Roof flashing repair in Phoenix at walls, vents and valleys

Roofing materials shed water well in the open field. The trouble is at every edge, corner and hole: where the roof meets a wall, where a pipe comes through, where two slopes meet in a valley. Flashing bridges those joints. It is usually galvanized steel, aluminum or lead, bent to direct water back onto the roof surface. On tile roofs, flashing sits under the tiles; on shingle, it weaves between courses; on foam, it is usually sprayed over and coated.

Phoenix is hard on flashing because of temperature swings. Metal on a south-facing wall can heat well past 150 F in summer afternoon sun, then cool quickly after dark. That expansion and shrinking works fasteners loose and splits any sealant that bridges metal to stucco. Flashing that is designed to move, with proper laps and counterflashing, lasts. Flashing that depends on caulk usually does not.

On a wall joint, the right setup has two pieces. Base or step flashing lays on the roof and turns up the wall. Counterflashing comes down from the wall and laps over it, so water running down the stucco is directed onto the roof and not behind it. On many Valley homes, the counterflashing was skipped and the base flashing was simply caulked to the stucco face. When that caulk fails, water runs straight behind the roofing.

Fixing it properly means cutting a reglet, a shallow groove, into the stucco and inserting counterflashing, or installing a surface-mounted counterflashing with a sealed top edge. It is more work than a caulk bead, but it is the fix that lasts. Where stucco damage is involved, we patch the cut so it blends. Along parapet walls on flat roofs, the same principle applies, which our parapet wall repair page covers in detail.

Plumbing vent boots are one of the most common leak sources on Valley roofs. The rubber collar cracks in the sun within a decade or so, sometimes sooner. We replace them with UV-resistant boots or lead jacks, and on tile roofs we install a proper flashing base under the tiles so the boot is not the only line of defense. Attic vents, exhaust fans and AC curbs get the same check.

Skylights have their own flashing kits, and many older skylights have curbs that were flashed with sealant only. If the skylight itself is cracked or fogged, our skylight repair and replacement work handles the unit, and we flash it as one job. Chimneys, which are less common here but still found on older homes, need step and counterflashing on all four sides plus a cricket on the uphill side if the chimney is wide.

Open metal valleys carry the runoff from two slopes at once, so they move more water than any other part of a tile roof. In the Valley they also collect dust, leaves from palo verde and mesquite, and the occasional tennis ball. That buildup slows water down and pushes it sideways under the tiles that border the valley, which is why so many leaks start a foot or two from the valley center rather than in it.

When we repair a valley, we clear it fully, check the metal for rust and pinholes, and look at the felt under the edge tiles on both sides. Worn valley metal is replaced with a wider, heavier piece with a center rib that keeps water from crossing over. We cut edge tiles so they leave an open channel instead of crowding the metal, which keeps debris moving downhill.