Section through the segmental vault supporting the areaway bridge on the north side of the White House, created byBenjamin Henry Latrobe in 1807–8. James Hoban extended the vault one bay to the east and one to the west in1829–30 to support the North Portico. The shaded area on the left of the image marks the groined arch used to direct the downward thrust of the vault around a door opening in the north wall. When he expanded the vaulting Hoban replicated this structural feature for the two windows flanking the door.