How do the harpies fix Aeros's palace floor in the section?

When the heroes reach Aeros's room, they initially can't go further than the entrance because there is no floor. Everyone in the place floats over to him. Of course the heroes cannot do this so Mellie has to order the harpies to secure the floor. they do so nailing down plywood and taping rubbish together. It looks flimsy, but the floor manages to hold everyone perfectly.