Resembling the food after which they are named, concrete waffle slabs are reinforced concrete floors and roofs that use a square grid of deep sides. This form of construction is used in airports, parking garages, commercial and industrial buildings, bridges, residences and other structures requiring extra stability.
There are three basic designs for concrete slabs that improve the strength-to-weight ratio. For each design, the top surface is flat while the underside is modulated with either a corrugated, ribbed or waffle design.
Corrugated slabs are created when concrete is poured into a wavy metal form. This shape prevents the slab from sagging. Ribbed slabs add strength in one direction, while the concrete waffle slab design adds strength in perpendicular directions. Concrete slabs can be reinforced with rebar for additional strength.
Concrete waffle slabs can be purchased and shipped to the construction site as prefabricated or precast sections, or they can be poured on-site. If prefabricated products are not in the budget, consider purchasing casts for the concrete waffle slabs. According to Tradeline, waffle slab construction is defined as "a building system using concrete 'waffle slab' floors supported by columns. The waffle slab is a monolithic-poured concrete slab with a flat top surface and an under-surface made of a rectangular grid of deep concrete beams running at right angles. The floor area between the grid beams is a thin flooring section. From the underside, the slab resembles a waffle. The floor is supported by columns spaced typically 30 feet on center."
Concrete waffle slabs are often used in clean rooms or in other areas that require isolation from low-frequency vibrations, and areas that require low-floor deflection.
PolySteel sells concrete waffle forms for walls. According to the company, insulating concrete forms earned a 4-hour fire rating and have a 27-year track record. The forms are available in 6", 8" and 10" sizes, plus 45 and 90 degree forms.
Whether purchasing precast products or pouring the concrete on-site, concrete waffle slabs have many uses for commercial, industrial and residential projects.