By The Roofing Brief Team. Last reviewed: October 2026.
The screw pattern for metal roofing is the row-by-row layout of exposed fasteners across a panel: a screw at every rib along the eave, endlap and ridge, field lines at each purlin or about 24 inches on center up the slope, and a stitch row down each sidelap at 12 to 20 inches on center. Western States Metal Roofing’s planning rule is about 80 screws per roofing square at 24 inch lines on 36 inch panels, or square footage multiplied by 0.8. Metal Sales warns that overdriven fasteners distort panels, so the pattern and the seating both decide whether the roof leaks.
The chart and tables below give the screws per line, spacing and screws per square for R-panel and PBR, AG-panel (Classic Rib), 7/8 inch corrugated, 5V crimp and 7.2 Western Rib, with the maker document behind each number. Standing seam uses concealed clips at 24 to 48 inches on center in Petersen’s ICC-ES report, covered near the end. Maker instructions and your local wind design override every default here.
The complete metal roofing screw pattern, row by row
An exposed-fastener metal roof is fastened in five rows or lines, each with its own spacing. McElroy Metal’s Multi-Rib / R-Panel manual (MM498) puts the tight pattern, a 1/4-14 x 7/8 inch Lap Tek screw at every rib, at the eave, endlap and ridge, and a lighter pattern at intermediate purlins. The table pairs each row with its published spacing and source.
| Row / line | Where it sits | Spacing | Why it is there | Source |
|---|---|---|---|---|
| Eave row | Bottom edge, over the eave purlin or starter, through the inside closure and tape | Every rib (McElroy Pattern #1) | Highest uplift zone; anchors the panel start | McElroy MM498 |
| Field rows | Across the panel between eave and ridge | At each purlin, or about 24 in on center on solid deck; Western States gives 18 to 36 in as the range | Holds the panel flat to the deck | Western States Metal Roofing (Mar 2020) |
| Endlap row | Where one panel overlaps the next up-slope | Every rib, through a 6 in endlap with tape about 3 in from the lower panel’s end | Seals the horizontal joint against wind-driven water | Metal Sales Classic Rib guide; McElroy MM498 |
| Ridge row | Top edge, under the ridge cap | Every rib; on 5V crimp, a row 1 ft below the ridge trim at 1 ft on center | Second-highest uplift zone; secures the top | McElroy MM498; ABC 5V Crimp manual (Rev E) |
| Sidelap (stitch) row | Vertical seam where panels overlap | 12 to 18 in (Western States); 12 in (Metal Sales PBR and Classic Rib); 20 in (McElroy R-panel) | Clamps panel edges so they cannot flutter or gap | Maker guides as listed |
The endlap and sidelap rows are joints, and both need tape as well as screws: Metal Sales lays tape sealant across the full width of the eave panel’s upper end at every endlap, and McElroy runs 1 in tape on the lower panel 5 3/4 in down from its end. Picture the roof as a grid: a horizontal line at each purlin or every 24 inches up the slope, a screw at each rib along the eave, endlap and ridge lines, and stitch screws down the vertical seams.
Where each screw lands on the panel cross section
On a panel cross section, the screw lands in the flat pan next to a major rib on R-panel, PBR and 7.2 Western Rib, and in the high of the corrugation on 7/8 inch corrugated roofing, per Western States Metal Roofing. Read the profile end-on: the ribs are the raised ridges, the flats are the low pans between them, and the sidelap is the overlapping rib at each panel edge where two sheets join.
Look at an R-panel from the gable end. Metal Sales’ PBR guide shows a trapezoidal major rib every 12 in, 1 1/4 in tall, with small stiffening ribs in each flat and an overlapping rib at the panel edge. The screw seats in the flat beside each major rib, driven straight down so the washer compresses evenly against the pan. Classic Rib, an AG-panel profile, puts 3/4 in ribs on 9 in centers. On 7/8 inch corrugated the wave repeats about every 2.67 in, and Western States puts a screw in the high of every third corrugation. Follow the fastening guide for the exact panel you bought.
