If you’ve exclusively worked in residential construction, there’s a possibility you’re not very familiar with drywall control joints. In the construction world, control joints are commonly associated with materials like concrete, where gaps are strategically placed to manage forces such as temperature and humidity changes, which can lead to cracks.
Drywall control joints serve a similar purpose, but they are designed for finished gypsum board walls and ceilings. These small gaps at specific junctions between gypsum panels are connected using specialized beads or flanges, allowing the sheetrock to expand or contract as needed without causing unsightly or hazardous cracks in the finished drywall.
Typically, drywall control joints are most frequently utilized in commercial construction projects that involve long, uninterrupted stretches of drywall, commonly seen in office buildings, hospitals, and schools. Nevertheless, control joints find applications in various types of buildings.
Drywall Control Joint Requirements
The Gypsum Association outlines several precise requirements for drywall control joints.
The standard specifications for installing control joints are provided in the technical documents GA-216-2021 and GA-234 by the Gypsum Association and ASTM C840 by the American Society for Testing and Materials.
The Purpose of Control Joints in Drywall
Control joints are carefully planned spaces or joints strategically placed between adjacent surfaces in walls and ceilings to minimize cracking and stress resulting from the expansion and contraction of gypsum board.
Despite being frequently overlooked by contractors and architects, drywall control joints are an essential element that should be included in your design plan and executed properly.
Why Do We Need Control Joints in Drywall?
Control joints are essential to manage the internal expansion and contraction stresses of drywall. Gypsum board can expand and contract in response to changes in temperature and relative humidity.
For example, a 100-foot plane of drywall would expand by over half an inch if the temperature in an area increased by 50 degrees. A 300-foot-long gypsum board wall would experience over an inch of expansion if the relative humidity changed from 10% to 50%.
If control joints are neglected or improperly installed, drywall will expand, leading to cracks. While it’s impossible to completely eliminate drywall cracking, control joints protect gypsum board from cracking due to the normal movement expected during a building’s lifespan.
Where Are Drywall Control Joints Needed?
Most manufacturers and standard specifications recommend installing control joints in specific locations:
- Walls: Control joints should be installed in walls or partitions that span an uninterrupted, straight plane exceeding 30 feet. If there is perimeter relief, you can space them up to 50 feet, following USG’s recommendation.
- Ceilings: In interior ceilings, control joints should be placed at intervals of 30 feet, which can extend to 50 feet if the interior ceiling has perimeter relief. If specific stress points occur at intervals less than 30 feet in these internal ceilings, control joints may be installed at shorter intervals. The same 30-foot rule applies to exterior ceilings and soffits.
- Where specified: The architect should identify other control joint installation points on building plans. These spots may include where partitions, walls, or ceilings intersect construction joints or where ceiling framing members change direction.
Types of Drywall Control Joints
Control joints can take various forms, with some designed as open gaps. However, leaving a gap between sheetrock joints may not be aesthetically pleasing and may require covering with trim and a generous amount of joint compound.
Companies like Trim-Tex produce control joint products that provide a visually appealing and finished look while accommodating drywall seams‘ expansion and contraction. These products are typically made of metal or PVC vinyl.
For application, the choice of control joint material, much like the selection of studs and joists, doesn’t significantly affect the process. Ensure that you adhere to specifications and architectural design.
How to Install Drywall Control Joints in Gypsum Partitions
Historically, installing drywall control joints was a complex task, involving installing 2 or 3 strips of drywall on the interior webbing of back-to-back wall studs. This created the necessary space to manage thermal expansion and prevent drywall cracking. However, once the drywall was installed, sanded, and finished on the exterior face of the studs, there was no way to verify if the control joint was installed correctly.
Today, control joints made of metal or vinyl material can be conveniently installed. Leave a gap between gypsum panels and insert the control joint product (typically resembling a small ‘V’) between them. The joint can be glued, stapled in place, or embedded with joint compound, similar to drywall corner bead. Some products have a tear-off strip to maintain adequate space for proper functionality.
Always consult your control joint manufacturer’s installation instructions, just as you would refer to the Gypsum Association and ASTM technical documents for control joint requirements. While a misplaced drywall control joint is unlikely to cause structural damage, drywall cracking can range from a minor cosmetic issue to an insulation and fire safety hazard, often becoming the responsibility of the drywall contractor.
Drywall Control Joints in Rated Partitions
In rated partitions, control joints must be parallel and adjacent to the framing materials on each side of the gap. These assemblies are designed to contain a fire for a specified duration.
Modern fire-rated control joints will close the gap between gypsum panels to prevent airflow from fueling and spreading a fire. Therefore, control joints in rated partitions should be installed to ensure continuous gypsum board strips.
Drywall Ceiling Control Joints
Control joints in drywall ceilings are needed at 30-foot intervals or less, extending the entire ceiling width from wall to wall. The exact spacing may vary according to the architect’s design.
Prior to installing or beginning the drywall finishing process, always seek clarification on the precise location of control joints in ceilings. Ensure that control joint submittals and product data are approved by the architect.
What’s the Difference Between a Drywall Control Joint and Drywall Expansion Joint
Drywall control joints are predetermined gaps in gypsum panels that help manage drywall movement and reduce cracking in the finished material.
On the other hand, building expansion control joints, sometimes referred to as construction joints, are predetermined gaps placed in various building materials, such as concrete, block walls, exterior sheathing, and acoustical ceilings. These joints are designed to mitigate the effects of movement caused by factors like temperature changes, live loads, settling, wind, seismic activity, and more, on building materials.
Furthermore, building expansion joints extend through the entire building envelope, from interior wall to exterior wall, allowing for deflection or slight building movement and sealing the joints with caulk to prevent moisture and insects from entering the building.
Due to the similarity in describing predetermined gaps in building materials, the terms “control joints” and “expansion joints” are sometimes used interchangeably when discussing sheetrock installation. It’s essential to specify the precise type and location of the control joint to avoid confusion.
Control Joints for Beginners or DIYers
If this is your first experience with control joints in a commercial project, make sure to consult the plans and specifications for precise locations and types of control joints.
Submit product data for approval to the architect before ordering materials. Also, present shop drawings indicating where you intend to install control joints on wall elevations and reflected ceiling plans. Do not proceed with drywall installation until your shop drawings and submittals have been approved.
For homeowners contemplating whether control joints will reduce drywall cracking, consult your home builder to identify potential stress points or locations where control joints would be beneficial in your new home construction.
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