InterNACHI Roof Inspector cheat sheet

Asphalt shingles are graded by weight and reinforcement: organic-mat (felt) shingles are older and heavier; fiberglass-mat shingles dominate current production and carry class A fire ratings when properly installed.

Standard 3-tab shingles have a nominal 12-inch exposure with 36-inch-long strips; architectural (laminated) shingles use two laminated plies and typically carry 25- to 50-year manufacturer warranties.

Underlayment: asphalt-saturated felt comes in No. 15 (approx. 15 lb per 100 sq ft) and No. 30 grades; synthetic underlayments are lighter, tear-resistant, and usually slip-resistant when wet.

A "square" of roofing equals 100 square feet of roof area; bundles per square vary by product (commonly 3 bundles for 3-tab, 3-5 for architectural).

Metal roofing categories: standing seam (concealed fasteners, raised seams), through-fastened panels (exposed screws with washers), and metal shingles/tiles; minimum slope requirements differ by profile and seam type.

Clay and concrete tile require a minimum slope (commonly 2.5:12 or steeper depending on underlayment system) and rely on battens or direct fastening plus a secondary water barrier.

Wood shakes are split; wood shingles are sawn. Both need spaced sheathing or solid decking per code and are commonly limited to slopes of 3:12 or steeper for shakes.

Roofing components to identify: deck/sheathing, underlayment, drip edge, valley flashing, step flashing, counterflashing, ridge and hip caps, vents, boots, and ice/water shield at eaves in cold climates.

Slate is graded by thickness and grading (e.g., standard, graduated); fastening method (nail vs. hook) and headlap determine weather resistance, and repairs require matching thickness and hole placement.

OSHA fall-protection trigger for general industry construction work is 6 feet; residential roofing work commonly requires guardrails, safety nets, or personal fall-arrest systems when that height is exceeded.

Ladder setup rule: 4:1 ratio (1 foot out for every 4 feet of working height), extending at least 3 feet above the roof edge or landing surface, on firm level ground.

Ladder duty ratings: Type III (200 lb), Type II (225 lb), Type I (250 lb), Type IA (300 lb), Type IAA (375 lb); the rating plus the inspector's tools and body weight must stay within limits.

Walking a roof is optional, not required, under most standards of practice; the inspector may use binoculars, a ladder at the eaves, or a pole camera and must state the method used.

Unsafe-to-walk conditions: wet or frosty surfaces, moss or algae film, steep slopes (commonly above 6:12 without harness), fragile coverings (clay tile, slate, aged wood), and deteriorated decking.

Electrical hazard: keep ladders and tools at least 10 feet from energized overhead power lines; metal ladders near service drops are a recognized electrocution risk.

Three-point contact on ladders: two hands and one foot, or two feet and one hand, at all times; face the ladder and do not carry loads that prevent grip.

Chimney and skylight fall hazards: never step on skylights or fragile plastic domes; treat them as openings and route around them.

Granule loss on asphalt shingles shows as bare patches or granules in gutters; causes include age, foot traffic, hail, and manufacturing defects, and it signals reduced remaining life.

Hail damage on asphalt shingles appears as random, soft, dark spots ("bruising") where granules are displaced; test by pressing; distinguish from blistering and mechanical damage.

Wind damage: creased or torn shingles, missing tabs, lifted or unsealed edges; check sealant strips and note that unsealed shingles can be lifted by modest winds.

Water intrusion paths: failed flashing at chimneys, valleys, and sidewalls; missing kick-out flashing at roof-to-wall terminations; deteriorated pipe boots; and ice-dam backup at eaves.

Ice dams form when warm upper roof areas melt snow that refreezes at cold eaves; indicators include icicles, stained soffits, and interior staining near exterior walls.

Attic ventilation rule of thumb: roughly 1 square foot of net free ventilation per 150 square feet of attic floor when no vapor retarder is present (1/300 with a proper vapor retarder), balanced between intake and exhaust.

Poor ventilation and warm, moist interior air cause condensation, sheathing rot, delamination, and frost on roof deck underside in cold climates.

Structural defects: sagging ridges, uneven rafter lines, cracked or rotted sheathing, and ponding water on low-slope roofs indicate framing or drainage problems.

Biological growth: moss holds moisture and lifts shingle edges; algae (Gloeocapsa magma) causes dark streaking; lichen and mildew indicate prolonged moisture exposure.

A roof inspection report describes the roof covering, its approximate age if known, observed defects, the method of inspection (walked, eave-level, binoculars, drone), and any limitations.

Standards of practice commonly require the inspector to report the roof covering material and type, and to describe observed conditions that materially affect performance.

Inspectors are generally not required to predict remaining service life, warranty coverage, or code compliance; recommendations for further evaluation by a specialist are appropriate.

Report language should be factual and condition-based ("observed," "appears," "not visible") rather than conclusive about causation or cost.

Photographs should be dated, labeled by location, and referenced in the narrative; include wide shots for context and close-ups for defects.

Limitations to disclose: areas not accessed, snow or debris cover, unsafe conditions, and concealed components such as underlayment and flashing beneath the covering.

Report defects by location and severity: missing/damaged shingles, flashing defects, active leaks or staining, and drainage issues, with recommended action (monitor, repair, evaluate).

Maintain a consistent report structure: description, observations, limitations, recommendations; use plain language the client can act on and avoid alarming or minimizing tone.

