Filler joist slabs

Filler joist' as an early form of floor slab construction, which was commonly used between about the 1880s and 1920s. A number of patented systems were developed at the end of the 1800s. It was formed from iron or steel joists spaced up to about 1 m apart and in-filled with unreinforced concrete. Loads applied to the concrete were transferred to the joists, with the concrete acting as a shallow arch. The soffit of the slab was flat, unlike the type of construction using 'jack arches'.