JOINT SIZING -- SIMPLIFIED
A critical element of proper joint sizing is to keep movement types and movement range in mind.
It’s important to understand the measurements the engineer specifies for movement. The simplest way to do this is to request the nominal joint size and the movement range. The movement range is simply expressed as a dimension of how far the joint is anticipated to open and close. Asking for the movement expressed as a dimension will help the architect write a clearer specification for the finished assembly.
Simplify Terminology Used for Sizing Expansion Joints
Nominal Joint Width
is the specified size of the joint opening.
Width of the joint
without movement
Minimum Joint Width
is the narrowest linear gap that the joint is expected to close to. *Avoid 0”
2” (nom) – 1” (close) =
1” min joint width
Maximum Joint Width
is the widest linear gap that the joint is expected to open to.
2” (nom) + 1” (open) =
3” max joint width
It is important to keep the following in mind:
Avoiding 0” is important when material such as joint cover retainers or a fire barrier will be present inside the joint opening. Any such element should be reviewed and confirmed, as it will affect the joint’s sizing and could be compromised if a joint closed to 0”. The available space for the material should be outlined during the planning phase.
1. Joints smaller than 4” can usually close to half of the nominal joint size.
2. Joints larger than 4” should allow for 4 inches for the fire barrier.
3. Turnbars and retainers are two integral pieces that also affect the joint’s sizing.
Always review movement data to ensure that the model selection meets your requirements.
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