Carpenter Ants at the Rafter Tails: What an Inspection Finds

A roof inspection usually focuses on shingles, flashing and the deck. Some of the most useful findings sit inside the eave, where a carpenter ant colony or a long run of moisture has softened the rafter tails, the short ends of the rafters that stick out past the wall line and hold up the soffit. When an inspector finds this, the roof surface may look fine, but something under the edge has been wet for a long time. This page explains what the inspector is looking for, what it means, and what you should be able to see in the written report.

Inspection

Carpenter ants do not eat wood the way termites do. They excavate it, pushing out small piles of shavings mixed with insect parts. Pest control operators call that material frass. On a roof inspection it usually shows up as a fine, sawdust-like pile on a soffit board, on top of a gutter, or on a window sill near the eave, or as a dusting in the attic under the rafter tails. Pale, dry frass may be old. Fresh frass tends to look clean and loose, and on a warm afternoon you may see a line of ants moving along the same path.

The reason they are there is almost always moisture. Ants pick wood that is already damp or soft, often from a slow leak at a valley, a pipe boot, or a gutter that has overflowed behind the fascia for years. The ants are the symptom. The water is the cause, and the inspector's job is to trace that water back to its source on the roof.

Where the wet wood hides

Rafter tails are the most common place. They run out past the exterior wall, usually under the soffit, and the soffit hides them from the ground. A ladder inspection lets the inspector look at the underside of the soffit board and sometimes at a gap where the soffit meets the fascia. A soft tail often has a dark stain running along its grain, and the paint may be blistered or peeling in a line.

The roof sheathing at the eave is the second place to check. Where the overhang is wide, the edge of the deck can take water that blows in under the drip edge or runs back from a clogged gutter. If the inspector gets into the attic, the sheathing edge along the eave should be checked from above and below. A dark edge with a soft feel, or a stain that follows the rafter line down toward the wall, tells the inspector that water has been reaching the wood for a while.

The third place is the fascia board at the rake, where wind-driven rain gets in and where gutter brackets hold the trim. A rotten fascia can look fine from the ground because the paint hides the damage. A probe test is what separates sound wood from failing wood.

What the inspector does with a screwdriver

A flat-blade screwdriver is the usual tool. The inspector pushes the tip into the wood at the suspected spot. Sound wood resists. Soft wood gives way, and when it does, the tip leaves a dent or a small hole. An inspector who finds this should not guess at the depth. They should record where the probe went in, how far it went, and whether the wood around it felt dry or wet.

The probe test does not answer every question. A tail can be soft on the outside and sound at the core, and a sound-looking tail can still have ants inside it. For that reason, a probe result is a finding that calls for more looking, not a final answer. If the wood is clearly failing, the next step is opening the soffit, and that becomes a repair question that goes beyond the roof covering alone.

Moisture meters help too. A pin meter reads damp wood, and the inspector should say what the reading was and where it was taken. A number without a location is not much use, so ask that the readings be listed with the spot they came from.

What the photo file should show

A good inspection file for this problem has four kinds of image. First, a wide shot of the eave from the ground that shows the soffit and fascia in one frame. Second, a close shot of any frass pile or ant trail, with a ruler or a coin beside it so the size is clear. Third, the probe mark, taken straight on with the screwdriver still in frame if possible. Fourth, a view of the same rafter tail or sheathing edge from the attic, so the same spot can be matched from both sides.

The written scope should name the location in plain words, such as north eave over the bedroom, third rafter from the corner. Vague locations like "the back of the house" are hard to act on later. If the photos are numbered, the scope should refer to them by number.

What this does not tell you

Finding frass does not tell you how many ants there are, and it does not tell you the colony is gone after a treatment. Killing the ants is a pest control job, and pest control is a separate trade from roofing. A roofer can document the damaged wood and the water path, and can repair the wood and the flashing that let the water in. The colony belongs to a pest control operator, and if one treats your home, ask for the treatment record in writing.

A roof inspection also cannot tell you whether the wood will hold once the moisture stops. Some soft rafter tails dry out and stay usable. Others need to be sistered or replaced. That decision depends on how much of the wood is affected and where the load goes, and it should be stated in the written scope rather than assumed.

What it costs

The inspection itself is priced by the contractor, and you should ask whether it is included in a repair or billed on its own. If the inspector finds rafter or fascia damage, the wood repair belongs on its own line, separate from the roof covering. Ask each contractor to price those lines separately so you can see what the shingles cost and what the wood cost. Pest treatment is a separate bill from a separate company. Keys documents damage with photos and measurements and puts a written scope in your hands, and the cost of any repair should appear as its own item in that scope.

What to ask

• Which spots did the inspector probe, and what did each probe show?
• Was the frass checked for fresh activity, and how did the inspector judge its age?
• Is the water path to the wood traced to a source on the roof, such as a valley, a pipe boot, or a gutter?
• Are the photos numbered, and does the scope refer to them by number?
• If wood is to be replaced, is that a separate line with its own price?
• Who handles the ants, and will you get the treatment record in writing?

Ask for these answers before you sign anything. If the inspector cannot say where the probe went in, the file is not finished. To book an inspection, call Keys Roofing at (314) 220-2333.