Proper Conduit Penetration Flashings on Tile Roofs for Solar Panels

Oftentimes the work a “competitor” does leaves me shaking my head (SMH). We received a call from a super nice lady in Naples, FL who purchased a solar photovoltaic system from and out of town contractor. That was the first mistake she made, given that people who come from hours away rarely support clients after the sale and installation. The second mistake was hiring someone that has no clue what they were doing.

When installing solar panels on a tile roof, you need a contractor with experience. You need a contractor that uses the right materials. And you need a contractor that cares about your home and your money.

Shockingly Poor Workmanship

What I found was shocking. The drywall ceiling was badly damaged in this home. The owner had sent her adult son into the attic to try to stem the tide of water using some sealant and a bucket. Fortunately, she called us before any major roof or structural damage occurred, and before wiring got wet and potentially started a fire.

The installer had simply screwed an outdoor rated switch box directly to the roof deck (with no sealant). They tried to use waterproof wire entry fittings for the high voltage DC wires (the wrong ones). They just drilled a hole in the box without a waterproof fitting to get the ground (bonding) wire into the attic. In some places, they just drilled a hole in the roof to get the ground wire into the attic. Then they completely encased the box in mortar with the high voltage wires unprotected and going right through the concrete.

Totally Wrong Conduit Roof Penetration Method
Totally Wrong Conduit Roof Penetration Method

There were four conduit penetrations, all done in this manner. This level of incompetence and disregard for safety and workmanship is completely unacceptable. Contractors who do this need to be purged from the ranks of licensed professionals.

It Got Worse

What we found in the attic was arguably worse. They had simply screwed Handy boxes to the roof deck from the underside in some cases, or screwed boxes to trusses. The boxes need to be installed away from the roof deck to prevent damage during re-roofing at a minimum. It’s simply bad practice.

But most importantly, they had flexible metal conduit strewn about the attic with virtually no supports. This conduit is generally required to be supported within 12 inches of a junction box and every 4-1/2 feet after that.

Conduit Penetration Fix
Before and after pictures of conduit penetration flashings on a tile roof.

Proper Conduit Penetrations

There are a few products on the market to properly get conduit into the attic on a tile roof. We prefer to use the conduit penetration flashings from Quick Mount PV. These provide both a base flashing and a top flashing. Flashing the penetration at the underlayment level is the first line of defense to prevent water intrusion to the attic. The top flashing ensures that water does not get beneath the tile where the conduit penetrates the tile surface.

In this case, we actually modified a Quick Mount PV tile replacement mount top flashing because the tile itself was obviously missing. The tile replacement mount mimics the shape of the missing tile. It provides a positive seal at the tile level. Normally used for rack mounting standoffs, this flashing also works great, with proper planning, for conduit penetrations.

Conduit Penetrations Are Critical

It’s not easy to properly flash a conduit penetration on a tile roof. Other roof types provide simpler flashings with less technique to master. Tile roofs require a special set of knowledge and skill. For the most part, solar panel attachments are far less likely to leak, especially if done properly with the right materials and methods. But conduit flashings have unique issues.

Courtesy: Quick Mount PV Website | Three Course Flashing Method for Solar Panels on Tile Roofs
Courtesy: Quick Mount PV Website | Three Course Flashing Method for Solar Panels on Tile Roofs

Solar panel mounting penetrations are simply screws. There are no big gaps to seal. It is much easier to seal a mounting point. Conduit penetrations, on the other hand, require that a hole larger than the conduit be drilled. There is necessarily a gap between the conduit itself and the roof deck. Sealing this gap is not as simple as a little sealant around the hole. That is the reason we use both a base flashing and a top flashing for all penetrations. Special care needs to be taken with conduit penetrations.

With new peel-and-stick roof underlayments, and older rolled asphaltic underlayments, we use the three-course method to seal the base flashing. This is the preferred method approved by the Tile Roof Institute and Florida’s Association of Roofing Professionals. This is a rock-solid method of waterproofing conduit penetrations at the deck level.

Finally, the conduit itself must be well secured. Any movement of the conduit can eventually work the sealants and the base flashing loose, causing cracks and leaks.

Ultimately, it’s all about using the right products and installing them properly.


Installation video from Quick Mount PV’s website:

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