Cat 5 R Guard Elastomeric Weatherproofing Membrane

PROSOCO R-Guard Cat 5 — Category 5-Rated Elastomeric Air & Water Barrier Membrane

PROSOCO R-Guard Cat 5 is a single-component, silyl-terminated polymer (STP) fluid-applied membrane engineered for contractors who demand a proven, high-performance air and water barrier on exterior sheathing, CMU back-up walls, and pre-cast concrete. Applied with a sprayer or roller, it cures to a seamless, elastomeric weatherproofing membrane that seals the building envelope against both everyday weather and extreme conditions. Cat 5 is designed for use as the primary air barrier over above-grade structural surfaces, working within the R-Guard system alongside Joint & Seam Filler and FastFlash.

Unlike sheet-applied membranes that rely on laps and adhesion to remain seamless, Cat 5 is fluid-applied, eliminating seams entirely and conforming to complex substrate geometries. Its silyl-terminated polymer chemistry combines the flexibility of polyurethane with the durability of silicone, and the formulation is solvent-free, isocyanate-free, and phthalate-free — complying with all VOC regulations.

Key Features & Benefits

Category 5 Hurricane Wind Resistance

Cat 5 is proven to prevent air and water penetration under 155-mph wind conditions — the threshold of a Category 5 hurricane. For contractors building in high-wind or coastal zones, this rating provides documented performance at the extreme end of the spectrum, not just everyday weather events.

Seamless Elastomeric Membrane

The fluid-applied process produces a continuous, seamless membrane with no laps, seams, or mechanical fasteners to create potential leak paths. Elastomeric properties allow the membrane to flex with structural movement, maintaining integrity over the life of the assembly.

Single-Component STP Chemistry

As a single-component product, Cat 5 requires no mixing or ratio management on site, reducing applicator error and simplifying quality control. The silyl-terminated polymer chemistry delivers a balance of flexibility and durability suited to the thermal and structural demands of exterior cladding assemblies.

Solvent-Free, Isocyanate-Free, Phthalate-Free

Cat 5 contains no solvents, isocyanates, or phthalates, and complies with all VOC regulations including California Air Resources Board (CARB) 2007 requirements with a VOC content below 30 g/L. This simplifies jobsite safety management and supports green building documentation for LEED, LBC, CALGreen, WELL, and Fitwel projects.

Spray or Roller Application

Cat 5 can be applied by sprayer or roller, giving crews flexibility to match the application method to the project scope and substrate configuration. Both methods deliver the uniform, continuous film needed to achieve rated performance.

Green Building Program Support

Cat 5 carries a Declare label (PRO-0005) and is Living Building Challenge Red List Approved, supporting material ingredient transparency requirements. The product is CDPH Standard Method v1.2-2017 compliant with total VOCs at or below 0.5 mg/m³ after 14 days, and supports documentation for LEED 2009, LEED v4.x, CALGreen, Living Building Challenge 3.x, WELL v2, and Fitwel.

Common Applications

Exterior Sheathing

Cat 5 is applied directly over prepared exterior sheathing as a continuous air and water barrier, protecting the building envelope at the most vulnerable transition zone between structure and cladding.

CMU Back-Up Walls

On concrete masonry unit backup walls, Cat 5 bridges the porous, irregular surface to form a seamless weatherproofing layer, preventing water infiltration through the masonry substrate.

Pre-Cast Concrete

Cat 5 is suited for application over pre-cast concrete panels, sealing the substrate against air and water penetration while accommodating the minor movement and joint irregularities typical of pre-cast assemblies.

Above-Grade Structural Surfaces (Primary Air Barrier)

Cat 5 functions as the primary air barrier for above-grade structural surfaces when used in conjunction with Joint & Seam Filler and FastFlash to fully detail the building envelope.

Compatible Materials

• Exterior sheathing
• CMU (concrete masonry unit) back-up walls
• Pre-cast concrete
• PROSOCO R-Guard Joint & Seam Filler (surface prep/detailing)
• PROSOCO R-Guard FastFlash (surface prep/detailing)

Product Documents

• Product Data Sheet
• Product Data Sheet (Canadian French)
• Product Data Sheet (Spanish)
• Safety Data Sheet
• Safety Data Sheet (Spanish)
• Safety Data Sheet (Canadian French)
• VOC Compliance
• ABAA Certification
• Product Test Data
• NFPA 285 Compliant Wall Assemblies
• LEED Verification Letter
• SCS Certification
• LBC Red List Conformant Product Summary
• LBC Red List Conformant Product Summary (2021)
• ICC-ES Evaluation Report ESR-3416

Technical Specifications

Frequently Asked Questions

Q: What green building certification programs does Cat 5 support?
A: Cat 5 provides submittal information supporting LEED 2009, LEED v4.x, CALGreen, Living Building Challenge 3.x, WELL v2, and Fitwel, covering both indoor environmental quality and sustainable materials credits.

Q: Is Cat 5 safe to use without solvent or isocyanate precautions?
A: Cat 5 is formulated to be solvent-free and isocyanate-free, which removes two common hazard categories associated with fluid-applied membranes. Always consult the Safety Data Sheet for full handling requirements.

Q: What surface preparation products are required before applying Cat 5?
A: PROSOCO specifies that surfaces be prepared with R-Guard Joint & Seam Filler and R-Guard FastFlash prior to applying Cat 5 as the primary air barrier layer.

Q: Does Cat 5 meet NFPA 285 requirements?
A: PROSOCO provides an NFPA 285 Compliant Wall Assemblies report for Cat 5. Refer to the document linked in the Product Documents section for specific assembly configurations.