Installing Solar On Metal Shingle Roofs

Over the past few years, our tech support staff has fielded a growing number of questions about metal shingle roofs. Metal shingle installations are more challenging than asphalt shingle roofs or even tile roof projects and require partnering with a qualified roofer. As a result, fewer solar installers bid these projects. However they can be more profitable than other projects as they are less subject to intense competitive pressures. Metal shingles are noticeably more expensive than asphalt shingle and tile roofs. Homes with metal shingle roofs are often in affluent areas with owners that are more likely to invest in solar. These homeowners tend to be less concerned about the modest savings common in grid tie competition and are usually more concerned with an attractive installation that preserves the aesthetic appeal of their pricey metal shingle roof.

To help make sense of this more challenging installation, we contacted the largest metal shingle manufacturers, and developed several methods for installing on metal shingle roofs. While there is a wide array of metal shingles, they typically fall into three basic mounting configurations:

Figure 1: Decra interlocking metal shingles with Quick Mount PV QBase mount installed over Decra underpan

Figure 1: Decra interlocking metal shingles with Quick Mount’s QBase Comp Mount installed over Decra underpan

Interlocking
Interlocking metal shingles most often resemble asphalt shingles or slate. They are directly nailed or screwed to the deck and have interlocking lips on the upper and lower edges, or sometimes on all four sides. These interlocking lips lock together for a lightweight, highly wind resistant roof. This style of metal shingles often requires complete removal of the roof from the ridge to the bottom of the array.

Figure 2: Batten mounted metal shingle

Figure 2: Batten mounted metal shingle


Batten Mount
Batten Mount metal shingles often resemble shake or tile. They typically mount to horizontal wood battens attached directly to the deck with screws inserted into the leading edge of the shingle. Batten mount metal shingles are relatively easy to install solar onto, because the individual shingles can be removed by taking off the screws at the top and bottom of the shingle and installing the mount. 
Figure 3: Counter batten roof

Figure 3: Counter batten roof

Counter Batten Mount
Counter Batten Mount metal shingles are installed onto a grid work of horizontal wood battens secured to vertical wood battens attached to the roof deck. This arrangement is best in a wet climate as it allows for rapid drainage of water that might leak past the metal shingles. An important caution is in order: before quoting any metal shingle project, always check for old shingle or shake roofs under the array. If you find an old shingle or shake roof under the metal shingles, the best strategy is the “strip and go” procedure outlined below. It is very challenging to effectively seal mounts on roofs of this configuration.

There are four methods for installing Quick Mount PV mounts on metal shingle roofs.

Figure 4: The light blue underpan extends under the mount and channels any rainwater harmlessly off the roof just below the mount. Note how the upper edge of the underpan is sealed to the underlayment.

Figure 4: The light blue underpan extends under the mount and channels any rainwater harmlessly off the roof just below the mount. Note how the upper edge of the underpan is sealed to the underlayment.


1) Underpan: Quick Mount PV has worked closely with Decra (the largest manufacturer of metal shingles) to develop a procedure for installing solar arrays on Decra metal shingles (aka stone coated metal panels). Decra is unique in offering a clever drainage pan configuration referred to as underpans. These underpans are positioned under the mount location with a flashing installed over the mount and the shingle installed over the flashing. Any water that hits the mount flows harmlessly down the underpan to the shingles lower down the roof. Since Decra stone coated metal panels are galvanized steel, any contact between the aluminum mount and the metal shingle is protected with a barrier material like a fully adhered underlayment.

Figure 5: The flashing shingle sandwich installation method requires a flashing installed between 2 metal shingles. Note that the lower metal shingle does not need to match color of the upper visible metal shingle.

Figure 5: The flashing shingle sandwich installation method requires a flashing installed between 2 metal shingles. Note that the lower metal shingle does not need to match color of the upper visible metal shingle.


2) Flashing sandwich: For batten mounted metal shingles that do not use underpans (like Gerard), you may be able to use the flashing sandwiching method. This requires purchasing enough of the exact same shingle as is currently on the roof. Color is not important, as these new shingles will be installed under the original shingle with a flashing sandwiched in between. The mount is bolted to the roof deck. Next, cut a 4” diameter hole into the new shingle and install over the QBase Comp Mount. Trim the top edge of the flashing as needed to fully cover the shingle. Finish by installing the original shingle over the top of the flashing. Cut small 1″ wide drainage slots in the butt edge of the top shingle to allow any water that gets onto flashing to easily drain. If the shingles are galvanized steel, use a self adhered underlayment on the top and bottom of the flashing to protect against galvanic corrosion caused by aluminum to galvanized steel contact. Finish by applying sealant around flashing cone to minimize water getting past flashing cone and sprinkle color matching granules into wet sealant to produce an attractive color matched mount. In this configuration, the bottom shingle serves the same function as the underpan in the method above.

