Systems and methods are provided for treating products containing wood fibers to provide protection against wood destroying organisms and fire, and resistance against leaching of the preservative from the wood by water in exposed environments such as exterior applications. The methods involve applying to a substrate a first aqueous composition containing a boron compound, a source of zinc, and ammonia, followed by application of a second aqueous composition containing an alkali metal silicate. The compositions may be applied by vacuum and/or pressure treatment or dip treatment under atmospheric pressure.