Screw pattern decision table
The substrate (wood deck or steel purlin) and the panel decide which row applies, and supports more than 2 ft apart change the load math. Match your roof to a row before you snap the first chalk line.
| If your roof is | Then fasten | Screw | Source |
|---|---|---|---|
| Ribbed panel over solid wood deck | Lines about 24 in on center; every rib at eave, endlap and ridge | #10-14 woodscrew, 1 to 2 in | Metal Sales fastener guide; Western States |
| Ribbed panel over steel purlins | A line at every purlin; every rib at eave, endlap and ridge | #12-14 self-driller, 1 to 2 in | Metal Sales PBR guide (4/24) |
| Purlins wider than 2 ft apart | Check the panel load table first; Classic Rib 26 ga drops from 125 psf at 2 ft to 56 psf at 3 ft inward | As above | Metal Sales Classic Rib guide (8/19) |
| 5V crimp on plywood, 26 ga | 4 screws across the 24 in panel, 3 ft on center along it, for UL 90 Construction #453 | #14-10 x 1 1/2 in Type A with 5/8 in steel washer | ABC 5V Crimp manual (Rev E, 12/24) |
| Florida or coastal wind zone | The spacing in the product approval; TAMCO 5V goes from 71.25 psf at 16 in to 127.5 psf at 8 in | Per approval | Florida Product Approval FL16667-R4 |
| Standing seam | Clips only, at the spacing in the evaluation report | Clip screws, for example two #10-12 x 1 in pancake head | ICC-ES ESR-4173 Table 2 |
Metal roof screw spacing chart by panel type
This chart gives screw position, spacing and screws per square for six profiles, each tied to a named maker or supplier document. Field figures assume 24 in lines on solid deck unless the source says otherwise; eave, ridge and endlap lines take a screw at every rib. The fastening guide for your exact panel and your site’s wind design override any chart.
| Panel type | Screw position | Field spacing | Eave / ridge / endlap | Sidelap | Approx screws / square | Source guide |
|---|---|---|---|---|---|---|
| R-panel / PBR (36 in, ribs 12 in on center) | Flat, beside each major rib | 3 panel + 1 lap screw per line | 5 panel + 1 lap screw per line | Stitch 12 to 20 in on center | About 80 | Western States; McElroy MM498 |
| AG-panel, Metal Sales Classic Rib (36 in, ribs 9 in on center) | Flat beside the rib | Per the guide’s fastening pattern | Every rib; trim screws 8 to 12 in on center | Stitch 1 ft on center | About 80 on 3 ft panels | Metal Sales Classic Rib guide (8/19) |
| 7/8 in corrugated roofing | High of the corrugation, every third one | 4 screws per line | Per maker detail | Western States: no metal-to-metal sidelap screws needed on 7/8 in corrugated roofing | About 80 | Western States |
| 5V crimp (24 in, 26 ga) | Beside the V ribs, a line at the double V | 4 per line, lines 3 ft on center (UL 90) | Ridge row 1 ft below trim, 1 ft on center | Per maker detail | Fewer at 3 ft lines | ABC 5V Crimp manual |
| 7.2 Western Rib | Every panel low | 5 panel + 1 lap screw per line | 5 panel + 1 lap screw per line | Stitch 12 to 18 in on center | About 80 | Western States |
| Standing seam (snap-lock or mechanical) | Concealed clip at each seam | Clips 24 to 48 in on center in ESR-4173 assemblies | Closer spacing at perimeter per engineering | No exposed field screws | Clips, not screws | ICC-ES ESR-4173 |
Screws per square in the chart count field and endlap fasteners at 24 inch lines; sidelap stitch screws and perimeter trim are added on top. Western States’ 80 per square figure assumes 36 inch panels and 24 inch lines, and Metal Sales gives 80 per square for its 3 ft wide panels and 40 per square for 2 ft wide panels in the Classic Rib guide.
On 5V Crimp, spacing also sets the wind rating. In the evaluation report for TAMCO’s 5V Crimp, Florida Product Approval FL16667-R4, tightening screws from 16 to 8 inches on center raises the allowable design uplift from 71.25 psf to 127.5 psf. For the full tables, see our guide to 5V fastener spacing and Florida uplift ratings.
How far apart should metal roof screws be?
Field screw lines sit at each purlin over open framing, and about 24 inches on center on solid wood decking, the spacing Western States Metal Roofing uses for its 80 per square rule; it gives 18 to 36 inches as the working range. Eave, endlap and ridge lines take a screw at every rib. Sidelap stitch screws run 12 to 18 inches on center in Western States’ guidance, 12 inches in Metal Sales’ PBR and Classic Rib guides, and 20 inches (1 ft 8 in) in McElroy’s R-panel manual.
Across the width of each panel, R-panel and PBR take 3 panel screws plus 1 lap screw on a field line and 5 plus 1 at panel ends, per Western States. On 7/8 inch corrugated, the screw goes in the high of every third corrugation, 4 per line. Closer spacing adds holding power and penetrations at the same time; the 5V example above shows halving the spacing from 16 to 8 inches lifts the rated uplift from 71.25 to 127.5 psf.
