Because of finishing techniques for shotcrete construction, some tolerances must be larger than those achievable with formed construction. This allowance for increased tolerances need not diminish the serviceability, durability, or integrity of a structure. Tolerances provide an indication of the expected finished product and can identify applications where additional effort and cost may be required, or where a particular construction method may be inappropriate. Therefore, knowledge of tolerances that are consistently achievable is needed by owners and specifiers so that project requirements can be stated clearly.
A disregard for achievable tolerances can unduly reduce construction quality. On the other hand, specifying tolerances that are not consistently achievable can produce rejection of sound work and lead to unnecessary project confrontations. Insistence on overly strict tolerances can, in fact, lead to reduced shotcrete quality if overworking of surfaces is required to achieve the tolerances. In applications where visual appearance of the completed structure is an essential design consideration, full-scale mockups should be considered for protection of all parties. Such a mockup prevents unrealistic expectations on the part of the owner and designer and also sets a permanent, site-specific standard for future construction quality.