Albert Barnes Commentary Ezekiel 42:6

"For they were in three stories, and they had not pillars as the pillars of the courts: therefore [the uppermost] was straitened more than the lowest and the middlemost from the ground." — Ezekiel 42:6 (ASV)

The front of the higher stories was not supported on pillars, but there was a narrowing from the lowest (chambers) and from the middlemost (chambers) from the ground.