Roofing terms, A to Z
The roofing wiki: roofing terms explained for the people who pay for the roof
Forty entries, one per term, each with a definition that links to its source, a plain account of why the thing matters, and a note on what it costs and who does the work. Written for homeowners and property managers, not for the trade.
Updated September 12, 2026 · Every figure links to its source · Sources
Roofing terms, A to Z
Forty entries. Each opens with a sourced definition and ends with where to find a contractor for the work.
A
- Architectural shingles · Material
Asphalt shingles built from two or more laminated layers, giving a thicker, shadowed look than a flat three-tab shingle.
B
- Built-up roofing · System
A low-slope roof membrane built on site from alternating layers of bitumen and reinforcing felt, usually topped with gravel.
D
E
- Eave · Component
The lower, horizontal edge of a sloped roof, usually projecting past the wall; finished with a fascia and a soffit.
- EPDM roofing · System
A single-ply membrane of ethylene propylene diene terpolymer, a synthetic rubber, laid in large sheets on low-slope roofs.
F
- Fascia · Component
The vertical board fixed across the ends of the rafters at the roof edge, closing the eave and carrying the gutter.
- FORTIFIED roof · Standard
An IBHS designation for a roof installed with a sealed deck, ring-shank nails, stronger edges and rated covers, verified by an evaluator.
G
- Gable roof · Shape
A roof of two sloping planes meeting at a ridge, closed at each end by a triangular wall called the gable.
- Gable vent · Component
A louvered, screened opening set in a gable end wall to let air move through the attic.
- Gambrel roof · Shape
A two-sided roof with two slopes on each side — a steep lower slope and a shallower upper one — leaving a large space beneath.
- Green roof · System
A roof assembly with a waterproof membrane, root barrier, drainage layer, growing medium and plants; extensive (shallow) or intensive (deep).
H
- Hail damage · Defect
Damage to a roof covering from hailstones: bruised or fractured shingles, granule loss, dented metal and cracked tile or skylights.
- Hip roof · Shape
A roof that slopes on all four sides, the sides meeting at inclined external corners called hips; it has no gable ends.
I
- Ice and water shield · Component
A self-adhering polymer-modified bitumen sheet applied under the roof covering at eaves, valleys and penetrations.
- Ice dam · Defect
A ridge of ice that forms at the eave when snow melted by attic heat refreezes at the cold edge, ponding water behind it.
L
- Low-slope roof · Roof type
A roof with too little slope for shingles or tiles, covered instead with a continuous membrane and designed to drain rather than shed.
M
- Mansard roof · Shape
A four-sided roof with two slopes on every side, the lower slope steep and the upper slope shallow, enclosing a full storey.
- Modified bitumen · System
A factory-made asphalt roof membrane with polymer modifiers (APP or SBS) and a reinforcing mat, supplied in rolls for low-slope roofs.
P
- Parapet · Component
The portion of an exterior wall that extends above the roof surface, capped with a coping and flashed where it meets the roof.
- Pipe boot · Component
A flashing for a round pipe through the roof: a flat base flange under the shingles with a raised collar that seals against the pipe.
- Purlin · Component
A horizontal structural member in a roof: under wood rafters, a braced timber that reduces their span; in metal roofing, the member panels fasten to.
R
- Rafter · Component
One of the sloped structural members running from the ridge to the eave that support the roof deck and its loads.
- Rake · Component
The sloped edge of a roof at a gable end, running from the eave up to the ridge; finished with a rake board and drip edge.
- Ridge vent · Component
A continuous exhaust vent installed over a slot cut along the roof ridge, capped with shingles, that lets attic air escape at the highest point.
- Roof cricket · Component
A small peaked structure built on the uphill side of a chimney or other projection to divert water around it.
- Roof decking · Component
The structural panels or boards fastened over the rafters or trusses that carry the roof covering and everything on it.
