Metal roofing screw placement depends on the panel profile and the support below it. For most exposed-fastener panels, screws pass through the metal and into the roof deck, rafter, purlin or another structural support.
The correct location varies by panel:
- Ribbed and 5V steel panels usually take screws beside the ribs or in the fastening areas shown by the manufacturer.
- Some corrugated panels use screws through the crest.
- Some residential exposed-fastener panels use screws through the flat pan between ribs.
- Standing-seam roofing uses concealed clips or fasteners, so you should not screw through the visible panel.
Follow the installation diagram for the exact panel. There is no universal crest or valley rule for every metal roof profile.
Metal Roofing Screw Placement at a Glance
| Roof system | Where the screws go |
|---|---|
| Exposed-fastener ribbed panel | Through the panel at the specified support lines, often beside or between ribs |
| 5V steel roofing | Alongside the ribs in the specified fastening pattern |
| Corrugated roofing | Usually through the crest, although some profiles require valley fastening |
| Residential pan-style panel | Through the flat pan or designated fastening strip |
| Standing-seam roofing | Through concealed clips, not through the exposed panel |
| Panel side laps | Through the overlapping metal with stitch screws and sealant where required |
| Ridge, eave, rake and valley | At the dedicated trim, closure and flashing details |
Where to Screw Exposed-Fastener Metal Roofing Panels
Place the main panel screws where they will reach the supporting structure below the metal. Depending on the roof assembly, that support may be:
- Every wood purlin
- Every rafter or truss line
- The roof deck
- Metal framing or girts
- Another substrate listed in the panel instructions
Union Corrugating's 5V steel roofing guide calls for screws at every purlin and shows the required positions in its fastening detail. The guide also warns against placing screws through the anti-siphoning channel.
Do not fasten only into the thin metal between supports. A screw that misses the purlin, rafter or deck may have less holding power and can leave a hole that leaks.
Should Screws Go in the Rib, Valley or Flat Pan?
The correct location depends on the panel profile. Use the fastening diagram for that product instead of copying the pattern from another roof.
Ribbed and 5V Panels
Many ribbed and 5V panels use screws alongside a rib rather than through its center. Union Corrugating's 5V steel approval documentation places fasteners alongside the center, underlap and overlap ribs according to the approved fastening detail.
Corrugated Panels
Corrugated panels do not all use the same fastening location. Palram says crest fastening is usually preferred for its corrugated products, while some products require valley fastening. The product installation guide determines which method applies.
Flat-Pan Residential Panels
Some exposed-fastener residential panels are designed for screws through the flat part of the panel. American Building Components' SL-16 instructions show exposed fasteners passing through the center of the pan and into sealant tape beneath the panel.
Where to Screw the Panel Side Laps
Install stitch screws through the overlapping edges of adjacent panels. Do not place them randomly through the middle of the lower panel.
Use the following:
- The stitch-screw size listed by the manufacturer
- Sealant tape or approved sealant where required
- The stated maximum spacing
- A screw long enough to join both panels without leaving an unnecessarily long exposed point
ASC Building Products recommends panel lap screws at a maximum of 18 inches on center for the profiles covered by its light-gauge installation guide. The guide also recommends sealant along the roof sidelaps.
Where the instructions call for it, position the overlap away from prevailing weather. That arrangement helps limit wind-driven rain entering the lap.
Where to Screw at the Eaves, Ridge and Roof Edges
Roof edges often need a different fastening pattern from the middle of the roof. Check the details for the:
- Eaves
- Rakes or gable edges
- Ridge caps
- Valleys
- End laps
- Roof penetrations
- Gutters and flashing
Wind loads are often higher near the roof perimeter, so the instructions may call for closer spacing or additional fasteners in those areas. MBCI says spacing depends on the substrate, design loads and roof location, including the eaves, rake and ridge.
Do not replace a ridge, valley or flashing detail with a general screw pattern. These areas may require closures, butyl tape, sealant, pancake-head screws or fasteners installed in a particular position.
How Tightly Should Metal Roofing Screws Be Driven?
Drive each screw until the sealing washer sits firmly against the metal without crushing it.
A properly driven screw has:
- A washer compressed enough to seal
- No visible gap beneath the washer
- No large dimple in the metal
- No split, distorted or extruded washer
- A screw head sitting straight rather than tilted
Overdriving can deform the panel and damage the washer. American Building Components warns that excessive tightening can force out the neoprene washer, expose it to sunlight and shorten its service life.
Underdriving leaves a gap beneath the washer. ASC's installation guide shows underdriven, correctly driven and overdriven sealing fasteners as separate conditions.
What Type of Screw Should You Use?
Choose a fastener approved for both the panel and the substrate:
- Wood deck or dimensional lumber: Corrosion-resistant wood-grip roofing screws
- Plywood or OSB: Manufacturer-approved screws with enough thread engagement
- Metal framing: Self-drilling screws rated for the framing thickness
- Panel laps and trim: Stitch screws or lap screws with sealing washers
- Standing seam: Concealed clips and fasteners supplied or approved for the system
ASC Building Products lists different fasteners for plywood or OSB, dimensional lumber, metal framing, panel laps and trim. The correct fastener therefore depends on the panel and what supports it.
Where Not to Screw Metal Roofing
Avoid these mistakes:
- Do not screw into unsupported panel areas when the fastener should reach a purlin, rafter or deck.
- Do not place screws through an anti-siphoning channel unless the panel instructions require it.
- Do not overdrive the washer.
- Do not leave a missed screw in place. Remove it and seal the hole using the approved repair method.
- Do not use ordinary indoor screws or incompatible metals.
- Do not screw through a standing-seam panel.
- Do not use a fastening pattern from another panel profile.
ASC also recommends isolating roofing and flashing from incompatible dissimilar metals to help reduce corrosion.
The Simplest Answer
For an exposed-fastener steel roof, screw through the fastening area shown in the panel instructions and into every required support below. Ribbed panels often take screws beside or between the ribs. Some corrugated panels use the crest, while some residential panels use the flat pan.
The panel manufacturer's installation diagram is the final authority. For standing-seam roofing, use concealed clips rather than exposed screws.