Photograph of a basement floor slab crack Standards for Repair of Cracks in Poured Concrete Floors

  • POST a QUESTION or READ FAQs about the standards for acceptable repairs to concrete floor cracks - when and at what size should a crack be repaired or sealed?

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This article describes some Standards for Repair of Cracks in Poured Concrete Floors.

This article series describes how to recognize and diagnose various types of foundation failure or damage, such as foundation cracks, masonry foundation crack patterns, and moving, leaning, bulging, or bowing building foundation walls.

Types of foundation cracks, crack patterns, differences in the meaning of cracks in different foundation materials, site conditions, building history, and other evidence of building movement and damage are described to assist in recognizing foundation defects and to help the inspector separate cosmetic or low-risk conditions from those likely to be important and potentially costly to repair.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Standards for the Acceptance or Repair of Cracks in Concrete Floors in New Construction

Settlement cracks may form a tripping hazard even if they are not traced to a structural concern. While there are few construction acceptance standards for floor slab cracking, one, "Quality Standards for the Professional Remodeling Industry" NAHB, , recommends that cracks in basement floors which exceed 3/16" in width or 1/8" in vertical displacement should be repaired.

The same standard provides that cracks in slab-on-grade floors shall not exceed 1/16" in width or in vertical displacement. The same standard provides that cracks occurring in control joints in concrete slabs are normal and acceptable. [We suggest that this last criteria should apply to crack width but not to vertical displacement.]

Cracks in concrete floors or slabs occur in poured concrete slabs may be found both in basement and in slab on grade or "patio home" construction and have a variety of causes and cures that we discuss beginning

Measurements of the degree of levelness or flatness of concrete slabs and floors

How to Slab "F" numbers to describe the flatness and levelness of a poured concrete slab

The traditional objective for levelness of a poured concrete slab was that the slab could be tipped or concave or convex in an amount equal to or less than 1/8" in 10' of slab surface in any direction. A perfectly uniform surface might tip from one end to the other by up to 1/8" across a ten foot distance and still be acceptable.

However other conditions of variation in concrete slab surface flatness and degree of levelness occur, such as variations out of flatness level at other intervals across the same distance - making such measurements and standards ambiguous. An "F-number" system is currently used to describe the degree to which a poured concrete floor or slab is flat and level.

The formulas for "F" are more complex than just using a level and tape measure:

A little online course and tables of recommended "F" numbers to provide a standard for flatness and levelness for different types of poured concrete floors is at Technical Reviewers below.

Concrete Crack Diagnosis & Repair Articles


Continue reading at SETTLEMENT CRACKS in SLABS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

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CRACK REPAIR STANDARDS for FLOORS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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Publisher - Daniel Friedman