The NCIDQ IDPX exam tests the designer’s knowledge of construction detailing, particularly methods to accommodate building movement and prevent damage to finishes like gypsum wallboard (GWB) ceilings. Building structural movement, such as expansion, contraction, or settling, can cause cracking in rigid materials like GWB if not properly addressed.
Option A (J mold):J mold is a trim piece used to finish the edge of GWB, typically whereit meets another surface (e.g., a window frame). It does not address structural movement or prevent cracking within the ceiling plane.
Option B (U channel):A U channel is often used to frame or support GWB at edges, but it is not specifically designed to accommodate movement within the ceiling. It does not prevent cracking due to structural movement.
Option C (Control joint):This is the correct choice. A control joint (also called an expansion joint) is a deliberate break or seam in the GWB ceiling that allows for controlled movement. Installed at regular intervals (e.g., every 30 feet or as specified by the Gypsum Association), control joints absorb stresses from structural movement, preventing random cracking by directing movement to these predetermined locations.
Option D (Elastic sealant):Elastic sealant is used to fill gaps or joints and can accommodate some movement, but it is not typically used within a GWB ceiling plane to prevent cracking. It is more commonly used at perimeter joints or between dissimilar materials.
Verified Answer from Official Source:
The correct answer is verified from NCIDQ’s official study materials on construction detailing and GWB installation standards, referencing guidelines from the Gypsum Association.
“To prevent cracking in GWB ceilings due to building structural movement, control joints should be installed at regular intervals to absorb stresses and allow for controlled movement.” (NCIDQ IDPX Study Guide, Detailing and Construction Section)
The NCIDQ IDPX Study Guide, supported by Gypsum Association standards, specifies that control joints are the appropriate method to prevent cracking in GWB ceilings by accommodating structural movement. This aligns with Option C, making it the correct answer.
Objectives:
Understand construction detailing to prevent material damage (NCIDQ IDPX Objective: Detailing and Construction).
Apply knowledge of building movement to design durable interiors (NCIDQ IDPX Objective: Building Systems).
[References:, NCIDQ IDPX Study Guide, Detailing and Construction Section., Gypsum Association, GA-216: Application and Finishing of Gypsum Panel Products., National Council for Interior Design Qualification (NCIDQ), IDPX Exam Blueprint, Section on Detailing and Construction., ]
