Roofing Glossary: The Terms, Plainly Defined

Reference

The roofing glossary

50 terms, defined the way estimators, inspectors, and the measurement report actually use them. Every term has a stable link, so a definition can be cited on its own.

15 terms

Roof anatomy

The parts every steep-slope roof has, named the way estimators and inspectors name them.

Ridge#: The horizontal line where two roof planes meet at the top. Ridges are typically finished with cap material and often carry ventilation.
Hip#: A sloped external line where two roof planes meet, running from the ridge down to the eave. A hip roof has no gables; its planes slope on all sides.
Valley#: The internal line where two roof planes meet and water concentrates. Valleys carry more water than any other line on the roof, which is why their detailing matters so much.
Eave#: The lower horizontal edge of a roof plane, where water leaves the roof, usually into a gutter. Drip edge metal protects the edge of the decking here.
Rake#: The sloped edge of a roof plane at a gable end, running from eave to ridge.
Fascia#: The vertical trim board at the roof edge, behind the gutter. Staining or peeling here is one of the ground-level signs worth recording. Roof self-check
Soffit#: The underside of the roof overhang. Soffits often carry intake vents that feed the attic's airflow.
Decking (sheathing)#: The structural boards or panels the roof covering is fastened to. Decking condition is only established from up close, which is one reason an on-site inspection outranks any aerial estimate.
Underlayment#: The water-resistant layer between the decking and the roof covering. On tile roofs the underlayment does much of the waterproofing and ages on a shorter clock than the tile above it. Tile roofing
Facet#: One continuous plane of roof. A simple gable roof has two facets; complex roofs can have dozens, and facet count is one input to a waste estimate. Roof measurement
Pitch (rise over run)#: Roof steepness expressed as inches of vertical rise per 12 inches of horizontal run: a 6/12 roof rises 6 inches per foot. Pitch decides which roof systems are appropriate and how work is priced and staged.
Gable#: The triangular wall section under the end of a ridge, between two rakes.
Drip edge#: Metal flashing at eaves and rakes that directs water off the edge and protects the decking's edge grain.
Ridge cap#: The finish material covering the ridge line. Lifted or missing caps after wind are visible from the ground and worth recording.
Penetration#: Anything that passes through the roof plane: pipes, vents, flues, skylights. Every penetration is a detail that has to be flashed, and details are where most leaks start.

7 terms

Flashing and details

The metalwork where roof planes meet walls and each other. Most leaks are detail failures, not field failures.

Step flashing#: Individual L-shaped metal pieces woven into each course of roofing where a sloped roof meets a wall. Each piece laps the one below so water steps down and out, never behind.
Counterflashing#: A second layer of metal set into or against the wall above step flashing, covering its top edge so water cannot get behind the assembly.
Reglet#: The groove cut or formed into a wall or chimney that counterflashing locks into.
Apron (head-wall) flashing#: The flashing where the top of a roof plane meets a vertical wall, bridging the joint so water runs onto the roof surface.
Kick-out flashing#: The small angled piece at the bottom of a roof-to-wall intersection that throws water into the gutter instead of letting it run down the wall face. Missing kick-outs are a classic source of hidden wall damage.
Pipe boot#: The flashing collar that seals around a plumbing vent pipe. Cracked boots are one of the most common single-point leak sources on aging roofs.
Secondary water barrier#: A sealed layer at the decking, taped seams or a peel-and-stick membrane, that resists water entry even if the covering above is lost. A recognized wind-mitigation feature in Florida.

8 terms

Steep-slope systems

The covering families for pitched roofs, in the same terms the roof-systems library uses.

Architectural (dimensional) shingle#: Asphalt shingles built from laminated layers for a thicker profile and higher wind ratings than older three-tab designs. The most common residential covering in the markets we serve. Architectural shingles
Granules#: The mineral surface of an asphalt shingle, protecting the asphalt beneath from UV. Granules collecting in gutters or below downspouts are a ground-level sign of shingle wear or impact.
Standing seam metal#: Metal roofing whose panels join at raised, interlocking seams with concealed fasteners, so no fastener heads penetrate the weather surface. Standing seam metal
PVDF (Kynar) finish#: A high-performance factory paint system for metal roofing, known for fade and chalk resistance. Kynar 500 is a widely licensed PVDF resin brand.
Stone-coated steel#: Steel panels formed to the profile of tile or shake and finished with bonded stone granules, pairing a tile look with metal's weight and wind behavior.
Clay tile#: Fired clay roofing, including barrel and S-profiles. Long-lived as a material; the underlayment beneath it does much of the waterproofing and is evaluated separately. Tile roofing
Concrete tile#: Molded concrete roofing tiles in flat and profiled shapes. Heavier than most coverings, which makes structure part of any tile conversation.
Synthetic slate#: Engineered polymer or composite tiles that reproduce the look of natural slate at a fraction of its weight.

