Clear scope. Clean execution.
Commercial skylights are one of the most maintenance-intensive roof components in San Antonio's climate. The UV index in San Antonio regularly reaches 11 or higher during summer months - in the extreme category that accelerates degradation of polycarbonate and acrylic glazing panels. A skylight unit that carries a 10-year manufacturer warranty based on testing in a temperate climate may begin to yellow, craze, and crack in 6 to 8 years under San Antonio's UV load. When glazing degrades past the point of structural integrity, it is a water intrusion path and a safety hazard.
Curb flashings are the other primary skylight failure point. The curb is the raised frame that supports the skylight unit above the membrane surface - a critical relationship, because the membrane must run up the curb wall and under the skylight frame to prevent water from entering at the curb base. When the curb flashing separates from the wall, lifts at the termination bar, or develops a break at the corner, water enters the building at the curb perimeter regardless of the condition of the glazing.
We rebuild curb flashings and replace glazing panels on commercial skylights across San Antonio. We have executed skylight repair on the atrium skylights at retail centers along the Loop 410 corridor, on the barrel vault skylights in the Pearl District's historic brewery buildings, and on the flat-panel commercial skylights on the medical office buildings near University Hospital on Floyd Curl Drive. Each repair scope is documented with before and after photography keyed to the roof zone diagram.
Curb Flashing Rebuild - The Correct Scope
What fails: The curb flashing sequence on a properly installed commercial skylight has the membrane field running up to the curb base, a compatible membrane strip running up the curb wall to within 2 inches of the top, and a termination bar and sealant at the top of the membrane on the curb wall. At outside corners of the curb, the membrane must be cut and coped correctly - bridged membrane at a corner cracks under thermal cycling. At inside corners, a strainer piece fills the void. When any part of this sequence fails - termination bar pull-out, corner crack, adhesion loss - water enters at that location.
Rebuild process: We strip the curb flashing back to the membrane field. We inspect the curb frame for rot, corrosion, or displacement - a curb that has moved relative to the deck produces a gap at the bottom that no flashing detail can close permanently without addressing the structural condition first. We install new curb flashing per the membrane manufacturer's published detail - corner strainers, full wall adhesion, termination bar at the top edge. We probe-test all seams and photograph each step against the manufacturer's detail sheet.
Curb height: International Building Code requires skylight curbs to be a minimum of four inches above the finished roof surface. On San Antonio commercial roofs that have been re-roofed multiple times, the membrane surface may have risen to the point where the original curb height is no longer code-compliant. When we find this condition, we document it and provide options - curb extension to restore code height, or membrane-surface management to restore the four-inch clearance.
Glazing Replacement - Panel Options
Polycarbonate single and double-wall: The most common commercial skylight glazing in San Antonio. Polycarbonate has good impact resistance and reasonable UV performance when coated. Under San Antonio's UV exposure, uncoated polycarbonate yellows and crazes within 5 to 8 years. Replacement panels should carry a UV-protective co-extrusion or coating - not a field-applied UV coating, which degrades rapidly. We specify glazing with manufacturer-certified UV protection rated for a minimum 10-year service life under UV index conditions of 10 or higher.
Acrylic (Plexiglas): Clearer than polycarbonate but more brittle and more vulnerable to hail impact. We see cracked and shattered acrylic panels on buildings across Bexar County after the significant hail events - the 2023 Stone Oak / Boerne hail corridor produced widespread acrylic panel failures on commercial skylights. Replacement with polycarbonate is often the better long-term choice on buildings in San Antonio's hail corridor.
Tempered glass: Used on higher-end commercial and institutional buildings. Longest service life and best UV stability. Heavy - requires verification that the curb frame and deck can support the additional load before specifying glass over an existing polycarbonate unit. We do not substitute glass for polycarbonate without structural confirmation.
Silicone glazing tape and frame seal: The glazing tape that seals the panel to the frame is a separate failure point from the panel itself. Failed glazing tape allows water to enter the frame before reaching the curb flashing, and this water is not visible as a roof leak - it drips into the skylight well. We replace glazing tape at every panel replacement and inspect it independently at annual inspection.
San Antonio UV Context
San Antonio's latitude (29.4°N) places it in the high-UV band for North America. The city averages approximately 300 sunny days per year, and the UV index reaches Category 10 (Very High) from April through September and Category 11 or higher (Extreme) on peak summer days. This UV load is 30 to 40 percent more intense than Chicago, 20 percent more intense than Atlanta, and comparable to Phoenix - but without Phoenix's low humidity that reduces atmospheric UV absorption.
What this means for skylight service life: Manufacturer warranties on polycarbonate panels are typically written against ASTM G154 accelerated UV testing conducted at standard laboratory conditions - conditions that are roughly equivalent to South Florida UV exposure. San Antonio's UV load is higher than that standard. We advise owners to expect 60 to 70 percent of the manufacturer's stated service life in San Antonio conditions and to schedule annual inspections of glazing clarity, structural integrity, and frame seal condition.
Relationship to hail damage documentation: When a hail event cracks or crazes skylight glazing, that damage is a covered insurance event. We photograph each damaged panel with hail impact locations marked, document the pre-existing UV degradation condition separately (existing crazing versus fresh impact fractures), and structure the documentation so the carrier can see clearly what was storm-caused versus age-related. This distinction matters for the claim amount.
Frequently asked questions
The skylights in our building are yellowed but not leaking. Do we need to replace them?
Yellowing and crazing of polycarbonate glazing indicates UV degradation that reduces the panel's structural integrity even before it develops a visible crack. A panel that is heavily crazed can fail suddenly under mechanical load - foot traffic, hail impact, or wind pressure - rather than developing a gradual leak. We assess glazing condition during inspection and rate it on a scale that distinguishes cosmetic yellowing (light tint, no structural concern), moderate degradation (surface crazing, recommend replacement within 12 months), and advanced degradation (structural compromise, replace before next significant weather event).
Can you match the glazing panel to what is currently on the building?
We can match panel thickness, glazing type (polycarbonate, acrylic, glass), and profile (flat, corrugated, standing seam) to the existing units. Exact color match depends on the original manufacturer and the degree of UV fading on the existing panels - panels installed at the same time often fade at different rates depending on their exposure position, so a single new panel in a run of faded panels will be visibly different. We advise on panel-matching options during the scope meeting.
The skylight curb is leaking but the glazing looks fine. Can you repair just the curb?
Yes. Curb flashing rebuild is independent of glazing replacement - we can strip and rebuild the curb flashing without replacing the glazing unit. We do inspect the glazing condition as part of the curb repair scope so you have a complete picture of the skylight assembly. If the glazing is in good condition, curb-only repair is the right scope.
Skylight leaking or glazing degraded on your San Antonio commercial building?
We rebuild curb flashings and replace UV-degraded glazing - with documentation of each repair step and a written assessment of the remaining glazing service life.
Request a Roof Scope