G.B. Corrugated “400” Siding and Roofing Material — National Gypsum Co.

G.B. Corrugated “400” Siding and Roofing Material was a cement-based construction product manufactured by National Gypsum Company and sold under the G.B. product line. Produced from approximately 1954 through 1981, this corrugated sheet material was used in industrial, agricultural, and commercial construction projects across the United States. Workers who handled, installed, cut, or demolished this product during its years of production may have been exposed to chrysotile asbestos fibers released during normal use.

Product Description

The G.B. Corrugated “400” was a corrugated sheet product designed for use as exterior siding and roofing material on industrial and commercial structures. Its corrugated profile provided structural rigidity, allowing large sheets to span roof purlins and wall framing without additional backing material. This made it a practical and cost-effective choice for warehouses, factories, agricultural buildings, and similar applications where durability under weather exposure was a primary concern.

National Gypsum Company, headquartered in Buffalo, New York, was one of the largest building materials manufacturers in the United States throughout much of the twentieth century. The company operated under multiple product lines and brand names, and the G.B. designation identified a segment of its fiber-cement and related construction materials. The “400” designation referred to a specific product formulation within the corrugated siding and roofing category.

This product was manufactured during a period when asbestos-reinforced cement was a standard industry material for exterior cladding. The corrugated format was widely adopted in industrial construction, and the G.B. Corrugated “400” competed in a market that included similar products from other major manufacturers.

Asbestos Content

The G.B. Corrugated “400” Siding and Roofing Material contained chrysotile asbestos as a reinforcing fiber component. Chrysotile, also known as white asbestos, is a serpentine-form mineral fiber that was the most commercially prevalent form of asbestos used in building products during the mid-twentieth century.

In fiber-cement siding and roofing products of this type, chrysotile asbestos served several manufacturing functions. The fibers were mixed into a Portland cement slurry and formed into sheets using a process similar to the Hatschek method, in which successive thin layers of fiber-cement were deposited on a rotating drum and then pressed into flat or corrugated sheet form. The asbestos fibers reinforced the brittle cement matrix, providing tensile strength, resistance to cracking, and improved weathering performance.

The finished product, when intact and undisturbed, generally presented a low risk of fiber release. However, under conditions of cutting, drilling, grinding, weathering, or demolition, the cement matrix could be disrupted and asbestos fibers released into the surrounding air. The regulatory framework established under the Asbestos Hazard Emergency Response Act (AHERA) and OSHA’s asbestos standards recognizes that fiber-cement products of this type can become friable and hazardous when mechanically disturbed.

How Workers Were Exposed

Industrial workers are among the trade groups identified in litigation records as having potential occupational exposure to the G.B. Corrugated “400” product. Exposure pathways associated with this category of corrugated fiber-cement sheeting are consistent with the general patterns documented across asbestos-containing building materials of similar composition.

Workers involved in fabrication and installation of this siding and roofing material would have encountered the product in conditions where mechanical disturbance was routine. Cutting sheets to fit structural dimensions required the use of hand saws, circular saws, or angle grinders — operations that could generate significant quantities of fine dust. This dust, containing respirable chrysotile fibers, could accumulate in enclosed or semi-enclosed work areas and be inhaled by workers in the immediate vicinity as well as bystanders and coworkers in adjacent areas.

Fastening and fitting operations involving drilling through the corrugated sheets similarly had the potential to release fiber-containing debris. Roofing and siding installation work was also subject to variable weather and wind conditions, which could carry airborne fibers beyond the immediate installation zone.

Workers involved in renovation, repair, or demolition of structures where G.B. Corrugated “400” had been installed faced an additional exposure hazard. Over time, asbestos-cement products can weather, develop surface degradation, and become more susceptible to fiber release. Demolition activities — including breaking, smashing, or mechanically removing corrugated sheet panels — could produce substantial concentrations of airborne asbestos fibers.

Plaintiffs alleged in litigation involving National Gypsum products that workers were not adequately warned of the health hazards associated with asbestos-containing materials during the product’s years of manufacture and sale. Plaintiffs further alleged that National Gypsum knew or should have known of the risks posed by asbestos-containing products, including chrysotile-reinforced fiber-cement sheeting, and that the failure to provide adequate warnings contributed to preventable asbestos-related disease.