A retention tie system for pre- or post-construction installation to stabilize masonry or composite walls. The system comprises a tie member anchored in an anchor hole bored into the existing foundation and a tensioned against a base plate and a cover plate seated along the top of the wall. A bracing member is used to provide lateral stability to the respective plate members. A tension washer is used to ensure that the tie members are tensioned to the appropriate load. A guide member is installed within the masonry wall to brace the tie members against lateral deflection.