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Exposed-fastener metal panels are screwed through the flat beside the ribs in rows along every purlin or support. The 1st Coast Metal Roofing Supply installation guide shows rows 24 in apart with one #10 × 1 1/2 in screw beside each major rib of its 9 in rib panel (4 per 36 in panel), and 12 in across the panel for PBR, with two screws at each rib on the end rows and #12 × 1 in stitch screws in the side lap at 12 in. Gable trim is screwed every 12 in, eave trim up to 24 in, and the ridge cap at every major rib on both sides. Side laps overlap one rib and need sealant below 3/12; end laps are always sealed; trim laps 3 in and flashings 6 in. Enter the eave length, panel length, slopes, profile and row spacing: a 30 ft eave with 21 ft panels on two slopes takes 960 panel screws plus 200 for ridge and trim — 1,160 in all.
Exposed-fastener metal panels are screwed in rows along every purlin or support, through the flat beside the ribs. The patterns here follow the 1st Coast Metal Roofing Supply installation guide.
| Where | 9 in rib panel | PBR / R-panel |
|---|---|---|
| Rows | Every purlin or support, 24 in max | Every purlin or support, 24 in max over wood |
| Field rows | One beside each major rib — 4 per panel | 12 in across the panel — 3 per panel |
| End rows | 4 per panel | Two at each rib — 6 per panel |
| Side lap | Overlap one rib | #12 × 1 in stitch screws at 12 in |
| Ridge cap | One at every major rib, each side | One at every major rib, each side |
| Gable / eave trim | Every 12 in / up to 24 in | Every 12 in / up to 24 in |
Screws go in rows along every purlin or support line, in the flat of the panel beside the ribs, with the washer snug but not crushed. For a 36 in panel with 9 in major ribs, 1st Coast's Armour Rib detail puts one #10 × 1 1/2 in screw beside each major rib — 4 per panel — in rows 24 in apart. PBR (R-panel) uses 12 in across the panel in the field, two at each rib at the panel ends, and #12 × 1 in stitch screws in the side lap at 12 in.
Rows follow the supports, at most 24 in apart for residential panels. Across the panel the spacing is set by the ribs: about 9 in for 9 in rib panels and 12 in for PBR. Trim is screwed every 12 in along gables and up to 24 in along the eave, and ridge cap gets a screw at every major rib on both sides.
With 9 in rib panels on 24 in rows, about 76 panel screws per 100 sq ft on a 21 ft panel — 960 for a 1,260 sq ft roof — plus trim and ridge screws. PBR with 12 in field spacing and sidelap stitch screws comes to about 98 per square. Short panels need more per square because each end row is denser.
For exposed-fastener panels over wood, in the flat beside the rib, where the washer seats on a flat surface over the wood. Ridge cap and some trim are fastened through the rib so the cap is not crushed.
Side laps overlap one rib and face away from the prevailing rain; below 3 in 12 they need sealant, and the panels in the 1st Coast guide need at least 1/2 in 12. All end laps need sealant. Ridge cap, eave and gable trim overlap 3 in minimum, and flashings lap at least 6 in and are sealed.
Rows follow the purlins — the purlin spacing calculator lays them out at 24 in on centre or less.
Need the whole roof at once? The free roofing calculator works out roof area, squares, shingle bundles, underlayment, drip edge, ridge cap and installed cost from one set of measurements.