Roof repair

Most roof leaks are not holes in the roof

A leak is a symptom. The repair that lasts is the one that finds the defect, and the defect is almost always a detail rather than the field of the roof.

Where residential leaks actually come from

Sorted roughly by how often they turn up on a house in this market:

1. Pipe boots. The rubber collar around a plumbing vent hardens in sunlight and splits. On this coast that happens fast — ultraviolet exposure here is relentless — and a boot regularly fails a decade before the shingles do.
2. Step flashing at a wall or chimney. Particularly where somebody has replaced proper step flashing with a continuous strip of metal and a bead of sealant.
3. Wind-driven rain past a detail that works in ordinary rain. A lap, a headwall, a counterflashing or a rake edge that sheds vertical rain perfectly well and lets water in when it arrives horizontally. This is the leak that has a season here.
4. Valleys. Nails driven too close to the center line, or debris damming up and holding water against the shingle edge.
5. Counterflashing at masonry. Surface-mounted and sealed instead of let into a cut reglet. The sealant shrinks, and then the chimney wets from the inside.
6. Nail pops. A fastener backing out lifts the shingle above it and leaves a hole under it. Thermal cycling on a hot deck is what backs them out.
7. Attic condensation mistaken for a leak. Humid air meeting a surface cooled by the air conditioning — a duct, a plenum, the underside of the deck under a working attic — drips exactly like a roof leak and has nothing to do with the roof.

Each of these is a component in the roof anatomy drawing, with what it is, how it fails, and what happens if it is left.

How a leak gets traced

1. Start inside

   The attic tells you more than the roof does. Daylight, staining on the underside of the deck, rusted nail tips and wet insulation all point uphill to where water is actually getting in.

2. Ask what the weather was doing

   Every rain, only heavy rain, or only when the wind is from one direction. The third answer changes the search completely: it points at laps, edges and flashings on that elevation rather than at a hole anywhere.

3. Follow the water up

   Water runs down rafters and along the deck before it drops. The entry point is uphill of the stain, sometimes well uphill.

4. Inspect the suspect detail from above

   Once the attic narrows it down to a penetration, a wall line or a valley, the detail gets looked at directly and photographed.

5. Repair the detail, not the drywall

   A repair that replaces a boot, rebuilds a flashing or reworks a valley fixes the cause. Sealant over the top of a defect buys a season.

When a repair is the wrong answer

Repair is the right call when the rest of the roof has real life left and the defect is local. It stops being the right call when:

• the same roof has needed three or four separate repairs in a couple of years, which usually means the failures are age-related rather than incidental;
• the shingles are brittle enough that lifting one to work under it breaks it, which makes any repair destructive — and a sun-baked mat gets there sooner here than the calendar suggests;
• the decking is soft around the repair area, because there is nothing sound to fasten to;
• granule loss is widespread and the mat is visible in the field, which means the surface has already lost the layer that protects it from the sun.

Emergency and after-hours

Active water coming into a room is a different situation from a stain you noticed last week. If water is coming in now, the first job is to stop it getting worse — see emergency tarping — and the diagnosis follows once the weather allows a proper look.