The Lower House was the domain of Mister Monday. Due to Monday's affliction with sloth, its bureaucratic affairs became impossibly inefficient until Monday's loss of power, after which Dame Primus, as the Steward of Arthur's regime, has attempted to make the Lower House manageable. The remaining Morrow Days have attempted to impede this effort by swamping the Lower House with paperwork.
The Lower House is guarded by the Corps of Inspectors, by the robots known as Metal Commissionaires, by Denizen Commissionaire Sergeants, and by Midnight Visitors. These are under the control of the office of Monday's Dawn, Noon, and Dusk, respectively.
Doorstop Hill, and on it the Front Door of the House, is located in the Lower House. The Front Door of the House is a means by which one may leave the House and enter a Secondary Realm, and vice versa. To enter it from the Secondary Realms, one must be able to see the House. It is a pair of wooden doors surrounded by constantly shifting wrought-iron patterns whose movements are mesmerizing to human eyes. The Door is guarded by the Captain Keeper; in his absence, the Lieutenant Keeper of the Door, an ally of Arthur's, has guarded it ever since.
The Coal Cellar is a deep pit in the Lower House where Denizens that have been punished are sent to mine and shape coal for delivery to buyers within the House. The Old One is also imprisoned here. He is bound by two chains extending from a minute and hour hand on a clock face. At midnight each night, two clockwork figures appear and claw out his eyes. This is the punishment laid upon him by the Architect for his attempting to interfere in the Secondary Realms, which was directly forbidden by the Architect. His escape is impossible; according to Monday's Dusk, the Seven Keys combined could not free him. In Lady Friday, Dr. Scamandros mentions that something odd is happening in the Coal Cellar; not with the Old One, but the collectors. The nature of what is happening is not stated. It is revealed in Superior Saturday that flowers have started growing around the Old One's clock-face prison, and that his clockwork torturers have been destroyed by the Old One and that he will soon be able to escape.
The Seven Dials is a set of seven grandfather clocks in a room accessible from Monday's Dayroom, the main office of the Lower House. Using them, one can travel to the current time in any given Secondary Realm. Thus far, only Sneezer, Monday's butler, has operated them. When the Lower House was consumed by Nothing, Dr. Scamandros says that the Seven Dials would move themselves to safety, but did not reveal where they have gone.
Nearly all of the Lower House was destroyed by Nothing that had leaked from the dam in the Far Reaches, being unleashed by Superior Saturday. The bulwark between the Lower House and the Far Reaches only lasted a few hours, during which important records and some Denizens were saved. However, the bulwark eventually collapsed and the Lower House was devoured. Only part of the Deep Coal Cellar survives, due to the protections around the Old One's prison; but it is slowly dissolving as the prison weakens.