Does Kilz Kill Mold? (How to Kill Mold and Mildew Growth with Primer)

How do you deal with molds or mildew? For most of us, the answer is a spray bottle of peroxide or other mold removal solutions from your local store. 

What if I tell you a few sprays of Kilz primers can also get the job done? Shocking, right? 

Primers like the Kilz Mold & Mildew primer contain biocides—chemical solutions for killing different types of mold and mildew, including black molds. It can also prevent the growth of future mold. Talk about a two-in-one solution.

Read this article to discover more about how Kilz mold-resistant primer can treat the source of mold and mildew growth—and prevent the growth of mold.

Why Bleach Doesn’t Always Work on Molds

Let’s debunk a common myth: Using chlorine bleach on mold-infested surfaces is not always the best solution to a mold issue. It’s preferable to use chlorine bleach when dealing with molds or mildew on non-porous interior and exterior surfaces. 

applying Kilz primer on a molded wall

A few weeks ago, I was renovating the bathroom. I tore up the sheetrock on the bathroom walls, only to see black mold growing and feeding off the paper on the drywall. It wasn’t a surprise since excess moisture and wet paper are the perfect substrates for mold growth.

I tried a few sprays of bleach and lightly rubbed it to remove the mold. Now, here’s a common mistake that we all make: Bleach is not adequate for killing molds on porous surfaces. 

In fact, the Environmental Protection Agency (EPA) does not recommend using chlorine bleach as a routine solution to cleaning up molds and mildew. 

Drywalls like sheetrock have layers filled with spores that your bleach can’t reach. Bleach can’t soak into the material like a primer does, meaning it can’t get rid of mold on drywall.

Don’t be shocked when the mold keeps on appearing despite cleaning it with bleach. A few recommendations from my contractor set me straight. I didn’t realize I had the solution all along. Kilz Clear Max cleared the mold and filled in the pores of the drywall, preventing more mold stains in the future.

How Does Kilz Work on Molds and Mildew?

Let’s start with the basics. Black molds and mildews produce mycotoxins that trigger asthma and different allergic reactions. Mold colonies emit these mycotoxins via mold spores released in the air. 

Therefore, effective mold and mildew removers must kill these spores, eliminate the mold roots on the surface, and penetrate the mold hidden within the substrate. 

Now, these mold removal solutions and some Kilz Primers have something in common: they contain biocides, which are active chemicals that break down molds and mold spores on a molecular level. It is also effective against other microbes, including viruses.

Which Kilz Primer is Best for Molds and Mildew? 

a man wearing a mouth-nose mask and gloves inspecting a moldy wall

Kilz is a prominent brand that consists of different products, each designed to focus more on specific problems. For example, the Kilz 3 Premium primer has a robust stain-blocking attribute, while the Kilz Restoration is popular for sealing pet odors. 

Some Kilz primers contain a higher concentration of biocide and are best for killing molds and mildew. These products include:

Kilz Mold & Mildew Interior/Exterior Primer 

The Kilz Mold & Mildew Interior/Exterior is quite popular for its versatility. It functions as a powerful stain remover and also prevents mold outgrowth on damp surfaces. A few coats of this solution will remove stains from mold growth, pet urine, and even crayon marks.

Kilz Mold & Mildew contains a high concentration of biocide to prevent mold and mildew from growing on moist surfaces. The EPA-approved chemical forms a mold and mildew-resistant film on these surfaces. It is also known to kill black molds.

Besides these attributes, it is also a strong option for plugging leaking walls. You’ll often find this product as an aerosol can at your local hardware store or online.

Kilz 3 Premium Primer 

The Kilz 3 Premium is one of the top primers in the Kilz product line. It is a three-in-one solution for damp and moist wall surfaces.

The Kilz 3 Premium primer can withstand up to 12 PSI of water pressure in walls, making it an excellent primer for waterproofing. 

Furthermore, it has better stain-blocking abilities than most Kilz primers. With only a coat or two, you can easily hide stains and seal in odors from mildew, mold, pet urine, and cigarette smoke

Although it is mainly for waterproofing damp walls, this primer also eliminates molds and mildew as it contains biocide.

How to Apply Kilz Primers to Kill Molds 

priming the molded door jamb with a primer

Now that you know the best Kilz primers to kill molds or mildew, the next step is to apply the primer on the affected surface. Follow these instructions to start the process:

  1. Get an N-95 face mask to cover your nose and prevent you from inhaling the primer. 
  1. Pour the required quantity into a small container.
  1. Scrape or lightly sand down the mold or mildew. 
  1. Gently apply the primer over the mold or mildew-infested area. Add two coats for good measure. 
  1. Wait for a while and watch the mold shrivel up. 
  1. If you’re using an aerosol version, spray it on the affected region. 
  1. Wait for 24 hours to see the result.

Note: Wear disposable clothes while applying the primer. Mold spores can attach to clothing and affect you later if you don’t dispose of it.

When you do dispose of any infested clothing, burn it in a ventilated area or place it in a polythene bag and dispose of it according to local, state, and federal regulations.


Products that contain biocides are exceptionally effective for killing microorganisms like mold and mildew. Since Kilz primers contain biocides, you can effectively use them to easily clean mold-infested areas.