How to Inspect an Attic for Rodent Activity

Why this matters

The attic inspection is where a rodent job gets priced, and most underpriced exclusion jobs were inspected from the hatch. The tech pokes a head up, sees droppings, sets a few traps and writes "seal entry points", then spends the next visit on the roof finding the four openings nobody listed. Animals in an attic got in somewhere specific, and the inspection's job is to find every one of those places and write them down with a size, a location and a photo, so the exclusion quote is a list rather than a guess. This card owns that inspection. Cleaning up what the animals left is a separate job with its own procedure. See related: Attic Rodent Cleanup and Sanitation.

Before you go up

Respiratory protection goes on before entry, not after you see droppings. Attics with rodent activity hold dried droppings and urine in insulation, and every step stirs them. Follow 'Rodent Droppings and Hantavirus for the Trades': a respirator under a written program per 29 CFR 1910.134, which means a medical evaluation and a fit test before anyone wears one, plus gloves and eye protection. A tech who is not in the program does not do this inspection. Coveralls keep insulation off your skin and out of the truck.

Insulation you do not recognize stays undisturbed. Gray-brown, pebbly loose-fill that looks like vermiculite can contain asbestos. If you see it, do not walk through it, dig in it or move it; inspect from the hatch and the boards, note it, and tell the customer it needs testing before anyone works in it.

Walk only on joists or boards. Step between joists and your foot goes through the drywall ceiling into the room below, and you go with it. Keep weight on framing, use a board laid across joists to work from, and carry a light that leaves both hands free.

Wiring. Look at cables, do not handle them. A gnawed cable with bare copper is energized until someone proves it is not. Note it, photograph it from a distance, keep tools and hands clear, and route it to a licensed electrician where your state or locality licenses that work.

Heat, nails and stings. Summer attics get hot enough to cause heat illness quickly; go up early in the day, limit time, carry water. Roofing nails come through the deck overhead, so a bump cap is worth wearing. Look for wasp nests at the hatch before you put your head through.

The ladder. Set it on firm footing at the hatch, extended so you can step off onto framing rather than climbing over the hatch edge, per your shop's ladder procedure.

Start outside

A walk around the house before going up tells you where to look first. With binoculars from the ground, look at:

• Roof returns, where an eave meets a wall or a lower roof meets a higher wall. The trim joint there often leaves a gap behind the fascia.
• Gable vents for torn or missing screen.
• Soffits and fascia for gaps, sagging panels and chewed edges.
• Plumbing vent boots and roof penetrations.
• Tree limbs within jumping distance of the roof, and utility lines running to the house, which roof rats and squirrels use as highways.
• Rub marks around any of these, which show as dark stains on light trim.

Write each candidate down before going up. Inside, you will be confirming or ruling out each one.

The inspection, in order

1. At the hatch, stop and look before climbing in. Put the light across the insulation surface. Runways show as trails: compressed, tunneled or flattened paths through loose-fill or across batts, usually running between an eave and the center of the attic or along a top plate.

2. Turn your light off for a minute and look for daylight. Light showing at an eave, a roof return or a gable vent from inside is an opening to outside. Note each one against the outside list.

3. Work the perimeter first, along the top plates. Rodents enter at the eaves and travel along the tops of exterior walls. Look for droppings, gnawed wood, rub marks on rafters and plates, and nests. Concentrations of droppings close to an eave usually sit near the entry.

4. Check every candidate opening from the outside list. For each: is there light, rub marks, droppings, gnawing, hair caught on the edge? An opening with sign is confirmed. An opening without sign is still an opening; list it, because a mouse can pass about 1/4 in and a rat about 1/2 in, and the exclusion has to close everything that size, not just the ones in use today.

5. Look at the wiring along the routes for gnaw marks and exposed conductors. Do not touch.

6. Look at ducts and pipes. Flexible ducts get chewed and nested in; bathroom fan ducts often end loose in the attic instead of at an exterior hood, which is both a code problem for the right trade and an easy rodent route.

