The Internet Movie Database lists locations for movies (look up any movie and click on “Locations”).

Sadly they don’t give specifics for this one, it simply says, “Toluca Lake, Los Angeles, California, USA (frontage to Addams Family mansion)”
http://www.imdb.com/title/tt0101272/locations

According to this site, “Sadly, there’s no Addams Mansion to see. The frontage of the house was built for the film on a mountain overlooking the Burbank Hills at Toluca Lake (The TV pilot did use a real house – coincidentally on Adams Boulevard – just south of Hollywood. You can still see it during the show’s opening credits, but a painting was substituted for the run of the series).”

Thanks