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Tech Talk
  Advice on specifing control joints in drywall construction is included in the following Tech Talk information below.
 
  Don't Overlook Control Joints in Drywall Construction
    By George M. Kutcher, Jr., CDT, CSI
   

One component of gypsum board construction often overlooked by architects and contractors is the control joint. Architects sometimes fail to specify control joints. In some cases when control joints are specified, the drawings are not coordinated with the specifications and the control joint details are frequently missed. Even in the best of circumstances, when control joints have been specified and properly detailed, estimators may neglect to include them in the bid, and project managers are faced with managing a job with unforeseen costs.

Gypsum wallboard, as well as other building products and materials, is subject to some form of movement induced by changes in moisture, temperature or both. To relieve the stresses that occur as a result of such movement, control joints are required in both partitions and ceilings.

Control joints are frequently necessary to prevent cracking in gypsum wallboard. Cracking may also be caused by stresses resulting from building movement. Isolation joints should be installed where structural elements such as slabs, columns or exterior walls can bear directly on non-load bearing partitions.

Control joints should be employed in long expanses of partitions at 30-foot intervals, from floor to ceiling. Control joints are recommended at doorjambs, extending from door head to ceiling. Where doorjambs extend from floor to ceiling and are spaced less than 30 feet apart, no control joints are required.

When "through wall" control joints are required in fire-rated assemblies, special details (See drawing) are necessary. These details are based on Warnock Hersey International, Inc. Report WHI 651-0318.1.

Control joints are required in ceilings to limit areas to 2,500 square feet. Additionally, control joints should be installed in ceilings to limit dimensions in either direction to 50 feet. Control joints should be installed where ceiling framing or furring changes direction.

Even if control joints do not appear to be specified they are often covered by reference specification. Carefully read PART 1, GENERAL, Paragraph 1.02 REFERENCES, of the Gypsum Board specifications. More than likely, the architect has referenced either ASTM C 840, The Standard Specification for Application and Finishing of Gypsum Board; GA-216, the Gypsum Association Recommended Specification for Application and Finishing of Gypsum Board; or both. The requirement for control joints is addressed in both of these documents.

 

     
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