John Calvin Commentary Isaiah 22:10

"and ye numbered the houses of Jerusalem, and ye brake down the houses to fortify the wall;" — Isaiah 22:10 (ASV)

And you numbered the houses of Jerusalem. He means that the city was closely examined on all sides, so that no house or building would be undefended. Others think that the houses were numbered so that they might have a supply of watchmen.

But the former interpretation is preferable and is confirmed by what the Prophet afterwards adds: that the houses were thrown down for the purpose of rebuilding the walls of the city. This precaution is commonly neglected in times of peace, as the houses of private individuals are often built on the very walls. Therefore, in times of war, they must be torn down, both to supply the means of fighting and repelling the enemy, and also to prevent secret communications with the enemy from being maintained through houses so near the wall.