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Review Round-Up: Zinsser Mold-Killing Primer

June 9, 2021

Springtime brings warmer weather, but it also brings rain. Moderate temperatures, overcast skies and days of precipitation are a recipe for mold and mildew growth (yuck!) Bothered by mold on surfaces that aren’t getting much sunlight? There’s a paint product for that.

Zinsser Mold-Killing Primer

Rustoleum’s Zinsser primer is the only product on the market that claims to kill – not just prevent – mold. While the primer is EPA registered and comes with a limited mold-killing warranty, we thought we would gather reviews on the product to see what homeowners had to say.

Positive Reviews

Overall, Zinsser’s 4.5 stars on Google and 4.4 on Amazon falls just shy of Phillips’ 4.6 star average, so it seems the product is well-received by homeowners and contractors. Below is a selection of some informative positive reviews, followed by negative reviews further down.

“Worth every penny”

5/5 stars

“We moved back to Virginia from Texas in June only to discover that our renters had allowed a tiny little leak in one of the bathrooms to get so bad that the bathroom had to be gutted due to black mold. Once it had all been properly removed, everything stripped to the studs, my husband painted with Zinsser mold killing primer, just in case! Since It was next to the laundry room, there was a small amount of mold in there as well, on one wall, once It was removed, he painted the room with Zinsser too. It has been months and still no mold. For my peace of mind, he is also painting the adjacent bedroom with Zinsser when he remodels it.”

“It really works if you are patient”

5/5 stars

“This really worked on my fireplace mantle. I have bleached that mantle 100 times with no luck. I was concerned at first that this primer would not kill and cover the mold after the first three or four coats. Just don’t expect to do a standard two coats for it to work. I have probably put ten coats or so on the mantle, but it absolutely did kill the mold and cover the dark discoloration. Just be patient and let it thoroughly dry between coats. The fungicide needs time to work. And be willing to do numerous coats. It saved me hundreds of dollars or more since I do not have to replace the fireplace mantle.”

“Economical option to take care of mold”

5/5 stars

“I was afraid I would have to spend lots of money to have professionals fix my mold problem. But this stuff really works! It goes on thick and kills the mold and makes a great base coat of paint too. It has a smell to it, but not too overwhelming. I used it in my basement where I did not have good ventilation. I had a spot of green and black mold in a corner of the walls from rain water damage causing moisture and mold. I did not even have to put a second coat. It took care of it with one. I may reapply if mold comes back, but it seems to be doing the trick for now. It is a lot more economical this way than hiring a professional who would do the same thing basically. I recommend.”

Negative Feedback

Both of the most informative negative reviews revolve around the use of Zinsser on porous surfaces like lumber. Zinsser does not have a mold-killing warranty on these surfaces. As always, Phillips recommends replacing rotten and otherwise worn-down boards on your home with new lumber or, even better, fiber cement – there is no substitute for replacement!

“It’s not guaranteed for porous surfaces (wood)”

2/5 stars

“I painted a new piece of exterior plywood with Mold Killing Primer and after a couple of months mold grew on it. I repainted again and the same thing happened. The wood is in a covered carport that might occasionally get blowing rain. I called Rustoleum who bought Zinsser and was told they don’t guarantee on porous surfaces like wood. They said you can use on wood just like any other primer and theirs just has a moldicide added to help prevent mold growth. So don’t expect it to kill mold on wood. I’ve had the best luck spraying on vinegar and wiping away any residue myself. Call rustoleum before you blindly try this product.”

“I Should Have Read the Instructions!”

2/5 stars

“I had an air-handler leak in the attic which stained the halls and bedrooms ceiling and walls. After fixing the problem, I washed the areas with TSP and rinsed several times before letting the surfaces dry out for two years.

“I was planning to use this product to block the stains before applying a primer topcoat. But the instructions clearly state “use for non-porous surfaces only” … which means “china coat” surfaces in my case and not the drywall [gypsum/paper] I have. (Rustoleum’s video on their website suggests it will work satisfactorily over enamel surfaces.)

“Since I don’t believe I have an ‘active’ mold issue, I’ve done an experiment. Used this product combined with their Stain Blocker product in the hall and just the Stain Blocker in the BR. They both look fine now; the true test will be in several years.

“I think Zinnser needs to clarify … very specifically … where the product should NOT be used.”

Wrapping Up

Based on these reviews, it seems Zinsser Mold Killing Primer really does kill mold on select surfaces. However, if you have an active mold situation in your home, Phillips recommends replacing any damaged porous surfaces like wood (undamaged exterior surfaces can be powerwashed by a trained professional using TSP instead). After cleaning and possibly replacing, Zinsser primer should be applied first as part of the two-step surface coating process.

If you’re in the Dallas-Fort Worth area and would like help ridding your home of mold and mildew, give Phillips a call at (972) 867-9792. We’re happy to assist!