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Primer vs Undercoat: Which One Does Your Wall Actually Need?

20, January 2026

Painting your home walls can make a room feel refreshed. However, the paint itself is only half of the story. Before the topcoat goes on, your wall needs a base that helps paint adhere properly. This is why products like wall primer and undercoat are used. In this blog, we will learn about the difference between the two, and which one does your wall actually need?

What Is Wall Primer and Why Is It Used?

A wall primer paint is a preparatory coat applied before the actual paint. It does not act as the final colour, but rather creates a foundation that helps the paint perform better. Consider primer as the base layer for your topcoat, so it lasts longer and looks more even.

For instance, Birla White ActivCoat Primer is a white cement-based liquid primer designed specifically for walls. It offers excellent opacity and whiteness. This helps the paint to appear more vibrant. A primer also improves adhesion and prevents early peeling or flaking of the topcoat paint. 

Primer vs Undercoat: What’s the Difference?

The terms “primer” and “undercoat” can sound similar, but they serve distinct purposes:

  • A primer is the first coat applied to a bare or porous surface. Its job is to prepare and seal the surface. This helps ensure the topcoat paint sticks properly.
  • An undercoat is typically applied after the primer and before the final colour coats when needed. Its main role is to make the surface even and help the topcoat look more uniform. 

Do I Need Undercoat After Primer?

Not always, especially when you are using a high-performance primer like Birla White ActivCoat. Designed to offer excellent opacity and adhesion, ActivCoat often creates a sufficiently strong and even base for painting. This is why an additional undercoat is unnecessary in many cases.

Key Features of Birla White ActivCoat Primer

  • White Cement-Based Primer: ActivCoat is formulated with white cement. Its composition helps the primer bond strongly with cementitious surfaces. 
  • Better Opacity and Whiteness: It offers excellent opacity and whiteness, which helps the topcoat paint appear true to colour.
  • Strong Adhesion: The primer provides excellent adhesion to topcoat paints, reducing the risk of peeling or flaking.

What Happens If Primer Is Not Applied?

Using paint without first applying a primer for painting can lead to several issues:

  • Paint may absorb differently across the wall. This will make colours look patchy or dull.
  • Without primer, paint may not grip the surface well. This will lead to flaking or peeling over time.
  • You might need extra layers of paint to get a consistent and even look, which will increase cost and time.

Primer essentially prepares and conditions the wall so that the paint lasts longer. Skipping this step often results in a less durable and less attractive finish in the long run.

How Many Coats of Primer or Undercoat Should I Use?

For interior walls, two coats of primer are recommended to achieve the best finish and long-term performance. The process starts with one coat of primer applied on a clean, sanded surface. This first coat helps seal the plaster or wall surface. After it dries, two coats of wall putty are applied to smoothen imperfections. Once the putty is dry and sanded, a second coat of primer for painting is applied.

Can I Use White Paint as Primer?

No. Regular white paint is not for surface preparation. It is formulated only for colour and finish. A wall primer paint like Birla White ActivCoat is specifically designed to bond to plaster or putty surfaces and to create a quality base for your final paint. Using regular white paint will not perform well over time or provide the durability that a proper primer setup offers.

Choosing the right foundation for your walls is just as important as selecting the best paint colour. A good wall primer improves adhesion, enhances colour brightness, and ensures your topcoat lasts longer. Go for a reliable solution like Birla White ActivCoat primer for your wall needs. To know more details, visit www.birlawhite.com.

 

Also Read: Which Comes First, Putty or Primer? A Step-by-Step Guide to Perfect Wall Preparation