Commercial Roofing Services
Skylight, Curb and Penetration Flashing in Federal Way, WA
Every penetration on the roof gets a tag before any work begins. The crew leader walks the deck with a clipboard and marks each skylight, pipe, conduit, vent and curb with a number and a photograph, because a roof with forty openings has forty chances to leak. Most leaks on a sound membrane start at one of those tagged spots, not out in the field.
Flashing is the part of the roof that bridges the field membrane and whatever pokes through it. On commercial buildings in Federal Way, WA, that means skylight curbs, rooftop unit curbs, plumbing vents, electrical conduit, gas lines, hatch frames and exhaust fans. Each moves a little with the weather, vibrates with the equipment and gets stepped on by service technicians. Flashing is where a roof is most likely to fail, and where a small repair does the most good.
What fails around a skylight?
A skylight has three places that leak: the curb flashing where it meets the membrane, the seal between the curb and the frame, and the glazing itself. Curb flashings crack at corners when the membrane shrinks or the sealant dries out. Frame seals open as the unit expands and contracts through the seasons. Glazing fails when a gasket hardens or an acrylic dome crazes and cracks.
Condensation fools many owners. A skylight that drips on a cold morning may not be leaking at all, and the moisture may come from warm indoor air meeting cold glass. We check the weep holes and the curb interior before calling it a leak. If it is a flashing problem, we rebuild the curb wrap in the membrane manufacturer's detail with a base flashing, a counterflashing and sealed laps, and set the glazing back on new gasket.
Old skylights sometimes reach the end of their useful life. Where the glazing is cracked and the frame is corroded, replacement is the better spend, and we coordinate it with any roofing work so the new curb is flashed into the new membrane.
Large warehouse roofs in the Kent Valley and Fife can carry rows of skylights, and each curb on a long run is worth a hands-on check after the first hard rain of the season.
How are pipes, vents and conduit flashed?
Small round penetrations use pre-molded boots or field-formed flashing. A pre-molded boot is a rubber or thermoplastic collar that fits over the pipe and is welded or adhered to the membrane. It is quick to install and works well until the rubber cracks in the sun and the clamp loosens. Field-formed flashing uses reinforcing fabric and liquid flashing resin and is better for odd shapes, clusters and pipes that sit close to a curb or wall.
Pitch pans, the old-style open-top boxes filled with sealant, are a persistent source of leaks. The fill shrinks and cracks, and rainwater sits in the pan. We replace pans with boots or liquid flashing where the geometry allows it. Where it does not, we rebuild the pan with a proper cap and fresh fill.
Conduit and gas lines have their own problem: they move. A supported conduit that slides on a pad can wear through the membrane, and a line that rests on the roof deck can puncture it. We install walkway pads and supports that raise the line off the surface. This overlaps with rooftop equipment curbs and supports, where the curb is tied to the equipment loads.
What about curbs under rooftop units?
An equipment curb carries the unit above the membrane and must be flashed on all four sides. The most common failure is a base flashing that has pulled away at the top edge, where it is exposed to sun and tied only by sealant. Technicians who open the unit and set tools on the curb can crack the sealant or tear the membrane.
Repair starts with removing the failed termination, checking the curb's wood nailer and cap for rot, and replacing damaged parts. A new base flashing goes up the curb, and a termination bar or counterflashing holds the top edge. If the unit is close to the parapet or other curbs, the gap between them gets its own detail so water cannot pool in the tight space.
On retail buildings along Pacific Highway South, where each tenant may have its own rooftop unit and exhaust, the number of curbs on one roof can be high, and each is a repair candidate. On a medical office roof, work around air intakes needs to be coordinated with the facility team before a unit is disturbed.
How does the wet season test these details?
Tacoma averages roughly 155 wet days a year, and Auburn collects 37 inches a year, led by November and December. Flashings in this climate are soaked for months at a time, so a hairline gap that would pass in a dry climate lets water in repeatedly. Thermal swings from a dry July to a long wet winter also stress sealants and the membrane at the edges of each curb.
Debris is a quieter problem. Needles and leaves pile up behind curbs and around pipes, hold moisture against the flashing and help moss take hold. We clear those spots during every visit and recommend a seasonal cleaning for roofs under trees. A maintenance program catches a failing boot or a dried-out sealant joint long before it drips inside.
What does the repair record show?
Each tagged penetration is photographed before and after, with a note on what was found and what was done. That record shows property managers which details are at the end of their service life, and it supports a flashing failure repair plan when several fail in the same roof. For owners comparing roofs across a portfolio, the pattern tells them where to plan replacement. Tie-ins are tested by hose or by water test before we leave.
Commercial Roofing Questions
Can a leaking skylight be fixed without replacing the unit?
Often yes. If the glazing and frame are sound, the repair is usually the curb flashing and the perimeter seals, which can be rebuilt without removing the skylight. We pull a section of the flashing to see the curb and the substrate before we decide. If the glazing is cracked or the frame is corroded, replacement is the better value.
How many penetrations can one roof carry before it becomes a problem?
There is no set number, but every penetration adds a seam and a maintenance item. Roofs that have collected pipes and conduit from many tenants usually have the most leaks per square foot. We recommend consolidating lines and removing abandoned penetrations during a reroof, which reduces the number of details to maintain.
Should we ask the HVAC technician to leave the roof as they found it?
Yes, and a pre-visit and post-visit photograph of the curb makes it easy to check. Technicians open panels, set tools on the roof and sometimes cut or drill without flashing the new hole. We can set walk paths and protection pads around the unit, and we inspect the curb after a major service call.
What is a counterflashing and why does it matter?
A counterflashing is a metal or membrane piece that laps over the top of the base flashing and sheds water away from the seam. Without it, the top edge of the base flashing depends on sealant alone, and sealant alone dries out. Adding or replacing the counterflashing is one of the most effective upgrades at curbs and walls.
Send the roof plan and a count of the openings
Send the roof plan, a list of the skylights and equipment, and any leak locations. We will tag every penetration on the roof with your superintendent and return a priced list sorted by how soon each one needs attention.
