Ezekiel 41:9

The thickness of the wall, which was for the side chamber without, was five cubits: and that which was left was the place of the side chambers that were within.

Cross-reference

Ezekiel 41:5 gives the side chamber width; here the thickness of the outer wall is specified — complementary details.

Ezekiel 41:11 describes the doorways and open space width — further detail on the same structure.