13.2. Circular Dome with Standing Seam System

Description: Copper standing seam panels can readily be applied to domes. The basic principles of standing seam roofing apply, see Roofing Systems - Standing Seam Roofing. The differences are that the pans are elliptical and the seams are curved to fit the shape of the dome. See Steps for Dome Panel Layout.

The standing seams converge throughout their run from the base to the crown of the dome. At the crown, the seams are laid flat and terminate at a spun copper cap. See Detail 8.2B (Roofing System - Standing Seam) for similar condition. For seams converging to less than 6" spacing, alternate panels can be deleted and replaced with larger panels in order to facilitate installation, as shown in the left side of Detail 13.2B.

The transverse seams are staggered on adjacent pans. Since the pitch of the dome varies from the top to the bottom of the dome, different transverse seam details must be used at different locations. Where the pitch is below 6" per foot, a "low pitch" design must be used, as shown in Detail 13.2C. Where the pitch exceeds 6" per foot, the "high pitch" detail, shown in Detail 13.2D, can be used. See Roofing Systems - Special Design and Installation Considerations for special slope detail requirements.

Substrate: Continuous nailable substrate.

Fastening Method: Cleats. The spacing of cleats should be at approximately 12" o.c. along the radial seams. For domes approaching 6 feet in diameter, cleat spacing should be approximately 4" o.c.

The minimum recommended weight for standing seam pans is 16 ounce cold rolled copper.

The minimum practical diameter for a 3/4" high standing seam dome is 6 feet. For smaller domes, soft temper copper should be specified.

13.2A. Elevation

This detail illustrates staggered transverse seams. A spun copper cap is used to flash and terminate the top of the dome. A cupola or a similar ornamental termination is also suitable.

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13.2B. Plan

The converging pattern of standing seams is shown. The cap should be sized such that the seams are not less than 6" apart where they terminate at the perimeter of the cap.

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13.2C. Layout of Pattern

The number of pans required to complete the dome depends upon its size and the seam spacing chosen. Standing seam roofing pans typically finish 12" to 18" wide. Once the number of pans is determined, lines can be drawn on the dome to locate both the standing seams and the transverse seams. The size of each pan can then be measured directly on the dome. For example, the points ABCD correspond to the corners of a pan.

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13.2D. Pan Layout

The pans outlined in Detail A can be field or shop fabricated. For a one-inch standing seam, the long sides of the pans are cut to the dimensions shown and turned up. At the upper end of the pan, the copper is folded over. A continuous copper lock strip is soldered to the pan for low pitch transverse seams. This strip is not required for steep pitch seams. The bottom edge of the pan is folded under. See Steps for Dome Panel Layout. Panel blanks are roughly elliptical in shape.

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13.2E. Transverse Seam - Low Pitch

This seam is used where the roof pitch is less than 6" but greater than 3" per foot, to reduce the chance of water penetration. The cleat shown is used to help position and hold the pan during installation and to resist wind uplift.

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13.2F. Transverse Seam - High Pitch

This loose lock seam is used where the roof pitch is 6" per foot or greater. It should not be used near the dome apex, where water, snow, or ice can accumulate due to the shallow dome pitch. The high pitch transverse seam is identical to Section 8.2C Detail 2.

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13.2G. Dome Cap Detail - Non Venting

Dome cap flashing can be achieved in a wide variety of ways, including segmented or spun copper caps, finials, or spires. The detail shows a copper cap that is locked and soldered into the upper edge of the roofing pans. Cleats are used to fasten the copper pan to the dome substrate. This detail may be used where a vent is not desired at the top of the dome. If venting is desired, a vented cap may be used, see Detail 13.1D.

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For Additional Information:

Equipment Available:
Special tools are available to stretch the standing seams onto curved surfaces.