13.6. Arched Barrel Vault with Standing Seam

Description: Copper standing seam roofing can be readily applied to barrel vaults, by following a number of guidelines. The guidelines, described in Detail 13.6B below, address issues of expansion and contraction, and watertightness. The basic details are the same as those for regular standing seam roofing, see Roofing Systems - Standing Seam.

The minimum recommended weight for standing seam roofing is 16-ounce copper.

Substrate: Continuous nailable substrate.

Fastening Method: Cleats.

13.6A. Axonometric of Barrel Vault

This detail shows an overall view of a barrel vault that abuts a brick wall. The key elements of the copper roof are indicated - the standing seams and staggered transverse seams. Also illustrated is the stepped flashing used at the wall.

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13.6B. Plan

This detail addresses a number of issues critical to achieving a durable, functional, and good looking standing seam roof on a barrel vault. Lay out the roofing pans so that the pattern is centered on the centerline on the vault. Do not locate transverse seams in areas where the pitch of the vault is less than 3 inches per foot. Fill the standing seams in those areas of the vault where the pitch is less than 3 inches per foot with sealant. Stagger transverse seams in adjacent runs. Use fixed cleats to anchor the roofing pans at mid-length at the centerline of the vault. Use expansion cleats to facilitate thermal movement from this mid-length point of anchorage to the end of each run. The maximum pan run should be maintained at approximately 30 feet, see Roofing Systems- Long Pans for more information.

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13.6C. Section at Wall

The copper roofing pan and copper base flashing are formed as shown in Detail E. The base flashing extends a minimum of 9" up the wall, where it is held by cleats, spaced a maximum of 12". In brick or other unit masonry walls, stepped counter flashing can be used. The counter flashing is held by a copper receiver laid into the wall, as shown.

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13.6D. Elevation at Wall

This detail shows a close-up of the stepped flashing method used on unit masonry walls.

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13.6E. Section at Eave

If the roofing pans are longer than 10 feet, then long pan roofing details must be used to accommodate expansion and contraction, see Roofing Systems - Long Pan.

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13.6F. Section

This detail shows one method of incorporating a gutter at the base of a vault. The basic principles of gutter design are described in the Gutters and Downspouts section. The copper roofing pans are terminated a few inches above the upper edge of the gutter. Copper flashing is used between the pans and the gutter. The flashing is held at its upper edge by cleats, where it locks into the roofing pans. The bottom edge of the flashing is locked onto a continuous copper lock strip, which is soldered to the gutter. This method permits replacement or repair of the various components with minimal disturbance to other components.

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For Additional Information:

Equipment Available: Special tools are available to stretch the standing seams and the wall flashing over the barrel vault.