Can The Finish System And Outside Insulation Be Deemed Non-Combustible?

Noncombustible exterior wall assemblies with stone wool insulation can comply with code requirements while avoiding additional fireblocking. These systems, such as steel-frame construction and EIFS, are nonstructural, nonload-bearing, and consist of an insulation board attached to the wall construction outside the sheathing. The finished product is resistant to water, sunlight, weather, abrasion, fading, and impact.

EIFS is considered combustible due to its polystyrene foam insulation, but actual fire performance depends on factors like material defects and poor material quality. The finished product is resistant to water, sunlight, weather, abrasion, fading, and impact. Composite panels using non-combustible insulation are not allowed to be classified as non-combustible.

EIFS is a lightweight system designed for use in non-combustible construction but can be treated as combustible. Fire retardant treated wood does not qualify as noncombustible. EIFS alone do not have a fire rating, but testing has been conducted.

Manufacturers offer MCMs with fire-resistant cores, which can reduce the hazard level for these assemblies. The StoTherm® ci Mineral System incorporates non-combustible, mineral wool exterior insulation and continuous moisture and air barrier with EIFS systems and exterior wall coverings not required to have fireblocking pursuant to Section 718.2.6.1 of this code. Incorporating noncombustible materials within EIFS foam at each floor line is a possibility, although difficult, and can be discussed with the manufacturer.