Actually, they didn't. They just took over the ceiling. And it wasn't like anyone was living there. And there were perfectly harmless spiders, just eating away at the bugs.
"An Immense Concentration of Orb-Weaving Spiders With Communal Webbing in a Man-Made Structural Habitat"
http://www.entsoc.org/PDF/2010/Orb-weaving-spiders.pdf
