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FortiFiber FortiFlash Butyl Flashing Membrane, Self-Sealing 25 mil Waterproof Vapor Retarder, 4 in. x 75 ft. Roll
Regular price $28.75Orders start at $399 — combine any items to reach the minimum. Learn more
FortiFiber FortiFlash Butyl Flashing Membrane, Self-Sealing 25 mil Waterproof Vapor Retarder, 4 in. x 75 ft. Roll
FortiFiber FortiFlash is a Class I, self-bonding, waterproof vapor retarder membrane combining an SBS modified asphalt layer with a high-strength cross-laminated polymer film. This 25 mil roll measures 4 in. x 75 ft. and self-seals around nails and fasteners for lasting watertightness.
Key Features:
- Class I barrier: A premium Class I vapor retarder and moisture barrier.
- Self-sealing: Self-seals around nails and fasteners for lasting watertightness.
- Heat resistant: Withstands extreme temperatures up to 250 degrees F.
- Split-back liner: Split-back release design for easy handling during installation.
- Conforms to detail: Installs around protrusions and into tight corners without delaminating or tearing.
Specifications Table:
| Specification | Details |
|---|---|
| Brand | FortiFiber |
| Sell unit | 1 roll, 4 in. x 75 ft. (25 mil) |
| Product line | FortiFlash |
| Dimensions | 4 in. x 75 ft. roll |
| Thickness | 25 mil |
| Material | SBS modified asphalt with high-strength cross-laminated high-density polymer film |
| Nominal size | 4 in. x 75 ft. |
| Wind / fire / impact rating as printed | Class I vapor retarder |
| Approvals | Class I (as printed); other certifications not stated |
| Intended use | Waterproof flashing; moisture barrier under wood panel subfloors over concrete slabs |
Coverage & How Much You Need:
One roll measures 4 in. x 75 ft., yielding 25 linear feet of flashing per inch of width equivalent; a full roll is 75 linear feet of 4-inch-wide tape. Size jobs by linear footage of seams, window and door perimeters, or slab edges.
Fit and Compatibility:
Suited under floating or mechanically fastened wood panel subfloors beneath hardwood, carpet, laminate or resilient floors, and for flashing details around protrusions. Sold as a single roll; no fasteners or primers are included.
Frequently Asked Questions (FAQ):
Q: What is included?
A: One 4 in. x 75 ft., 25 mil roll of FortiFlash butyl flashing membrane.
Q: What does it self-seal around?
A: It self-seals around nails and fasteners to maintain watertightness.
Q: Can it handle heat?
A: Yes, it withstands extreme temperatures up to 250 degrees F.
Q: How easy is installation?
A: A split-back release liner makes handling easy, and the membrane conforms to tight corners and protrusions without tearing.
Q: What is it made of?
A: A two-part construction: an SBS modified asphalt base layer and a high-strength cross-laminated high-density polymer film.
Q: How much area does a roll cover?
A: One roll provides 75 linear feet of 4-inch-wide membrane; calculate coverage by the linear length of seams or perimeters you need to flash.
Expert Verdict — Reviewed by the SuperArbor Pro Desk
FortiFlash is a go-to self-adhered flashing for window and door rough openings and under subfloors on concrete slabs, replacing old felt-asphalt assemblies without the mess. Prime porous substrates per manufacturer guidance, and roll the membrane firmly to activate full adhesion. For wider laps or heavy water exposure, step up to a wider roll width.
Follow the manufacturer's installation instructions and confirm flashing requirements with local building codes before enclosing the membrane behind finishes.
Order FortiFiber FortiFlash 4 in. x 75 ft. self-sealing flashing membrane for watertight detailing.
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