 
3) Adhered flashed mount: Metal shingles that are fully interlocked on all four sides require a different approach. There are two possible approaches for “Aluminum Lock Roofing” shingles. The first method involves trimming the top edge of the Classic Comp Mount or E-Mount so the bottom edge of the flashing is just above the butt edge when the top edge is wedged all the way up in the interlock area above the penetration. The flashing is then coated with a sufficient amount of sealant, and the lag bolt is carefully torqued to the proper setting (when the QBlock stops pivoting). When installed properly, the gasket seal is tightly compressed between the flashing above and shingle below providing a reliable long term seal. The second option for interlocking shingles requires cutting a slit in the interlock just above the penetration and slipping the upper edge of the flashing under the second course of shingles until the block is positioned in the proper location. Sealant is applied to the cut area and under the flashing.

Figure 6: This metal shingle roof is installed over an old asphalt shingle roof. The best solar mounting option for this configuration is "strip and go".

Figure 6: This metal shingle roof is installed over an old asphalt shingle roof. The best solar mounting option for this configuration is “strip and go”.


4) Strip and go: If there is an old shingle or shake roof under the metal shingles, the easiest approach would be what is commonly referred to as, “strip and go”. First, a qualified metal shingle roofer would “strip” off the metal shingles from under the field of the array. Then the roofer would “go” by installing a new asphalt shingle roof under the field of the array. This installation method is a compelling option since the customer gets a new roof that lasts the life of the array, and the roofer can warranty the roof and flashed mounts. The long term cost benefits of a new roof under the array are dramatic- saving thousands in repair costs during the life of the solar system. When done properly, “strip and go” has the attractive appearance of Building Integrated PV Systems (BIPV), particularly when installed on batten mounted metal shingles shaped like curved tile or shake. There are six basic steps in the “strip and go” process.

  • Step 1: Roofer removes existing metal shingles under and around field of array.
  • Step 2: Solar installer secures QBase Comp Mounts over new underlayment into rafters using lag screws.
  • Step 3: Roofer installs shingles AND flashings over mounts.
  • Step 4: Solar installer assembles array.
  • Step 5: Roofer installs flashing around perimeter of shingles.
  • Step 6: Roofer installs metal shingles around perimeter of array.

While metal shingles require a bit more research, learning how to install on this high-end roofing system can boost your bottom line and bring solar to homeowners that often struggle to find a willing and able solar installer.

To learn more, register for our next metal shingle webinar on February 12. Or visit our website to download the presentation slides or view a previously recorded webinar.

Comments

  1. says

    I’ve always been interested in reducing my environmental footprint. Installing solar panels on my roof seems like something that I would be very interested in! How much electricity do the solar panels generate? I would love to not have a power bill!

    Alex Jennings |

    • Jeff Spies says

      There are many variables, but my 4.68 kW system in the Phoenix area produces 7500-8500 kWh per year. My electricity is valued at 10-11 cents/kWh, so my system is producing around $800/year in electricity.

  2. says

    This article has been very informative and helpful for someone who is going to redo their roof. I have wanted to have solar panels for quite some time, and they are finally more affordable for the average family. The only tricky part is preparing your roof and electrical system to accommodate the panels. I’m hoping to use this opportunity to replace our very old roof with a good new one.

  3. Wood says

    Interesting Discussion:
    but will Installing Solar directly on my roof INVALIDATE my 50 Yr Warranty with DECRA regarding my roof install. My roof cost 19K to Install Not interested in messing that up , that is almost 3 times the cost of an architectural roof in my area..
    Wood in Virginia

    • says

      Decra has approved our roof mounts when used in the prescribed manner with their underpan. This means the Decra warranty is valid if installation is done per the mfgr installation instructions.

      • Joseph Schafer says

        If the Decra roof is already installed, I’d assume that there are no underpans, right? So, is it practical and cost effective to remove portions of an installed Decra roof, install an underpan, install the flashings and mounts, and then re-install the Decra tiles that were removed?

  4. says

    My family and I live in a fairly stormy area, and we have recently decided to do a pretty big remodeling project. We are a little concerned with what kind of roofing we should do on a garage that will be separate from the house. I have been considering installing solar panels on it, and this article was very helpful to me! I will definitely be looking into this, thank you!

  5. says

    I always wanted to have a affordable solar panel for my house and since my house is having a Metal Shingle Roof I was worried about the exact match. But finally I have found a good option here. Thanks a lot for sharing this info in this article it will be very useful to me :)

  6. says

    Would this be easier to do with a metal roof or shingled roof already constructed? I’d assume no since you’d have to rip up the current roofing to make room for the solar panels. I’m thinking about doing this in the spring, do you have any advice?

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