If you get a wand and destroy the base plate of a building, all of the bricks collapse. But while they fall apart you can just walk through them.
On a server the admin got us all in a tower than destroyed the bottom. It was a terrorist attack. It would have been fun to run around as the building falls apart, but instead we just fell through all the bricks and it wasn't very good at all.
I think the bricks should remain solid throughtout.