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STI SpecSeal WF320 Fire Barrier BlazeStop WF Intumescent Caulk 20oz Sausage
Latex based, high solids firestop caulk. Seals penetration openings in wood frame construction against the spread of fire, smoke and combustion byproducts. When exposed to elevated temperatures, WF300 expands rapidly to seal off voids left by the burning or melting of combustible materials.
$13.16
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SKU
22970
STI SpecSeal WF-320 Fire Barrier BlazeStop WF Intumescent Caulk – 20 oz Sausage
WF-320 is a latex-based, high-solids, intumescent firestop sealant packaged in a 20 oz sausage for production installs. In wood-frame construction, it expands when exposed to heat to help close voids left by melting or burning plastics, forming a durable smoke- and fire-resistant seal at penetrations and joints. The red, paintable formula installs easily, cleans up with water, and is water resistant when dry.
Key Features
- Intumescent, latex-based firestop for wood-frame floors, ceilings, and walls.
- Expands under heat to help seal openings around combustible penetrants.
- Water cleanup; water resistant after cure; paintable once dry.
- High-solids formula; won’t separate or shrink when dried.
- Auto-bonding; adheres to lumber, gypsum board, and common penetrant materials.
- Low VOC, non-halogenated; Class A surface finish to ASTM E84.
- Convenient 20 oz sausage for efficient gunning and reduced change-outs.
Applications
- Through-penetrations and annular spaces in rated wood-frame assemblies.
- Perimeter gaps and construction joints per tested firestop designs.
- Electrical, plumbing, and HVAC penetrations using listed systems.
- Retrofit resealing during maintenance or tenant improvement work.
Technical Specifications
| Color | Red |
| Chemistry | Latex, intumescent, high solids |
| Free Expansion | Up to 5× original volume under heat |
| Expansion Begins | Approximately 350°F (176°C) |
| Flame / Smoke (ASTM E84) | Flame 0; Smoke 20 (Class A surface finish) |
| STC Rating | 61 (relates to specific construction) |
| VOC Content | Approximately 28 g/L |
| Solids (by weight / volume) | About 81% / 77.6% |
| Density | ~10.2 lb/gal (1.22 kg/L) |
| Application Temperature | 35°F to 100°F (2°C to 38°C) |
| In-Service Temperature | Less than 185°F (85°C) |
| Storage Temperature | 40°F to 95°F (4°C to 35°C) |
| Shelf Life | 24 months (unopened, proper storage) |
| Compliance | ASTM E814 (UL 1479), CAN/ULC-S115; systems up to 2 hours (wood frame) |
| Unit Size (this item) | 20 oz sausage (592 mL) |
| Case Quantity / Each Weight | 12 per case / ~1.70 lb each |
Frequently Asked Questions
Where is WF-320 used?
In rated wood-frame floor/ceiling and wall assemblies to seal penetrations and joints per tested firestop systems.
Is it paintable and water resistant?
Yes. It can be painted when dry and is water resistant after cure; clean up with water before curing.
Does it work with plastics?
It is designed to be safe with many plastic pipes and cable insulations. Confirm compatibility with the penetrant manufacturer.
Any electrical precautions?
The wet sealant is conductive until dry. Do not apply in the presence of exposed or energized conductors.
What certifications does it meet?
Tested to ASTM E814/UL 1479 and CAN/ULC-S115; Class A surface finish when tested to ASTM E84.
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