Commercial Roofing
A tenant on the north side of a distribution building in Edinburg, TX reports drips over the same pallet bay after every hard rain, and the roof surface shows nothing: no tear, no puncture, no missing fastener. The membrane has a seam running through that bay, and the seam is the suspect. Seams are where one sheet meets another, and they carry the load of every temperature cycle the roof goes through. The Valley's heat-safety season runs from May through October, so the sheet spends half the year at high surface temperature and then cools overnight, over and over.
My job is to find the exact stretch of seam that has opened, prove it with a probe and a moisture reading, and decide whether the repair is a few feet of lap or a broader condition.
The early signs are subtle. A lap edge that has lifted a hair above the sheet below, a dark line of dirt collecting along the edge, a bead of sealant that no longer touches both surfaces. On a welded sheet, I look for a weld that stops short of the edge or a bead that is thin in places. On a rubber sheet with adhesive or tape, I look for creep, where the lap slowly slides apart under temperature movement. Any of these can sit unchanged for a season and then open in a storm.
I photograph each finding beside a scale and mark the length on the sheet with paint so the same stretch can be found again.
Corners and intersections deserve extra attention. Where three sheets meet at a T-joint, the layers stack up and the weld or bond has to reach all of them, and that is the spot where a marginal seam shows itself first. I check each one by hand. At the base of a wall, a seam that runs into a flashing is another place where two details meet and either can fail.
The probe is the main tool. I run a blunt edge along the lap and note every place it slides under. Then I compare the interior report with the roof plan, because water enters at one seam and shows up at another place entirely. If a section is suspect, a small amount of water poured along a dry lap, with a person watching the interior, can confirm the path. A moisture survey shows the spread underneath so the work reaches the wet insulation as well as the opening.
The roof is tested again after repair, because a seam that was clean in the morning can open again if it was rewelded over contamination.
Contamination decides whether a repair will hold. Dust, oils from rooftop equipment and the film that builds on an aged sheet all keep a new weld or bond from taking. I wash and scrub the lap, test a small area and only then commit to the full length. A repair on a dirty surface can pass a glance and fail within weeks, so the cleaning step goes in the record along with the method used.
It changes everything about the method. A TPO roof is welded with hot air, and a repair needs a clean surface and a weld that actually fuses the layers. A rubber roof relies on tape or adhesive, and the surface must be cleaned and primed for the new splice to bond. Modified bitumen laps are heat-sealed or adhered, and a built-up roof depends on the felts below. If I do not know what is overhead, I cut a small sample and identify it before choosing a method.
Fastening matters too. On a mechanically attached sheet, the seam lies over a row of fasteners, and if those have backed out the lap flutters and works itself loose. I check the plate heads along the lap and replace any that have lifted, since re-welding a seam over loose fasteners treats the symptom and leaves the cause. A look at the flashing at nearby transitions often shows whether the roof is moving as a whole.
A good boundary runs beyond the visible opening on both ends, covering sound seam where the bond is tight. I clean the lap, repair or cap it with a patch that suits the sheet and weld or adhere the edges. Then I probe the finished work and record the result. If seams on the same roof section are opening repeatedly, the boundary changes from a length of lap to a whole panel, because the sheet may have aged to the point where it will not hold another repair.
I show the facility director the pattern on the plan, so the choice between continued repair and a section replacement rests on evidence.
Temporary protection is part of the plan when rain is coming. A strip of compatible tape or a sealed patch can hold a lap for a short time, and the record shows exactly where it was placed so the permanent repair can replace it and not hide it.
Seam repair is usually quiet and compact. The work area is small, the equipment is light and the crew can stay away from air intakes and loading doors. Commercial sites along the north edge of the city, where Doolittle Road and FM 2812 projects are on TxDOT's list and I-69C/US 281 passes the city's northern edge, get the same approach: confirm access, mark the area and keep the opened portion small. Along the US 281 and I-69C corridor, a standard photo record lets an owner compare one building's seams with the next.
When probing shows widespread softening, repeated failures or wet insulation across large areas, patching stops being economical. The choice then moves to a phased restoration or a full replacement, which I compare in the report by cost, disruption and remaining life. A coating restoration can extend a sound roof, while a recover adds a new layer when the base is dry and the structure allows it. The related issue of water collecting at low spots is handled under ponding water repair, since ponds and seam failures often appear together.
Where a roof has to stay in service during a larger restoration, the work is split into sections that can each be opened, repaired and sealed in one shift. The sequence starts with the sections that leak into the most sensitive areas and moves outward, so the building gets relief early and the facility director can watch the progress against the photo record.
Often, when the sheet is clean, flexible and the insulation beneath is dry. I clean and re-weld or re-bond the lap, then probe it. If the sheet has hardened or the seams are failing repeatedly, patching only moves the stress to the next lap.
Heat expands the sheet, sunlight degrades the surface and cooling at night pulls the lap in the other direction. The deciding factor is how well the seam was made. A fully fused weld or a well-bonded splice absorbs movement far better than a marginal one.
Mark where the water appears inside and look at the roof directly above, but remember that water travels. A technician can trace it with a probe, a moisture reading and sometimes a controlled water test.
A repair made on a sound sheet with a clean surface should last as long as the sheet around it. I record the method and test results so a future inspection can check the work.
It can, depending on the terms. Send the paper if you have it, and I will read the notice and repair requirements before work begins.