Self-flashing Skylights on Commercial Warehouses Are Beginning to Leak

Today, many commercial roofers are dealing with a large-scale problem—reinstalling and replacing leaky self-flashing skylights on commercial warehouses. I have seen firsthand how improper installation of self-flashing skylights has become a headache for commercial property owners.

many of the skylights installed on commercial warehouse properties in the western Sunbelt states were installed improperly because they were installed first and foremost as fall protection for the open floor in the roof during construction by the builder and not by the roofer.

Many of the self-flashing skylights installed on commercial warehouse properties in the western Sunbelt states were installed improperly because they were installed first and foremost as fall protection for the open floor in the roof during construction by the builder and not by the roofer.

Around the late 1970s and early 1980s, intermodal freight became a huge part of global distribution. To handle the increase in freight projects, warehouse construction exploded. The Port of Oakland, for instance, invested heavily in intermodal container transfer capabilities in the ’80s. In fact, the aggressive growth of intermodal freight distribution continued into the early 2000s.

The cheapest and easiest way for skylights to be installed on these warehouses was to use self-flashing skylights. The metal curb or L bracket attached to the bottom of the skylight was, in theory, supposed to be set on top of the built-up roofing material and then stripped in, sandwiching the flange between he roofing layers. The result would be roofing material, then skylight, then more roofing material over the flashing on the skylight.

Unfortunately, many of the skylights installed on commercial warehouse properties in the western Sunbelt states were installed improperly because they were installed first and foremost as fall protection for the open floor in the roof during construction by the builder and not by the roofer. Our teams have seen thousands of these original self-flashing skylight installations where self-flashing flanges are set directly on the plywood roof deck, below all the roofing materials.

Most of the original roofers didn’t budget in the time and money it took to pull the skylight assembly apart from the roof deck and re-install it the proper way. Nor did they wash the oils off the new metal from the galvanizing process or use asphalt primer to prep the steel flanges of the assembly and ensure the roofing asphalt would stick properly. Over the years, as the metal of the skylight flanges expanded and contracted and the built-up roof did the same, but at a different rate, the roofing system eventually separated from the skylight, leaving a self-flashing skylight that’s now turned into what we jokingly refer to as a “self-leaking skylight”. This is part of the reason why everyone thinks skylights always leak.

The best way we’ve found to install leak-free skylights on a commercial warehouse roof, especially when re- placing the self-flashing skylights on an existing building, is to use a curb-mounted skylight. A curb-mounted skylight fits like a shoebox lid over a new curb the roofing contractor fabricates as part of the installation. This curbed design eliminates the metal flange and offers waterproofing redundancy in critical areas of the installation, so water can’t get into the building at the skylight opening. Because the new skylight is installed on a curb, it’s also much easier to address any future issues with the skylight or to replace it down the road if necessary. This especially comes in handy when owners lease to new tenants. New building occupancy regulations mean skylights may be required by municipalities to be changed out for smoke vents to comply with fire codes.

If you’re dealing with one or more self-flashing skylight leaks, there are a few things to keep in mind:

  • Check if there is condensation on the inside of the skylight; a lot of skylights have a trough where condensation runoff will leak into the building.
  • Be sure to check the juncture where the skylight and the roof meet (the skylight base flashing), which can sometimes include up to 5 inches of mastic at the base flashing.
  • If the skylight has a frameless acrylic cap without a metal frame around the outside, check the acrylic dome for stress cracks. It is possible to replace some acrylic domes on some skylights but often the cost of an acrylic dome is roughly the same as the cost of a new skylight, and if you’re already considering installing a new roof with a 15- to 20-year warranty, it doesn’t make much sense to leave the “self-leaking skylight” frame in place. Replacing the skylights during the reroofing project is much more cost-effective than re- turning to replace skylights later. In addition, skylight technology is far better now than it was 15 or 20 years ago (think about today’s impact-resistant polycarbonate and better UV and fall protection).

Above all else, don’t let self-flashing skylights give you and your roofing business a bad name. Instead, address the issue with your commercial clients and educate them about the best choices for their skylights and how they can stay current with the International Building Code and municipal codes. You’ll be helping them protect one of their biggest assets by ensuring their skylights stay leak-free.

