Page 247 - Construction Waterproofing Handbook

5.6 CHAPTER FIVE
Spacing and sizing joints
Once the appropriate types of joints are determined, calculations are necessary to deter-
mine proper spacing and sizing of the required joint opening. Following are established
guidelines used frequently in the industry; note that these are not meant to replace actual
engineering calculations.
Basic rules for joint design, Fig. 5.5, include:
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1. Joint size no smaller than 4 in
2. Joint size no larger than 1 in
3. Joint opening a minimum of four times anticipated movement at the joint opening
Basic rules for sealant design, Fig. 5.6, include:

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1. Material thickness no less than 4 in
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2. Joints up to 2 in wide; depth of material is equal to width of material
3. Joints wider than 2 in; depth of material is one-half the width
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4. Maximum recommended width is 1 in
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5. Maximum depth is 2 in
The number and spacing of joints are determined by:

1. Anticipated substrate movement, determined by coefficient of expansion
2. Length of substrate material span
3. Joint width

Design for movement is usually based on a temperature differential of 150°F. This is
movement occurring in a selected material in a change of temperature of 150°F.

FIGURE 5.5 Design of substrate joint.