Before rebuilding the house, Jimmy and Roland had a few things to take care of. They prepared some materials in advance, and the basement walls were covered with wooden boards. The position of the door and the controller were both hidden behind the boards. This way, even if the workers accidentally entered the basement during construction, it wouldn't be exposed. At most, they would just be puzzled about why the basement of this house wasn't rebuilt, and there would be no worry about them wandering into the Dark Tower World or other worlds.
Of course, if someone deliberately sabotaged it, that's another matter. They could only hope the construction workers wouldn't be that bored. Jimmy couldn't keep watch on the site all the time since he needed to work, and Roland had left New York once his leg wound didn't affect his mobility.
