The screw pattern for metal roofing is the row-by-row layout of exposed fasteners across a panel: a tighter row at the eave, field rows spaced 24 inches on center, a doubled row at every endlap, a row at the ridge, and a stitch row down each sidelap. Get the pattern right and the roof sheds water and holds against uplift for decades. Get it wrong and the fasteners themselves become the leak path.
This guide maps the full pattern as one liftable table, then breaks down spacing, per-line screw counts by panel profile, and the adjustments for gauge, purlins, and wind. It covers exposed-fastener panels (corrugated, R-panel or PBR, and Western Rib). Standing seam roofs use hidden clips and have no field screw pattern, covered near the end.
The complete metal roofing screw pattern, row by row
An exposed-fastener metal roof is fastened in five distinct rows or lines, each with its own spacing. The pattern below is the standard layout for a screw-down panel over solid decking or purlins. Manufacturer instructions and local wind code always override these defaults, but this is the layout most residential and agricultural panels follow.
| Row / line | Where it sits | Spacing | Why it is there |
|---|---|---|---|
| Eave row | Bottom edge, over the eave purlin or starter | Every low rib, tightened row | Highest uplift zone; anchors the panel start |
| Field rows | Across the panel between eave and ridge | 24 inches on center down the slope, one screw in the flat beside each rib | Holds the panel flat to the deck |
| Endlap row | Where one panel overlaps the next up-slope | Doubled row, one line each side of the lap, plus butyl tape | Seals the horizontal joint against wind-driven water |
| Ridge row | Top edge, under the ridge cap | Every low rib | Second-highest uplift zone; secures the top |
| Sidelap (stitch) row | Vertical seam where panels overlap | Stitch screws 12 to 18 inches on center | Clamps panel edges so they cannot flutter or gap |
The two rows people skip most often are the endlap and the sidelap stitch row. Both are joints, not field, and both leak when under-fastened. A field screw carries load; a stitch screw carries the seam.
How far apart should metal roof screws be?
Field screw lines on metal roofing sit 24 inches on center on solid wood decking, tightening to 12 to 18 inches in high-wind zones and opening to 36 inches only on light-duty, low-exposure runs. Over open metal purlins, you fasten at every purlin line instead of a fixed dimension, since the purlin spacing sets the rhythm. Sidelap stitch screws run 12 to 18 inches on center regardless of substrate.
Across the width of each panel, a fastener goes in the flat next to every rib on R-panel and PBR profiles. On corrugated sheet, the common rule is a screw every third corrugation in the field, closing to every corrugation at the eave, ridge, and both edges. Closer spacing is never wrong for holding power; it only adds penetrations and cost.
Screws per screw line by panel profile
Each panel profile has its own count of screws per horizontal line, because rib spacing and coverage width differ. The table gives the standard field and end-of-panel counts for the three most common exposed-fastener profiles, based on manufacturer fastening guides such as those from McElroy Metal and Western States Metal Roofing.
| Panel profile | Screw position | Field line | Panel-end line | Lap / stitch screws |
|---|---|---|---|---|
| 7/8 inch corrugated | High of the corrugation | 4 per line | 5 panel + 1 lap | 12 to 18 inches on center |
| R-panel / PBR | Flat, beside each major rib | 3 panel + 1 lap | 5 panel + 1 lap | 12 to 18 inches on center |
| 7.2 Western Rib | Every panel low | 5 panel + 1 lap | 5 panel + 1 lap | 12 to 18 inches on center |
Sidelaps on R-panel and Western Rib also need butyl or mastic tape under the overlap before the stitch screws go in. The screw clamps the seam, but the tape does the sealing.
Rib or flat: where each screw lands
On R-panel, PBR, and 7.2 profiles, screws go in the flat next to the rib, where the gasket seats squarely against the panel and the deck. On classic round-wave corrugated, the traditional position is the high of the corrugation, which keeps the head out of standing water but relies on a longer screw and a clean gasket seat. The panel profile, not personal preference, decides the position, so follow the manufacturer spec for the exact panel you bought.
The rib-versus-flat question is narrow enough to have its own answer. For the full case on each position and how gasket compression drives it, see our guide on where to place each screw, rib or flat. The pattern on this page tells you which rows and spacing to use once that position is set.
How many screws the whole roof needs
A screw pattern at 24-inch lines uses roughly 80 screws per roofing square, or square footage multiplied by 0.8. A 3,000 square foot roof needs about 2,400 field and end screws before you add sidelap stitch screws and trim fasteners. Sidelaps add a separate count, and trim takes about one screw per lineal foot.
