A fire retardant wooden door that prevents the spread of fire through the door during a fire. The fire retardant wooden door has at least one door panel connected to stiles and rails by tongue and groove joints, and the tongue and groove joints have intumescent material therein. Each of the tongue and groove joints includes a tongue section having the intumescent material along a distal edge of the tongue section which expands upon exposure to heat or fire to seal the tongue and groove joints in order to prevent the heat or fire from passing through the door during a fire. Each of the tongue sections includes an interior channel extending along the axis of the tongue section, and the interior channel extends into the door panel. The interior channel has the intumescent material embedded therein which expands upon exposure to heat or fire to further seal the tongue and groove joints in order to prevent the heat or fire from passing through the door during a fire.

The present invention provides a building material derived from straw, such as rice straw, that has significantly improved fire-resistance properties over traditional cellulose-based materials. In one embodiment, the invention provides a method of fabricating a board from milled rice straw. The milled rice straw is blended with a binder to form a mixture. The mixture is then formed into a mat with sufficient size to achieve a predetermined board thickness and density. The mat is then pressed into the board. In another embodiment, the present invention provides a fire resistant board that includes milled rice straw, a resin binder, and a fire retardant material such as an organic phosphate, zinc borate, aluminum trihydrate, sodium silicate, or even rice hulls.

Fire resistant door, glazing, and mullion frames include intumescent material at least partially embedded in the frame adjacent the door or glazing. Trim materials are positioned over the intumescent material to prevent tampering with and damage to the intumescent material while improving the aesthetic appearance of the frame. The jamb trim has a thickness that allows heat to be transmitted to the intumescent material in the event of a fire so that the intumescent material will expand and fill a clearance space between the frame and the door or glazing. The expanded intumescent material retards the passage of heat and, by sealing the clearance space, inhibits the transmission of smoke, flames and gases from one side of the door or glazing to the other. After expanding, the intumescent material will char and solidify, which may provide an added benefit of structural support for the door or glazing.

Door and glazing frames include intumescent material positioned in a dado that is formed in a jamb side surface. Trim materials are positioned over the intumescent material to improve the appearance of the frame and to prevent tampering with and damage to the intumescent material. The jamb trim is preferably made of a cut hardwood panel having a thickness that allows heat to be transmitted to the intumescent material in the event of a fire so that the intumescent material will expand and fill a clearance space between the frame and the door or glazing. The expanded intumescent material inhibits the transmission of smoke and heat between the door and door frame. After expanding, the intumescent material will char and solidify, which may provide an added benefit of structural support for the door and or glazing.