7. Identify the animal from droppings and sign. Mouse droppings are small, about 1/8 to 1/4 in, pointed; rat droppings larger, on the order of 1/2 in. Roof rats are the common attic rat in many southern and coastal areas; Norway rats more often burrow low and come up through walls. Squirrel sign includes larger chewed openings, nest material of leaves, and daytime noise reported by the customer. Detailed sign is in 'Pest Activity Signs Reference'.

8. Photograph each finding with something for scale and a number written in the frame or noted in the photo log.

9. Back outside, confirm the access each opening needs: ground ladder, roof work, or a lift. That goes on the list too, because it drives the quote.

Worked example: a ranch with an attached garage roof

The house. A single-story ranch with gable ends, and an attached garage whose roof ties into the side of the main house roof. Customer hears scratching at night over the master bedroom. Trees on the east side overhang the roof.

From outside. Candidates: a gap behind the fascia at the roof return on the southwest gable corner; the east gable vent screen, which looks torn; the soffit where the garage roof meets the house wall; limbs over the east roof; a dark stain on the fascia at the northeast corner.

At the hatch. Runways in the loose-fill blown insulation: two trails, one from the southwest corner, one from the east gable, meeting at a nest pushed into the insulation above the master bedroom. Insulation is light-colored blown fiberglass, not vermiculite.

Lights off. Daylight at the southwest roof return and at the east gable vent. None at the garage junction or northeast corner.

Along the plates. Rat droppings, about 1/2 in, heavy along the west top plate within a few feet of the southwest return, and at the east gable vent. Greasy rub marks on the rafter at the southwest return. At the garage junction, no daylight, but droppings and gnawed wood at a gap between the house top plate and the garage roof framing. Northeast corner: clean inside; the stain outside is mildew.

Wiring. One cable near the east gable vent gnawed, copper visible. Not touched, photographed, flagged.

The entry list, as it goes to the office:

 ATTIC ENTRY LIST, ACCT 4410, ROOF RATS
 #  location           size     sign      access
 1  SW roof return,    ~1 in    light,    ladder
    behind fascia               rub,drop
 2  E gable vent,      screen   light,    ladder
    screen torn        torn     drop
 3  garage roof to     ~3/4 in  drop,     roof
    house wall, top             gnaw
    plate gap
 4  E roof, overhang   limbs    path to   trim
    limbs              over     roof      tree
                       roof
 FLAG: gnawed cable at E gable, bare Cu,
 refer electrician. Photos 1 to 9 in log.

Reading the list. Three openings are confirmed with sign. Two were estimated at about 1 in and about 3/4 in, both well over the 1/2 in a rat needs, and the third is a torn screen, which is open whatever its size. Item 4 is not an opening but a route, and the quote that leaves out tree trimming reseals openings that get chewed again. The northeast stain is ruled out and stays off the list, which saves the quote from a ladder set that finds nothing. The gnawed cable is a separate referral, not part of the exclusion price.

What the office does with it: prices each item by material and access (two ladder items, one roof item, tree work referred or quoted), schedules exclusion with trapping inside to remove the animals already in, and books the cleanup after the exclusion is proven by no new sign. Materials and gap sizes for each item are in 'Rodent Exclusion Materials and Opening Sizes'.

What changes the method

A floored attic with stored items. Runways are in the dust on the boards and around stored boxes; boxes are harborage and need to be looked into. Openings at the eaves are often behind stored items, so ask before moving them.

A cathedral ceiling or no attic access. No inside inspection is possible. The exterior list carries the whole job, and the report says so.

Squirrels or other wildlife. Openings are larger and the exclusion must not trap an animal inside, especially young in spring. Wildlife work has its own rules and, in many states, its own license; check your state wildlife agency.

The finish test

The office has a numbered entry list with location, size, sign, access and a photo for every opening and route, the ruled-out candidates noted, and any hazard (wiring, suspect insulation) flagged separately. Someone who has never seen the house can price the exclusion from it.

References

• See related: Rodent Droppings and Hantavirus for the Trades
• See related: Attic Rodent Cleanup and Sanitation
• See related: Rodent Exclusion Materials and Opening Sizes
• See related: Pest Activity Signs Reference
• 29 CFR 1910.134, respiratory protection programs