Description: Roofing material on flat roofs is subjected to extreme temperature changes. As a result, the material experiences significant thermal expansion and contraction. All roofing types are designed to accomodate a certain amount of movement. This adjustment occurs at the roof perimeter. However, with large flat roofs, it may be necessary to divide the area into smaller parts, in order to keep the total movement within acceptable limits. Roof area dividers perform this task. The roofing manufacturer's recommendations should be followed in determining the need for and placement of roof area dividers.
Roof area dividers rely on wood curbs to effectively frame areas of the roof. The roofing material extends up the curb, much the same as it does at the roof perimeter. Copper cap flashing is used to cover the curbs and the ends of the roofing.
The minimum recommended weight for the copper caps is 16 oz.
9.13A. Typical Roof Area Divider
The copper cap flashing is held on each side of the wood curb by continuous copper lock strips. Adjacent caps are joined with drive cleats or single flat lock seams.
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9.13B. Roof Area Divider at Perimeter Wall
This detail shows how an area divider is terminated at a wall. The top surface of the copper cap is extended and bent up under the continuous counterflashing of the roof perimeter. Small copper flashing sheets are formed and inserted under the adjacent flashing to complete the corners.
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For sections greater than 10 feet, cap seams must be designed to accomodate expansion and contraction, see Roofing Systems - Long Pan for additional information.