What Is Primer? The Complete Guide

Primer, often overlooked in the painting process, serves as the foundation for a successful paint job. It’s not just an extra step; it’s a crucial preparatory layer that sets the stage for a durable and long-lasting finish.


What Does Paint Primer Do?

So, what exactly does primer do? Primers enhance adhesion, improve paint durability, and effectively block stains, ensuring that your paint job looks great for years to come.

Paint Primer Enhances Adhesion

Primer creates a bonding surface for the paint, allowing it to grip onto the substrate more effectively. This results in a smoother and more durable finish that resists peeling and flaking over time.

Paint Primer Improves Paint Durability

By sealing the surface and providing a uniform base, primer helps protect the underlying material from environmental factors such as moisture and UV radiation, thus extending the lifespan of the paint job.

Paint Primer Blocks Stains

Stains on the surface, such as watermarks or grease marks, can bleed through the paint and tarnish the finish. The primer contains additives that block these stains, ensuring they do not resurface after painting.


When To Use Paint Primer

Knowing when to use primer is essential for achieving optimal paint adhesion and durability. Whether you’re working with bare surfaces, dealing with stains or discolorations, or transitioning between different types of paint, primer ensures that the paint adheres uniformly and withstands environmental factors over time.

Before Painting Bare Surfaces

Bare surfaces, such as new wood or unpainted masonry, are porous and uneven, making them prone to uneven paint absorption and adhesion issues. Applying primer before painting helps seal the surface and creates a smooth, uniform base for the paint.

Over Stained or Discolored Surfaces

Stains or discolorations on the surface can affect the appearance of the paint and may bleed through the new coat if not properly sealed. Using primer over these areas helps block the stains and ensures a consistent paint finish.

When Switching between Oil-based and Latex Paints

If you’re transitioning between different types of paint, such as from oil-based to latex or vice versa, using a suitable primer helps promote adhesion and compatibility between the layers, preventing issues such as peeling or cracking.


How Many Coats of Primer Do I Need?

Determining the number of primer coats required depends on factors such as surface porosity and condition. While one coat is often sufficient for most surfaces, bare surfaces or highly porous materials may require an additional coat to ensure proper coverage and adhesion.

Depends on Surface Porosity

Porous surfaces may require multiple coats of primer to achieve adequate coverage and adhesion. It’s essential to assess the surface and apply primer accordingly to ensure optimal results.

Usually One Coat, but Two for Bare Surfaces

In most cases, one coat of primer is sufficient to prepare the surface for painting. However, bare surfaces or highly porous materials may benefit from an additional coat to ensure thorough coverage and adhesion.


Reasons to Prime Before Painting

Priming before painting offers numerous benefits, from providing a stable base surface to covering stains and enhancing paint adhesion. By addressing these crucial aspects, primer sets the stage for a smoother painting process and a more professional-looking finish.

Primer Provides a Stable Base Surface

By filling in imperfections and creating a uniform surface, primer helps the paint adhere better and ensures a smoother, more professional-looking finish.

Primer Covers Stains

Stains on the surface can ruin the appearance of the paint job if not properly addressed. Primer contains ingredients that block stains, preventing them from bleeding through the paint and marring the finish.

Enhances Paint Adhesion

Proper adhesion is crucial for a long-lasting paint job. Primer promotes better adhesion between the paint and the substrate, reducing the risk of peeling, flaking, or chipping over time.


When to Use Paint Primer

Understanding the specific scenarios in which primer is necessary can help you plan your painting project effectively. From porous surfaces to glossy finishes and color transitions, knowing when to use primer ensures that your paint job stands the test of time.

If the Surface Is Porous

Porous surfaces, such as raw wood or concrete, absorb paint unevenly, resulting in blotchy or patchy coverage. Primer seals the surface and promotes uniform paint absorption, ensuring a smooth and consistent finish.

If the Drywall Is Skim-Coated

Skim-coated drywall surfaces are uneven and may absorb paint differently in various areas, leading to an uneven finish. Applying primer before painting helps create a uniform base and improves paint adhesion for a flawless result.

If the Previous Coat Is Glossy

Glossy or shiny surfaces can be challenging for paint to adhere to, resulting in poor adhesion and durability. Primer creates a rougher surface for the paint to grip onto, enhancing adhesion and ensuring a long-lasting finish.

