irestopping plays a critical role in protecting buildings and maintaining life safety. For contractors and specifiers looking for a reliable, easy-to-install solution for sealing penetrations and construction joints, SpecSeal® LC120 Endothermic Firestop Sealant from STI delivers proven performance with installer-friendly application.
Available through Hewson Brothers, LC120 is a latex-based, high-solids firestop compound designed to seal penetration openings and joints against the spread of fire, smoke, hot gases, and water when properly installed.
Reliable Firestop Performance
SpecSeal® LC Sealant is engineered to form a flexible, non-shrinking barrier that helps prevent the spread of fire and smoke through penetrations and joints in wall and floor assemblies.
The sealant has been tested to major industry standards, including:
- ASTM E814 (UL1479) for penetration firestop systems
- ASTM E1966 (UL2079) for fire-rated joint systems
- CAN/ULC-S115 for Canadian firestop testing
These tested systems can achieve up to a 3-hour fire-resistance rating using as little as 1/4″ of sealant depth, or up to 4 hours with 1/2″ depth, depending on the system design. In addition to fire resistance, the sealant maintains movement capability and has been tested through 500 movement cycles with joint movement up to ±12.5%, supporting real-world building movement.
Endothermic Protection
A key advantage of LC120 is its endothermic formulation. The sealant contains fillers designed to absorb heat and release water when exposed to fire, helping slow heat transfer and maintain the integrity of the fire barrier. Combined with its high-solids composition, this design helps minimize shrinkage during curing while maintaining the integrity of the seal.
Designed for Jobsite Efficiency
LC120 is designed with contractors in mind. The material adheres well to virtually all common construction surfaces and can be installed using standard caulking equipment or applied with a trowel or putty knife, making it suitable for a wide range of jobsite conditions.
The sealant’s thixotropic consistency allows it to be applied to vertical and overhead surfaces without slumping, while still offering excellent caulking properties and high-build capability.
Once installed, the material dries to form a durable, flexible seal that is resistant to water and will not re-emulsify after curing, helping ensure long-term reliability.
Versatile Applications
SpecSeal® LC120 is designed primarily for sealing construction joints, gaps, and penetrations involving noncombustible penetrants. Tested applications include:
- Single metallic pipe penetrations up to 30 inches in diameter
- Multiple penetrants through masonry or gypsum wallboard assemblies
- Steel-sleeved penetrations
- Electrical and communications cable penetrations
- Joint and gap sealing in rated assemblies
This versatility makes LC120 a dependable option across mechanical, electrical, and plumbing penetrations in commercial and institutional construction.
Built for Safety and Sustainability
SpecSeal® LC Sealant is formulated with both safety and environmental considerations in mind. The product is water-based, low-VOC, non-halogenated, and contains no asbestos or inorganic fibers, supporting safer handling and improved indoor air quality. It also meets LEED v3, v4, and v4.1 low-emitting material requirements, helping projects contribute to sustainable building certifications. For easy inspection on the jobsite, the sealant is available in distinct red coloring, allowing installers and inspectors to quickly verify proper installation.
A Dependable Firestop Solution
With its combination of endothermic fire protection, flexible movement capability, and installer-friendly application, SpecSeal® LC120 Endothermic Firestop Sealant offers a dependable solution for sealing penetrations and joints in rated assemblies.
At Hewson Brothers, we’re proud to supply STI firestop solutions that help contractors meet code requirements while maintaining installation efficiency on the jobsite.
For more information on SpecSeal® LC120 Endothermic Firestop Sealant, or to discuss your firestopping requirements, contact your Hewson Brothers representative today.
