Loadmaster Duraflex Mineral Board

DESCRIPTION: Loadmaster Duraflex mineral board is a specially designed high density, weather resistant fiberglass panel designed to perform multiple functions in the Loadmaster assembly. The Duraflex mineral board is ½ or 5/8-inch thick, 4 feet wide and 12 feet 6 inches long, with paper bonded to all surfaces except panel ends. Four longitudinal rows of numbers along the length of the board provide location markings for the placement of screw fasteners in accordance with specified Loadmaster Duraflex Mineral Board attachment patterns. Edges of the board are tongue and grooved for interlocking installation. Ends are square cut to form tight butt joints.

FUNCTION: Loadmaster Duraflex mineral board functions as a structural element in the assembly by providing flexural rigidity. In addition, it serves as a substrate for the application of roofing. Special design considerations have given it outstanding qualities to provide load distribution, permeability, low water absorption, high indentation resistance, fire retardant characteristics, compatibility with hot bitumen, resistance to moving, static and impact shock loads, as well as excellent resistance to vibration and wind uplift forces. High compressive strength also provides a tough traffic-bearing substrate which increases penetration resistance for roofing membranes.


Thickness ½” or 5/8”
Weight (lb./sq.ft.) 2.0 nom or 2.5 nom
Length 12’-6”
Width 4’-0”
Core Compressive Strength 400 psi nom
Flame Spread ASTM E84* 15
Permeability 16 perms

*The numerical flame spread rating as determined by ASTM Test Method E-84 is not intended to reflect hazards presented by this or any other material under actual fire conditions.

ASTM SPECIFICATIONS: Loadmaster Duraflex mineral board meets or exceeds the performance criteria in ASTM Specification C-79.

WEATHERABILITY: In accordance with the accepted criteria governing the design of roofing substrates, the Loadmaster Duraflex mineral board is not in itself a waterproof element. The board is specifically designed to allow for the proper transmission of water vapor and a degree of moisture migration so that water, which might enter the substrate during initial construction and/or subsequent roof leaks, can be quickly dissipated without creating an excessive build-up of vapor pressure. While these essential functional characteristics are somewhat opposed to weatherability characteristics, the Loadmaster Duraflex Mineral board is, nonetheless, weather resistant within the scope of its intended use. While it is recommended the roofing be applied as soon as practical after the board is in place, it is not essential to do so, within reasonable limits.

SUITABILITY FOR ROOFING: Should a Loadmaster Duraflex Mineral Board get wet prior to application of roof covering, restrict foot traffic and allow Duraflex board to air dry.  The deck is ready to roof when the mineral board appears dry, and no frying or sizzling sound occurs during application of hot roofing asphalt.