FRX® wood has been tested in accordance with ASTM D 143 and MIL-L-19140E. Following are the design value adjustments for FRX wood.
Appearance
The treatment has little effect on the color of the lumber. Deposits of FRX fire retardant solution may appear on the surface of wood (“efflorescence”) or exude from the edges of plywood during drying (“intumescence”). This is a result of injection of adequate chemical to achieve desired fire protection, and is considered normal. On most species, discoloration is barely noticeable.
Marks made by stickers, used to separate the layers of lumber during the kiln drying following treatment, will be noticeable on lumber. For structural use, this is not objectionable. The pressure treatment and subsequent drying may result in a slight waviness in plywood; for normal applications this is not objectionable as the plywood can be straightened when nailing.
FRX exterior FRT wood, when specified, can be special ordered with the good face free of sticker marks. Slight irregular water marks may at times show on such material.
