A seam is a joint, and joints fail where the roof moves most. In a climate that swings through freeze and thaw all winter, every lap on a flat roof is working. Commercial Roofing Flagstaff repairs split and open seams on commercial roofs in Flagstaff, AZ, and the sequence is simple. Probe the lap, find the width of the defect, clean it, and close it with the same method the roof was built with.
An open seam does not leak right away. Water enters, freezes in the gap and lifts the edge a little further every night. By spring the gap is wide enough to stain a ceiling tile. Catch it in fall and it is a small repair. Catch it in March and it is a bigger one.
Seams differ by roof system, and the repair has to match the system. We identify the type before touching the lap.
A weld failure usually shows as a gap along the lap edge, sometimes with a visible bead of unfused material. An adhesive failure shows as a loose edge you can lift with a probe. Metal seam failures show as backed-out fasteners or dried sealant. Each tells us a different story about why the joint opened.
The first cause in this town is thermal movement. Roof sheets expand in daytime sun at about 7,000 feet and contract hard on a night that drops below freezing. Over many cycles the stress concentrates at laps. Hard frost is back by late September, and the minus 30 degrees F record shows how severe the cold gets.
The second is contamination on the day the seam was made. Dust, moisture or cold adhesive weakens a bond from day one. A seam made in November on a damp morning can look fine and fail the next spring.
The third is tension from the structure. When a deck deflects under snow, the membrane is pulled across its laps. A heavy winter can show up as a row of opened seams along a purlin line. The late February 2023 storm, which put 24.5 inches on parts of the city by March 2, showed how heavy the load can get. Open seams behind a pond are common, since standing water softens the bond. If open seams appear in a pattern, we flag the deck for a sag check rather than just closing the lap.
Visual inspection misses a lot. A seam can be tight on top and open underneath, and a lap near a wall base often fails with the flashing beside it. We walk the entire roof with a rounded probe, pressing along every lap, and mark any that give. Fish-mouths, wrinkles and wet insulation under a lap go on the same marking plan.
On bigger roofs we recommend a drone pass or an infrared moisture survey to see where water has already traveled. Infrared shows wet insulation that the surface hides, which tells us how far a single seam failure has spread. That keeps us from patching a lap and leaving a soaked board below it.
The marking plan becomes the repair list, with each seam sorted as clean-and-reweld, cover strip or full replacement of the sheet section.
Industrial buildings in the parks along I-40 and I-17 carry a lot of single-ply sheet in some cases, and every added foot of sheet is another lap to probe. In the Pulliam Airport and Technology Park area, the park's Phase I includes a hotel, a restaurant and office and research buildings, and any membrane roof among them gets its laps probed after a winter.
An open lap over clinical space cannot wait, and a Level I trauma center like Flagstaff Medical Center, open since 1936, shows why. Water entry above patients calls for a response in hours, not weeks. A manufacturing floor, such as the plants of employers like W. L. Gore or Joy Cone, loses time to a drip as well, so a lap repair there is timed around the shifts.
For any occupied building, we schedule seam work around tenant hours and keep noise and fumes away from air intakes.
Single-ply laps are cleaned, dried and rewelded with a hand welder, then the edge is probed again. Where the sheet is too aged to take a weld, we install a cover strip over the lap, welded on both edges. Adhesive seams on EPDM are stripped back, cleaned and rebonded with splice adhesive and sealed with lap sealant at the edges. Bituminous laps are cleaned, primed and torched or heated with a patch ply that overlaps the defect on all sides.
Metal seams are cleaned, resealed and refastened. Where fasteners have backed out, we replace them with larger fasteners in a fresh hole.
We stop short of making a roof pretty. If more than a handful of laps are failing, the membrane may be at the end of its life, and a fresh patch does not change that. We say so, and offer a planned repair program or a conversation about a recover. Cost depends on lap length, access and whether insulation underneath is wet.
Look for a raised edge, a visible gap, a wrinkle running along a lap or dirt streaks that follow a seam line. Press along the lap with a flat screwdriver handle: a bond that gives under light pressure is already failing. We probe every lap on a walk, because the first sign is rarely a stain.
Welding needs a clean, dry surface, and cold air slows the work. We can weld in low temperatures with the right equipment and probe tests, but we avoid it when the sheet is frozen or damp. In deep winter we install a temporary dry-in and schedule the permanent weld for a clear day.
Not by itself. An isolated failure on a sound sheet is a repair. A pattern of open laps across the roof, or seams that reopen after rewelding, points to an aging membrane. We map every defect and compare repair cost with the remaining life of the roof before we recommend anything larger.
It comes out. Saturated board holds water, loses insulating value and spreads moisture to the deck. We find it with a moisture meter or infrared scan, cut out the wet section, replace it and close the membrane over fresh board. Skipping that step turns a seam repair into a repeat call.
It can. Many manufacturer warranties require repairs by approved methods and with matching materials, and unauthorized patches can complicate a claim. Tell us the roof system and send the warranty paperwork if you have it. We repair in the manufacturer's recognized method and document the work with photos.
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A walk of the roof with photos, findings and a written scope.
Active leaks, storm damage and blocked drains get a fast response.
Roofing across Flagstaff and nearby Arizona communities.