What Is Primer Paint? When To Prime Walls, Wood, Or Metal | Improovy (2024)

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by Andre Kazimierski | Jul 11, 2021

Priming before painting can be an essential step for a quality paint job that lasts and looks great. But when should you prime and when’s it a waste of time?

In this primer paint guide for homeowners, we’ll cover what type of primer to use based on the surface being painted and how to do it right. From priming walls and bare wood to metal primers, we’ll show you how to avoid common mistakes.

Additionally, we uncover instances when priming may do more harm than good. Thus creating more work than needed for a quality finish topcoat.

As always, our goal with this paint primer guide is to help make your life easier and simplify the interior or exterior painting process.

Let’s start by diving into what primer is and what it does.

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What Is Primer Paint?

Primer is a base coat used to help treat a surface before applying a topcoat. Accordingly, primer is formulated to ensure maximum adhesion. Better paint adhesion means your paint job lasts longer.

Likewise, primer acts as a sealer for porous surfaces that would otherwise absorb the first few coats of paint.

Lastly, you can use primer as a stain-blocker for walls. This is necessary for surfaces that typically flash through a single coat.

Indeed, there are a number of benefits of priming before painting, and using the right primer at the right time is essential.

In some cases, primer can reduce the number of painting coats needed for proper color coverage. It also strengthens the bond between the surface and topcoat, extending the life of your paint job.

However, there are times when using a primer is not necessary.

When Not To Use Primer

You don’t need to use primer on previously painted surfaces that are in good condition. This goes for both interior and exterior surfaces that are not peeling or chipping.

Likewise, most modern quality exterior and interior paints are self-priming. This means they are formulated to adhere to most previously painted surfaces without the need for a prime coat.

Typical flat or eggshell finishes found on walls and ceilings don’t require primer if they are smooth and clean. However, you should lightly sand and prime before painting over certain gloss finishes or if drywall repairs are required.

Expert Painter Tip:

When buying primer, ask the paint store to tint it to match your desired paint color. Now it’s worth noting that the tinted primer color will look lighter than your final color. Don’t worry, the tinted primer will simply help your next few coats of paint retain the new color better. Most importantly, this will come in handy when painting over a dark color with a lighter shade.

While primers are generally less expensive than paint, avoid substituting a prime coat for a full coat of paint. Given this fact, why not just buy the cheaper primer and use it as one of your coats of paint?

Whether you tint the primer color or not, it does not replace an extra coat of paint. Remember, primer is formulated to act as the glue for the paint to stick to and not to hide or cover colors.

Let’s say that a new wall color needs two coats of paint to cover. You won’t be able to get away with one tinted primer coat and one top coat of paint. In this scenario, you’ll probably need a second top paint coat anyways.

Next time, skip the tinted prime coat and budget for two topcoats of quality self-priming latex paint.

Paint and Primer In One

You’ve likely seen paint and primer in one product offerings from Behr, Sherwin-Williams, and Benjamin Moore. Let’s be clear, “paint and primer in one” is simply a clever marketing label to sell expensive paint.

Likewise, buying a primer and paint in one versus a gallon of decent quality “normal” paint won’t save you time or money. Here are a few reasons why.

Pros and Cons of Primers & Paint In One

Let’s start with the cons of “primer and paint in one”. First, most quality residential paint products made within the last ten years are already self-priming. This means that “normal” paint will easily bond to most previously painted surfaces already.

This can backfire when you use a “primer & paint in one” products in lieu of a specialized primer. We’ll go through each of these situations in the next section of this article.

Best Paint-and-Primer-In-One Scenario

But wouldn’t buying a primer and paint in one save me time and money on a second coat?

Honestly, I’ve yet to meet someone who has used it to cover in one coat where two coats would be needed.

The Typical Process For Homeowners:

1. You buy the best paint-and-primer-in-one thinking it will naturally cover in one coat. Plus, think of all the time and money you’ll save by skipping the 2nd coat.
2. After you finish your first coat, you’ll see the old color flashing through the new coat of paint. At this point, you begrudgingly realize that a second coat was needed all along.
3. Next, you’ll drive back to Home Depot, Lowes, or Walmart to purchase more of the product. In the end, the paint manufacturers get richer and you feel duped.

The moral of the story, skip the paint and primer in one and buy high-quality paint instead.

When To Use A Primer Before Painting

Next, let’s cover when to use a primer before painting. In some cases, priming is an absolute necessity. Moreover, skipping this crucial step when it’s required can lead to big headaches down the line.

We’ll start by showing you the most common scenarios when priming is needed, surface by surface.

Interior Walls With Stains

Interior walls need to be spot-primed if they have stains, require extensive patching or drywall repairs, or are damaged. Typically, stains on interior walls are caused by water damage, smoke, mildew, and wood tannin bleeding.

To neutralize interior wall stains, use an oil-based stain block primer from Kilz or Zinsser. When you need to seal in heavily stained walls, use a shellac primer or solvent-based primer & sealer. Remember, stain-blockers are best used in rooms with smoke stains or drywall with water damage.

Major Color Changes

In addition, you’ll want to consider priming walls before painting if you are going from a darker color to a light color. High-build acrylic latex primers also help hide more vivid wall colors like red or yellow. Because these wall colors are generally tough to cover, you should plan for a 2nd or 3rd coat.

