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Like insulating concrete forms for wall construction, ICFs for decks are reinforced stay-in-place polystyrene forms that become the structure of the floor or roof assembly when placed and filled with concrete. The forms provide an thermal resistance of approximately R-3.8 per inch, and provide sound attenuation once assembled. After shoring, bracing, and reinforcement are installed, 2” to 4” thick concrete is placed on top of the deck assembly. The concrete can be finished decoratively, and can include piping for hydronic or radiant heating systems.
Form shapes and method of installation vary between manufacturers. One manufacturer produces a two-foot wide foam panel by the overall span length, with integral steel joists that provide temporary support for the deck. Another manufacturer produces foam forms that measure 32” long x 24” wide x 12” thick, that rely on steel joists, spaced at 16” o.c. and purchased separately, for temporary deck support. However, most systems require temporary shoring of the deck.
The maximum span capability of the systems depends on the thickness of the form and concrete and placement of reinforcement. Span capability of ICF deck systems, under residential loading, ranges from 20 to 40 feet, depending on design and specifications. Some manufacturers supply forms that can also be used as temporary forms for precast concrete walls and decks.
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ICF floors over unheated basements or crawl spaces will provide a well-insulated thermal barrier.
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Reinforced concrete construction is an inherently permanent, fire-, termite-, and water-resistant material.
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ICF floor decks are water-resistant. They may provide a solution for decks on raised foundations where flooding can occur.
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Because many horizontally installed ICF floor decks require a shoring system to support the dead weight of construction materials until the concrete cures, system assembly is somewhat more labor intensive than traditional wood construction.
Provision for service utilities that will penetrate the floor assembly must be made prior to the concrete pour, so MEP (mechanical, electrical and plumbing) trades may require two trips to the site to complete a rough-in. Because of this, a good set of architectural plans that include service utility layouts is necessary. Some ICF deck forms do include integral chases that will accommodate pipes, wires or high-velocity ducts. Trade labor can be saved by allowing the ICF installer to form voids in the assembly around the required MEP system penetrations, and designing so that most of the MEP installations are not in the deck assembly. Bulkheads, soffits, and stacked interior walls can provide for pipes, wires, and duct runs.
Buildings that follow the prescriptive insulation requirements of the IRC 2006 (Chapter 11) will require additional insulation in the roof deck for code compliance. Likewise, floors over unconditioned space in the coldest four climate zones of the country will require additional insulation.
There is an initial cost premium when ICF floor decks are compared to engineered wood decks with OSB underlayment. However, ICF floors can be installed for less than some other assemblies with similar performance features, like metal joist and pan floorv systems with lightweight concrete (common in commercial or multi-family construction).
ICF floor deck assemblies are very durable, will not rot or provide a food source for insects or mold, and will require minimal maintenance.
The International Code Conference (ICC) does not include prescriptive methods for constructing floor and roof systems with insulating concrete forms. Code provisions, however, “…are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by the code, provided that any such alternative has been approved.” The manufacturer can obtain an ICC-ES evaluation report on the product, and submit it with the architectural plans at the plan review phase of the project. Most building code officials will also accept certification of the system by a registered professional engineer or architect, under the “Alternative Materials” section of the building code.
None Availabe
ICF deck form products vary considerably from manufacturer to manufacturer. Some have integral steel joists, while others require installing steel joists for support as the first step in the process. All foam form deck products will require reinforcement and concrete topping over the forms. Review installation guides and consult with the manufacturer’s technical service representative for individual system details. Some manufacturers also provide installation training.
Not Applicable
Insulating concrete form decks can be stronger, more rigid and span greater distances than conventional wood floor assemblies.ICF decks can easily provide a 2-hour fire-resistance rating, sound and vibration attenuation, and a medium for in-floor radiant heating and decorative concrete finishes.
Building codes do not provide prescriptive requirements for ICF decks, so case-by-case approval may be required in order to build with the forms.Approval may require engineering design and certification.
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