InterNACHI Roof Inspector key terms

The vertical rise of a roof over a stated horizontal run, usually expressed as a ratio such as 4:12. Slope determines which materials and underlayments are permitted and how quickly water drains.

A roof with a slope generally at or below 3:12, commonly covered with membrane or built-up systems. Water drains slowly, so seams, ponding, and flashing details matter more than on steep roofs.

A roof steeper than roughly 3:12, typically finished with shingles, tiles, shakes, or standing-seam metal. These assemblies rely on gravity shedding plus overlapping layers rather than a fully sealed membrane.

A roofing unit made of a fiberglass or organic mat coated with asphalt and mineral granules. Inspectors note granule loss, tab sealing, nail placement, and whether the product is rated for the roof slope.

A thicker, laminated asphalt shingle with a dimensional, layered appearance and usually longer warranty than a standard three-tab. Multiple layers can hide or complicate the reading of wear and hail damage.

A sheet material such as asphalt felt or synthetic membrane installed over the deck beneath the roof covering. It provides a secondary weather barrier and is required in valleys, eaves, and low-slope areas.

The panels, usually plywood or oriented strand board, fastened over rafters or trusses to form the nailable surface for roofing. Soft, delaminated, or stained sheathing signals past or active moisture intrusion.

The internal intersection where two roof planes meet and concentrate runoff. Valleys are lined with metal or woven underlayment and are among the most common locations for leakage and debris accumulation.

Small L-shaped metal pieces interwoven with roofing courses where a sloped roof meets a sidewall or chimney. Each piece sheds water onto the course below, so missing or reversed pieces cause wall and ceiling stains.

Metal embedded in a masonry wall or chimney and bent down over the top edge of step or base flashing. It keeps water from entering behind the flashing and should be visible and tight in a proper installation.

A metal strip along eaves and rakes that directs water away from the fascia and deck edge. Its absence, or installation under rather than over the underlayment, is a frequently reported installation defect.

Any object passing through the roof plane, such as a vent pipe, skylight, chimney, or HVAC curb. Each penetration needs its own flashing system, and these are high-probability leak points during an inspection.

A preformed collar, often rubber or neoprene, that seals around a vent pipe where it exits the roof. Cracked or UV-degraded boots are a very common cause of small, hard-to-find ceiling stains.

The combination of base, step, and counter-flashing that seals a masonry chimney to the roof. Inspectors check for deteriorated mortar, missing cricket on wide chimneys, and flashing pulled loose by settlement.

A small peaked diversion built on the upslope side of a wide chimney to split water around it. Required above a certain chimney width, its absence promotes debris buildup, ice damming, and leakage.

Metal or membrane components that waterproof junctions between the roof and other surfaces, such as walls, valleys, and penetrations. Flashing defects are among the most consequential findings an inspector can report.

A trowelable asphalt-based sealant used to patch seams and seal flashing edges. Inspectors treat heavy, smeared applications as evidence of past repairs rather than as a reliable long-term repair method.

A sloped structural member that supports the roof deck, typically spaced at regular intervals. Sagging, split, or notched rafters visible from the attic help explain visible roof-plane deformation.

A prefabricated engineered framework of chords and webs that supports the roof deck. Trusses are design-specific, so field cutting or modification of any member is a reportable structural concern.

Intake and exhaust openings that move air through the space under the roof deck. Poor ventilation traps moisture, heats the deck, and contributes to condensation, ice damming, and premature shingle aging.

A projecting roofed structure containing a window or vent that interrupts the main roof plane. Dormer sidewalls, valleys, and low-slope transition areas are common trouble spots for flashing and ice damming.

A glazed opening in the roof that admits daylight. Inspectors check the curb, flashing, sealant, and interior for condensation or staining, since skylight leaks are frequent and sometimes concealed.

The planned path and capacity for water leaving the roof, including slope, valleys, gutters, and downspouts. Inadequate drainage shows up as ponding, overflow at eaves, and erosion or staining below discharge points.

A channel along the eave that collects runoff and carries it to downspouts. Loose hangers, seams, or back-sloping gutters cause fascia rot and water at the foundation, so attachment and pitch are checked.

The vertical pipe that carries gutter water to grade or a drainage system. Discharge too close to the foundation, missing extensions, or crushed sections are commonly reported and easily corrected.

The finished board along the roof edge that carries the gutter and closes the rafter ends. Softness, peeling paint, or separation visible from the ground often indicates water behind the gutter.

The underside panel at the eave, frequently perforated to admit attic intake air. Blocked or painted-over soffit vents are a common cause of inadequate attic ventilation and winter condensation.

A ridge of ice at the eave that traps meltwater and forces it under shingles. It results from warm upper roof surfaces and inadequate insulation or ventilation, and it damages both roof and interior finishes.

A self-adhering waterproof membrane installed at eaves, valleys, and penetrations before the main underlayment. It protects the deck where ice dams or wind-driven rain can force water past the roof covering.

A rolled low-slope membrane of asphalt modified with polymers, applied in layers or as a cap sheet. Inspectors look for open seams, blisters, and granule loss, especially on older or foot-trafficked areas.

A raised, bubble-like separation between roofing layers caused by trapped moisture or air expanding under heat. Blisters can break open and admit water, so their size, quantity, and condition are noted.

Standing water on a low-slope roof that remains many hours after rain. It adds load, accelerates membrane deterioration, and points to inadequate slope, clogged drains, or settled structure.

The wearing away of the mineral surfacing on asphalt shingles, exposing the asphalt beneath. Uniform loss suggests age; localized loss on slopes and ridges may indicate hail or mechanical damage.

Impact marks on roofing that can range from granule displacement to bruised or fractured mats. Because it is easily confused with normal wear, inspectors describe what they see and recommend specialist verification.

Visible sagging or unevenness in the roof plane, best judged by sighting along ridges and eaves. It can reflect undersized framing, damaged sheathing, or concentrated loads and warrants attic verification.

Any condition that impairs the roof's ability to shed water or perform as intended, from installation errors to deterioration. Reports should describe the defect, its likely consequence, and the recommended action.

Traversing the roof surface to inspect it directly. The decision depends on slope, material, weather, and the inspector's own comfort and equipment, and it is never required by the standards.

An extension or articulated ladder used to reach the eave safely. Proper three-point contact, secure footing, and a ladder extending above the eave are basic requirements before any roof access is attempted.

Equipment such as a harness, lanyard, and anchor point designed to stop a fall. It is used where fall hazards exist and must be attached to a suitable anchor, not improvised around vents or thin metal.

The published minimum expectations defining what a roof inspection includes and excludes. Following them keeps reports consistent and defensible, and they should be referenced when explaining limits on the inspection.

A stated restriction on what was inspected and why, such as snow cover, steep slope, or inaccessible areas. Documenting limitations protects both client and inspector and directs the client to further evaluation.

The written deliverable describing roof materials, observed conditions, defects, limitations, and recommendations. Clear, plain language and photographs help clients understand risk and prioritize repairs without implying a warranty.

A visual, non-invasive examination of the roof covering, flashings, drainage, and accessible related components. It is not a guarantee of condition or a prediction of remaining service life, and it is limited by access.

A material that restricts moisture vapor movement through the building assembly. Misplaced or missing vapor control in the ceiling contributes to condensation on the roof deck and to attic moisture problems.