Asphalt shingles are graded by weight and reinforcement: organic-mat (felt) shingles are older and heavier; fiberglass-mat shingles dominate current production and carry Class A fire ratings when properly installed.

Standard 3-tab shingles have a nominal 12-inch exposure with 36-inch-long strips; architectural (laminated) shingles use two laminated plies and typically carry 25- to 50-year manufacturer warranties.

Underlayment: asphalt-saturated felt comes in No. 15 (about 15 lb per 100 sq ft) and No. 30 grades; synthetic underlayments are lighter, tear-resistant, and usually slip-resistant when wet.

A square of roofing equals 100 square feet of roof area; bundles per square vary by product (commonly 3 bundles for 3-tab, 3-5 for architectural).

Metal roofing categories: standing seam (concealed fasteners, raised seams), through-fastened panels (exposed screws with washers), and metal shingles or tiles; minimum slope requirements differ by profile and seam type.

Clay and concrete tile require a minimum slope (commonly 2.5:12 or steeper depending on underlayment system) and rely on battens or direct fastening plus a secondary water barrier.

Wood shakes are split; wood shingles are sawn. Both need spaced sheathing or solid decking per code and are commonly limited to slopes of 3:12 or steeper for shakes.

Roofing components to identify: deck or sheathing, underlayment, drip edge, valley flashing, step flashing, counterflashing, ridge and hip caps, vents, boots, and ice or water shield at eaves in cold climates.

Slate is graded by thickness and grading (for example standard or graduated); fastening method (nail versus hook) and headlap determine weather resistance, and repairs require matching thickness and hole placement.

OSHA fall-protection trigger for general industry construction work is 6 feet; residential roofing work commonly requires guardrails, safety nets, or personal fall-arrest systems when that height is exceeded.

Ladder setup rule: 4:1 ratio (1 foot out for every 4 feet of working height), extending at least 3 feet above the roof edge or landing surface, on firm level ground.

Ladder duty ratings: Type III (200 lb), Type II (225 lb), Type I (250 lb), Type IA (300 lb), Type IAA (375 lb); the rating plus the inspector's tools and body weight must stay within limits.

Walking a roof is optional, not required, under most standards of practice; the inspector may use binoculars, a ladder at the eaves, or a pole camera and must state the method used.

Unsafe-to-walk conditions: wet or frosty surfaces, moss or algae film, steep slopes (commonly above 6:12 without harness), fragile coverings (clay tile, slate, aged wood), and deteriorated decking.

Electrical hazard: keep ladders and tools at least 10 feet from energized overhead power lines; metal ladders near service drops are a recognized electrocution risk.

Three-point contact on ladders: two hands and one foot, or two feet and one hand, at all times; face the ladder and do not carry loads that prevent grip.

Chimney and skylight fall hazards: never step on skylights or fragile plastic domes; treat them as openings and route around them.

Granule loss on asphalt shingles shows as bare patches or granules in gutters; causes include age, foot traffic, hail, and manufacturing defects, and it signals reduced remaining life.

Hail damage on asphalt shingles appears as random, soft, dark spots (bruising) where granules are displaced; test by pressing; distinguish from blistering and mechanical damage.

Wind damage: creased or torn shingles, missing tabs, lifted or unsealed edges; check sealant strips and note that unsealed shingles can be lifted by modest winds.

Water intrusion paths: failed flashing at chimneys, valleys, and sidewalls; missing kick-out flashing at roof-to-wall terminations; deteriorated pipe boots; and ice-dam backup at eaves.

Ice dams form when warm upper roof areas melt snow that refreezes at cold eaves; indicators include icicles, stained soffits, and interior staining near exterior walls.

Attic ventilation rule of thumb: roughly 1 square foot of net free ventilation per 150 square feet of attic floor when no vapor retarder is present (1/300 with a proper vapor retarder), balanced between intake and exhaust.

Poor ventilation and warm, moist interior air cause condensation, sheathing rot, delamination, and frost on roof deck underside in cold climates.

Structural defects: sagging ridges, uneven rafter lines, cracked or rotted sheathing, and ponding water on low-slope roofs indicate framing or drainage problems.

Biological growth: moss holds moisture and lifts shingle edges; algae (Gloeocapsa magma) causes dark streaking; lichen and mildew indicate prolonged moisture exposure.

A roof inspection report describes the roof covering, its approximate age if known, observed defects, the method of inspection (walked, eave-level, binoculars, drone), and any limitations.

Standards of practice commonly require the inspector to report the roof covering material and type, and to describe observed conditions that materially affect performance.

Inspectors are generally not required to predict remaining service life, warranty coverage, or code compliance; recommendations for further evaluation by a specialist are appropriate.

Report language should be factual and condition-based (observed, appears, not visible) rather than conclusive about causation or cost.

Photographs should be dated, labeled by location, and referenced in the narrative; include wide shots for context and close-ups for defects.

Limitations to disclose: areas not accessed, snow or debris cover, unsafe conditions, and concealed components such as underlayment and flashing beneath the covering.

Report defects by location and severity: missing or damaged shingles, flashing defects, active leaks or staining, and drainage issues, with recommended action (monitor, repair, evaluate).

Maintain a consistent report structure: description, observations, limitations, recommendations; use plain language the client can act on and avoid alarming or minimizing tone.