Standing Seam Installation

A standing seam roof uses long metal panels that run from eave to ridge and join along raised vertical seams. The fastening is concealed: clips fixed to the deck engage the panel edges and are covered by the next panel's seam. Panels may be factory-made or roll-formed on site from steel, aluminium, copper or zinc.

Panel types

• Snap-lock. One panel edge snaps over the edge of the adjoining panel and its clips without tools.
• Mechanically seamed. The seam is folded with a hand or powered seamer into a single lock (one fold) or double lock (two folds, sometimes called a 180-degree or 360-degree seam). Double-lock seams give the highest weather resistance.
• Nail-strip (fastener-flange). One edge is screwed through slotted holes and the next panel covers the screws.

Common panel widths are 12 to 18 in (300 to 460 mm) and seam heights about 1 1/2 to 1 3/4 in (38 to 44 mm).

Slope and underlayment

Canadian guidance notes that most architectural metal roof systems are designed for a minimum slope of 1:4 (25 percent, or 3:12). Below that, mechanically seamed panels with sealant in the seams are required. The same guidance calls for at least one ply of No. 30 felt with a slip sheet where the panels could bond to it, plus eave, valley and penetration membranes.

Installation outline

1. Install underlayment, eave and rake trims and any eave cleat.
2. Lay out the panels so widths are balanced at each end of a visible roof plane and seams meet at hips and valleys.
3. Set the first panel square to the eave, engaging or hemming its lower end over the eave cleat.
4. Fix clips along the seam at the spacing required by the panel system and design wind loads.
5. Place the next panel over the clips and snap or seam it.
6. Finish with ridge, hip and wall flashings and closures.

Thermal movement

Metal expands and contracts with temperature. Long panels must be able to move between eave and ridge, typically by fixing them at one point and using clips that let the panel slide elsewhere. Failure to allow for movement can loosen flashings and cause leaks. Oil-canning, a visible waviness in the flat pan, is a cosmetic issue reduced by thicker metal and stiffening ribs.