Batten Seam Roofing

Batten seam (or batten roll) roofing is a traditional seamed-metal method in which pans run parallel to the slope and are separated by battens fixed to the deck. The pan edges turn up against the battens, and a metal cap is folded over each batten and loose-locked into the adjacent pans. The result is a roof with bold, evenly spaced ribs. It is used in copper, zinc, lead (as wood-cored rolls), terne-coated stainless and other metals.

Construction (copper example)

Copper Development Association details describe:

• Battens nominally 2 x 2 in (about 50 x 50 mm), assuming caps about 1.5 in (38 mm) high.
• Pans up to about 20 in (510 mm) wide in 16 oz copper; wider pans, over about 24 in (610 mm), in 20 oz copper.
• Caps of the same weight as the pans, joined end to end with 1/2 in (13 mm) locks or lapped at least 3 in (75 mm).
• A gap of about 1/16 in (1.6 mm) between pan leg and batten so the metal can move. Tapered battens, slightly narrower at the base, are the preferred way to give this clearance.
• Cleats at transverse seams on shorter pans; one type is set as battens are installed, another is nailed to the battens.

Slopes

Steep-slope transverse seam details apply from about 6 in per foot (1:2); low-slope details cover 3 to 6 in per foot (1:4 to 1:2). Roofs below 4 in per foot, or in snowy and wet climates, need special design attention.

Regional variants

In Europe, zinc and copper batten roll roofs follow similar principles with metal caps over timber rolls. In UK lead roofing, wood-cored rolls play the same role, accommodating movement between bays.