Home Improvement

Undercoat Paint – What Does It Do?

Picture this – you got tired of the colour of your living room walls. Or maybe you want to restore some old wooden patio furniture. The problem is – you’ve never painted anything by yourself before!

Looking up information online, you get bombarded with all those painting terms you don’t understand. What does undercoat paint do? Why do you need it? Aren’t primer and undercoat the same thing?

Fear not! In this blog post, we will shed light on exactly what undercoat paint does, when you need it and how it differs from primers.

Table of Contents:

So, if you are:

  • New to DIY painting;
  • Wondering what undercoat paint is used for;
  • Looking for the difference between undercoat and primer,

Keep reading! This post has the answers.

What is undercoat paint?

To put it short – undercoat paint is the layer applied after priming and before painting a surface. It is the second step to painting any base, spread over a coat of primer or sealer. It is best used to prepare surfaces that are already primed or painted.

There are specific types of undercoat, created for use on different surfaces, such as wood, metal, and plasterboard. Keep in mind the type of base you will be working on and choose your undercoat accordingly.

What is undercoat paint used for?

So, why use undercoat? Well, the best painting results are achieved when the surface is properly prepared, and it is part of that process. Undercoat paint has several important functions:

  • It protects the surface.
    Similar to a primer, undercoat provides a protective film to the base, stopping any external elements (such as moisture) from making their way through and damaging it.
  • Covers small imperfections.
    Undercoat is a good way to fill in tiny gaps and dents in the surface you’re painting. This provides a smooth and uniform base to apply the topcoat over. Some types of paint finish are prone to showing off every imperfection, and undercoat can help hide them.
  • Ensures even coverage.
    Choosing the right paint colours is great, but they might not look as well as you hoped if the wall isn’t prepared. Undercoat is often coloured white or grey, so applying it over the surface provides you with an even base and neutral colour to paint over with your selected shade. This ensures that there are no discoloured spots or uneven places that may affect the look of the topcoat once it dries.
When choosing your undercoat, think about what kind of colour you’re aiming for. Darker, deeper colours may benefit from a grey undercoat, while light, pastel and vivid shades will need a white base.
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What is the difference between primer and undercoat?

While both primer and undercoat are used to prepare the surface for painting, they serve a different purpose. They are essentially two steps of one whole process. A good rule to keep in mind is – if you’re painting a bare surface, use primer. If the base has been primed or previously painted, use undercoat.

Primer paint is the first layer applied when painting a raw surface. Its purpose is to give the following coats a good base to stick to. It helps reduce the absorbency of porous materials, such as wood and concrete, so less coating is necessary to achieve a solid colour.

Primer also provides a layer of protection, preventing stains from bleeding through the topcoat and appearing on your walls. Additionally, it makes it easier to work with hard-to-paint surfaces, such as glass or metal.

As mentioned previously, undercoat paint is the coat that follows the primer. Its purpose is to improve the overall look of the topcoat and provide an even surface to work with. It ensures even and unaltered colour application and protects the base from moisture.

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  • Undercoat paint is the second preparation coat applied to a surface before painting.
  • It is used to provide a smooth, neutral base to work with and ensure even colour application.
  • Keep in mind what kind of material you’ll be painting and choose your undercoat accordingly.
  • Primer is used on bare surfaces as a first coat, while undercoat is applied over primed or painted walls.
  • Primer gives the paint a good base to stick to. Undercoat improves the overall look of the final coat of paint.


Did you enjoy this article? Do you have any additional questions about painting? Let us know in the comments below!

Image source: shutterstock / N_Sakarin

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