- Roof flashing · Component
Pieces of sheet metal or membrane that waterproof the joints where a roof meets walls, chimneys, valleys and penetrations.
- Roof inspection · Process
A documented examination of a roof’s covering, flashings, penetrations, drainage and attic to find defects and estimate remaining life.
- Roof pitch · Measurement
The steepness of a roof, expressed as inches of vertical rise per twelve inches of horizontal run, e.g. 6:12.
- Roof truss · Component
A factory-built frame of top chords, a bottom chord and webs, joined with metal connector plates, spanning wall to wall to carry the roof.
- Roof valley · Component
The internal angle formed where two sloping roof planes meet, along which the water from both drains; lined with metal or membrane.
- Roofing contractor · Trade
A contractor who installs, repairs and replaces roof coverings and their flashings, underlayment and decking, under a permit where one is required.
- Roofing square · Measurement
The roofing trade’s unit of area: 100 square feet of roof surface. Materials and labour are priced per square.
S
- Skylight · Component
A glazed opening set in a roof to admit daylight, either mounted on a raised curb or set directly on the deck, and flashed into the covering.
- Soffit · Component
The finished underside of a roof overhang, closing the space between the fascia and the wall; usually vented for attic intake air.
- Soffit vent · Component
An intake ventilation opening in the eave soffit — a continuous strip, individual louvers or perforated panel — that admits outside air to the attic.
- Standing seam metal roof · System
A metal roof of vertical panels whose edges are joined at raised seams above the drainage plane, held by concealed clips rather than exposed screws.
T
- TPO roofing · System
A single-ply thermoplastic polyolefin membrane, usually white, with heat-welded seams; the commonest new low-slope roofing in the U.S.
U
- Underlayment · Component
A water-resistant sheet — felt, synthetic or self-adhering — laid over the roof deck under the covering as a secondary weather barrier.
How to read an entry
Every entry opens with a definition. Where the roofing trade has an agreed meaning, the definition follows the NRCA roofing glossary; where a building code sets the rule, it follows the International Residential Code or the International Building Code, and the section is named so you can check it. The source is linked on the sentence itself, not buried in a footnote.
The sections that follow answer the three questions a homeowner actually has: what the thing is and where it sits on the roof, why it matters (what fails when it is missing or wrong), and what it costs and who does the work. The cost sections describe how a job is priced and which trade does it; they do not quote prices, because a roof price depends on the roof. Where the National Roofing Directory publishes a cost guide or a how-to for the term, the entry links to it.
Entries are grouped by kind: components (drip edge, fascia, flashing), systems (TPO, standing seam, built-up roofing), shapes (hip, gable, gambrel), defects (ice dam, hail damage), processes (roof inspection) and the trade itself. The kind is shown beside each name in the index below.
What this wiki is not
It is not a manual for installing a roof, and it is not a substitute for the code that applies where you live. The IRC and IBC are model codes; each state and many cities adopt them with amendments and on their own schedule, so the section an entry cites is the model text, and the local version governs. Your building department can tell you which edition is in force.
It also carries no reviews, ratings or recommendations of any contractor. When an entry ends with a link to find a roofer, it goes to the National Roofing Directory's contractor listings, where a contractor's licence can be checked against the state board — the directory keeps a state-by-state licensing reference for that purpose.
Frequently asked questions
Short answers; the sections above carry the detail and the sources.
Who writes the roofing wiki?
Are the code sections quoted here the law where I live?
Why are there no prices?
How do I find a roofer once I know what I need?
Next step
Find a roofer who does this
Once you know the name of the part or the system, the next step is a contractor who does that work. The National Roofing Directory lists roofing contractors by state and city, with the details you can cross-check against the state licensing board.
Sources
- Roofing glossary — National Roofing Contractors Association (NRCA)
- 2021 International Residential Code, Chapter 9: Roof Assemblies — International Code Council (ICC)
- 2021 International Building Code, Chapter 15: Roof Assemblies and Rooftop Structures — International Code Council (ICC)