Why do long winter storms find leaks that light rain does not?
A long soaking storm saturates the sheathing and the framing, and wet wood holds water against the joints for longer. A joint that stayed dry in a light rain can take water once the wood beneath it is full.
Light rain runs off the covering and drains quickly. A sustained storm soaks the layer under the covering, and the water then has to go somewhere. It finds the weakest joint, which is usually a nail hole, a lapped flashing or a sealant line that has begun to age.
The technician therefore reads the attic for the days after the storm, not only for the stain on the storm night. Wet wood that is still wet days later is evidence that a sustained wetting reached it, and the route of that wetting is what is traced.
What does the attic show that the roof surface does not?
The attic shows the path water has taken through the sheathing and along the framing. The stain on the ceiling is the end of that path, and the wet wood is the middle of it.
A valley that is leaking sends water down a line of sheathing, and the line shows as a dark band on the boards beneath. A vent that is leaking shows as staining in a circle around the pipe, and a flashing that has lifted shows as a wet stripe running down the rafter from the joint.
The attic is read from the access hatch with a torch, and nothing is cut until the readings have been taken. Each mark is photographed from the same spot so the next check can compare.
How is a water test run without causing new damage?
A water test runs a measured flow over a section of the roof, from the lowest section upward, with the attic watched for the first sign of entry. It is done in short runs so the water does not pool and find a new route.
The hose is held at a low rate and moved slowly across the section. The watcher in the attic calls out when the first drop appears, and the spot is marked. If no entry appears within the set time, the next section is tested.
The test stops at the first sign of a stain in a room, so no ceiling is soaked. After a storm, the crew also checks the surfaces below for water that is already in the building.
What goes in the record of a storm leak?
The record holds the date, the stain's location, the attic photographs, the moisture readings, the cause and the repair. It is what the owner keeps for the repair, for a claim and for a sale.
Photographs are taken before anything is moved, from the same spots, and labelled with the room and the time. A repeat leak is easier to resolve when the earlier record is available, so the technician reads any previous file before the first step.
The record does not decide what an insurer pays. That is set by the policy and the insurer, and the owner should read the policy before relying on any statement about coverage.
What does a flood watch mean for a roof?
A flood watch means flooding is possible, and for a roof it means a long rain is coming that may saturate the ground and the building's surfaces. It is the signal to check the outlets and the valleys before the rain, not after.
The National Weather Service issued a flood watch for the Bay Area on 4 and 5 January 2023, according to Valley Water. A flood watch is a forecast of possible flooding, not a report of it, and a roof owner who reads one has a short window to clear the outlets, check the valleys and fix anything loose.
A roof that is checked on the day of a flood watch is in a better state than one checked after the water has come. The owner's record of the check, with the date, is useful if the storm leaves a leak to trace.
How do creek floods and roof leaks relate?
Creek floods and roof leaks are separate faults, but they arrive in the same storm, and the owner who has both must deal with both. The creek water is outside the building, and the roof water is inside it.
Valley Water recorded localised flooding along several creeks in January 2023, including San Francisquito, Upper Penitencia, West Little Llagas and Uvas creeks. Water that rises at a creek can reach the foundation of a low house, and the roof's gutters and downspouts add to the flow at the same wall.
A technician looking at a roof leak in a storm of that kind checks the roof and the outlets first, then the drainage at the foot of the wall. Where the outlet discharges into soil that is already saturated, the water can pool and find the foundation, and that is recorded on the scope.
