In the first part of this two-part article, I explored the various types of roof membranes and roofing systems commonly found in commercial and industrial (C&I) buildings. Identifying the type of roof is a critical first step when planning for a roof-mounted solar installation. This information directly influences design choices, engineering decisions, and overall system performance. While these follow-up considerations may not be the main focus, they are essential to ensuring the safety, durability, and efficiency of the solar project.
After all, structural integrity, waterproofing, and balance of system (BOS) factors must be carefully addressed to prevent issues like roof collapse, leaks, or even system failure due to environmental stressors.
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### **Structural Considerations**
When it comes to C&I roof-mounted solar projects, the structural assessment is often the most crucial phase. It sets the foundation for everything that follows. Here’s a breakdown of key areas that need attention:
**Reserve Capacity Evaluation**
Most existing C&I buildings are designed to meet minimum code requirements. Adding a solar array can significantly increase the load on the structure. A qualified structural engineer should review the building’s original design and current condition to determine if it has enough reserve capacity to support the new system. This includes evaluating both gravity and lateral loads, as well as any modifications made over time—like added rooftop equipment or extra layers of roofing.
In some cases, the structure may need reinforcement to safely accommodate the solar installation. The engineer's experience and judgment play a vital role in identifying the most cost-effective and structurally sound solutions.
**Mechanical Attachments**
While ballasted systems are common for low-slope roofs, some installations require mechanical fastening. These attachments must be carefully planned to avoid unnecessary weight and ensure stability. For example, in certain cases, removing insulation and replacing it with wood blocking helps reduce torsional deflection. Different attachment methods—like U-bolts, OMG Power Grips, or S-5! clamps—are used depending on the roof type and construction.
When using S-5! clamps on standing seam metal roofs, it's important to verify the existing attachment points between the roof panels and the structure. These details are often hidden and require close inspection.
**Roof Loading Plan**
Once installed, the solar system distributes its weight relatively evenly across the roof. However, during installation, materials like PV modules, inverters, and ballast are temporarily concentrated in specific areas. A proper loading plan ensures that these heavy items are staged over strong structural elements—such as beams or columns—to prevent damage or overloading.
This plan also outlines safe weight limits for each staging area, helping to avoid potential structural risks during the installation process.
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### **Waterproofing Considerations**
Beyond structural concerns, waterproofing is another critical aspect of roof-mounted solar projects. Any penetration into the roof creates a potential pathway for water infiltration. Therefore, careful planning and coordination with roofing professionals are essential.
**Roof Flashing and Drainage**
Proper flashing is key to preventing water from entering through penetrations, joints, or transitions between horizontal and vertical surfaces. Working with an experienced roofer ensures that the flashing is compatible with the existing roof system and that the installation meets manufacturer specifications.
Low-slope roofs are not truly flat—they have shallow slopes to allow proper drainage. Features like crickets, drains, and scuppers help manage water flow. Solar installations must not interfere with these systems, as blockages can lead to water ponding, increased load, and premature roof degradation.
**Preventing Roof Damage**
Single-ply membranes are particularly vulnerable to damage during and after installation. Foot traffic, dropped tools, and long-term environmental stress can all cause harm. To mitigate this, installers can use temporary walkways or protective padding during the build phase.
For long-term protection, slip sheets or separator pads are often installed between the mounting system and the roof membrane. These sacrificial layers help prevent abrasion and prolong the life of the roof. In some cases, permanent walkways may be necessary to manage ongoing maintenance and access needs.
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If you're looking to minimize risks and maximize the performance of your C&I roof-mounted solar system, consider working with experts who specialize in value-engineered designs and detailed construction drawings. At Pure Power Engineering, we provide tailored solutions to ensure your project is safe, efficient, and compliant. Contact us today to learn more.
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