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Roof Structure

Structural Deterioration And Damage

Problem: Roof sheathing panels rise up at joints, causing ridging.

Cause: Roof panels installed too tightly.

Panel sheathing products are often used to "square" the roof and as such are installed with the ends of the panels placed tightly together. When moisture or temperature causes roof sheathing panels to expand, there is no tolerance, resulting in ridging at panel edges.

Solutions: Space roof panels adequately.

  • When using strandboard, waferboard or plywood for roof sheathing follow building code stipulations of gap between sheets of not less than 1/16 inch (2 mm). Manufacturers of roof sheathing panels may recommend a larger amount of spacing for their own panels. By using some types of H-clips, you automatically ensure an adequate space between panel edges. However, you must provide adequate spacing along the ends as shown in Figure 20.

Roof Panel Edge Spacing

Figure 20 - Roof Panel Edge Spacing

Note 1: Minimum 1/8 inch (2 to 3 mm) spacing between panels.

Note 2: Some H-clips (Figure 20a) are designed to provide adequate space between panel edges.

h-clips for roof sheathing

Figure 20a - Roof sheathing H-clips

Additional information on roofs and roofing