spots or detachment.

5. Correct Cement-to-Sand Ratio and Plaster Thickness

A proper mix ratio ensures strength. Civil engineers recommend a 1:4 or 1:5 ratio of cement to sand. Interior plaster should ideally be 10–12 mm thick. Excessively thick plaster increases the risk of cracks and falling plaster due to its weight.

6. Consistent Finishing

Ensure the plaster is applied evenly across the wall or ceiling without leaving gaps. Uniform plastering improves paint finish and surface aesthetics. Uneven or bumpy plaster not only looks poor but also increases paint consumption.

Following these guidelines during plastering can significantly reduce the chances of future cracks and help maintain the beauty and durability of your home.