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 Western States Metal Roofing’s field and end-of-panel counts for the three most common exposed-fastener profiles. For one 3/4 inch rib profile in detail, see our master rib metal roof guide.
| Panel profile | Screw position | Field line | Panel-end line | Lap / stitch screws | Source |
|---|---|---|---|---|---|
| 7/8 inch corrugated (roof) | High of the corrugation | 4 per line | Per maker detail | No metal-to-metal sidelap screws needed on roofs | Western States (Mar 2020) |
| 7/8 inch corrugated (wall) | High of the corrugation | 5 panel + 1 lap | 5 panel + 1 lap | 12 to 18 inches on center | Western States (Mar 2020) |
| R-panel / PBR | Flat, beside each major rib | 3 panel + 1 lap | 5 panel + 1 lap | 12 to 18 inches on center | Western States (Mar 2020) |
| 7.2 Western Rib | Every panel low | 5 panel + 1 lap | 5 panel + 1 lap | 12 to 18 inches on center | Western States (Mar 2020) |
Sidelaps on R-panel and PBR also get tape sealant under the overlap for roof use before the stitch screws go in; Metal Sales and McElroy both show it. The 1/4-14 x 7/8 inch stitch screw clamps the seam, and the tape seals it.
Screws per square by panel profile
A standard exposed-fastener pattern at 24 inch field lines uses about 80 screws per roofing square (100 square feet), or square footage multiplied by 0.8, per Western States Metal Roofing. The figure counts field and panel-end screws and assumes 36 inch panels. Sidelap stitch screws and trim screws are counted on top of it.
| Panel profile | Field position | Field line spacing | Perimeter spacing | Approx screws per square | Source |
|---|---|---|---|---|---|
| 7/8 inch corrugated | High, every third corrugation | 24 in on center | Per maker detail | About 80, plus trim | Western States |
| R-panel / PBR | Flat, beside each major rib | 24 in on center or each purlin | Every rib at eave, endlap, ridge | About 80, plus stitch and trim | Western States; McElroy MM498 |
| Classic Rib, 3 ft panels | Flat beside the rib | Per guide pattern | Every rib at eave and endlap | 80 | Metal Sales Classic Rib guide |
| 7.2 Western Rib | Every panel low | 24 in on center | 5 + 1 per line at panel ends | About 80, plus stitch and trim | Western States |
That is the field-count shortcut. For sidelaps, Western States divides square footage by 3, then by 1.5, so a 3,000 sq ft roof needs about 667 stitch screws, and it adds 1 screw per lineal foot of trim. For the full math by panel width, see how many screws a full metal roof needs.
How to lay out and drive the pattern, step by step
A chalked grid keeps every screw on framing and every line parallel. Work eave to ridge, with one panel fully fastened before the next overlaps it, and install against the prevailing wind, as Metal Sales’ Classic Rib guide directs.
- Square the first panel. Metal Sales checks each slope for square by comparing its two diagonals, and sets the inside closures square to the building because they control alignment of every 36 in panel that follows.
- Mark the field lines. Snap chalk lines up the slope at each purlin, or about 24 inches on center on solid deck, so screw rows land on framing.
- Set the gun. Triangle Fastener’s guidance is a screwgun with a 2,500 rpm maximum, 2,000 rpm or less into steel 1/4 inch or thicker, with torque control or depth sensing. It says not to use impact tools for drill screws.
- Fasten the eave row first. Drive a screw at every rib through the panel, closure and both tape runs, straight down at 90 degrees.
- Fill the field rows. On R-panel, drive 3 panel screws plus 1 lap screw per line in the flat beside each rib.
- Seat each washer. Per Metal Sales, correct shows a thin line of sealant at the washer edge; none means loose; a deformed washer means tight.
- Stitch the sidelaps. Add 1/4-14 x 7/8 inch stitch screws 12 to 18 inches on center down each overlapping seam, over tape sealant on roofs.
- Close the endlaps and ridge. Lap panels 6 inches over tape, fasten every rib through both panels, then fasten the ridge line at every rib under the ridge cap.
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 washer seats against the panel and the deck below. On 7/8 inch corrugated roofing, Western States places them in the high of the corrugation. A screw in the flat clamps the panel directly to the deck or purlin, which is why every R-panel line in Western States’ counts sits in the flat. Follow the maker spec for the exact panel you bought.
