Will installing solar panels create roof leaks?

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Will solar panels cause roof leaks on pitched, asphalt-shingle roofs?

It is one of the most common questions we field when speaking with homeowners, and justifiable so. Solar panel attachments, unless they're ballasted (impossible for most sloped-roof single family residences in the United States), involve roof penetrations, most commonly a lag bolt driven through the rafter. Missing the rafter, penerating the decking and not properly sealing the penetration is one of the more common causes of roof leaks. An experienced solar installer will be able to sound out rafters, minimizing excess penetrations. And if excess penetrations around the rafter are made, an experienced installer will seal them properly.

More recently, solar installers have begun to use deck-mounted attachments. These attachments can be secured to the decking or sheathing underneath the shingles. The great benefit here is that installers don't need to locate or plan attachment points according to rafters. Solar systems can be laid out and installed more quickly. However, the uplift force each attachment can withstand is lower, so more attachments are needed.

Lag Bolt

Lag bolt attachments are mechanically flashed, whereby an asphalt-shingle is replaced with a metal one and sealed around the lag bolt penetration. Modern mechanical solar flashing, like the Ironridge Flashfoot 2, are longer lasting and better at water proofing than the shingles on most roofs in Westchester, NY. in the case of the Flashfoot 2, the lag bolt sits underneath an umbrella of rubber and metal. Should the rubber fail, the penetration is still covered by the lag bolt. This is probably a 100 year product.

Mechanical flashing may be made from aluminum, galvanized or stainless steel, or copper. Each of there materials has advantages and disadvantages. Copper lasts long, but is more expensive. Aluminum is lighter and cheaper. Galvanized steel is heavy and rigid, and stainless steel lasts long, but is difficult to cut.


Deck-mounted attachments typically use more penetrations, as you need more screws and bolts to fasten securely to the decking than you do to the rafter. Many deck-mounted options use sealants, like butyl, a kind of liquid rubber. This is the case for one of Rivertown Solar's preferred attachments, the RT-Mini.

Another kind of deck-mounted attachment is the Flashloc Duo 2, which uses a liquid sealant called Duralink 50.

Roof Condition

Before we install solar on your roof, we will be sure to assess your roof condition. We'll look for signs of aging, like shingle discoloration and upward curvature, or cracking. Exposure to fluctuations in temperature over many years causes shingles to crack, as they expand and contract repeatedly. Cracked shingles cause leads, and if your roof is already leaky, that needs to be addressed before we install solar on it.

Proper Installation

Ultimately, the best way to prevent leaks, aside from installing on a roof that's in good condition, is to install attachments per manufacturer instructions. Often times installers will cut corners, use less attachments or screws than required per specifications, or install on slopes for which the attachments is not rated. At Rivertown Solar, regardless of whether we're using deck-mounted or lag bolt attachments, we make sure to get it right the first time and to install as intended by the manufacturer. That's why we feel comfortable offering a 15-year workmanship warranty, whereby we guarantee against leaks caused by our installation for 15 years.