Why does a roof leak show in the ceiling rather than on the roof?
Water runs along the rafters and the decking before it drops through, so the stain can appear several feet from the entry. The attic is where the path is visible.
Rafters and joists act as channels. A leak at a flashing can run along a rafter for many feet before it drops through the ceiling, and the stain shows wherever the water finally comes out. The tracing follows the wet insulation and the staining on the decking rather than the stain in the room.
In houses with plaster ceilings, water can sit between the plaster and the lath for a long time, and the first sign may be a soft or bulging area that looks harmless. The readings are taken across the ceiling, not only at the stain.
What should a homeowner check on the roof after a storm?
A look from the ground at the flashings, the vents, the ridge and the valleys can show a lifted or missing shingle. Anything that looks wrong should be checked by a roofer, not by climbing onto a wet roof.
Look for shingles that are lifted, cracked or missing near a valley, a chimney or a vent, and for flashing that has pulled away from the wall. Debris from the trees should be cleared from the roof and the gutters where it can be reached safely from the ground.
Do not climb onto a wet or steep roof to inspect it. A roofer has the equipment and the training to check the roof safely, and the owner can point the roofer at the entry point the attic showed.
What is the insulation doing to the drying?
Attic insulation holds water in its fibers and is hard for air to reach once it is compressed. It is the slowest material to dry, and it is removed where it is saturated.
Wet insulation can cling to the underside of the decking and keep it damp for weeks. Where the insulation is removed, the framing beneath is dried directly, and the air is moved through the attic so the decking reaches its goal.
Replacing insulation is a separate job. The restoration work removes what is wet and records the area, and the new insulation is quoted by the trade that installs it.
How long does drying take after a roof leak?
Drying runs until the insulation, the framing and the ceiling reach their goal. The attic and the ceiling are often the slowest part, and the time depends on how much water reached them and how humid the outdoor air is.
A ceiling that is closed too early can stain again within weeks, and the readings are the only reliable way to know whether the cavity is dry. The equipment comes out when the readings are back within range, not when the stain has faded.
Humid summer weather slows the drying of the attic, and the plan allows for that. The record shows the outdoor conditions alongside the readings, so the owner can see why the attic took the time it did.
How long should a roof leak be watched after the repair?
A repaired roof is watched through the next two or three storms. The attic and the ceiling are checked after each one, and any new stain or drip is recorded with the date and the readings.
The check is simple and it is the best evidence that the entry point was closed. A roofer who wants to see the record can be given a copy.