Technical Questions

ACI Committees, Membership, and Staff have answered common questions on a variety of concrete related topics.

Acceptable concrete cracking

Q. What is considered as acceptable concrete cracking in cast-in-place foundation walls and slabs per ACI documents? My company is the concrete contractor on a large warehouse project, and I want to discuss the potential for cracking with the contractor and the owner.


A. Concrete cracks are possible on any project, so it’s wise to set reasonable expectations for yours. Foundation walls are normally designed as reinforced concrete. Reasonable crack widths for reinforced concrete under service loads are listed in Table 4.1 of ACI 224R-01. However, a footnote warns that, with time, “a significant portion” of the cracks in a structure can exceed these values. Commentary Provision R24.3.1 of ACI 318-19 discusses flexural reinforcement for one-way slabs and beams. That provision indicates that visible cracks will develop under service loads, and crack widths are usually widely scattered and influenced by “shrinkage and other time-dependent effects.” The associated Code provision provides reinforcement detailing requirements for controlling crack widths (that provision applies to the design team, so you should consider including at least one more party in your discussions).

In general, when it comes to slabs, both ACI 302.1R-15 and ACI 360R-10 state in their prefaces that it’s unrealistic to expect crack-free and curl-free floors regardless of the best design and construction practices. Also, those documents state that the designer and contractor need to advise every owner that “it is normal to expect some amount of cracking and curling on every project.” ASCC Position Statement #33 provides similar guidance, stating that:

“ASCC concrete contractors will meet with the design team, construction manager, and general contractor to discuss crack expectations for the project. Concrete contractors want to ensure awareness by all parties that cracking will occur when the structure is built in accordance with the Contract Documents.”

For more information on educating your clients and minimizing legal issues related to cracking, refer to Coleman’s article, “ Cracking…Defect or Normal?


References: ACI 224R-01; ACI 318-19; ACI 302.1R-15; ACI 360R-10

Topics in Concrete:  Cracking in Concrete; Durability of Concrete; Slab, Concrete

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