What a re-roof uncovers: the attic wiring most homes never inspect
The attic is the one part of a house almost nobody measures, because almost nobody goes up there. A re-roof changes that for a few days. It is the cheapest access you will ever have to the wiring and the service entrance that sit closest to the roofline, and the window closes the moment the new deck goes down.
Why the attic is the blind spot
Every other room on this site gets attention because people live in it. The attic gets none, because people do not. Yet the attic is where a surprising amount of a home's electrical story is written: the service entrance often lands there, feeder cables cross it on their way to the panel, old junction boxes hide under insulation, and decades of additions leave splices that no inspector has looked at since the day they were buried. A magnetic field does not care whether a person is standing next to the source. It only cares about the geometry of the current, and the bedroom directly under a busy attic junction inherits whatever that junction is doing.
The problem has always been access. You are not going to pull up attic insulation and crawl the rafters on a normal Saturday, and you should not. But there is one moment when the attic and the roofline are already open, already being walked by a crew, and already the center of attention: a roof replacement.
The service mast, where power actually arrives
On a house with overhead service, the power does not enter at the panel. It enters at the roofline, through the weatherhead and down the mast, and only then travels to the meter and the panel. Everything on the power lines page about the service drop applies right here, at the top of your house, inches from the roof deck. When a roof is replaced, that mast is frequently in the way. Sometimes the utility has to detach the drop; sometimes the mast flashing is what was leaking in the first place; sometimes the mast is loose and no one noticed until the old shingles came off around it.
This matters for two reasons. The obvious one is water: the point where the mast penetrates the roof is a classic leak site, and a re-roof is when it gets sealed correctly or not at all. The one this site cares about is that the entrance conductors and the mast are the single highest-current path in the house, and the re-roof is the only time you will have eyes on where they meet the structure. If the drop has to be reset, that is also the moment to confirm the work is done by the utility and a licensed electrician, permitted, and not improvised to save a return trip.
What the open attic lets you inspect
With the crew already working the roof and the attic accessible, a short list of things becomes checkable that are otherwise sealed away for another twenty years:
Junction boxes. Every splice in the attic is supposed to live in an accessible, covered box, a point the National Fire Protection Association makes for fire reasons long before anyone thinks about fields. Buried splices under insulation, open boxes, and cables joined with tape are exactly the improvised connections that produce the miswiring patterns described on the net currents page. An open attic is when you find them.
Knob-and-tube and old feeders. Older homes still carry runs of legacy wiring across the attic. Some of it is dead, some is live, and the live sections buried under blown-in insulation are both a fire question and a field question. You want to know which is which while someone is already up there.
Bathroom and kitchen fan runs. Exhaust fans, their switch legs, and the cable bundles feeding them often cross the attic directly above bedrooms. A loaded bundle running over a sleeping area is the same proximity problem this site raises everywhere, just one floor up.
The attic meter pass
If the attic is open and safe to enter, a five-minute sweep with a gaussmeter is worth doing while the access is free. Walk the run of any feeder you can see, hold the meter near each junction box, and note anything that reads high, especially over a room where people sleep. The point is not to alarm yourself over a reading near a working cable, which is normal. The point is to catch the outliers: a broad elevated zone that follows a specific cable, or a box that reads far hotter than its neighbors, which is the classic signature of a net current from a wiring error. Found now, with the roof open, it is a note to the electrician. Found later, it is a project.
Why the roofer is part of this
None of this happens if the crew on your roof treats the job as shingles only. The good ones do not. A dependable roofing company walks the attic before they start, photographs the mast and the deck, flags a loose service mast or a suspicious junction rather than roofing over the evidence, and coordinates with the utility and your electrician when the drop has to move. That is the difference between a crew that replaces a roof and one that leaves the whole top of the house better documented than they found it. If you are hiring for long island roofing and the home has overhead service or an unfinished attic, ask the estimator directly how they handle the service mast and whether they will let you or your electrician look at the attic wiring while the access is open. The answer tells you a great deal about the crew.
The payoff
A roof gets replaced a few times in a house's life, and each time the attic and the service entrance are briefly, cheaply accessible. Used well, that window is when the buried wiring gets a look, the mast gets confirmed sound and sealed, and any field problem hiding over a bedroom gets caught while the fix still costs a note on the electrician's list. Used poorly, everything up there goes dark again under a new deck for another two decades. The roof is the reason to look. The wiring is the reason it matters.