If You Are Changing the Color From Dark to Light

Transitioning from a dark to a light color can be difficult, as the underlying color may show through the new paint. Using a tinted primer helps block out the existing color and ensures a true, vibrant finish for the new paint color.

If the Surface Is Stained

Stains on the surface, such as watermarks, smoke residue, or grease marks, can bleed through the paint and tarnish the finish. Primer contains stain-blocking additives that seal the stains and prevent them from showing through the paint.


Which Type of Primer to Use

Choosing the right type of primer is essential for achieving optimal results. Oil-based primers, shellac primers, and latex-based primers each offer unique benefits and are suited to different surfaces and conditions. By selecting the appropriate primer for your project, you can ensure compatibility and long-lasting performance.

Oil-based Primers

Oil-based primers are durable and provide excellent adhesion on a variety of surfaces, including wood, metal, and masonry. They are ideal for blocking stains and sealing porous surfaces, making them suitable for exterior applications.

Shellac Primers

Shellac primers are known for their superior stain-blocking properties and fast drying time. They are effective at sealing in stubborn stains such as watermarks, smoke damage, and tannin bleed, making them ideal for challenging surfaces.

Latex-based Primers

Latex-based primers are versatile and easy to use, making them suitable for a wide range of interior and exterior surfaces. They dry quickly, have low odor, and clean up easily with water, making them a convenient option for many painting projects.


How Much Primer You Need

Calculating the amount of primer required ensures that you have an adequate supply for your project while minimizing waste. Considering factors such as surface area and the number of coats needed helps you estimate primer usage accurately and budget accordingly.

Calculating Based on Square Footage

To determine the amount of primer needed for a project, calculate the total square footage of the surface to be primed and consult the manufacturer’s coverage recommendations. It’s advisable to purchase slightly more primer than necessary to account for any wastage or additional coats that may be required.

Considering Multiple Layers for Optimal Coverage

Depending on the condition of the surface and the desired finish, multiple coats of primer may be necessary to achieve optimal coverage and adhesion. Factors such as surface porosity, texture, and the type of paint being used should be taken into account when determining the number of primer coats needed.


When You May Not Need Paint Primer

While primer is typically recommended for most painting projects, there are situations where it may not be necessary. Understanding these scenarios can help streamline your painting process and save time and effort.

If the Walls Are Very Clean

If the surface is clean, smooth, and free of grease, dirt, and stains, primer may not be necessary. However, it’s essential to inspect the surface carefully and address any imperfections or stains before painting to ensure a professional-quality finish.

If You Are Painting From One Color to a Similar Color

When painting from one color to a similar color with good coverage, primer may not be required. However, it’s essential to ensure that the existing paint is in good condition and properly adhered to the surface before proceeding with the new coat.


Using Self-Priming Paints

Self-priming paints offer a convenient all-in-one solution for painting projects, combining primer and paint in a single product. However, it’s essential to understand their limitations and application requirements to achieve the best results.

Understanding Self-Priming Paint Technology

Self-priming paints contain built-in primers that eliminate the need for a separate primer coat. They are designed to provide excellent adhesion, coverage, and durability in a single product, making them a convenient option for many painting projects.

Application Tips for Self-Priming Paints

When using self-priming paints, it’s essential to follow the manufacturer’s instructions carefully for best results. Proper surface preparation, including cleaning and sanding, is still necessary to ensure optimal adhesion and finish.

Limitations of Self-Priming Paints

While self-priming paints offer convenience, they may not be suitable for all surfaces or conditions. It’s essential to assess the surface and consider factors such as porosity, texture, and existing coatings before deciding whether self-priming paint is appropriate for your project.

Cost Considerations with Self-Priming Paints

To be frank, self-priming paints may be slightly more expensive.



Understanding the importance of primer in exterior painting projects is essential for achieving professional-quality results that stand the test of time. Primer serves as the foundation for your paint job, enhancing adhesion, improving durability, and blocking stains. 

Knowing when and how to use primer, as well as selecting the right type for your surface, can make a significant difference in the outcome of your project. Whether you’re painting bare surfaces, covering stains, or transitioning between paint types, primer plays a crucial role in ensuring a flawless finish. 

Additionally, considering factors such as surface porosity, coverage, and the use of self-priming paints can further streamline the painting process and enhance the longevity of your paint job. By following these guidelines and incorporating primer into your exterior painting routine, you can achieve lasting results that enhance the beauty and value of your home.