Solar Power World
By Archit Patnaik, PE, PMP, NABCEP PVIP, Pure Power Engineering | August 12, 2026
In commercial and industrial solar PV work, the mounting surface is rarely the engineer’s choice. Factors of geometry, land availability, shading and budget affect that determination, and the design team inherits the result. But the harder task is what comes next: recognizing how the mounting platform reorders the design before a single module is placed.
Imagine designing across a portfolio of rooftop, traditional ground-mount and carport systems placed next to one another. That challenge applies just as much to any one of those foundations taken on its own.
The platform decides the problem, not just the mounting hardware. Roof, ground and carport each answer to a different controlling discipline, different fire and electrical codes and each engages a different engineer before the PV design even begins. The equipment on top can look identical from one platform to the next; the engineering underneath does not.
A rooftop PV system on an existing building. Roof access and fire pathways, not the available roof area, often determine a system’s size. Credit: Johnson Controls.
On a rooftop, the array attaches to a structure that already exists and that people occupy. Modules, framing and ballasts are dead load added to a building very likely never designed to host a rooftop generator, and they have to be checked against the roof’s residual capacity under the full load combinations of the American Society of Civil Engineers standard (ASCE 7-22), not against a racking catalog’s limits. The attachment method is its own tradeoff: mechanical attachment adds roof penetrations, uplift anchorage and waterproofing detailing, while ballast avoids penetrations but adds dead load and seismic demand the roof may not have to spare. Where capacity is marginal, the structural finding, not the solar resource, sets the ceiling on system size.
The roof is also a surface people work on and fight fires on, and both require space. Under the 2024 International Fire Code (IFC), fire-access rules remove usable roof before a single module is placed. There must be a clear perimeter pathway, 6 ft at the edge and reducible to 4 ft under defined conditions, plus interior access and smoke-ventilation gaps between array sections (§1205.3).
That is why two roofs of identical area can yield very different system sizes, and why the roof carries the heaviest fire-layout burden of the three platforms. Work at 6 ft or more also triggers fall protection under OSHA standards CFR 1926.501 and 1926.502, so guardrails, anchor points and walking routes belong in the design, not the field.
The electrical scope is constrained. Because the array sits on the building, it carries rapid-shutdown provisions that quickly de-energize the PV conductors for firefighter safety (2023 National Electrical Code, NEC §690.12). Across buildings of different ages and construction types, no two roofs present the same combination of these constraints, so the rooftop standard has to be a repeatable method, not a fixed layout.
Unlike rooftop solar, engineering a ground-mounted array is a geotechnical process, not a racking selection. Credit: Johnson Controls.
Off the roof, the discipline shifts from structural to civil and geotechnical. The array no longer borrows capacity from an existing structure; it builds its own, and the choice of foundation is a conclusion drawn from the soil, not a selection from a racking catalog. Driven piles, ground screws, helical piles and ballasted footings each answer to different soil strength, frost depth, groundwater, corrosiveness and uplift conditions, which is why the geotechnical investigation under the International Building Code (2024 IBC, Chapter 18) precedes the electrical layout rather than following it.
The site itself becomes an engineering problem in a way a roof never is. Grading, access roads, trenching, and equipment pads redirect drainage across the array, so civil design leads and PV layout follows. Fire constraints move too. With no roof surface for firefighters to work, the code turns to the perimeter, requiring a brush-free zone around the array (2024 IFC §1205.5.1) that consumes land and, converts fire safety into vegetation management obligation rather than a one-time plan review item.
A carport is often the most interdisciplinary of the three because it is not an elevated ground-mount; it is a new occupied structure placed in a working parking lot, sitting over vehicles and people. That puts two engineers in the critical seat at once: a carport structural engineer sizing the canopy for dead load, wind uplift and seismic demand under ASCE 7-22, and a civil or architectural engineer protecting everything the canopy lands on. The parking lot uses the same geotechnical conditions as any ground structure, but the harder constraints sit at grade.
Accessibility usually governs the layout. Under the 2010 Americans with Disabilities Act Standards for Accessible Design, accessible stalls and access aisles — their widths, slopes and clearances — must survive the introduction of canopy columns and beams. Required vehicle and van clearances are easy to violate when a canopy beam, a hung conduit or a gutter is not coordinated with the parking geometry from the first sketch.
A solar carport over a public parking lot. The canopy is a new structure inserted into a working lot, not an elevated ground mount. Credit: Johnson Controls.
Columns cannot land in accessible aisles, fire lanes, drainage paths or over buried utilities. Vehicle-impact protection is engineered into the design, typically seen as a raised concrete pier at each column base, with bollards added where inverters or disconnects are mounted on the column.
Either way, it is structural protection for the load path that carries the array. Fire coordination shifts with all of this, away from roof pathways and toward fire-apparatus circulation and site access across the lot.
Each platform brings its own set of problems. A roof array is first a structural problem; a ground array is a geotechnical and civil one; a carport is a structural, civil and accessibility problem at once.
These engineering disciplines change, the governing codes change and the engineer who must be satisfied first changes with them. What does not change is the obligation underneath: on every platform the array has to be structurally sound, code-compliant and safe for the people around it.
The practical lesson is not that any one of these is hard, the industry designs all three well, but that the mounting surface silently decides which problems you must solve to meet that obligation before the PV design begins. Knowing each platform’s governing requirements at the outset is what lets an engineer design it efficiently, engaging the right disciplines first and letting the real constraints drive the layout from the start.
That understanding, more than the array itself, is what separates the platforms.
Archit Patnaik, PE, PMP, NABCEP PVIP, is a senior project manager at Pure Power Engineering, where he leads electrical engineering for commercial and industrial (C&I) solar PV systems, including rooftop, ground-mount and carport installations. His work spans design oversight and project execution for developers, EPCs and asset owners.
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