I live now in a 6 story brick coopr- 48 units in building. Steam heat. I am on the top floor corner apt. I have an exterior steam pipe running up through the bathroom to the ceiling. I guess to the roof. Have air /steam valve on the pipe. No problems with heat or valve.

But the pipe moves about a 1/2" up then down some times. I have never observed it moving but can tell from the area painted and base of pipe in floor. Does not crack the ceiling . It seems to be in a metal sleeve on top and a metal and concrete sleeve at the base/floor. No leaks from the ceiling/roof or from the base/floor

Never saw anything like this before. Any ideas why it moves? I think just during heating season.

Expansion and contraction. This is why the dead men (the old guys that installed and serviced steam) used to install them outside so as to prevent this problem in the walls