Construction Tolerance Conflicts in Reinforced Concrete - Page 4

AVAILABLE CLEARANCE = 0 to 1/2" TOLERANCE = 1"
Fig. 6 Attachment of Brick, Precast or Curtainwall	Fig. 7 Window Frame in Concrete Opening

CONCLUSIONS
    These examples are only a few of the many areas of conflict relating to the construction of a structure to acceptable tolerances that could be made easier by the closer cooperation of the parties involved.
    The ACI tolerances for the reinforced frame are generally reasonable but increased pressure to build faster with less cost makes them harder to maintain. Building the frame to more exacting tolerances is possible but should only be called for when absolutely necessary as the additional cost can be significant. The other trades are faced with similar problems.
    The Architect/Engineer must be continuously aware of tolerances and design accordingly. Where it is necessary to be more restrictive at specific locations, these locations and their requirements should be shown on the design drawings or in the project specifications. Pre-design conferences with Contractors, Subcontractors and Suppliers will frequently point out areas of possible conflict. Most of the discussed conflicts can be avoided by recognizing that variations, as allowed in ACI 117, will occur and by acting accordingly.
The Architect/Engineer and Contractor should be aware of the potential discrepancies between the exact dimensions and locations shown on design drawings, and the variance of practical dimensions which make tolerances necessary in order for the various trades and suppliers to construct a reinforced concrete structure. A concerted effort should be made to coordinate the work of the various trades, anticipate problems of fit, and resolve a potential conflict prior to its occurrence. Last minute disputes at the jobsite are an expensive alternative.

REFERENCES
Nichols, J. R., "Tolerances in Building Construction", ACI Journal, April 1940.

Standard Tolerances for Concrete Construction and Materials, ACI 117-90, 1990.

"Reasonable Tolerances for Cast-in-Place Concrete", Concrete Construction Magazine, May 1974.

Beall, C., "Specifying Construction Tolerances", The Construction Specifier, August 1990.

Birkeland, P.W., and Westhoff, L.J., "Dimensional Tolerances in a Tall Building", ACI Journal, August 1971.

This publication is intended for the use of professionals competent to evaluate the significance and limitations of its contents and who will accept responsibility for the application of the material it contains. The Concrete Reinforcing Steel Institute reports the foregoing material as a matter of information and, therefore, disclaims any and all responsibility for application of the stated principles or for the accuracy of the sources other than material developed by the Institute.