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. The Lower House is one of two demenses where the entire contents is not in one area. The Lower House has the Atrium as well as Monday's Dayroom, the Lower Coal Cellar (and possibly other coal cellars) as well as offices akin to the one formerly resided in by Suzy Blue.
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 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. Every Noon and Midnight, 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, Doctor 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.
Nearly all of the Lower House was destroyed by Nothing that had leaked from the dam in the 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. In Lord Sunday, the last of the Lower House is washed away by Nothing, destroying the Old One's prison.