Ezekiel 41:6-7

6And the side chambers were in three stories, one over another, thirty in each story. There were offsets all around the wall of the temple to serve as supports for the side chambers, so that they should not be supported by the wall of the temple.

7And it became broader as it wound upward to the side chambers, because the temple was enclosed upward all around the temple. Thus the temple had a broad area upward, and so one went up from the lowest story to the top story through the middle story.