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. Choosing the fastener itself, from #10 and #12 diameters to washer types, is covered in our roundup of the best metal roofing screws. Metal Sales lists #10-14 woodscrews and #12-14 self-drillers in 1, 1 1/2 and 2 inch lengths for its PBR panel.
Adjusting the pattern for gauge, purlins, and wind
Three variables tighten or open the standard pattern. Thinner panels and wider supports carry less load, and higher wind zones need closer screws. None of these override the manufacturer table, which bakes in the panel’s tested capacity, or the uplift load calculated under ASCE 7 and enforced through the International Building Code.
- Gauge: in Metal Sales’ Classic Rib table at 2 ft supports, 29 gauge carries 97 psf inward and 26 gauge 125 psf, so thinner panels need closer supports for the same load.
- Support spacing: the same 26 gauge panel drops from 125 psf at 2 ft supports to 56 psf at 3 ft and 32 psf at 4 ft (inward load, three or more spans). For sizing and spacing wood purlins and steel purlins, see our purlin guide.
- Wind: for UL 580 Class 90, Metal Sales’ PBR Construction No. 161 calls for #12-14 x 1 in self-drilling screws with 5/8 in washers and endlaps of at least 4 in over purlins. Perimeter and corner zones under ASCE 7 take the tighter rows.
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. In ICC-ES ESR-4173, Petersen’s Tite-Loc clips at 30 inches on center on aluminum panels rate 127 psf allowable uplift, while Snap-Clad clips at 36 inches on 24 gauge steel rate 45 psf. 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
Most fastener leaks trace to one of these five errors; Metal Sales’ PBR guide states the first directly: overdriven fasteners distort panels.
- Overdriving: Metal Sales defines it as a deformed washer with sealing material pressed beyond the fastener edge. Stop when sealant just shows at the washer edge.
- Underdriving: No sealant visible at the washer edge means too little compression to seal. Seat it until a thin line shows.
- 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 over each purlin, or every 24 in on solid deck, before you start.
- Skipping the endlap or stitch rows: Field screws alone leave the 6 in endlaps and the sidelaps unfastened. Both joint rows are part of the pattern.
If the roof already leaks, see our walkthrough on finding and sealing a metal roof leak by source, and our roofing knowledge hub for fundamentals.
What length screw for each substrate
Screw length is set by what sits under the panel. Metal Sales’ PBR guide says fasteners should extend 1/2 inch or more past the inside face of the support material, and Triangle Fastener’s rule for steel is at least three full threads beyond the substrate. Metal Sales lists #10-14 woodscrews and #12-14 self-drillers in 1, 1 1/2 and 2 inch lengths.
| Substrate | Screw type | Lengths listed | Minimum penetration | Source guide |
|---|---|---|---|---|
| Solid wood deck or wood purlin | #10-14 woodscrew, Type A, with sealing washer | 1, 1 1/2, 2 in | 1/2 in or more past the inside face of the support | Metal Sales PBR guide (4/24) |
| Steel purlin, 22 to 12 gauge | #12-14 self-drilling, with sealing washer | 1, 1 1/4, 1 1/2, 2 in | At least 3 full threads past the steel | Metal Sales PBR guide; Triangle Fastener tips (June 2018) |
| Steel 1/4 in or thicker | Self-driller with a drill point rated for the thickness | Per fastener maker | 3 full threads past the steel; drive at 2,000 rpm or less | Triangle Fastener tips |
| Over rigid insulation or a retrofit layer | Longer screw sized to the full stack | Panel + insulation + deck | 1/2 in past the inside face of the deck | Metal Sales PBR rule applied to the full stack |
Pull-out capacity drops with thinner substrate. Metal Sales lists #10-14 woodscrew pull-out values of 428 in 5/8 in plywood, 328 in 1/2 in plywood and 183 in 7/16 in OSB, and 555 in 2x Southern Yellow Pine. Match the length and the screw to the substrate rather than reusing one box across a whole job.
Torque and gasket seating
Correct seating, not torque, is what makes a gasketed screw watertight. Triangle Fastener recommends a screwgun with torque control or a depth-sensing feature to protect the sealing washer, at 2,500 rpm maximum and 2,000 rpm or less into steel 1/4 in or thicker, and says not to use impact tools for drill screws. Metal Sales describes three washer states, shown below.
| Seating | What it looks like (Metal Sales) | Result |
|---|---|---|
| Correct | Sealing material slightly visible at the edge of the washer | Watertight assembly |
| Too tight | Washer deformed; sealing material pressed beyond the fastener edge | Panel distortion and a damaged seal |
| Too loose | Sealing material not visible | Not enough compression to seal |
Screws per square: a worked example
For a simple gable roof with two 40 by 18 foot planes, 1,440 square feet or 14.4 squares, the field and endlap count is 1,440 multiplied by 0.8, about 1,152 screws, using Western States Metal Roofing’s rules. Sidelap stitch screws and trim screws are added on top, then a waste margin.
