Do you see cracks in the wall and wonder why? Would you like to prevent that from happening? We recommend using control joints. Foundation settlement, structural movement and thermal expansion and contraction will occur, and these forces often manifest in material finish cracks.

It takes a little upfront planning. But by properly indicating where control joints should be on your plans, you can help prevent cracking and minimize unwanted jobsite meetings.

Follow these industry-proven guidelines:

• Install control joints where a wall or partition runs in an uninterrupted straight plane exceeding 30 linear feet (50 linear feet on center for ceilings with perimeter relief).
• In your “Gypsum Board Assemblies” or “Gypsum Board” specification, include the recommendations for installing gypsum board per GA-216 or ASTM C840 instructions. These industry-approved technical documents provide the necessary guidance for locating and installing control joints.
• You should indicate the location of control joints on your drawings, especially where appearance is important. Be clear and specific. As noted in GA-216 “Application and Finishing of Gypsum Panel Products,” section 4.7.2, “Control joints shall be installed where indicated on the plans.” and in section 4.7.3, “Control joints in the gypsum panel products shall be specified by the architect or designer where any of the conditions described in Sections 4.7.3.1 through 4.7.3.7 exist.

Top Questions and Answers About Control Joints

Control joints play a crucial role in maintaining your design intent and ensuring the long-term endurance of specified building materials. National Gypsum Company’s construction design managers and 1-800-NATIONAL^® technical experts often receive questions about control joints, including the following:

Q: What are the guidelines for control joints – and are there any exceptions?

A: The Gypsum Association technical document GA-216 “Application and Finishing of Gypsum Panel Products” and ASTM C840 “Standard Specification for Application and Finishing of Gypsum Board” provide the same guidance to install control joints. For details about blocking behind the control joint in a fire-rated system, consult GA-234 “Control Joints for Fire-Resistance Rated Systems.”

 
Q: What is the difference between control joints and expansion joints?

A: These terms are often used interchangeably, so it depends on who you ask. Control joints prevent cracks in finish materials. Expansion joints (also called construction joints) can reduce the effects of building movement on building materials, and they separate the building structurally. Buildings move due to wind, temperature fluctuation, live loads, deflection or seismic stress.

Q: Do I need a control joint if I have a deflection track?

A: No, not unless your wall exceeds 30 linear feet. Then the use of a deflection track does not eliminate the need for control joints.

Q: For a hyper-sensitive visual project, can I reduce or eliminate the use of control joints?

A: No, not without limiting straight planes of gypsum board to 30 linear feet.

Q: Does the gypsum board thickness affect the design of the joints?

A: No, the design of the control joint is the same for all gypsum board, regardless of thickness.

Q: Should I install control joints on exterior gypsum sheathing?

A: It is not mandatory. The standard for the installation of gypsum sheathing, ASTM C128 “Standard Specification for Application of Exterior Gypsum Panel Products for Use as Sheathing,” does not require control joints for the sheathing. The weather barrier and cladding manufacturers will determine the need for control joints. Follow their recommendations.

Q: Does the framing material matter when designing control joints? Is the design different for wood-framed assemblies versus steel-framed assemblies?

A: No, the guidelines are the same for both.

Q: Is there a preference in the control joint material – vinyl or metal?

A: Control joints are available in vinyl and metal, but metal control joints dent more easily. For more guidance, consult Gypsum Board specification section 09 29 00 or Gypsum Board Assemblies specification section 09 21 16 under “Trim Accessories.” 

Q: When installing PermaBASE CI^® Insulated Cement Board as part of the exterior cladding to meet the continuous insulation requirements of the IECC, where are control joints needed?

A: For exterior installations, consult finish manufacturer for spacing requirements. For exterior tile applications, control joints should be spaced a maximum of every 12 linear feet. If no recommendation is available, allow a maximum of 16 linear feet between control joints. Control joints must be installed in the following locations (and other locations might also be required): Where expansion joints occur in the framing or building (discontinue all cross-furring members located behind joint); when boards abut dissimilar materials; where framing material changes; at changes of building shape or structural system; at each story separation. Place control joints at corners of window and door openings or follow identified locations as noted on the drawings and as required by the specification. Control joint cavity shall not be filled with coating or other materials. 

Q: Are control joints necessary in exterior ceilings and soffits?

A: Yes. As stated in the GA-216, section 4.7.3.5, “Control joints in exterior ceilings and soffits shall be installed so that linear dimensions between control joints do not exceed 30 ft.”

Want More Information About Control Joints or GA-216 and GA-234?

Contact me today for more information or to request copies of the GA-216 and the GA-234.

Additional Resources

About Control Joints:

• Guidelines and Best Practices for Installing Control Joints
• Blog: Specifying and Installing Control Joints to Prevent Cracking
• NGC Construction Guide™
• PermaBASE CI Insulated Cement Board Applications

For control joints in fire-rated systems:

• Review National Gypsum’s The PURPLE Book^® (pages 38, 58, 66 and 88) and The Wood Book™ (page 27) for additional guidance on designing control joints for fire-rated systems.

Most-downloaded resource: Gypsum Board Guide Spec

Most searched-for fire-rated design: UL V497

Product Spotlight

PermaBASE CI^® Insulated Cement Board

• Improves Energy Efficiency
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• Meets or exceeds most continuous insulation requirements