A limb on the roof wears at the house; a limb on the wire is the utility's call first.
A limb resting on the roof and a limb resting on the line to the house look like one sign from the fence, but they are two problems. The first wears at whatever it touches and can give squirrels and carpenter ants a way in. The second puts a wire in the job, and the utility on the power bill comes before anyone's saw.
General field guidance, not a diagnosis from a distance. A tree can hide problems from the fence line and hide strengths too.
A limb lying on the roof wears what it touches
A limb lying on the roof moves in the wind, and NC State Extension's "Biology and Control of Carpenter Ants" names the damage: tree limbs that press up against walls or the roof "also scratch and can damage siding and shingling." Extension's home-maintenance checklist opens its roof items with the fix: "Trim back tree branches that scrape against or overhang the roof."
Contact by itself works slowly: a live limb on the shingles wears them. A dead or cracked limb over the same roof is a falling question, with signs of its own: big dead limbs and a crack at the fork.
Squirrels and carpenter ants use limbs to reach the house
The NC Wildlife Resources Commission says squirrels "can gain access to the roof of a house by jumping from nearby trees or climbing along wires/cables connected to your home." A limb need not touch the shingles to be a squirrel's route, only be near enough to jump from. What they want is shelter: the Commission says they move into attics as an alternative to tree cavities and leaf nests, getting in through existing holes, openings they make or chimneys.
NC State Extension's carpenter ant guide says carpenter ants "may travel along tree limbs or shrubs that touch the siding and roof, gaining access to attic areas," and that telephone, electric and cable TV lines give them a path inside too.
The tree's part of the fix is a cut. NC State Extension says "To reduce squirrel access to roofs and homes, remove overhanging branches," and its carpenter ant guide says to keep tree limbs pruned back away from the house. How far back is its own question.
A limb on the line to the house goes to the utility first
A limb resting on the line to the house puts a wire in the job, and the utility comes first. What Duke Energy and EnergyUnited say about that service line appears on what drives a tree trimming quote, and pole-to-meter ownership is settled on a tree on a power line. NC State Extension's gardener handbook says it in one line: "Never attempt to prune a tree that touches a power line."
Why contact reads as Worth watching, and what moves it up
On the fence-line check, limbs on the roof or lines sit under Worth watching. Contact shows plainly from the ground and changes slowly: the case for watching it. In the USDA Forest Service guide's terms, used throughout the hazard tree field guide, a hazard needs both a defect and a target. A limb lying on a roof has its target already; the open question is whether the limb has a defect.
A change in the limb or the weather moves it up: a limb that dies or cracks becomes a different sign, read as Worth a call, and an ice storm loads limbs over a roof with ice, the season ice storms and Piedmont trees prepares for.
Which limbs come off, and from which tree, is settled at the tree
Clearing limbs off a roof falls under tree trimming and pruning. The limb on the shingles is part of a tree, and which limbs come off, in what order, is planned from the whole tree: its size, where its trunk stands and what else hangs over the house.
On the home page that is step two, "We look at it with you," where the plan for the cuts gets explained in plain words.
What is the limb touching, and which tree does it grow from?
Questions people actually ask.
Do squirrels need a limb touching the roof to get onto it?
No. The NC Wildlife Resources Commission says squirrels can reach a roof by jumping from nearby trees or by climbing along wires or cables connected to the house, so a limb only has to be close enough to jump from.
Can squirrels in the attic damage the wiring?
Yes. NC State Extension's gardener handbook says squirrels that den in buildings can gnaw through siding and electrical wires, creating a fire hazard, and the NC Wildlife Resources Commission lists wiring around homes among the damage their chewing can do.
Will taking the limb off the roof keep squirrels out of the attic?
Not on its own. The NC Wildlife Resources Commission calls trimming limbs back one of the best preventative measures against squirrels, but it also names wires and cables as a route and existing holes as a way in, and its guidance covers sealing those holes once no squirrels are inside.
Can a branch near a chimney be a fire risk?
Yes, by NC State Extension's account. Its home-maintenance checklist says to keep branches away from the chimney "to avoid fire hazard and allow proper draft for safe and efficient chimney operation," so a limb over a chimney in use is a fire question and a draft question at once.