barrier / sealer compositions impart at least biostatic activity to porous substrates , particularly architectural building materials , such as wood products , providing extended protection against the development of damaging fungi , such as mold , mildew and yeasts , as well as bacterial infestation . the protective sealer compositions comprise at least one antimicrobial agent , such as a fungicide and a film forming combination comprising a continuous film forming polymer and a water repellent compound . the spectrum of activity can also be potentiated to impart expanded biocidal activity to effectively kill and clean infected porous substrates and extend the useful life expectancy of architectural building materials by the introduction of other additives , including peroxide and antibacterial quaternary ammonium compounds .