Did solar panels cause your roof to leak?

Do you have a solar home with a leaky roof? It's possible that a bad solar installation in the reason. Here's how to investigate it.

Photo of rain on a rooftop. (Credit: Gary Cole/Unsplash)
Credit: Gary Cole/Unsplash

Most solar homes and small business use rooftop-mounted arrays. This is cheaper than ground-mounted panels, but carries a small risk of roof leaks.

Solar equipment manufacturers make it as easy as possible to install solar panels on a roof without causing leaks, but there is still significant skill and training required to do the job properly. Even with the best equipment, a bad installation can cause your roof to leak. Sometimes, the leaking won’t be obvious until a few months or years after the work is done.

Do you have a solar home with a leaky roof? It’s possible that the solar panels are the cause, but it may also be coincidental. This article will go into the details of how a proper (non-leaky) solar installation should be done, how to investigate a leak, and what do you if you discover it.

Basics: how is a roof made waterproof?

The roof of your house keeps you dry because of several components that work together. While the construction details will vary depending on the type of roofing material you have, the basic details are similar.

Anatomy of a roof. (Credit: superstormrestoration.com)
Anatomy of a roof. (Credit: superstormrestoration.com)

Asphalt shingles are the most popular roofing material in the US. They’re cheap and durable, and can come with a warranty as long as 50 years. Shingles shed water and installed in an overlapping pattern so that wind-driven water can’t get underneath them easily.

If any moisture does penetrate the shingles, the underlayment below provides a final barrier to water entry.

These layers are nailed to the plywood or OSB decking underneath. Nails make holes, but roofing nails have large flat heads or plastic caps that protect the hole and shed water.

All of this is supported by rafters, which are strong beams (often 2x8s, 2x10s or 2x12s) that are set on edge and usually spaced 12" or 16" apart.

The decking should never get damp, but if it does, the roof is ventilated to remove moisture and allow the decking to dry to the inside. This why insulation is often on the floor of the attic rather than attached to the roof itself. (However, polyiso rigid insulation, which is water resistant, is now commonly used on roofs in energy efficient buildings.)

Common roofing types

If everything in the construction of your roof is done properly, it should never leak. This means that the method used to install solar panels must maintain that waterproof integrity.

Rooftop solar panels are attached to aluminum racks, which in turn are attached to footings that are anchored to the roof. (An exception is flat roofs, which may use racking systems that simply sit on top of the roof.)

The exact installation method and equipment depends on the roofing material. There are many materials in use, but three are among the most common.

Metal roofs are expensive, but extremely durable. They’re also often the best for solar installations, especially those with standing seam or exposed-fastened roofs. This is because solar racking equipment can be attached to a metal roof using only clamps, avoiding the need to drill holes into the roof. Even when holes are required, the built-in waterproofing that the racking systems have tend to pretty foolproof.

Tile roofs are trickier, especially those made with clay or lightweight concrete, which are brittle materials. There are different methods of installing solar on tile, including replacement tiles that mimic the shape of the original tiles but have an anchor system built in, and tile hooks that slip underneath the existing tiles.

However, the most common method is called a comp-out or picture framing. It involves installing an entirely new asphalt shingle roof underneath the existing tile roof, and leaving a gap in the tiles where the panels will be installed. With this method, waterproofing is provided by the asphalt roof rather than the tiles.

How are solar panels installed on a shingle roof?

Because installation on a tile roof often ultimately uses the same method as installing on an asphalt roof, that’s what this article will focus on.

There are several manufacturers that make roof attachments for home solar, but they all use the same basic approach consisting of:

  • An aluminum footing that is bolted to the roof
  • A method to shed water from the attachment point
  • Waterproofing to protect the entry hole in the roof

Sometimes the body of the footing itself is designed to shield the attachment point from water entry, while other designs use a wide sheet of metal (also known as flashing). Here’s a couple examples from SnapNrack:

SpeedSeal by SnapNrack
SpeedSeal by SnapNrack
Ultra Rail by SnapNRack
Ultra Rail by SnapNRack

The SpeedSeal design uses a footing with a wide body that protects the entry hole, while the Ultra Rail has a large piece of flashing that slides underneath the row of shingles above. In both cases, a sealant is used to waterproof the entry hole.

