Seam Failure Repair in Santa Rosa, CA

A roof seam does not open because the roof is old. It opens because something pulled on it: a building that moves, a pond that sat on it, a weld that never fully bonded, or a crew that rushed a lap on a cold morning.

That distinction decides the repair. Welding shut a seam without finding out why it split just buys a few months until it splits again, and on a big roof in Santa Rosa, CA the second split is usually longer than the first. Most single-ply seams are fixable in a day with the right tools and a clean surface. The harder, more honest job is working out whether you have one bad seam or a roof where every seam is marginal, and that is what we do first.

On a heat-welded sheet such as TPO or PVC, a good seam fuses two layers into one. A bad one only looks fused. Welds fail when the surface was dusty or oily, when the welder ran too fast or too cool, or when a long stretch of overlap was never probed after installation. The failure usually starts at a T-joint, where three layers meet, and works outward.

Taped and glued seams on EPDM fail differently. The primer dries before the tape is set, the tape lifts at the edge, and water wicks along the gap. On modified bitumen, the lap opens where the torch or adhesive missed an inch, or where granules were left in the bond. Whatever the system, a seam that has been under water for a season, or stretched by a building that shifts, is much more likely to open than one on a dry, stable roof.

A low-slope office or flex building with many rooftop units collects seams at every curb and walkway, which is worth remembering in the Airport Business Center, a business park of office, flex and light industrial buildings. Every time a unit is changed or a technician walks to the same machine, the sheet gets loaded along the same line. Repeated foot traffic along a seam that was marginal when it was welded wears it open.

The pattern follows the equipment, not the address. Near the Keysight headquarters in Fountaingrove, as anywhere else, a path wears into the roof wherever technicians keep returning to the same machine, and the seams under that path are where we start probing first.

We do not look for the seam that leaks. We probe all of them. A blunt probe is run along each lap, and any spot where it slides under the edge gets marked in paint. A pass with the probe on a typical low-slope roof finds problems far beyond the one the tenant reported, and we photograph each mark with its location so the repair list matches the roof.

The results fall into groups. Isolated marks are weld defects and get fixed spot by spot. A cluster along one stretch points to a cause: ponding, movement, a bad batch of work. A roof with marks everywhere has an installation or aging problem, and then the repair conversation turns toward a full roof inspection and a candid look at remaining life.

On TPO and PVC we clean the seam, re-weld it with hot air, and cover the repair with a welded cover strip over any T-joint. On EPDM we remove the failed tape or splice, clean back to bare rubber, prime and install new seam tape under pressure, since a new strip over a dirty old one does not stick. On modified bitumen, we re-lap with cold adhesive or heat, depending on the fire conditions on the day.

Where the seam failed because of ponding, movement or foot traffic, the cause gets fixed in the same visit with a walkway pad, a drain, a repositioned unit or a run of tapered crickets. This is the sort of commercial roof repair that holds, because it treats what pulled the seam apart.

Do not tape over dirt

The most common wasted repair is seam tape or mastic smeared over a dirty open lap. It looks tidy for a season, then peels, and the water that got under it has nowhere to go. A close second is a new coat of anything over seams that are still moving.

Do not rush to a recover either, unless the seams are widely failed and the insulation underneath is dry. Overlaying a roof with many open seams puts a new sheet on a surface that is still letting water in. Prove the seams, then decide.

A seam repair will not hold if nearby flashing failures still direct water under the membrane.

Commercial Roofing Questions

Can I see an open seam from the ground or a ladder?

Sometimes, if you know what to look for: a ridge along a lap, a visible gap, or water staining running in a straight line. Many failed seams look closed from above and only give way under a probe. If the roof has leaked along a line, assume the seam is the first suspect, and have someone walk it with a probe before it rains again.

A contractor said every seam on our roof needs redoing. Is that realistic?

It can be, but ask to see the probe results. If a few seams are marginal, redoing them all is wasteful. If most fail the probe, the roof is telling you its welds were weak from the start. We photograph each defect so you can judge for yourself, and we lay out what a full re-weld costs against replacement.

How long will a seam repair last on an older roof?

As long as the sheet around it stays flexible and the cause is gone. A patch on sound material can last for the rest of the roof life. On a sheet that has hardened or shrunk, the repair fails at its edge. Before we weld, we test whether the surrounding material still bonds, and we say so if it does not.

Do cold nights matter for seam work?

They do. Adhesives and tapes cure slowly in cold or damp air, and a weld on a cold, wet surface can look fine and fail later. Fog and low overcast often move into Santa Rosa in the mornings, so we wait for the surface to dry and warm up, or we use a method suited to the conditions. A seam done at the wrong hour is often the one that fails.

Will a roof coating seal a leaking seam?

Not by itself. A coating can bridge a hairline gap, but it does not bond a lap that has separated, and it cracks where the seam keeps moving. Repair the seam mechanically first. Once the laps are sound and the roof is dry, a coating may be worth considering to extend the life of the sheet.