Why You Can’t Just Poke Romex Cable Through a Wall Sheathing for a Light Fixture

Yes, we do a large number of Pre-Drywall Inspections, and during another recent Pre-Drywall Inspection, we found the wiring for an exterior light run like this:

At first glance, it looks simple—just poke the Romex through the wall sheathing, and once the siding is up, slap the light over it. But this method is not allowed and creates long-term safety and durability issues.

What’s Wrong in This Photo?

1. Romex is not exterior-rated
   NM (Romex) cable like this can only be used inside finished walls, ceilings, and floors. It must be protected by a proper electrical box or conduit where it penetrates the building envelope. Leaving it exposed like this violates NEC requirements.
2. WRB penetration is not sealed
   The weather-resistive barrier (house wrap) is designed to protect the wall from water intrusion. A cable poked through without flashing or sealing creates a direct pathway for water to enter and damage the sheathing, framing, and insulation.
3. No fixture support
   Light fixtures must be mounted to a listed exterior-rated electrical box. Without a box, the cable supports the fixture's weight, which is unsafe and non-compliant.

The Right Way to Do It

• Install an exterior-rated electrical box flush with the sheathing.
• Run the Romex into the box with an approved connector that clamps the cable.
• Seal the box to the WRB with flashing tape or a gasket to maintain water resistance.
• Attach the fixture to the box for proper support and code compliance.

✅ Bottom Line: What we found here is a shortcut that could become a hidden hazard if left in place. Pre-drywall inspections are the best time to catch this type of issue before it gets covered up by siding. If this client had not had a pre-drywall inspection, this would have gone undetected until it caused a problem or the light fixture needed to be changed out!  Yes, this home had already been passed by the local city inspector and was scheduled for the siding, insulation, and drywall to be installed in a few days!

📞 Trace Inspections – 615-302-1113
🔎 Serving Spring Hill, Thompson’s Station, Columbia, and the greater Nashville area
🌐 www.traceinspections.com

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