That is the field-count shortcut. For the full math including sidelap and trim add-ons, and how the number shifts by panel width, see how many screws a full metal roof needs. Pattern sets spacing; the count follows from it.
Adjusting the pattern for gauge, purlins, and wind
Three variables tighten or open the standard pattern. Lighter panels and higher wind zones pull the screw lines closer; heavier gauge and sheltered sites let them relax toward the maximum. None of these override the manufacturer table, which already bakes in the panel’s tested capacity.
- Gauge: 29-gauge and thinner panels bend and oil-can more easily, so they need closer field spacing than 26- or 24-gauge to stay flat.
- Substrate: Solid decking accepts a fixed 24-inch line; open purlins set the spacing by their own layout, so you fasten at every purlin.
- Wind and snow: Coastal and high-exposure zones and the eave, ridge, and rake edges take a tightened row, often 12 inches on center, because uplift peaks at the perimeter.
Standing seam has no field screw pattern
Standing seam metal roofs use concealed clips at each seam and carry no exposed field screws, so the row-by-row pattern above does not apply to them. The clips fasten to the deck and the seam folds over them, which is why standing seam avoids the gasket-aging problem that eventually reaches every exposed-fastener roof. If you are weighing the two systems, our guide to screw-down panels versus standing seam lays out cost and lifespan.
Screw pattern mistakes that cause leaks
Incorrect fastener installation is the single biggest cause of leaks on an exposed-fastener metal roof, not the panel itself. Most of the failures below come from rushing the pattern or ignoring the gasket, and each has a clean fix.
- Overdriving: Crushing the rubber washer flat pushes it out past the head and it fails in a few seasons. Drive until the washer swells to the edge of the head, then stop.
- Underdriving: A loose screw leaves the gasket uncompressed and lets water wick under the head. Seat it fully so the washer contacts the panel all around.
- Off-angle screws: Driving at anything but 90 degrees tips the washer and opens one side. Keep the driver square to the panel.
- Missing the framing: A screw that misses the purlin or decking holds nothing and the hole leaks. Snap chalk lines on the screw lines before you start.
- Skipping the endlap or stitch rows: Field screws alone leave the seams unfastened. Both joint rows are part of the pattern.
When a pattern has failed and the roof is already leaking, tracing the source is its own job. Our walkthrough on finding and sealing a metal roof leak by source covers fastener-driven leaks in detail. For the wider fundamentals, start at our roofing knowledge hub.
Frequently asked questions
How far apart should screws be on a metal roof?
Field screw lines run 24 inches on center on solid decking, tightening to 12 to 18 inches in high-wind zones. Across the panel, a screw goes in the flat beside each rib on R-panel and PBR, or every third corrugation on corrugated sheet. Sidelap stitch screws sit 12 to 18 inches on center. Over open purlins, fasten at every purlin line.
Do metal roof screws go on the rib or the flat?
On R-panel, PBR, and 7.2 Western Rib profiles, screws go in the flat next to the rib, where the gasket seats squarely. On classic round-wave corrugated, the traditional position is the high of the corrugation. The panel profile decides the position, so follow the fastening guide for the exact panel you bought rather than a single blanket rule.
How many screws do I need per square of metal roofing?
A standard pattern uses about 80 screws per roofing square, which is 100 square feet, at 24-inch screw lines. A quick estimate for a whole roof is square footage multiplied by 0.8. That figure covers field and panel-end screws only. Sidelap stitch screws and trim fasteners at roughly one per lineal foot are counted separately.
What screw pattern does corrugated metal roofing use?
Corrugated sheet is fastened every third corrugation in the field, giving four panel screws per line on a standard 37-inch panel, and closes to every corrugation at the eave, ridge, and both edges. Panel ends carry five panel screws plus one lap screw, and sidelap stitch screws run 12 to 18 inches on center with butyl tape under the overlap.
Does a standing seam roof have a screw pattern?
No. Standing seam metal roofs fasten with concealed clips at each seam and have no exposed field screws, so the row-by-row pattern for corrugated and R-panel does not apply. The clips attach to the deck and the seam folds over them. That hidden-fastener design is the main reason standing seam avoids the gasket wear that reaches every exposed-fastener roof over time.
How tight should you drive metal roofing screws?
Drive each screw until the rubber washer swells just to the edge of the metal head, then stop. Overdriving crushes the washer and it fails early; underdriving leaves it uncompressed and water wicks under the head. Set the driver clutch to seat the gasket consistently, and keep every screw square to the panel at 90 degrees so the washer compresses evenly.
Reviewed by The Roofing Brief Team. Last reviewed July 2026.