13.7. Barrel Vault With Flat Seam

Description: Copper flat seam roofing is an excellent material for covering barrel vaults. Flat seam roofing can be made watertight, where required, see Roofing Systems - Special Design and Installation Considerations.

At their crowns, vaults are essentially flat; soldered seams are used in this area and for some distance down each side of the vault. Expansion battens are used to divide the length of the vault into areas not to exceed 30 feet in order to accommodate thermal movement.

The minimum recommended weight for flat seam roofing is 20-ounce copper.

Substrate: Continuous nailable substrate.

Fastening Method: Cleats.

13.7A. Axonometric of Barrel Vault

This detail shows a barrel vault abutting a wall. The flat seam roofing is divided by expansion battens spaced no more than 30 feet apart.

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13.7B. Plan

Longitudinal Expansion battens should be positioned so that no more than 30 feet of fully soldered flat seam roofing. The eave conditions can be detailed similar to Detail 13.6E.

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13.7C. Section

For very large vaults, transversely located expansion battens may also be required. Their shape must be designed to allow positive drainage, as shown in the detail. These transverse seams are required to be soldered on low slope application.

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13.7D. Expansion Batten

A wood batten is nailed onto the barrel vault. Copper flashing is formed, as shown, over the batten. For shallow-curved vaults, a single piece batten cover can be used. For steep-curved vaults, a two-component batten cover/apron should be used, see Detail 13.3C. Special equipment can be used to stretch the batten cap components to fit the curve of the vault. The flashing is fully soldered to adjacent flat seam roofing panels. Expansion can be accommodated by tapering the battens or by using rectangular battens, but by bending the upturned legs of the flashing at less than 90 degrees, see Roofing Systems - Flat Seam.

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13.7E. Section At Reglet

This section shows how a reglet can be formed or cut into a wall to hold copper flashing. The wall can be constructed of unit masonry or concrete, new or existing. Copper flashing is formed and wedged into the reglet. Its lower end is locked into a continuous copper lock strip, which is soldered to the base flashing. The base flashing is soldered to the roofing pans, as described in Detail 13.7G. The reglet is filled with sealant to make it watertight.

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13.7F. Section at Edge

This section shows a method of constructing the condition at a freestanding edge or rake of an arched barrel vault. The copper pan is locked into the edge flashing and the seam is soldered if required by slope. The 3/4" fold allows for a straight edge that can compensate for structural irregularities.

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13.7G. Detail

The copper roofing pan is formed into a double fold and turned up the wall 5/8". Special stretching equipment can be used to curve this upturned leg to fit the shape of the vault. A base flashing with a minimum 9" vertical leg is cut on a curve to match the barrel vault curve. The lower edge of the base flashing is formed into a 5/8" leg and stretched to fit the curve. This leg of the base flashing is inserted into the roof pan double fold and fully soldered. Cleats, spaced a maximum of 12", fasten the base flashing to the wall. In brick or other unit masonry walls, stepped counter flashing can be used. The counter flashing can be laid into the wall using a receiver and its lower edge fastened by lock strips and cleats, as shown.

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