Jamieson, Fausset and Brown on 1 Kings 6:5

5. against the wall of the house he built chambers--On three sides, there were chambers in three stories, each story wider than the one beneath it, as the walls were narrowed or made thinner as they ascended, by a rebate being made, on which the beams of the side floor rested, without penetrating the wall. These chambers were approached from the right-hand side, in the interior of the under story, by a winding staircase of stone, which led to the middle and upper stories.