Lt Wt Toppings
All though the UL Fire Resistive Design Assemblies are difficult to read and understand the fact is "Yes," you can achive a One or two hour UL Fire Rating without Lt. Wt. Concrete or Lt. Wt. Gypsum Concrete.
Most of the UL Fire resistive designs have "options" to achieve the 1 or 2 hour fire ratings with or without Lt Wt Concrete or Lt. Wt. Gypsum Concrete toppings.
In most UL Fire resistive designs Item number 1 references the type materials need on top of the joist or truss.
Flooring System — The flooring system shall consist of one of the following: Under this Item there are several optional systems. each system shows the options available above the joist. See example below from L528.
System No. 1 Subflooring — Min 23/32 in. thick T & G wood structural panels, min grade "Underlayment" or "Single-Floor". Face grain of plywood or strength axis of panels to be perpendicular to the trusses with end joints staggered 4 ft. Panels secured to trusses with construction adhesive and No. 6d ringed shank nails spaced 12 in. OC along each truss. Staples having equal or greater withdrawal and lateral resistance strength may be substituted for the 6d nails.
System No. 2 Subflooring — Min 23/32 in. thick T & G wood structural panels, min grade "Underlayment" or "Single-Floor". Face grain of plywood or strength axis of panels to be perpendicular to the trusses with end joints staggered 4 ft. Panels secured to trusses with construction adhesive and No. 6d ringed shank nails spaced 12 in. OC along each truss. Staples having equal or greater withdrawal and lateral resistance strength may be substituted for the 6d nails. Vapor Barrier — (Optional) - Commercial asphalt saturated felt, 0.030 in. thick. Vapor Barrier — (Optional) - Nom 0.010 in. thick commercial rosin-sized building paper. Finish Flooring — Min 3/4 in. thickness of lightweight insulating concrete with Perlite Aggregate or Vermiculite Aggregate, or gypsum concrete. See Perlite Aggregate (CFFX) and Vermiculite Aggregate (CJZZ) categories for names of manufacturers.
As you can see above in system 1 there is no need for a poured material on the topside of the plywood to archive the 1 hour fire rating. You can achieve a one hour fire rating with just 1 layer of plywood.
In L528 alone there are 15 different systems (options) for the finishes above the plywood sub floor, without counting the acoustical matt options.
We are willing and able to assist you in navigating your way through the complex UL assemblies and designs, just e-mail us or call us toll free at 866-774-2100.
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