A new concrete rib floor system intended for use on the first floor over a basement can span up to 16 feet and is designed to be competitive with wood joist construction. Ribs are spaced 3 feet 6 inches on center and have tapered sides. The 2-inch-thick slab is reinforced with 6x6 W1.4xW1.4 wire mesh and rib reinforcement consists of one Number 6 bar placed with 3/4 inch of clear cover at the bottom of the rib. Concrete compressive strength required is 3000 psi.

By spacing the ribs 3 feet 6 inches on center, the wall contractor can use his 3-foot-wide foundation wall forms as deck forms. The deck forms are supported on collars of the rib forms. The adjustable rib form is supported by retractable pins bearing on the foundation wall and on a steel center beam. Length of the rib form is adjusted by setting two end sections that rest on an aluminum joist, then placing a slip filler between them. One shore post used at the midspan of each rib form provides support during concrete curing.

This concrete rib floor system offers many advantages to the homeowner, such as no vibration or squeaks, thermal mass for solar energy storage, and better fire and storm resistance than wood joist construction. The concrete contractor would also benefit from higher profits by placing more concrete in each house.