Roofing glossary.
Plain English.

Every roofing term homeowners end up Googling — defined in plain English, with the context that actually matters. 31 terms.

Roof anatomy13 Materials7 Process & measurement5 Insurance4 Weather & damage2

Roof anatomy

Decking (sheathing): The structural layer of plywood, OSB, or plank wood that the underlayment and shingles are attached to. Older Tri-Cities homes (pre-1980) frequently have plank decking; modern builds use OSB. Rotted decking is the single most common 'surprise' charge on a re-roof — typically $2–$5 per sq ft of replacement.
Drip edge: A metal flashing installed along the eaves and rakes that directs water away from the fascia and into the gutters. Required by code in Tennessee. Missing drip edge is a common cause of fascia rot.
Eave: The lower edge of the roof that overhangs the wall. The eave is where ice dams form in winter and where most water damage starts when underlayment or drip edge fails.
Fascia: The vertical board running along the lower edge of the roof, behind the gutters. Wood fascia rots from the back when gutters overflow or drip edge is missing. Replacement is often part of a re-roof scope.
Flashing: Thin metal pieces installed at joints and transitions (chimneys, walls, valleys, vents) to prevent water intrusion. Reusing old flashing on a new roof is a leak waiting to happen — every quote should include new flashing.
Hip: The external angle where two roof slopes meet at the corner of the roof. Hip roofs are more wind-resistant than gable roofs but cost more to roof because of the extra cuts and ridge cap material.
Gable: The triangular wall section at the end of a sloped roof. Gable-end homes are simpler and cheaper to roof than hip-roof homes, but more vulnerable to high-wind damage.
Ridge: The top horizontal edge of the roof where two slopes meet. The ridge is where ridge vents are installed for attic ventilation and where ridge cap shingles are placed last during installation.
Ridge vent: A continuous vent installed along the ridge that allows hot air to escape the attic. Combined with soffit vents, it creates the airflow that prevents premature shingle aging and ice dams. Most modern re-roofs in the Tri-Cities include ridge vent installation.
Soffit: The horizontal underside of the roof overhang at the eaves. Vented soffits draw cool air into the attic, balancing the ridge vent. Damaged or rotted soffits indicate ventilation problems and are often replaced with the roof.
Underlayment: A waterproof or water-resistant layer installed directly on the deck before shingles. Modern synthetic underlayment is the standard; old-school felt is cheaper but inferior. Underlayment is the secondary water barrier — when shingles fail, underlayment is what keeps your roof dry.
Valley: The internal angle where two roof slopes meet, channeling rainwater toward the gutter. Valleys are the most leak-prone part of any roof and require either ice-and-water shield underlayment or metal valley flashing.
Vent boot (pipe boot, pipe collar): The rubber or lead collar that seals around plumbing vents penetrating the roof. Vent boots typically fail before shingles do (rubber cracks in 8–15 years) and are a top source of small leaks. Replacement runs $40–$150 each.

Materials

Architectural shingle: Multi-layer asphalt shingle (also called dimensional or laminate) that's the standard in Tennessee residential roofing. Lifespan is 20–30 years depending on the product tier. Brands: Owens Corning Duration, GAF Timberline HDZ, CertainTeed Landmark.
3-tab shingle: Older flat-style asphalt shingle, generally rated 20–25 years. Cheaper to install than architectural but has lower wind ratings and less curb appeal. Rarely the right choice for a new install in 2026.
Standing seam metal: A metal roofing panel system where vertical seams run from ridge to eave with hidden fasteners. The premium metal-roof choice — 40–70 year lifespan, excellent wind resistance, $15,000–$35,000 installed for a typical Tri-Cities home.
Exposed-fastener metal (R-panel): Metal roofing with screws driven through the panels. Cheaper than standing seam but the gaskets degrade in 15–20 years and the screws need re-tightening. Common on agricultural and outbuilding roofs in rural East TN.
Ice-and-water shield: A self-adhering rubberized waterproof membrane installed at eaves, valleys, and around penetrations. Required by Tennessee code at the eaves of homes in regions where ice dams occur. Runs $300–$700 per typical home.
TPO: Thermoplastic polyolefin — a single-ply membrane used on flat and low-slope commercial roofs. Heat-welded seams, white surface for energy efficiency. The dominant flat-roof material for new installs in 2026.
EPDM: Ethylene propylene diene monomer — a black rubber single-ply membrane for flat roofs. Older than TPO, longer track record, glued or ballasted seams. Common on commercial and church roofs throughout the Tri-Cities.

Process & measurement

Tear-off: Removing the old shingles, underlayment, and damaged decking down to the substrate before installing new roofing. Tennessee allows two layers before mandatory tear-off; doing a third overlay is against code.
Overlay: Installing new shingles directly over an existing layer instead of tearing off. Cheaper upfront (saves $1,000–$2,500 in tear-off labor and dump fees) but cuts the new roof's lifespan by ~40%, hides decking problems, and creates code issues at resale. Almost always a bad deal.
Square (roofing measurement): 100 square feet of roof surface area. A typical 2,000 sq ft Tri-Cities home with a simple gable roof has roughly 22 squares. Hip roofs and dormered homes can run to 30–35 squares. Most quotes are priced per-square.
Pitch: The slope of the roof, expressed as inches of vertical rise per 12 inches of horizontal run. A 6:12 pitch is walkable; 12:12 requires roof jacks and harnesses, raising labor costs significantly.
Granule loss: The shedding of mineral granules that protect asphalt shingles from UV damage. Some loss is normal; significant accumulation at downspouts indicates the shingles are in their final 1–3 years of useful life.

Insurance

Actual Cash Value (ACV): The depreciated value of the roof at the time of loss — what insurance pays up front after a covered claim, minus your deductible. For a 12-year-old asphalt shingle roof, ACV might be 40–60% of the full replacement cost.
Replacement Cost Value (RCV): The full cost to replace the roof with materials of like kind and quality, in today's dollars. The total payout (ACV + recoverable depreciation) on a covered claim equals RCV minus your deductible.
Recoverable depreciation: The difference between ACV and RCV, paid by insurance after the work is completed and final invoices are submitted. Many homeowners forfeit this by hiring contractors who quote below RCV — the carrier won't release depreciation that the work didn't justify.
Wind/hail deductible: A separate, usually higher deductible specifically for wind and hail claims, listed on your declarations page. Often expressed as a percentage of dwelling coverage (1–2%) rather than a flat dollar amount. A 2% wind/hail deductible on a $400k dwelling is $8,000.

Weather & damage

Hail damage: Functional damage to shingles caused by hailstones, typically over 1 inch in diameter. Visible signs include bruises (soft spots), granule loss patterns, cracked shingles, and damaged metal accessories. Adjusters use 'test squares' to project total damage across the roof.
Ice dam: A ridge of ice that forms at the eaves when warm attic air melts roof snow that then refreezes at the colder edge. The dammed water backs up under shingles and into the home. Prevention: proper attic insulation, ventilation, and ice-and-water shield at eaves.

Roofing glossary.Plain English.

Roof anatomy

Materials

Process & measurement

Insurance

Weather & damage

Roofing glossary.
Plain English.