 As the North Tower collapsed on September 11 , 2001 , heavy debris hit 7 World Trade Center , damaging the south face of the building and starting fires that continued to burn throughout the afternoon . The collapse also caused damage to the southwest corner between Floors 7 and 17 and on the south face between Floor 44 and the roof ; other possible structural damage included a large vertical gash near the center of the south face between Floors 24 and 41 . The building was equipped with a sprinkler system , but had many single @-@ point vulnerabilities for failure : the sprinkler system required manual initiation of the electrical fire pumps , rather than being a fully automatic system ; the floor @-@ level controls had a single connection to the sprinkler water riser ; and the sprinkler system required some power for the fire pump to deliver water . Also , water pressure was low , with little or no water to feed sprinklers . 
