Every dwelling and every part thereof shall be maintained in good repair by the owner or agent and be fit for human habitation. The roof shall be maintained so as not to leak and all rainwater shall be drained therefrom so as not to cause dampness in the walls or ceilings. All floors, stairways, doors, porches, windows, skylights, chimneys, toilets, sinks, walls and ceilings shall be kept in good repair and usable condition.