Solar Panel Mounting On A Flat Roof

Learn the basics of solar panel mounting on a flat roof

Back in late 2022 we wrote a article on our website about The problems inherent in installing solar panels bolted directly through a flat or low slope roof parapet. This so common that we encounter problems associated with this type of installation all over Washington DC.   The referenced article can be seen at the following link:

 Read MoreWhy bolting solar panels through parapets is bad

bolting solar panels through parapets

Problems With Solar Panels On Roofs

We were on other roofs in January and February of 2022 with similar problems. This issue is so prolific and simultaneously so destructive that it would be good if homeowners or building owners become aware of the issue and start talking directly to their solar installers about using alternative means such as ballasting or mounting through an approved method.  The common method of cutting (or drilling) directly through the horizontal portion of their roof and installing a bolt is not acceptable and clearly causes leakage.  We have fixed been called upon to address the many times.

In the picture below you can see an example where solar panels were installed on a higher roof common on top of a parapet, where that building adjoins a neighboring property.

solar panels installed on higher roof

Should You Install Solar Panels On Flat Parapets?

The lower roof is attached and likely of newer construction, in many cases in DC though the property line will split the roof roof parapet.  Therefore, roof parapets are often considered shared elements, especially in rowhome or row building construction, as is so common especially in the historic neighborhoods of Washington DC. 

The picture below shows a closer view of the steel bolts that are mounting the purlin or PV rack system to the roof parapet. At each mounting location, there is a metal plate that attaches to the PV track system. That metal plate is then bolted down with 2 different wedge anchors, at each plate. The plate is flat and the parapet is relatively flat, but there is not consistent connection or attachment between the plate and the substrate masonry of the parapet because the masonry is relatively inconsistent, built with individualized brick units.

solar panel mounting with bolts

As the plate is pushed down, secured to the substrate of the parapet, at each of the solar panel mounting locations, the aluminum sheet metal coping is pushed further down.  This alone doesn’t significantly damage the parapet, but as each bolt requires a hole through the coping, the coping is now made perforated by all of the new holes.

At each of these mounting locations, gun-applied caulking has been squirted into around the area of penetration, but this is largely insufficient. The building code has specific requirements and almost every manufacturer of sheet metal coping requires that equipment is not set through the parapet coping. Manufacturers do not write the code, but the building code is written so that manufacturer installation requirements must be followed by the contractor or installer.

Maintaining Your Roof And Solar Panels

Smart proactive replacement, construction, upkeep and maintenance of low slope roof systems requires an enthusiastic interest and understanding of waterproofing principles and building science.   Here in Washington DC, historic and modern residential and commercial buildings are extremely expensive and the roof and related systems provide the shield that preserves the building. 

We encourage all of our clients, and all readers of this article and to our blog in general, to prioritize the value of quality construction and building maintenance, and develop a relationship with our company.  You can learn a lot more on our blog.  Feel free to check it out.  If you have questions about the roof and related systems of your building in Washington DC, contact us or fill out the webform below and drop us a line.  We will be in touch if we can help.

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