Reglets, Counterflashing and Masonry Walls
On masonry parapets and walls, the metal above the base flashing sits in a reglet cut into the wall or a surface-mounted receiver. When the mortar around that slot wears or the sealant in it dries out, the counterflashing loosens and gaps open behind it. Hand-formed sheet metal, set with proper laps and soldered at the corners where the metal allows, will outlast a stock part pressed in with caulk, and it will look right against the wall for the life of the building.
Old Pasadena has historic commercial façades, while Pasadena’s adopted plan for Lamanda Park supports light-industrial and research uses. Those places call for different roof surveys, but whenever an existing roof meets masonry, the repair starts by cleaning out failed sealant, checking the wall, and cutting a new reglet only where the substrate can take it.
Curbs, Boots and Penetrations
Every pipe, conduit, vent and equipment curb is another flashing, and the small ones fail quickly because they are fitted by hand and then forgotten. A rubber boot cracks at its collar under summer sun, a clamp on a pipe flange loosens, and the corner of a rooftop unit curb stretches the sheet around it until the seam at the corner splits.
Laboratories, clinics and tenant-improved offices accumulate these penetrations because systems keep being added. On a hospital that has grown in stages, as Huntington Hospital did with an east tower in 1998 and a west tower in 2008, systems added over the years leave abandoned conduit, capped lines and old curbs behind on the roof, each with its own flashing. Where a detail is no longer needed, we remove it and patch the roof solid. Where it is needed, we rebuild it as proper penetration flashing or as a flashed curb detail that is raised and sealed on all four sides.
Why Sealant Alone Does Not Last
Sealant has a place in a flashing detail, but only as one layer of it. A sealant joint is meant to move a small amount and stay closed, and it does that best when it is sized properly, set against clean metal and backed by a joint that is mechanically sound. Smeared over a gap that is already open, the same product dries, shrinks and cracks within a season, and the roof is back to leaking while the owner holds an invoice.
The repair we prefer starts by removing what has failed. We strip the loose sealant and any metal that has fatigued, correct the substrate, install the new base flashing, and then reset or replace the counterflashing so it covers the top of the membrane by a proper lap. Where the leak has already wet the wall or insulation, we handle the underlying damage as part of the leak repair so that the roof is dry, not just closed.
Afternoon Heat and Open Edges Near the Foothills
A recorded high of 113 F in June pulls sheet metal open in the afternoon and lets it settle at night, and over a season that movement works at every soldered corner, sealant joint and fastener in the flashing. Late-season spells, like the October 2023 advisory with highs near 100 F, keep that movement going well into autumn.
Near the foothills, an open flashing is also a path for embers. In Fire Hazard Severity Zones, wildland-urban interface rules call for a Class A roof assembly and ember-resistant vents, and a gap behind metal at a wall or curb is the sort of opening wind-driven embers find. We pair flashing repair with the review of heat and UV degradation on the membrane beside it, because a sheet that has aged out will not hold the flashing that depends on it.
Walking the Details Each Season
Flashing fails by degrees, so a short walk at the right times catches it. We look at every wall termination, curb corner and boot after the summer heat and again before the winter rain, pressing on seams and checking the top edge of the metal for gaps. We record what we find so the next visit can compare against it.
A written commercial roof inspection with photographs of each flashing gives a property manager a clear list to plan from, and it helps when a tenant reports a stain that seems to have no source. Where those leaks recur at a seam, the cause may sit just beside the flashing, and a seam failure is sometimes found when we follow the water back.
Commercial Roofing Questions
Why does the leak return every time the sealant around the flashing is redone?
Because the sealant is covering a joint that has already moved. If the metal is loose, the reglet is worn or the base flashing has pulled from the wall, a fresh bead only hides the gap until the next heat cycle opens it again. A lasting repair rebuilds the layer that failed, then uses sealant only to finish the joint.
How can we tell whether the flashing or the membrane is the source of the leak?
Look at where the water shows inside and trace it uphill. Stains that line up with a wall, curb or penetration usually point to flashing, while stains in the middle of a bay point to seams or the field of the sheet. A controlled water test at each suspect detail settles it without tearing anything open.
Does flashing on a brick parapet have to be replaced all at once?
Not necessarily. The mortar and reglet condition along each wall set the scope, and sections that are still sound can stay while the failed stretches are rebuilt. We mark the wall by condition, repair the failed lengths first, and show you what remains so the rest can be scheduled.
Is soldered sheet metal better than a sealed lap?
On copper and stainless steel, soldered joints give a continuous, long-lasting seam that moves with the metal. On other metals, a hemmed and lapped joint with a proper sealant bed and fasteners is the better choice. We select the method from the metal itself and the way the wall will move around it.
What makes one flashing repair cost more than another?
Access, length and condition move the price most. A short stretch at a low wall is quick, while a tall parapet, a wall of failed masonry, or a curb ringed by equipment takes scaffolding, repointing and extra care. We scope the repair by the foot and the detail, and we explain which part of the building drives the number.
