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The precision of cut stone projects make them a beautiful addition to a variety of commercial and residential settings. However, that same precision can quickly send timelines and budgets off course if stone tolerances aren’t clearly agreed to between contractor and customer upfront, or not met during installation.
Defining tolerances at the project outset protects both you and your customers. As a contractor, you’re sometimes held to an unattainable standard of protection. Tolerances acknowledge that variations could exist between the specs and the end product, and that those variations are mutually acceptable provided they fall within specific criteria. For your customer, tolerances provide peace of mind in knowing that the intended outcomes must meet certain standards and, should workmanship fall short, they have recourse in getting their project corrected at little or no cost.
Stone Industry Tolerances
In the stone industry, it’s common to hear about “plus or minus tolerances,” a name taken from the “±” spec notations that accompany them. The technical terms, however, are “bilateral” or “unilateral,” with each carrying a unique meaning:
Bilateral tolerances are allowable deviations that can be either greater or lesser than the desired value. This type of tolerance takes one of two forms:
- Symmetrical, meaning the tolerance is one that allows the same amount of deviation for both greater and lesser than the target value. For instance, considering a 1-1/4" (30 mm) thick slab, a tolerance of plus or minus 1/8" (3 mm) is considered to be a symmetrical bilateral tolerance.1
- Asymmetrical, meaning the actual value is allowed to deviate both greater and lesser than the specified tolerance, but not to the same extent. For instance, the depth of a continuous cut is allowed to be either deeper or shallower than specified, but it is only allowed to be 1/16" (1.5 mm) shallower, while it is allowed to be 1/8" (3 mm) deeper.2
Unilateral tolerances are those wherein deviation is allowed only in one direction. For example, the depth of a back anchor is allowed to be 1/16" (1.5 mm) deeper than specified, but never shallower.3
While tolerances are often a matter of millimeters, the impact can be significant. Working with natural stone experts to quarry quality product and finish it to these detailed specifications is imperative for efficiency. You’ll reduce installation labor time and costs, mitigate revision risk, and manage customer expectations to ensure their maximum satisfaction.
Meeting tolerances enhances the fluidity of cut stone projects, just as the one-of-a-kind characteristics of the natural stone you choose influences the aesthetics. Learn more about what to look for in natural stone and what to expect from each unique slab in Understanding and Selecting Natural Stone: A 5-Step Checklist. Click the button below to access your copy now.
1 ,2, 3 Source: Natural Stone Institute