John Gill Commentary Ezekiel 41:8

"I saw also that the house had a raised basement round about: the foundations of the side-chambers were a full reed of six great cubits." — Ezekiel 41:8 (ASV)

I saw also the height of the house round about
Not of the temple itself, but of the chambers, and the three stories of them, which went round about it; and particularly the height of the highest storey, which yet is not given: it could not be so high as the temple itself; for then there would have been no room for windows to let in light into it:

the foundations of the side chambers were a full reed of six great
cubits ;
not of the lowest storey of them, for that was but four cubits broad, (Ezekiel 41:5) , nor of the middlemost, which was five; but of the uppermost, which was six; and these were cubits of the largest size, a hand's breadth larger than the common cubit, and made one full reed, or three yards and a half; see (Ezekiel 40:5) , these foundations signify the same as the twelve foundations of the wall of the New Jerusalem; and which are no other than the one foundation Christ, ministerially laid by his twelve apostles; and who is the only foundation of his church and people, and is a sure one, (Revelation 21:14Revelation 21:19) (Ephesians 2:20) (1 Corinthians 3:11) (Isaiah 28:16) .