How to Install Exposed-Fastener Metal Roof Panels (R-Panel and Ribbed)

Step by Step

1. 1Step 1: Check the substrate, slope and trim layout

   Most ribbed panels specify a minimum slope of about 3/12, and some allow lower with extra sealant at laps and unspliced panels. Check the manual. Strapping or purlins should be straight and at the spacing in the panel data sheet, commonly 24 inches on centre. Check for bowed lumber and fix it, since every bow shows through thin panels.

   Install eave and rake trims first, as shown in eave trim and closures and rake trim, so panels have a reference edge and tuck into the trim.

2. 2Step 2: Choose the starting end and sidelap direction

   Ribbed panels have an overlapping edge that laps over the underlapping edge of the neighbour. Install so the lap faces away from the prevailing wind, which in much of the Fraser Valley means starting at the north or east end and working toward the south or west, where the weather usually comes from. The panel manual shows the lap direction for the profile.

   Where a roof sees wind-driven rain from the side, a lap that faces into the wind will let water blow up under the overlap. On a gable roof with a rake trim, the direction may also be set by the trim, so think through the layout before starting.

3. 3Step 3: Square and fasten the first panel

   Measure the same distance from the rake at the eave end and the ridge end, snap a line, and set the edge rib on the line. Check overhang at the eave, typically 1 to 2 inches past the fascia, so water falls clear. Check square with a diagonal measure.

   Drive screws at the eave, then up the panel, following the pattern. A common layout is screws at every purlin in the flat next to each rib, or on the ribs themselves for some profiles, with extra screws at the eave, ridge and edges. See metal roof screws and follow the panel manufacturer.

   Watch out: A first panel that is out by a few millimetres at the eave can be out by an inch at the ridge. Re-measure and adjust before driving every screw.

4. 4Step 4: Apply sealant tape and lap the next panel

   Stick the tape to the underlapping rib of the installed panel, or as the manual shows, then lay the next panel over it. Do not peel the backing until the panel is nearly in place, and do not slide the panel across the tape, which smears it. The tape compresses as the lap screw is driven and forms the seal.

   Fasten the lap screws through both ribs at the spacing the manual gives, commonly 24 to 36 inches. Keep the ribs aligned and do not force the lap if the panels do not fit. A panel that will not sit has drifted out of square, and forcing it only pushes the error up the roof.

5. 5Step 5: Correct drift as you go

   Ribbed panels vary slightly in width and lap, and small errors accumulate. After every three or four panels measure to the rake at the eave and ridge. If they differ, gradually rotate the next panel to bring it back rather than correcting all at once.

   Watch the ribs against a string line. Ribs that look crooked at the eave will look worse at the ridge.

6. 6Step 6: Install eave and ridge closures

   Closures are foam or rubber strips cut to the rib profile. The eave closure sits under the panel at the eave trim, and the ridge closure sits under the ridge cap. They seal the open ribs against birds, bugs and wind-driven snow. See eave trim and closures and ridge and hip caps.

   Choose vented closures where the roof is designed to breathe at the ridge. A solid closure on a roof that needs the airflow traps moisture under the panels.

7. 7Step 7: Cut panels cleanly at walls, hips and penetrations

   Never cut pre-painted panels with an abrasive blade, because hot particles embed in the paint and rust. Use shears or a nibbler. See cutting metal roof panels. Notch and fold ends where trim calls for it, as in hemming and bending panel ends.

   Around pipes, use the flashing in pipe flashing on metal roofs, and at walls follow wall flashing. Do not put a screw through the pan of the panel upslope of a penetration.

8. 8Step 8: Finish trims, clean the roof and touch up

   Finish trims last, fastening into the closures and lapping sections in the direction of water flow. Sweep the roof with a soft broom, because steel shavings rust and stain the paint within days. Do not use a wire brush.

   Check a sample of screws for compression. Washers should be flat and slightly bulged, not crushed or loose. Replace any that are bad while the roof is still accessible.

Where Exposed-Fastener Panels Fit Best

Maintenance Over the Life of the Roof

Common Mistakes

• Skipping the sealant tape in sidelaps, leaving a capillary path for water.
• Laying panels with the lap facing the wind, so rain blows under the overlap.
• Overdriven screws that crush the washer, and underdriven ones that leave it loose.
• Driving screws into the pan of the panel where the manual calls for the flat beside the rib, or the reverse.
• An unsquare start that pushes drift to the ridge.
• Forgetting closures, which let in insects and wind-driven snow.
• Using an abrasive cutting wheel and leaving swarf that rusts.