PHOTOS: Highland Commercial Roofing

Six Risks You Should Know Before Putting Skylights on Your Roof

Skylights are popular for a reason. They add an extra dash of beauty to any commercial building, and they’re a great source of free lighting. But there are also drawbacks, and, if you’re not aware of them, the costs can end up being far greater than the benefits. Whether you already have a skylight or are considering adding one to the design of a new roof, make sure you’re prepared to deal with the downsides:

  • 1. Leaks
    Skylights are famous—or maybe that should be infamous—for leaking. Over time, the seals and flashing can deteriorate, providing an opportunity for water to penetrate your roof. Things like rain, snow and debris can accelerate the process. Modern skylights are less prone to leaks than older versions, but even the best skylight can leak if it isn’t installed properly.

    There’s an additional leak risk, too: ice dams. Skylights transfer heat to the surrounding roofing material, causing any accumulated snow to melt. That, in turn, can contribute to ice dams, eventually causing even more leaks and adding to the cost of roof maintenance.

  • 2. Breakage
    Even standard roofs are vulnerable to the elements, particularly wind and storm damage, but skylights are even more so. Hail and flying debris, for in-stance, can easily crack a skylight. And, when it comes to snow loads, skylights can be the weakest part of the roof. If you calculate the maximum weight load based on the rest of the roof, your sky-light could fail from the excess weight of a heavy snowfall.

  • 3. Falls
    For workers performing roof maintenance, skylights pose a risk for serious injury, or even death. Some workers simply assume skylights are designed to bear their weight and will intentionally stand or sit on them. Tripping and falling onto a skylight presents yet another risk. That’s why the Washington, D.C.-based Occupational Safety and Health Administration puts skylights in the same category as other open holes and requires that each one is protected by a screen or guard rail that meets OSHA’s regulations.

    However, guard rails aren’t 100 percent safe either. Depending on the quality of the safety net or the weight of the victim, roof-maintenance professionals can fall through just as easily as they would through a skylight.

  • 4. Light Exposure
    While access to free natural light is one of the primary benefits of skylights, there’s also a drawback. Depending on the placement, skylights can actually let in too much light, contributing to glare and excess UV exposure. Not only can that be hard on employees, it can cause preventable damage to furniture, carpeting, art and more valuable items.

  • 5. Energy Loss
    In stark contrast to the lure of free lighting, skylights can have a significant negative impact on heating and cooling costs. Skylights simply don’t present the same barrier to heat transfer that more traditional roofing materials do. In the winter, heat escapes. In the summer, heat seeps into the building—and sun-light and glare only add to that effect. According to the National Fenestration Rating Council Inc., Greenbelt, Md., skylights can cause a building’s interior temperature to fluctuate by more than half the difference between the exterior temperature.

  • 6. Space Constraints
    Skylights take up rooftop space that could be used for equipment or other purposes. To get the maximum benefit of free natural lighting, you need to dedicate 7 to 10 percent of your roof to skylights. That’s space that can’t be used for things like rooftop equipment and supports. It also claims space that might be needed for workers to perform roof maintenance. And if you have a small roof, that is going to be a problem!

There’s no doubt that skylights contribute to a building’s aesthetic appeal, and they can also reduce the cost of electrical lighting. But they have drawbacks, too, and building managers have to consider both aspects to make an informed decision. When considering skylights as part of your building’s future, remember to think about the hidden costs, like increased roof maintenance, heating and cooling, and safety precautions.

After Years of Roof Leaks, a Laboratory That Produces Theatrical Equipment and Software Undergoes a Complex Reroofing

Founded in 1910, Rosco Laboratories is a multi-national producer of equipment, software and products for the theatrical, film, and television industries and architectural environment. As with every aging flat roofing system, water leakage was becoming a recurring problem at Rosco’s Stamford, Conn., facility. The severity of the leakage was further exacerbated by the lack of roof drainage (only two roof drains serviced the entire building) and poor deck slope conditions (less than 1/16 inch per foot).

The gypsum decking was cut out within the limits of the entire framing “bay” and infilled with galvanized metal decking. The longitudinal deck panel edge was seated atop the horizontal leg of the bulb-tee section (visible in the center of the photograph) and mechanically fastened using self-tapping screws. The ends were supported by the steel purlins. The underside of the decking was prepainted to match the ceiling finish. Supplemental structural support consisting of strips of 14-gauge galvanized sheet metal were attached to the bottom of each bulb-tee section contiguous to the repair to provide additional support for the adjacent gypsum roof decking segment.

