A commercial solar array is designed to produce for decades. Most commercial roof membranes are not. That mismatch is the single most expensive mistake we see facility owners make, and it is almost entirely avoidable with an honest assessment before anyone signs. The failure mode is simple. You install a large array on a roof with limited remaining service life. Several years later the membrane needs replacement. Now you are paying to remove the array, store it, re-roof, and reinstall — a cost nobody budgeted, on a schedule nobody planned, during which the system produces nothing. Here is what a serious pre-installation roof assessment covers. ## Remaining service life The first question is not "is the roof leaking." It is "how many years does this roof have left, and how does that compare to the life of the system we are about to attach to it." That means knowing the roof's age, its membrane type, its installation quality, and its maintenance history. A well-maintained TPO or PVC roof with most of its life ahead is a good candidate. A patched built-up roof nearing the end of its service life is not, regardless of whether it is currently dry. If the remaining life is meaningfully shorter than the system life, you have three honest options: re-roof first, plan and budget for a removal-and-reinstall later, or look at a ground mount or carport instead. All three are legitimate. Pretending the question does not exist is not. ## Structural capacity Solar adds dead load, and in some configurations it adds wind uplift considerations that change how the roof assembly performs. A structural review determines whether your building can carry the array as designed. Older buildings, buildings that have been re-roofed multiple times with layers left in place, and buildings with long-span steel deck all deserve particular attention. So do buildings where the array design concentrates weight — ballasted racking distributes load differently than an attached system. This review should happen during design, by someone qualified to sign off on it. Not after the racking is on site. ## Warranty coordination This one gets missed constantly. Your roof likely carries a manufacturer warranty, a workmanship warranty from the installer, or both. Penetrating that roof — or in some cases even loading it — can void those warranties if the work is not performed in a way the roofing manufacturer accepts. Before installation, someone needs to read the actual warranty documents and determine what is required to keep them intact. Often that means using a manufacturer-approved detail for penetrations, or having the original roofer perform the flashing work, or notifying the manufacturer in advance. If a solar contractor has never asked to see your roof warranty, they are not managing this risk. You are, whether you know it or not. ## Attachment method and detailing Ballasted systems sit on the roof without penetrations, held by weight. Attached systems penetrate the membrane and anchor to structure. Each has trade-offs. Ballasted avoids penetrations, which roofing manufacturers generally prefer, but it adds significant weight and is not appropriate on every structure or in every wind zone. Attached systems weigh less but every penetration is a potential leak path, which makes flashing quality the whole ballgame. There is no universally right answer. There is a right answer for your specific roof, and it should be determined by the structural and roofing conditions rather than by what the contractor prefers to install. ## Drainage and access Two practical items that surface later if ignored. **Drainage.** Racking that blocks water flow toward drains creates ponding. Ponding degrades membranes and adds load. Array layout should respect the roof's drainage design. **Access.** Someone has to service this system, and someone has to service the roof. Layouts that leave no walkable path to drains, HVAC units, or roof hatches make both jobs worse for the next twenty years. ## What to ask a contractor **Have you physically been on our roof?** A proposal built from aerial imagery has not assessed roof condition. It may still be a fine starting point, but it is not a basis for a final design. **What is your read on our remaining roof life, and how did you determine it?** You want a specific answer grounded in an inspection, not a reassurance. **How will you protect our roof warranty?** The answer should reference your actual warranty documents. **Who is responsible if there is a leak at a penetration in year three?** Get this in writing. When roofing and solar are handled by separate companies, this is where the finger-pointing happens. ## The straightforward version If your roof has plenty of life left, solar is a good fit and the assessment is quick. If your roof is near end of life, the honest recommendation is often to re-roof first and install after — which costs more upfront and delays the project, and which we will tell you anyway, because the alternative costs more over the life of the system. We assess the roof before we design the array, and we would rather lose a project on that conversation than win one that creates a problem for you in year six. If you have a facility in Southern California and are not sure where your roof stands, that assessment is a reasonable place to start regardless of who ultimately does the work.