Building codes require that certain structures shall be made with fire-retardant or flame resistant plywood. The use of this material in walls and partitions prevents the spread of fire from one part of building to others. Fire-retardant plywood successfully completes vertical through-roof firewalls, simplifying roofs construction and reducing building and reroofing costs.
The rules of modern construction require that firewall should be built through the whole building from foundation up to the roof surface. Fire-retardant plywood is usually used for roof decking at the both sides of firewalls, while the rest of the roof sheathing shall not be necessary fire-retardant.
Modern technologies provide various opportunities for production of fire-retardant plywood. Manufacturers choose to treat every veneer of plywood with fire-retardant chemicals or to overlay standard plywood with flame resistant coatings. Of course, chemical treatment or special coating cannot make plywood absolutely noncombustible, but they still guarantee low flame-spread rate compared to one of gypsum wallboards. The way of production influences the Hazard Level of the final product.
One of the problems of treated plywood is fast corrosion, but the development of new solutions with less acidic chemicals not only tends to solve it, but also contributes to raising the temperatures, which these fire-retardant materials can possibly withstand. To avoid the premature deterioration of plywood, it should be kept in a dry place before installation.