Although there is no substitute for appropriate landscaping and sanitation, rat repellents will assist in keeping rodents from entering a building.
Rat Repellent Products
Bonide Shotgun Repels All, when used around the perimeter will repel a variety of animals, including rats. Shotgun Repels All comes in liquid or granule forms.
DeTour is a gel product containing pepper. Applying DeTour on the entry points will serve as a repellent, and applying DeTour along the rodent trails will increase the trap kill numbers.
Ropel Animal Repellent and Detour For Rodents will help repel rodents. Ropel works by directly spraying the areas that the rodents may be chewing. Detour repels as a contact repellent.