Industrial Floor Design

Understand the basics in the design specification of commercial concrete flooring

ConcreteNetwork.com

Residential concrete slabs often have few design requirements to get between the contractor and completion of the job. If the contractor knows what he or she is doing and knows what the customer wants, then the lack of specifications is probably a good thing. Most residential projects only specify minimum concrete compressive strength. On commercial/ industrial floors, though, there are typically design requirements within the contract documents (drawings and specifications). That can be good for the contractor if the specifier knows what they are doing and the specification clearly states what is required. These requirements can, however, be a problem if the specification is overly stringent or unclear or has conflicting provisions.

Here are some basic things that should be included in the design and specification of a commercial or industrial floor:

  • Base and subbase materials—the preparation requirements should be specified along with the location of a vapor retarder (if one is required)

  • Concrete thickness—the designer determines the thickness based on the subbase and the anticipated loads; this is one of the primary design decisions

  • Concrete compressive strength, flexural strength, or both

  • Concrete mixture proportion requirements including what materials are to be used, water-cementitious materials ratio (w/cm), slump, and any allowable admixtures

  • Reinforcement—the type and location of reinforcement should be specified, including how it is to be positioned during construction; remember that for slabs on grade or slabs on metal deck, the reinforcement's purpose is only for controlling crack width

  • Surface treatment—if more durable surfaces are needed, the designer will specify mineral or metallic surface hardeners

  • Surface finish—with commercial or industrial floors, a hard troweled surface is the most common finish but beware of air entrained concrete, when hard troweling can lead to delaminated surfaces

  • Tolerances—tolerances are typically specified by referring to ACI 117, Standard Specification for Tolerances for Concrete Construction and Materials, this includes tolerances for the subbase, the slab thickness, and surface finish including FF and FLrequirements

  • Concrete curing—the specification may include curing requirements, including how to respond to hot or cold weather conditions

  • Joint filling material and installation techniques—if joints are to be filled

  • Preconstruction meeting, quality assurance, and quality control—precon and prepour meetings can solve lots of problems with more complex floors, and documenting your compliance with the specification can mean a rigorous QA/QC program

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Getting everything straight in a preconstruction meeting can mean the difference between success and failure.

Many of these requirements are defined by the Class of floor the owner wants—note that decorative concrete is typically a Class 1 floor. Floors are classified based on the intended use of the floor—see the table below that was adapted from ACI 302.1 R-04, Concrete Floor and Slab Construction. Each Class includes what ACI 302 calls "special considerations" and suggested finishing techniques. The designer may consider the Class when selecting the concrete properties and when specifying the placing, consolidating, finishing, and curing procedures. Note that the Class increases with increasing load and more stringent performance requirements; commercial or industrial floors may be anywhere between Class 3 and Class 9.

Classification Floor Chart: Click on the chart below to view it full size

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Classification of Concrete Floors Based on Intended Use

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