I live in an old rental house that seems to build up mold very quickly, I held off reviewing to see how this works over time and I'm pleased to announce that the mould is taking much longer to come back. In dry areas it doesn't come back as long as you do a good clean initially and then respray every other week. For wet areas, very mold prone like my current rentals bathroom, you do have to reapply frequently. Note it doesn't bleach mold out, kinda melts it off where it can but you might need to clean/bleach grouting a few days before applying this. I also like using this to disinfect my Kitchen