Metal Roofing Options, continued

Modular panels are either nailed directly to the roof deck or installed on 2x2-inch battens spaced approximately 14 inches apart (Figure 8). Installing battens is extra labor but levels out surface irregularities caused by old roofing and allows more elaborate profiles to be stamped into the panel. Modulars installed without battens have folds along the sides and bottom edge that hook on to preceding shingles and are nailed directly to the roof deck, through the old roofing (Figure 9). On both types, manufacturers specify felt or polyethylene underlayment to keep sheathing and old roofing from abrading the back of the panels and to offer some protection as a secondary water barrier.

Figure 9.Modular panels are installed over felt or proprietary underlayment either directly to the roof deck or on 2x2 battens. Systems without batten boards speed installation by eliminating the need to cut and nail down the wood pieces, but they can look flat compared to the deeply textured systems that use battens. Modular panels are frequently manufactured from the lightest-gauge metal (.015 inch), but stamping patterns into the metal adds strength, so careful footsteps are unlikely to crush them, although walking on the highest raised portions of the panel can be damaging. For roof areas with an unusual amount of foot traffic -- adjacent to air-conditioning equipment, for example -- manufacturers recommend optional foam backers to reinforce raised portions of the panel.

Manufacturers offer many preformed accessory pieces that speed installation, but complicated roof profiles can slow it considerably (Figure 10). Hips and valleys require custom cutting and bending, and although modular panels are easier to cut than the concrete or clay tile they're often made to resemble, you can't make cuts up on the roof with a utility knife like you can with asphalt shingles.

Figure 10.As with standing-seam and exposed-fastener panels, installing modular panels is made easier by coordinating trim accessories. Clockwise from top left are starter, hip cap, ridge caps, and rake trim from Classic Products.