Home Exterior Clues
Signs on siding, foundations, decks, and eaves
Clues on the house itself deserve faster attention than clues in the yard, because the stakes are different: a hole in the lawn is cosmetic, but a mud tube on the foundation or a row of holes in your siding can mean active damage to the structure. The encouraging part is that these signs are distinctive and easy to check. These guides show you how to identify the most common exterior warning signs, which ones are urgent, and what a professional will look for when you call.
Home Exterior Clues guides
Mud Tubes Near Your Foundation: The Termite Warning Sign Pencil-width mud tunnels running up your foundation wall are most likely shelter tubes built by subterranean termites — the single most important early warning sign of an active infestation. Mud dauber wasp nests and rain-splashed soil can look similar at a glance, but termite tubes follow continuous vertical paths from soil to wood. Of every clue on this site, this is the one that should never wait: schedule a licensed termite inspection promptly. Read the guide → Scratching Noises in Walls at Night: What's Living in There? Scratching in your walls at night most often means mice or rats, since both are nocturnal — light, fast scratching suggests mice, while heavier gnawing and movement suggests rats. If the noise happens in daylight, especially at dawn and dusk, squirrels are the likelier tenant. The time of day, the weight of the sound, and where in the house it comes from will narrow it down before you ever see the animal. Read the guide → Black Streaks on Your Roof: Algae, Moss, or Something Worse? Black streaks running down your asphalt shingles are almost always a blue-green algae called Gloeocapsa magma — a cosmetic problem, not mold and not roof failure. The streaks show up first on north-facing and shaded slopes where moisture lingers, and they darken as the algae colony spreads year after year. Moss, lichen, and chimney soot can look similar, but each behaves differently and only moss actually threatens the shingles. Read the guide → Chewed Wires and Screens: Rodent Damage and Fire Risk Chewed wires, cables, and window screens are almost always rodent work — mice, rats, or squirrels, whose front teeth grow continuously and must be worn down by gnawing. The size of the tooth marks and where the damage sits tells you which rodent, and chewed electrical wiring in particular is urgent: exposed conductors inside walls are a genuine fire hazard that needs both an electrician and a pest professional. Read the guide → Greasy Rub Marks Along Walls: The Sign of a Rodent Runway Dark, greasy smudges running in a line along your baseboards, foundation, pipes, or rafters are most likely rub marks — oil and dirt from rodent fur deposited as the animal follows the same route night after night. Prominent, continuous marks usually mean rats; smaller, fainter smudges mean mice. Because rub marks only build up through repeated travel, finding them means a runway is established, not that an animal passed through once. Read the guide → Round Holes in Wood With Sawdust: Bees, Ants, or Beetles? A perfectly round hole about 1/2 inch across with a pile of coarse sawdust beneath it is the signature of carpenter bees, especially on bare or weathered wood. Fine sawdust-like debris coming from cracks and seams rather than a drilled hole points to carpenter ants, while clusters of much smaller holes are usually old wood-boring beetle exits. The hole's size, the texture of the sawdust, and whether you see insect traffic will tell you which one you have. Read the guide → Wasp Nest Under the Eaves: Which Wasp, and How Careful to Be A nest under your eaves is most likely paper wasps if you can see open honeycomb cells on an umbrella-shaped comb, bald-faced hornets if it's a fully enclosed gray papery ball, or mud daubers if it's made of dried mud tubes. Paper wasps and hornets will defend their nest, while mud daubers almost never sting. Identify the builder from a distance first — the right response ranges from leaving it alone to calling a licensed pest control professional. Read the guide → Woodpecker Holes in Siding: Why They Drill and How to Stop It Holes pecked in your siding usually mean a woodpecker is foraging for insects, drumming to claim territory, or excavating a nest cavity — and rows of small holes often signal that insects like carpenter bee larvae are already living in the wood. A single clean half-inch round hole with sawdust below it, on the other hand, is typically the work of carpenter bees themselves. Because woodpeckers are federally protected, the fix is deterrence and repair, never harm. Read the guide →
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