4HR Fire Rating.pdf

Comfort Block has a 4-hour fire resistance rating, achieved through testing in accordance with ASTM standards by the National Concrete and Masonry Association (NCMA). The fire resistance rating is determined based on the equivalent thickness of the concrete masonry unit, with a minimum required equivalent thickness of 3.75 inches for a 4-hour rating. Comfort Block's CB-12 mix designs exceed this requirement, with an equivalent thickness value of 8.03 inches.

The fire resistance rating is based on the type of aggregate used in the concrete masonry unit, with different aggregates requiring different minimum equivalent thicknesses. The rating can also be affected by the use of finishes such as drywall, plaster, or stucco, which can provide additional fire resistance. However, the masonry alone must provide at least half of the total required rating, and the contribution of the finish on the non-fire-exposed side cannot exceed half of the contribution of the masonry alone.

To achieve the desired fire rating, Comfort Block wall assemblies must be entirely coated on both sides, and the finish material must be continuous over the entire wall. The coating also serves to weatherize the wall system and achieve the desired aesthetic. References include Design and Construction Guidelines for Dry-Stack Concrete Masonry (TMS 1430-21), Fire Resistance Ratings of Concrete Masonry Assemblies (NCMA TEK 07-01D), and Standard Methods of Sampling and Testing Concrete Masonry Units (ASTM C140).