3 Metal Panel Roofing Mistakes That Lead to Leaks | Indiana Metal

Metal panel roofing is one of the most durable and cost-effective roofing options available. But even a quality panel installed with the wrong technique can fail prematurely — and the mistakes that cause it are almost always the same three things.

We see it in the field. We see it in online roofing communities. And we’re seeing it come up more and more as contractors new to metal roofing take on jobs without getting proper guidance from their supplier.

Here’s what you need to know before your next metal panel install.

Mistake #1: Overdriven Screws

This is the most common mistake on exposed fastener panel roofs, and it’s the one that causes the most long-term damage.

Every screw on a metal roof has a rubber or EPDM gasket under the head. That gasket is what creates the watertight seal at each penetration point. When you overdrive the screw — meaning you compress the gasket past its designed limit — a few things happen:

• The gasket deforms and loses its ability to seal evenly around the screw head
• Over time, the cracked gasket allows water to migrate down the screw shaft and into the decking
• Freeze-thaw cycles accelerate the failure as the gasket shrinks and expands with no integrity left

The fix: Use an adjustable clutch drill — not an impact driver — set to the torque spec for your panel. The gasket should compress just enough to form a flat, even seal around the screw head without the metal dimpling around it. If the metal is dishing inward, you’ve gone too far.

Also worth noting: exposed fastener screws will back out over time due to thermal expansion and contraction. Retorquing every few years is legitimate preventive maintenance, not a sign of a bad install.

Mistake #2: Reversed Panel Lap

Every metal panel has a defined overlap side. Get it backwards and you’ve created a water trap instead of a water channel.

On a corrugated or ribbed panel, the edge that has a small flat leg or shelf along the rib is the “under” side — it goes beneath the next panel. The clean edge without the leg goes on top. When it’s reversed, water running down the roof hits a flat metal-on-metal seam instead of a vertical barrier, and it will wick under by capillary action.

The fix: Before you start laying panels, orient yourself to which edge is which. Hold a panel up and look at the rib profile at the overlap edge — the side with the small horizontal shelf laps underneath. The side that terminates cleanly laps on top. When in doubt, reference the install sheet from your supplier. Every panel profile is slightly different.

The side seam should be stitched with a shorter screw every 24 inches along the rib to lock the lap joint and prevent wind lift at the seam.

Mistake #3: Screws in the Wrong Location

There’s an ongoing debate in the roofing world about whether screws should go through the rib or through the flat (the pan). Here’s the practical answer: on most exposed fastener panels, screws go in the flat, close to the rib — not through the rib itself, and not in the center of the pan.

Why not through the rib? Because the rib creates a gap between the screw head and the decking below. That gap allows flex and movement at the connection point, which works the screw loose faster and compromises the gasket seal.

Why not center of the pan? Because that’s where the most water runs. Putting a fastener directly in the primary water flow path puts more stress on the gasket every time it rains.

The fix: Drive screws in the flat, approximately 1 to 2 inches from the rib on either side. Check your panel manufacturer’s install guide for exact spacing — screw patterns are specified and matter for wind uplift ratings.

Indiana Metal manufactures and distributes metal roofing panels, trim, and accessories from our Bainbridge, IN facility, with a new retail and will-call location opening May 15th at 6352 Airway Drive in Indianapolis. If you’re a contractor with questions about panel profiles, install specs, or accessories, our team is here to help. Stop in or give us a call.

Q1: What happens if metal roofing screws are overdriven?

Overdriven screws crush the EPDM gasket under the screw head past its designed compression limit. Once the gasket deforms, it can’t form a consistent seal around the fastener. Over time, water migrates down the screw shaft into the decking below. Freeze-thaw cycles accelerate the failure. The fix is using an adjustable clutch drill set to the correct torque — not an impact driver.

Q2: Which side of a metal panel goes on top when lapping?

The clean edge — the one without the small flat leg or shelf along the rib — goes on top. The edge with the purlin support leg laps underneath. When reversed, water can wick under the seam by capillary action instead of running off the vertical barrier the correct lap creates

Q3: Should metal roof screws go in the rib or the flat?

On most exposed fastener panels, screws go in the flat approximately 1 to 2 inches from the rib — not through the rib itself, and not in the center of the pan. Screwing through the rib creates a flex gap that works the fastener loose. Screwing in the center of the pan puts the fastener in the primary water flow path. Always check your specific panel manufacturer’s install guide for exact screw pattern specs.