Zinsser Mold Killing Primer, Did you read the label?

As a Mold Assessor I often come across remediation contractors who specify Zinsser as an acceptable encapsulate product for their remediation process. Zinsser is not an encapsulate material, It is a primer, part of a two step system manufactured by Rust-Oleum.

It is highly suggested that the labels and Technical Data Sheets (TDS) (see link for .pdf) be reviewed prior to use of this product. When reviewing the TDS it is further clarified by Rust-Oleum that this material is not intended for professional remediation.

Firstly, the TDS reads, “Mold Killing Primer is for use on non-porous interior and exterior.” Any material that requires encapsulation by a remediation company will be porous and therefore conducive to mold growth, mainly plywood and lumber. The Porous characteristic of a conducive material is what generally allows the material in question to grow mold. Material that is non-porous is typically non-conducive and is able to be wiped or scrubbed clean, such as metal, concrete and plastic.

Second, the label reads “Do not apply when air or surface temperature is below 50°F,” this would typically eliminate all winter attic remediation.

Third, the label implies that this is a first coat product and requires a top coat to complete the system and cover any stains.

To clear any ambiguity, Bald Eagle Inspection Services was involved in a call with the manufacturer’s technical department due to complaints and product failure. Under high heat and humid conditions Zinsser will fail, chip and peel from surfaces. Rust-Oleum manufactures warranty will not cover these types of failures and client removal is usually required out of pocket to necessitate repairs. The following topics were addressed:

1) Although the TDS lists attics as acceptable locations for use, please clarify the use of this product as wooden assemblies where this product would be used are porous. RESPONSE: This product can be used in a variety of buildings and their location, however, the material is not approved for use on porous materials in these locations, including wood.

2) Will Zinsser block staining or bleed-through of mold stains? RESPONSE: It is not recommended that Zinsser be used without a stain blocking application, such as BIN product.

3) Is Rust-Oleum considered an encapsulate alternative for use in mold remediation? RESPONSE: This material is not an encapsulate. It is intended as a primer. It’s use as an encapsulate is not guaranteed or warranted.

Where professional application is expected, longevity preventative coatings and full successful clearance is required, Zinsser shall not be utilized by professionals, therefore Zinsser falls under a category of products that Bald Eagle Inspection Services does not approve as a commercially acceptable product for professional remediation. Encapsulate materials are intended to be absorbed into the material being treated. This application will kill rooted fungi and seal the surface preventing further growth or new growth. Zinsser is a surface application. Zinsser will seal a surface and prepare it for a finish coat, but it will not be absorbed by the substrate being treated. Again, some Zinsser applications are known to fail and delaminate under high heat and relative humidity conditions. Rust-Oleum does not guarantee the use of Zinsser in an attic.

If you hire a professional remediation service, expect professional remediator work practices and materials.

Bald Eagle Inspection Services, LLC is a leading Mold Assessment company providing services in the Upstate New York areas and beyond.