Kapp has played third for his brother Andy Kapp since 1992. Together, they have won European Curling Championships (1992 and 1997), two silver medals at the World Curling Championships (1997, 2007) and three bronze medals (1994, 1995 and 2005). He competed for Germany at the 1998 and 2006 Winter Olympics, finishing in eighth place on both occasions. Kapp had to have season-ending knee surgery after the 2007 European Curling Championships, and thus could not attend the 2008 World Men's Curling Championship with the rest of his team. He retired from professional curling in 2009.