Jack Arch Floors

These floors are formed through constructing brick or concrete arches, called 'Jack arches' on the lower flanges of mild steel joists. The joists are spaced 1 to 1.5 m centre to centre, and are supported at their ends either on the walls or on longitudinal girders. The jack arches are commonly given a little rise of 1/12th of the arch span. The minimum depth of concrete at the crown is remaining equal to 15 cm. Because the super-imposed load is being borne through arch action, tension is developed on the supporting walls, especially at the end span. Because of this, steel tie rods are given at the end span, at suitable spacing, commonly 1.8 to 2.4 m c/c. The tie rods are 2 to 2.5 cm diameter, and are properly anchored within the wall. The end arch is supported on wall through either providing rolled steel joist into the wall or easily fixing an angle iron or mild steel in the wall. The bottom of the floor is not plane, that is the only disadvantage of this floor.