Learn · Pest identification
What is making scratching sounds in my walls or ceiling at night?
Overhead scurrying at dusk and dawn, scratching in the ceiling, or running sounds in the wall between bedrooms — almost always means something has moved into your attic or wall voids. Here is how to diagnose what it is by time of night, location, and sound pattern, and what to do about it before damage compounds.
The 30-second answer
In Arizona, overhead nocturnal scratching is almost always roof rats.
Roof rats are the dominant rodent in East Valley homes — they nest in attics, soffits, and wall voids, and they are active at dusk and dawn. If the sound is overhead, starts after lights-out, and continues for more than a few nights, it is almost certainly roof rats. Mice are the second most common cause and are heard lower and quieter. Other possibilities (birds, bats, HVAC, settling) are rare and behave differently.
Diagnose by time, location, and pattern
Three signals tell you what is up there.
Time of night
Dusk-dawn (peak)
Nocturnal rodents — roof rats or mice. Activity starts shortly after lights-out and tapers near sunrise.
Daytime
Birds in eaves, squirrels in attic vents, or possibly carpenter ants. Daytime activity rules out roof rats and mice.
Brief, infrequent
House settling. Pops and cracks as the structure cools, not continuous activity.
Location overhead vs low
Ceiling or attic
Roof rats. They run on ceiling joists, soffits, and the inside of the roof deck. Sound seems to come from above your head.
Walls, lower
Could be mice (running inside wall voids), pack rats (rare indoors), or rodents traveling between attic and lower areas.
Cabinets, pantry, baseboards
Mice. Usually quieter and ground-level, accompanied by droppings in cabinets and along baseboards.
Sound pattern
Scurrying or running
Rats running across beams or roof deck. Brief bursts of fast movement, sometimes thumping when they jump.
Light scratching, rapid
Mice. Quick scampering or scratching, much lighter than rat sounds.
Slow continuous gnawing
A rodent chewing wood, wire, or hard material. Often happens at the same time each night. Sustained chewing is a structural concern.
Rhythmic mechanical
HVAC ductwork, blower motor, or a flapping vent. Not rodents.
What it is NOT
Six common rule-outs that sound like rodents but are not.
Wind or house settling
Irregular pops and creaks, especially during temperature swings. Not continuous, not rhythmic, not nightly.
HVAC system
Air movement, blower hum, duct expansion clicks. Rhythmic, mechanical, often correlated with the thermostat cycling.
Birds nesting in eaves
Active during the day. Heard near vents, eaves, or soffits. Often accompanied by visible nest material at the entry point.
Bats
Rare in Phoenix metro homes but possible. Activity at dawn and dusk. Squeaking can sometimes be heard. Look for guano below the entry point.
Pipes or plumbing
Water hammer, pressure shifts, expansion of copper pipes. Sharp single pops or thuds, not scurrying.
Pet movement
Cat or dog walking on a roof, gutter, or attached structure. Heavier, intermittent, and usually obvious if you go look.
What to do
The five-step response when you think it is rodents.
Listen for 2-3 nights and note the pattern
Time, location overhead, sound type. The pattern is your diagnostic. If activity is overhead, nocturnal, and continuous, you almost certainly have roof rats.
Walk the exterior in daylight
Look for gaps where utility lines penetrate the wall, loose roof tiles, unscreened gable vents, soffit corners, weep screeds at the base of stucco. These are the entry points. Photograph anything suspicious.
Check the attic with a flashlight and a mask
Look for droppings, runway trails in the insulation, gnaw marks, urine staining, dead specimens, or fresh nesting material. Take photos before you touch anything.
Do NOT use poison bait inside
Poison-baited rodents die in inaccessible voids, decompose, and create odor and fly problems for weeks. Use snap traps in the right locations or call a pro who will.
Schedule inspection and exclusion
Trapping alone rarely holds if entry points stay open. Effective control combines targeted trapping, exterior bait stations where appropriate, and exclusion sealing of every gap a rodent could use.
Why time matters
Roof rat colonies grow fast — waiting costs more than calling.
A roof rat colony can double in size in 6-8 weeks under good conditions. A single pregnant female brings 5-8 pups, which mature in 3 months and breed again. By the time scratching is loud enough to wake you, the colony usually has 5-20 rats and is actively damaging insulation and possibly wiring. Acting in week 1 is faster, cheaper, and less destructive than acting in week 6. Photos of evidence help Firehouse identify the species and the entry-point pattern before the visit.
Related identification guides
More Arizona pest ID help.
Frequently asked questions
Scratching-sound diagnosis FAQs.
What is the most common cause of scratching sounds in walls in Arizona?
Roof rats. They are the most common rodent in East Valley homes and they nest in attics, soffits, and wall voids — exactly where scratching sounds come from. The classic signature is scurrying or scratching overhead at dusk or dawn, usually concentrated above bedrooms or living rooms. Mice are a distant second and are heard lower down, often near pantries and kitchens.
How do I tell rats from mice by sound?
Rats sound bigger and lower — clearly audible scurrying, thumping when they jump, the sound of something with weight moving across a ceiling beam. Mice sound lighter and faster — quick scampering, a soft scratching, often described as 'tip-tap' running. Rats can be heard through a closed door; mice usually need quiet to be heard. If you can clearly hear it from across the room, it is probably rats.
Could it be something other than rodents?
Yes. Birds nesting in eaves or vents make daytime scratching sounds. Carpenter ants (less common in Arizona than the Midwest) can produce a faint rustling in wood. Bats — rare in homes but possible — make small sounds at dusk and dawn similar to mice. HVAC ducts make rhythmic, mechanical sounds. Settling sounds from a house cooling at night are irregular and brief — one pop, not continuous activity. If the sound is continuous, nocturnal, and rhythmic-scurrying, it is almost always rodents.
Is the activity above the ceiling damaging the structure?
Roof rats and mice chew almost everything: wiring (a documented fire risk), insulation (R-value drops, urine staining), wood framing (entry-point enlargement), and stored items in attic boxes. Insulation is usually the first visible damage, but chewed electrical wiring is the most expensive consequence. The longer activity continues, the more damage compounds. Most attic rodent damage takes 1-3 months to become serious if entry points stay open.
I tried snap traps. The scratching continues. Why?
Several possibilities. (1) Trap placement was off — runways matter more than visibility. (2) The trap caught some rodents but not all. (3) Snap traps alone do not stop new rodents from entering through open gaps in the roof, soffits, weep screeds, or utility penetrations. (4) The rodents are accessing the attic from a neighboring property and continually recolonizing. Effective control combines trapping in the right places, exterior bait stations where appropriate, AND exclusion sealing of every entry point.
When should I call a professional?
Call if any of these are true: you have heard activity for more than a few days, you found droppings in multiple areas, you see chewed wiring, you smell ammonia from urine, you can hear it from multiple rooms, or DIY traps caught one or two but the sound continues. Roof rat colonies grow fast — waiting often costs more in damage than calling immediately.
Take control today
Hearing it tonight?
Most rodent jobs are easier to solve in week 1 than in week 6. Firehouse can inspect the attic and exterior, identify the species, set traps in the right locations, and seal entry points before the colony grows.