The gypsum decking was cut out within the limits of the entire framing “bay” and infilled with galvanized metal decking. The longitudinal deck panel edge was seated atop the horizontal leg of the bulb-tee section (visible in the center of the photograph) and mechanically fastened using self-tapping screws. The ends were supported by the steel purlins. The underside of the decking was prepainted to match the ceiling finish. Supplemental structural support consisting of strips of 14-gauge galvanized sheet metal were attached to the bottom of each bulb-tee section contiguous to the repair to provide additional support for the adjacent gypsum roof decking segment.


Rosco representatives employed traditional methods to control and/or collect the moisture within the building by use of several water diverters. This technique was effective but Rosco representatives soon recognized this was not a viable long term solution as the physical integrity of the roof structure (deck) became a principal concern to the safety of the building occupants.

The Fisher Group LLC, an Oxford, Conn.-based building envelope consulting firm was retained by Rosco in March 2009 to survey the existing site conditions and determine the need for roofing replacement. The existing roofing construction, which consisted of a conventional two-ply, smooth-surfaced BUR with aluminized coating, exhibited numerous deficiencies (most notably severe alligatoring) and was deemed unserviceable. Construction documents, including drawings and specifications and a project phasing plan were developed by Fisher Group to address the planned roof replacement.

Bid proposals were solicited from prequalified contractors in June 2010, and F.J. Dahill Co. Inc., New Haven, Conn., was awarded the contract on the basis of lowest bid.

Existing Conditions

The building basically consists of a 1-story steel-framed structure constructed in the 1970s. It is a simple “box”-style configuration, which is conducive to manufacturing.

In conjunction with design services, destructive test cuts were made by Fisher Group in several roof sections as necessary to verify the existing roofing composition, insulation substrate, moisture entrapment, and substrate/deck construction. A total of four distinct “layers” of roofing were encountered at each test cut. The existing roofing construction consisted of alternating layers of smooth- and gravel-surfaced, multi-ply felt and bitumen built-up roofing. The bitumen contained throughout the construction was fortunately asphalt-based. Succeeding layers of roofing were spot mopped or fully mopped to the preceding layer (system). The combined weight of the roofing construction was estimated to be upwards of 20 to 22 pounds per square foot when considering the moisture content. This is excessive weight.

The roof insulation panels were set into ribbons of low-rise polyurethane foam insulation adhesive. The adhesive was applied in a continuous serpentine bead, spaced 6 inches on-center throughout the field of the roof.

The roof insulation panels were set into ribbons of low-rise polyurethane foam insulation adhesive. The adhesive was applied in a continuous serpentine bead, spaced 6 inches on-center throughout the field of the roof.


It is interesting to note that a minimal amount of roof insulation was present in the existing construction. Insulation was limited to a single layer of 1/2-inch-thick fiberboard. Additional insulation would need to be provided as part of the replacement roofing construction to increase the roof’s thermal performance and comply with the prescriptive requirements of the Connecticut State Energy Conservation Construction Code.

The structural substrate, or decking, is conventional in nature, comprised of poured gypsum roof decking. The roof decking incorporates 1/2-inch gypsum formboard loose laid between steel bulb-tee supports spaced about 32 inches on-center. The poured gypsum roof decking in this instance was utilized as the structural substrate and for insulating purposes. Poured gypsum roof decking has a minimal insulating value of perhaps R-2 to R-3, which is obviously considered to be minimal by present standards.

A representative number of bulk material samples were obtained by Fisher Group from the existing roofing construction as necessary to determine the material composition. The sampling included field membrane roofing plies, coatings and cements, and associated roof penetration and perimeter flashings. Laboratory analysis revealed that the second, third and, in some instances, fourth roofing “layers” (field membrane plies) contained varying amounts—5 to 10 percent—of asbestos (chrysotile) which would necessitate full abatement of the roofing construction.

PHOTOS: The Fisher Group LLC

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Silicone Roof Coating Fixes Roof Leaks

Gaco Western's GacoElastomeric Silicone Roof Coating

Gaco Western’s GacoElastomeric Silicone Roof Coating

Gaco Western‘s GacoElastomeric Silicone Roof Coating offers customers a better choice for fixing roof leaks. Because acrylic elastomerics have issues with ponded water and UV degradation, they do not provide a lasting solution.

Not only does GacoElastomeric withstand ponded water, it remains flexible over time whereas acrylics become hard and brittle. It has higher solids than acrylics so more coating stays on the roof to provide better coverage and because of the unique chemistry it can be rained on after just two hours and won’t wash off the roof.