The reference is obviously to a palace. The phrase upper house
suggests there once was a lower house (= palace) upon whose ruins a new (= upper) house had been built. But by whom or in what circumstance is unknown to us (though obviously known to Nehemiah and his first readers). That palace, not surprisingly, had a tower and hence upper
room. Of course, when the Babylonians destroyed the city (2 Chronicles 36:19), they tore this palace down too so that the reference here is to the ruins.
25 and to the corner. Palal the son of Uzai repaired opposite the buttress and the tower projecting from the upper house of the king at the court of the guard. After him Pedaiah the son of Parosh