using Fraction tool on buildings in city sample project

Is there an easy way to use fraction tool on any building in city sample project without getting weird results ? because I have been testing for about 2 weeks but I only get bad results.

For example: in this video below I replaced the normal building with a destructible building using the fraction tool but I didn’t like the results.
https://www.youtube.com/watch?v=hTRAjaIu5n8

I want to destroy the building the same way as this video.
https://www.youtube.com/watch?v=u3ktiewcLpo&t=106s

for ex: in this picture below, I want to sparate each mesh from this building without having to rebuild it again and use the fraction tool on it to destroy each part of the building individually. Is this possible ?