Gloss Finishes and Oil-Based Paint

You’ll want to lightly sand and prime walls previously coated in a glossy finish or walls with oil-based paint. In this case, you want to use a bonding primer that creates a surface that paint will adhere to or “bite” onto. Luckily, oil-based paints are rarely used on walls these days. More often than not, you’ll be coating over latex paint and hopefully won’t need a primer.

No question, painting a gloss finish requires more skill and patience than your typical home improvement project. As a result, consider hiring a professional painter to do this type of work versus trying to DIY the job. Even painting with a semi-gloss finish gives most homeowners fits. Not to mention, the cleanup process after using any oil-based paints or primers is a giant headache.

Walls With Mildew Or Mold

If mold or mildew is present, you’ll want to wash the wall area with a mixture of bleach and water prior. After a good scrub to remove all of the mold spores, gently rinse with water and wait for the wall section to dry. Then lightly sand and apply a mold neutralizing oil-based primer. This will treat the surface before a finish coat is applied.

Using an oil or solvent-based primer kills any remaining mold spores and prevents future mold from forming as well. Lastly, you’ll want to use mold-resistant paint, preferably with a bit of sheen to it like satin or semigloss.

And since picking the perfect shade for your walls can be a pain, we highly recommend using our bathroom paint color guide to simplify the process.

As a rule of thumb, the more sheen or shine a paint has, the better it will repel future moisture or water damage. That’s why using a higher sheen paint in moisture-prone rooms like bathrooms or mudrooms is highly recommended.

Stucco Patch and New Stucco Priming

We just opened our new location in Phoenix, Arizona. If you live there (or if you own a stucco house) you might be wondering if you need to prime your house. If your stucco is already painted, you should be fine without primer. However, our previous notes about gloss and oil-based paint still applies. If the stucco is unpainted–or if you’re painting a new patch—you should prime first. A masonry primer should be your go-to for this kind of job.

New Drywall Priming

Last but not least, apply a full prime coat on any new drywall or recently skim-coated walls. Make sure to use a specialized latex-based drywall primer that seals in the porous surface.

These days, most new drywall primers are water-based. The best thing about water-based primers is that they are typically low-VOC or no-VOC. Generally speaking, low-VOC primers are better for the environment and result in fewer paint fumes.

Primer For Bare Wood

All unfinished wood or bare wood surfaces should always be primed prior to painting. This goes for both interior and exterior paint projects.

The reason you cannot skip bare wood priming is that wood is porous and has a grainy surface. Because primer contains high solids, it helps fill grains in the new wood.

What happens if you don’t prime bare wood is not pretty. Similar to new drywall, raw wood soaks up paint like a sponge. As a result, your surface will look blotchy since pores in the woodwork unevenly absorb the paint.

More importantly, the painted wood will likely peel in two or three years without primer. This makes sense as there is nothing to bind the topcoat to the bare wood surface. In fact, you should always also sand and use primer when painting over any previously stained surface.

Do You Have To Prime Before Staining a Deck?

The correct answer to this common question is no. Stain is a completely different product than paint. To elaborate, stain products are made to penetrate wood surfaces, allowing the natural wood grain to show through. Contrarily, paint is made to sit on top of wood surfaces, which is why priming is recommended if you choose to paint bare wood.

This is why you should never use paint or primer when coating a deck floor. Normal house paint is not made to withstand the wear and tear of foot traffic on a deck. Most likely, the deck surface will just continue to keep peeling year after year.

Can I Use Exterior Primer Inside?

Last but not least, you should never use an exterior primer for interior wood painting projects. The reason why is that exterior primers and paints often contain higher VOCs than interior products.

Since exterior primers are formulated for outdoor use, they inherently assume more airflow exists during application. As you can imagine, higher VOCs mean more paint fumes, which should be avoided if possible.

Oil Based Primers and Paints

Now, there are primers made for both interior and exterior use. These are typically solvent or oil-based products that are created to ensure maximum bonding and stain-blocking. Stain-blocking primers emit harmful fumes so it’s best to wear a mask and properly vent your work area before use.

Priming Metal Surfaces

Painting metal surfaces can be tricky. Common metal surfaces include metal staircases, wrought iron railings, galvanized steel gates, and mailboxes. Additionally, painted metal can include aluminum surfaces like trim, patio furniture, and exterior doors.

But does metal always need a primer before painting? The answer to this question depends on the condition of the metal being painted. In the case of bare metal surfaces, you most certainly will need a special metal primer before painting with a topcoat.

Glossy Finishes On Metal

Also, if the previously painted metal surface is a gloss or semi-gloss, you’ll want to properly sand the surface and then prime it before painting.

For previously painted metal surfaces with a gloss or semi-gloss finish, a best practice is to sand the sheen before priming. This involves using 60-120 grit sandpaper to scuff the shiny surface. In turn, allowing for excellent adhesion.

There are a ton of buildings with metal staircases and railings in Chicago. No question, they need to be painted regularly to protect from rust. That’s why you need this handy Chicago painting price guide to help understand the cost.

Rusty Metal Primer

To prep rusty metal, you will need to first remove the rust using a wire brush or rust grinding tool until the surface is sound. You will know the surface is ready for the next step when you don’t feel any of the graininess or rust dust residue when touching the surface.

Badly rusted metal surfaces may require the use of naval jelly or a specialized rust remover product. Once the rust treatment dries, you will want to follow up with a rusty metal primer like this one offered by Rust-Oleum. In addition, Sherwin Williams carries a similar metal priming product named Krylon.

These will be applied using a primer spray can, brush, or with a heavy nap roller. Be sure to apply the metal primer in multiple thin coats versus one thick coat.

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