What causes solar installations to leak?

There are a few ways that a solar installation can fail and cause a roof to leak. It will almost never be a failure of the manufacturer’s product, but instead be caused by poor installation work. Common reasons for failure include:

  • Not torquing the bolts to the specifications indicated by the manufacturer
  • Missing the rafters when bolting to the roof
  • Not using sealant, or using the incorrect sealant
  • Installing on a roof in poor condition

The common thread here is following the manufacturer’s directions for the racking product. Unfortunately, unless you climb up on the roof yourself, you won’t be able to check yourself whether the installation crew did every item correctly. However, there are a few steps you can take to help ensure that your installer does the work correctly.

Ask what racking system will be used for your system

The first thing you can do is ask the installer lots of questions about the installation process, including the racking system that will be used. Once you know the equipment, you can look up the installation instructions for the product on the manufacturer’s website. This will help you understand exactly how the system will be attached to the roof and what it should look like when it’s installed, including any penetrations that might be visible from the underside of the roof deck.

Take photos of the underside of your roof

If you have an unfinished attic and the underside of the roof deck is visible, it would be a good idea to get up there and take photos of the section where the panels will be installed, taking care to show where any current nails are located.

Having these photos will help you know what the original state of your roof was, and help you identify which penetrations were made by the solar installation.

If you have a leak, take photos of any water stains and other evidence.

If your roof is leaking, check the installation from underneath

The reason I said that you should ask the installer for details on the racking system is so that you can look up the correct installation procedures on the manufacturer’s website. While it’s impractical for you to crawl up on the roof with a torque wrench to check every bolt, there’s a couple key things you can look for in the attic.

The first thing to check is the location of the bolts for the racking system. In most cases, the manufacturer will specify that the system must be attached to the rafters. Finding where the rafters are from the topside is often tricky for installation crews. One common method for locating rafters is to drill small pilot holes through the roof, which will let the installer see from the underside if they hit a rafter or not.

Pilot holes are a common installation practice and are not a cause for alarm as long as they are sealed correctly afterward using flashing or a sealant.

If you see bolts penetrate through the roof deck when the manufacturer specifies that they need to hit the rafters, that can be a concern and a cause for leaks. The leaks might not happen right away. Because decking is much thinner than rafters, forces on the roof, such as wind uplift, can cause the bolts to slowly loosen through the decking over time.

However, not all manufacturers require their product to be attached to the rafters. For example, the SpeedSeal product from SnapNrack can be attached directly to decking. However, there can be exceptions: SnapNrack specifies that attaching to deck is still recommended in areas where high wind is a concern.

If you have water entry, try to identify in the attic where water staining of the decking has occurred. If you can trace it to holes made by the solar installation, you might have a warranty claim against the installer.

Making a warranty claim for a leaking roof

Your solar installer will provide a warranty for their work, and sometimes there will be a separate roof leak warranty. Hopefully, you’re already familiar with these - they should be one of your key factors in selecting a good company to work with.

Once you’ve identified that your roof is leaking, reach out to your installer and provide any evidence that you have, such as before and after photos that you’ve taken.

If you’re working with a high quality installer, they’ll investigate quickly and provide a resolution if their workmanship is the cause.

One thing to be aware of is that it’s not always easy to identify the cause of a leak. Water can migrate from one part of a roof to another, so just because you have water dripping in one location doesn’t mean that’s where the leak is. Disputes with an installer about the cause of a leak are a common issue.

If you’re having a dispute with your solar installer, one step you can take is to have a trusted roofer do an inspection and provide an independent report.

Make sure your roof is in good condition before going solar

The best way to prevent a solar installation from causing a roof leak is to make sure that your roof is in good condition before you undertake the project. Ideally you want your roof to have 25 years of life left before you install solar panels. If it has 15 years or less of life remaining, installing solar may not be a good investment.

While the solar installer will do their own assessment, it’s a really good idea is to hire an independent roofer to provide their own report before you decide to go solar. While many roofers provide free inspections, the National Roof Certification and Inspection Association recommends that an inspection should be something you pay for. This will help reduce the chance that a roofer is recommending repairs only because they want a job.

Doing a roof self-inspection (which is a good idea to do periodically anyway) is also a simple way to catch obvious problems.


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