The need for expansion joints is created by movement of materials as they shrink and swell from cyclic changes in moisture and temperature. Other physical stress also affects the integrity of wall and ceiling materials. Expansion joints also should be used when dissimilar materials, such as plaster and masonry, are joined because these materials expand and contract at different rates. Expansion joints also help absorb vibrations, serving as cushions against other forces that can create cracks. Large doorways that receive a lot of use by heavy equipment should also have expansion joints between the buck and the wall materials to help absorb vibration caused by traffic and minimize cracking of wall surfaces when the buck is scraped. Often overlooked when planning for expansion joints is the overhead area large ceiling penetrations for lighting troffers or access panels, and where beams that are attached to floors above penetrate ceiling materials. Both areas require expansion joint treatment.
Consideration and location of exterior expansion joints are important. Fascia and soffits should be designed with expansion joints in mind, especially in severe climate extremes. Expansion joints can also be the basis of a geometric design. A good example of this would be an expansion joint every 10 feet on stucco soffits. Four-sided perimeter stops can be created on many structures with well-designed uses of expansion joints.
An expansion joint with expanded webbing abutting the joint ensures secure embedment and gives the installer the option of using either wire ties or nails to secure the joint to the basic supporting frame. A return lip eliminates shrinkage separation between the surface material and the joint. A minimal investment in expansion joints properly specified and installed can prevent the spending of large sums of money for refacing cracked and distorted wall and ceiling surfaces over the life of a building.