"Roof?" Lexie asks, eyebrows shooting up, a surprised laugh that doesn't quite make its way out evident in her tone nevertheless. It's impossible to tell if he's joking or if he means it; if it's the former, it's funny, and if it's the latter, it's pretty incredible, if seemingly unbelievably dangerous. The response, she thinks, is the only one that covers either possibility. Head turned in his direction even as she leads them down the path (she does know them well, the Compound probably the place she goes most often), she bites her lip. "Wow. That's a, uh, pretty big undertaking."