9 terms

Low-slope systems

Commercial and flat-roof terms. The site's low-slope guide covers how these systems are chosen.

Low-slope roof#: A roof at 2/12 pitch or under, which sheds water slowly enough to need a membrane or continuous system rather than overlapping shingles or tile. The measurement report separates low-slope area for exactly this reason. Commercial low-slope systems
Single-ply membrane#: A roofing membrane installed in one layer, typically TPO, PVC, or EPDM, with seams welded or seamed to form a continuous surface.
TPO#: Thermoplastic polyolefin, a heat-weldable single-ply membrane, usually white and reflective. One of the most common low-slope systems installed today. TPO single-ply
EPDM#: A synthetic rubber membrane, usually black, with decades of service history on low-slope roofs.
Modified bitumen#: Asphalt sheets modified with polymers (commonly SBS) and installed in overlapping plies, torch-applied, self-adhered, or set in adhesive. Modified bitumen
SBS#: Styrene-butadiene-styrene, the rubber polymer used to make modified bitumen flexible and tolerant of building movement.
Roof coating#: A fluid-applied layer that restores or extends an existing low-slope roof. Eligibility depends on moisture and adhesion testing of what is underneath, never on the coating alone. Roof coatings
Ponding#: Water still standing on a low-slope roof roughly 48 hours after rain. Recurring ponding accelerates wear on most systems and points at a drainage problem worth diagnosing.
Scupper#: A drainage opening through a parapet wall or roof edge that lets water leave a low-slope roof, often feeding a downspout.

6 terms

Measurement terms

The vocabulary of the roof measurement report and the aerial tools, defined the way the methodology page uses them.

Roofing square#: 100 square feet of roof area. Roofing is estimated, ordered, and priced in squares: a 2,400 square-foot roof is 24 squares.
Waste factor#: The percentage added over measured area to cover cuts, starters, caps, and complexity when ordering material. Guidance, not an order: the documented on-site measurement and the chosen system decide final quantities.
Aerial roof measurement#: A roof measured from aerial elevation data and imagery rather than a tape on the roof. Useful for early conversations and planning; never a surveyed takeoff, a price, or a contract quantity. How the measurement works
Lidar#: Light detection and ranging: aerial laser scanning that produces precise elevation points. Public lidar surveys are the elevation source behind aerial roof measurement.
Digital surface model (DSM)#: An elevation grid of everything the aerial survey saw, rooftops included. Plane-fitting against the DSM inside a confirmed boundary is how facets and pitch are recovered.
Confidence tier#: The measurement report's honesty grade. Tiers A and B include the supported edge network; tier C means the data could support area and squares only, so the report shows only that.

5 terms

Storm and documentation terms

Terms from the storm tools and the documentation process, with the same boundaries the tools state.

Local storm report#: A public National Weather Service record of an observed hail or wind event at a point and time. Reports document what was observed nearby; they never establish that a specific roof was damaged. Storm history tool
Emergency tarping (mitigation)#: Temporary covering installed to stop active water entry until permanent repair. Mitigation protects the building and is distinct from the repair scope that follows. Emergency roofing
Documented inspection#: An inspection that produces a written record: what was physically examined, photographs tied to each finding and location, and a recommendation in writing. The standard this site points every estimate toward. Request an inspection
Carrier-ready documentation#: Storm documentation organized so an insurance carrier can evaluate it: dated photos, locations, and observed conditions. Whether damage is covered remains the insurer's decision under the policy. Storm restoration
Wind mitigation features#: Construction details that reduce wind damage risk, such as improved roof-to-wall connections and a secondary water barrier. In Florida these features are commonly documented for insurance purposes during a dedicated inspection.

When the term meets your roof

Definitions end where inspection begins

A glossary tells you what step flashing is; only a documented inspection tells you what yours is doing. Call (888) 669-7663 (888-NOW-ROOF) or request a documented inspection.