Skim Coating vs. Plastering: Find Out How to Apply Them!

Confused about the differences between skim coating and plastering? These terms are often heard in the construction world, but many people still don't know the difference between skim coating and plastering, or what each does.

Both stages are equally important in making the walls of a house look flat and neat, but there are differences in the materials' composition, layer thickness, and intended use.

Wall plastering is usually applied first to cover brick, block, or concrete surfaces, while skim coating is applied after plastering to fill pores and make the surface smoother.

Understanding the differences between the two not only helps achieve aesthetically pleasing walls but is also important for ensuring the building structure is stronger, more durable, and ready for finishing stages, such as painting or installing decorations.

To understand the functions of each, as well as when and how to use them, check out the following comprehensive review of the differences between skim coating and plastering!

What Are Skim Coating and Plastering?

Before discussing the differences between skim coating and plastering, it is important to understand their meanings. By knowing their definitions, you can more easily distinguish when to use plastering and skim coating on the walls of your home.

Definition of Skim Coating

Skim coating is a thin layer of a mixture of cement, sand, and water that is applied to walls or floors. The function of wall skim coating is to level the surface, conceal imperfections, and prepare the wall for a smoother finish before the next process, such as painting or installing tiles. With skim coating, the wall looks neater and is ready for finishing.

Definition of Plastering

Unlike skim coating, which focuses on smoothness, plastering aims to provide thickness and strength to walls or floors. Although it uses a mixture of cement, sand, and water, like skim coating, the proportions are different.

Plastering also helps cover cracks or holes, making the surface stronger and more durable before finishing, such as painting or installing ceramic tiles.

The Differences Between Skim Coating and Plastering

Before deciding how to finish your walls, it is important to understand the difference between skim coating and plastering. Although both methods are used to level surfaces, each has a different purpose, uses different materials, has a different thickness, and is used at different times. Here is the elaboration on the differences between skim coating and plastering:

1. Purpose of Use

Skim coating prepares the wall for a smoother, flatter surface before painting or decorating, and serves as the final stage in building construction.

Meanwhile, plastering is used to cover uneven or flawed wall surfaces, creating a strong and neat base layer before the finishing steps are carried out.

In other words, plastering levels the construction, such as bricks or blocks, while skim coating perfects the surface so that it is ready for the final stage.

2. Basic Materials

Skim coating is usually made from a mixture of cement and water, with a higher water-to-cement ratio, sometimes with other additives added to strengthen the wall surface.

Meanwhile, plaster is a mixture of cement, sand, and water, with lime or other materials added depending on the type of plaster required.

These differences in composition mean that plastering focuses more on leveling the surface, while skim coating emphasizes strength and smoothness.

3. Thickness

The difference between skim coating and plastering can also be seen in their thickness. Plastering layers are generally thicker, around 20–25 mm or more, depending on construction requirements, as they serve to cover the wall surface and any defects.

Conversely, skim coating applies a thinner layer, usually 5–15 mm, to smooth the surface and prepare it for the finishing stage. This difference in thickness reflects the focus of plastering on strength and leveling, while skim coating emphasizes the final smoothness.

4. Final Appearance

For the final appearance, plastering usually produces a textured surface as desired, ranging from rough and wrinkled to smooth. Meanwhile, skim coating provides a smooth, even finish, ready for subsequent stages such as painting or installing decorations.

This difference shows that plastering is more flexible for aesthetics, while skim coating focuses on surface perfection.

5. Time of Use

Skim coating should be used to prepare a smooth, even wall surface before the final stage, such as painting or installing tiles. With a smooth surface, paint usage can also be more economical.

Meanwhile, plastering is used when a thick layer is needed to strengthen walls, cover cracks or holes, and create a strong surface before finishing.

Tips for Applying Skim Coating

After understanding the difference between skim coating and plastering, it is also important to know how to apply skim coating correctly. Here are some tips for applying skim coating so that the results do not crack:

Ensure the correct ingredient ratio: For conventional skim coating, mix 1 part cement with 2–3 parts fine sand for optimal strength and adhesion.
Moisten the wall before plastering: A damp wall surface helps the skim coating adhere more evenly.
Apply thinly and evenly: The skim coating should not exceed 3 mm in thickness to prevent cracking.
Use quality products: High-quality cement or instant skim coating can reduce the risk of mold and paint peeling.
Perform maintenance after skim coating: Lightly spray the wall for 2–3 days to help the skim coating harden evenly and prevent cracking.
Avoid skim coating in extremely hot weather: Hot weather can cause water to evaporate quickly, leading to hairline cracks.

Tips for Applying Wall Plaster Correctly

Although both serve to level walls, plastering focuses on the thickness and strength of the layer before the finishing stage. Here are some tips for applying wall plaster correctly and achieving neat results:

Mixing plaster materials: Plaster is made from a mixture of cement and sand in a ratio of 1:3 to 1:5. Make sure the materials are free of dirt so that the mixture does not clump and the wall surface remains flat.
Making a plaster head: The plaster head serves as a reference for the thickness of the plaster layer, usually around 1.5-3 cm. Before applying the plaster, don't forget to wet the wall so that the mixture sticks well.
Using the overlapping layer system: Apply the plaster by sticking and throwing the mixture onto the wall. After that, fill in the thinner areas and smooth them out with a trowel, using the plaster head as a guide, so the surface is smooth and even.

That concludes the explanation of the differences between skim coating and plastering, along with tips for applying them to your home's walls to achieve a smooth, even finish. To ensure optimal results in plastering and skim coating, it is very important to choose high-quality building materials and ensure the structure of the building remains strong and durable.

One of the best choices is Semen Merah Putih Watershield. This product is equipped with water-repellent technology that provides double protection against water seepage, both from the outside and from the ground, making the house's walls more resistant to extreme weather.

This cement can be used for various applications, from plastering and skim coating to casting and bricklaying, making the work easier while maintaining the quality of the building and achieving maximum results.

To achieve smooth, neat, and durable walls, use Semen Merah Putih Watershield as the primary material. Contact us for more information and consult your construction needs!