From the official TLC site:
In this special, two sets of neighbors think they've signed on for a fun-filled regular episode of Trading Spaces. What they don't know is that when Paige gets them together for what they think is the key swap they receive the surprise of their life. Out of the TS trailer pours not just two designers and 1 carpenter, but the entire cast! That's right ... 10 designers and 3 carpenters — Paige and Trading Spaces: Family host Joe Farrell make 15!
Through The Roof gives viewers a chance to see a whole bunch of Trading Spaces firsts. The first time the whole cast is together on one episode. The first time with no limit on the number of rooms to be redone. The first time these highly opinionated designers are forced to collaborate on redecoration. The first time that some of the designers will be "demoted" to mere "designer assistants" and have to take orders from the "official" designer team of 3. That's a lot of firsts.
Will it be a complete disaster? Or a breathtaking whole house transformation?