- Field and endlap: 1,440 sq ft multiplied by 0.8 equals about 1,152 screws.
- Sidelap stitch: 1,440 divided by 3, then by 1.5, equals 320 screws.
- Trim: 1 screw per lineal foot of trim: 80 ft of eave, 40 ft of ridge and 72 ft of rake (four 18 ft rakes) is 192 screws.
- Subtotal: 1,152 + 320 + 192 = 1,664 screws.
- Add 10 percent for waste and stripped fasteners: about 1,830 screws, or eight bags of 250.
The arithmetic is Roofing Brief’s, built on Western States’ per-square, sidelap and trim rules. For the full count math across panel widths and trim, see how many screws a metal roof needs.
When to re-screw a metal roof
Plan to re-screw an exposed-fastener metal roof once the original washers harden and the screws back out. Our 2026 roofing material lifespan report puts gasket life at about 15 to 20 years and the realistic full-system life of exposed-fastener metal at 25 to 30 years. Signs it is due include screws standing proud, cracked washers, rust rings around the heads, and leaks that track to fastener lines rather than seams.
- Replace, do not just retighten. Back out the old screw and install one size up in diameter, for example a #12 in place of a #10, with a fresh washer so it bites into new material.
- Do the whole roof, not just the leakers. Washers installed the same year reach the 15 to 20 year gasket life together, so a full re-screw avoids chasing single leaks.
- Time it dry and cool. Panels expand in heat, so re-drive on a mild day so the panel does not shift under the head.
Already leaking? Our guide to finding and sealing a metal roof leak by source covers fastener-driven leaks.
Frequently asked questions
How far apart should screws be on a metal roof?
Field lines go at each purlin, or about 24 inches on center on solid decking, with 18 to 36 inches as Western States Metal Roofing’s working range. Eave, endlap and ridge lines get a screw at every rib. Sidelap stitch screws run 12 to 18 inches on center per Western States, 12 inches in Metal Sales’ guides and 20 inches in McElroy’s R-panel manual.
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 washer seats squarely. On 7/8 inch corrugated roofing, Western States puts them in the high of every third corrugation. The panel profile decides the position, so follow the fastening guide for the exact panel you bought.
How many screws do I need per square of metal roofing?
About 80 screws per roofing square of 100 square feet, at 24 inch lines on 36 inch panels, per Western States Metal Roofing; a whole-roof estimate is square footage multiplied by 0.8. Add sidelap screws (square footage divided by 3, then by 1.5) and 1 trim screw per lineal foot. Metal Sales gives 40 per square for 2 ft wide panels.
What screw pattern does corrugated metal roofing use?
On 7/8 inch corrugated roofing, Western States puts a screw in the high of every third corrugation, 4 screws per line, and says metal-to-metal sidelap screws are not needed on the roof. On corrugated walls it uses 5 panel screws plus 1 lap screw per line, with lap screws 12 to 18 inches on center.
Does a standing seam roof have a screw pattern?
No. Standing seam roofs fasten with concealed clips at each seam and have no exposed field screws. In ICC-ES ESR-4173, Petersen clips are spaced 24 to 48 inches on center depending on panel and deck, with allowable uplift from 37 to 127 psf. The clip spacing comes from the evaluation report or the project’s wind design.
How tight should you drive metal roofing screws?
Drive until the sealing material is slightly visible at the edge of the washer, Metal Sales’ definition of correct; a deformed washer means too tight and no visible sealant means too loose. Triangle Fastener recommends a torque-controlled or depth-sensing screwgun at 2,500 rpm maximum and no impact tools.
What length screw do I need for a metal roof?
Into wood, Metal Sales lists #10-14 woodscrews in 1, 1 1/2 and 2 inch lengths and says screws should extend 1/2 inch or more past the inside face of the support. Into steel, use #12-14 self-drillers long enough that at least three full threads pass the steel, per Triangle Fastener. Over insulation, size the screw to the full stack.
When should you re-screw a metal roof?
Re-screw when the washers harden and screws back out; our 2026 lifespan report puts gasket life at about 15 to 20 years. Watch for screws standing proud, cracked washers, rust rings and leaks at fastener lines. Replace with one diameter up and a fresh washer, and do the whole roof at once since same-age washers age together.