Screwing Through the Rib vs. the Flat on Metal Roofing: The Real Answer

Ask ten roofers where screws go on an exposed fastener metal panel and you’ll get three different answers. It’s one of the most debated installation details in the roofing world, and the confusion costs contractors callbacks and homeowners leaks.

Here’s the definitive answer, why it matters, and what happens when you get it wrong.

The Three Camps (And Why Two of Them Are Wrong)

Roofers typically land in one of three positions on screw placement:

• Through the rib
• Dead center of the flat (pan)
• In the flat, close to the rib

In the eyes of the manufacturer, the third one is correct. Here’s why the other two are not our recommendations.

Why You Don’t Screw Through the Rib

The rib is the raised structural element that gives the panel its strength and profile. When you drive a screw through it, a few problems compound:

• The rib profile creates a gap between the underside of the screw head and the panel surface. That gap means the EPDM gasket can’t compress evenly and flat — it bridges the gap, leaving the seal incomplete.
• Without a solid compression point, the screw has more movement at its connection. Thermal expansion and contraction — significant on metal — works the screw back and forth, enlarging the hole and loosening the gasket over time.
• The rib connection transfers less load to the deck below compared to a flat connection, which matters for wind uplift ratings.

Some manufacturers do specify rib fastening for certain panel profiles — particularly in high-snow-load regions where point loading on the panel is a concern. Always check your specific panel’s install guide. But for most standard exposed fastener residential and agricultural applications, rib fastening is not the standard.

Why You Don’t Screw Dead Center in the Flat

The center of the flat — the pan between ribs — is the primary water flow path on the roof. Every drop of rain that lands between two ribs runs down the center of that pan.

Putting a fastener directly in that path creates two problems: the gasket is under maximum hydrostatic pressure every time it rains, and any gap in the seal gets water driven into it rather than flowing past. This accelerates gasket wear and increases the chance of water entry at the fastener.

Center-pan fastening also provides less structural support than near-rib placement because the flat is the most flexible part of the panel profile — there’s more give, which means more movement at the fastener over time.

The Right Answer: Flat, Adjacent to the Rib

The correct location is in the flat of the panel, approximately 1 to 2 inches from the rib. This position gives you:

• A solid, even surface for the gasket to compress flat against — no bridging, no gap
• A connection close enough to the rib that the panel doesn’t flex excessively at the fastener point
• A location out of the primary water channel, so the gasket isn’t fighting maximum water pressure at every rain event

Always drive near-rib fasteners on each side of the rib according to your panel manufacturer’s specified screw pattern. Spacing matters for wind uplift ratings — don’t improvise it.

Not sure which screw pattern your panel profile requires? Indiana Metal’s team can pull the install spec for any panel we carry. Stop in at Bainbridge or our new Indianapolis location on Airway Drive, or give us a call or email