This is a cache of https://www.owenscorning.com/en-us/insulation/products/thermafiber-topstop. It is a snapshot of the page as it appeared on 2026-09-24T09:32:32.181+0000.
THERMAFIBER® TOPSTOP® | Owens Corning Insulation

Exceptional fire containment

Why choose mineral wool insulation for head-of-wall constructions?

Thermafiber® TopStop® Head-of-Wall Insulation provides fire containment in head-of-wall constructions. These pre-cut insulation products are made from mineral wool, making them non-combustible, moisture-resistant, non-corrosive, non-deteriorating, mildew-resistant, and vermin-resistant. TopStop® is a trapezoid-shaped pre-cut insulation designed for head-of-wall firestopping. It installs quickly and easily, saving time and reducing waste on job sites.

Key Features of TopStop®:

  • High-Temperature Fire Resistance - Withstands temperatures above 2,000ºF for reliable fire containment at head-of-wall joints.
  • Pre-Cut, Trapezoidal Design - Time-saving shape fits easily into wall-to-ceiling gaps.
  • Easy Installation - Compresses cleanly into fluted decks and meets firestop code requirements.
  • Highly Durable - Resists moisture, mildew, corrosion, and long-term deterioration.
  • Supports Green Building - Made with at least 70% recycled content*; may qualify for LEED® credits**.
  • Flexible Sizing - Offered in three trapezoidal sizes and standard forming strips.

*ICC-ES VAR-1025, verified by ICC Evaluation Service (ICC-ES)

**Owens Corning LEED® v4.1 Credits Guide, Pub. No. 10027523-A, identifying potential LEED® v4.1 credit contributions for Thermafiber® Mineral Wool Insulation products

Download Product Data Sheet
Block of Thermafiber® TopStop®

Building Enclosure Solutions

Owens Corning® Enclosure Solutions offers one of the largest portfolios of commercial insulation products for walls, roofs, and below-grade foundations. Engineered with Owens Corning technical expertise and supported by Building Science, Owens Corning® Enclosure Solutions deliver buildings that perform without compromising design.

View Enclosure Solutions

Performance Attributes

Thermafiber® TopStop® is designed to deliver reliable performance across multiple job site demands. It offers exceptional fire resistance, withstanding temperatures above 2,000°F (1,093°C), and remains stable under fire exposure. The mineral wool composition resists moisture, helping preserve material integrity in challenging environmental conditions. TopStop® also contributes to energy efficiency by supporting tight wall assemblies and minimizing gaps with its unique design. Made with a minimum of 70% recycled content*, it aligns with several green building objectives**. 

In addition to its physical performance, TopStop® simplifies the installation process with its specific pre-fabricated design. This pre-cut insulation is a key component in head-of-wall firestop systems, reducing the need for on-site cutting and making the process of sealing top-of-wall gaps, especially around uneven or ribbed deck surfaces, fast, clean, and more consistent.

*ICC-ES VAR-1025, verified by ICC Evaluation Service (ICC-ES)

**Owens Corning LEED® v4.1 Credits Guide, Pub. No. 10027523-A, identifying potential LEED® v4.1 credit contributions for Thermafiber® Mineral Wool Insulation products


Fire Resistance icon

Fire Resistance

Moisture Resistance icon

Moisture Resistance

Energy Efficiency icon

Energy Efficiency

Recycled Materials icon

Recycled Materials

Technical Information

TESTED TO ASTM C 518

TESTED TO ASTM C 518

TESTED TO ASTM E 84 UNFACED

TESTED TO ASTM E 84 UNFACED

Product Designation

Actual Density

“k” @ 75° [24°C] BTU.in/hr.sq. ft. °F

“R” value per inch of thickness*

Flame Spread

Smoke Developed

TSZ-16.0 pcf0.234.300
TSZ-26.0 pcf0.234.300
TSZ-36.0 pcf0.234.300
TSF-A26.0 pcf0.234.300
TSF-A46.0 pcf0.234.300
TSF-B26.0 pcf0.234.300
TSF-B46.0 pcf0.234.300

*R = thickness divided by ‘k’

Physical Properties

Property

Test Method

Value

Corrosion of Steel, Aluminum, and Copper

ASTM C665, HH-I-521FType 1
Non-CombustibilityASTM E136Non-Combustible
Non-CombustibilityCAN/ULC S114Complies
Water Vapor SorptionASTM C1104Sorption less than 1% by volume
Surface Burning CharacteristicsASTM E84

Flame Spread 0,
Smoke Developed 0

Surface Burning CharacteristicsCAN/ULC S102

Flame Spread 0,
Smoke Developed 0

Applications

Head-of-wall insulation is used to seal the gap where fire rated wall assemblies meet a fire rated ceiling assembly, a critical area for maintaining fire-resistance ratings. Building codes require this joint to be protected with materials that have been tested as part of full wall insulation assemblies. Thermafiber® TopStop® is a pre-cut insulation specifically designed for this purpose, with the added benefit of high density for secure compression and proper placement. The trapezoidal shape of this mineral wool product allows for quick, consistent installation at the head-of-wall joint, helping contractors meet code while reducing time on site.

  • Accessories and Specialty

Contact Us

Even though we're a global company, we're always ready to answer your questions. Call to speak with an Owens Corning representative.