Don't let roofing jargon confuse you. This plain-English glossary explains every term Washington homeowners need to know before hiring a contractor.
Understanding roofing terminology empowers you to communicate effectively with contractors, evaluate estimates accurately, and make informed decisions about your Washington home's most important protection system.
Roof Structure Terms
Deck (Sheathing) — The flat surface (usually plywood or OSB) that sits on top of the rafters and provides the base for all roofing materials. In Washington, moisture-resistant decking is critical due to our wet climate.
Rafters — The structural framing members that support the roof deck. In Eastern Washington, rafters must be sized to handle heavy snow loads per local building codes.
Truss — A pre-engineered framework that combines rafters, joists, and bracing into a single unit. Most modern Washington homes use trusses.
Ridge — The horizontal peak where two roof slopes meet. The ridge is the highest point of the roof.
Valley — The internal angle where two roof slopes intersect. Valleys channel water and are one of the most leak-prone areas — proper valley flashing is critical in rainy Western WA.
Eave — The lower edge of the roof that overhangs the exterior wall. Eaves help direct water away from the siding and foundation.
Rake — The sloped edge of the roof along the gable end.
Soffit — The underside of the eave overhang. Soffits provide ventilation to the attic space and should never be blocked.
Fascia — The vertical board that runs along the edge of the roof at the eave line. Gutters are typically attached to the fascia.
Roofing Material Terms
Shingle — Individual overlapping units that cover the roof surface. Available in asphalt, wood (cedar shake), composite, and other materials.
Architectural Shingles (Dimensional) — Premium asphalt shingles with a layered, textured appearance that mimics wood shake or slate. They last longer and perform better than standard 3-tab shingles.
3-Tab Shingles — Basic flat asphalt shingles with cutouts that create the appearance of three separate pieces. Lower cost but shorter lifespan.
Underlayment — A waterproof or water-resistant barrier installed directly on the roof deck beneath the shingles. Synthetic underlayment has largely replaced felt paper in Washington installations.
Ice and Water Shield — A self-adhering waterproof membrane applied to vulnerable areas (valleys, eaves, around penetrations). Required by Washington building codes in certain locations.
Flashing — Thin metal pieces installed at joints, penetrations, and transitions to direct water away. Common locations include chimneys, skylights, vents, and valleys.
Drip Edge — L-shaped metal flashing installed along the eaves and rakes to direct water into gutters and away from the fascia.
Ridge Cap — Specialized shingles or metal pieces that cover the ridge, providing a weatherproof seal at the roof's peak.
Starter Strip — The first row of roofing material at the eave, installed beneath the visible shingles to seal the edges.
Ventilation Terms
Ridge Vent — A continuous vent installed along the ridge that allows warm, moist air to escape from the attic. Paired with soffit vents for proper airflow.
Soffit Vent — Intake vents in the soffit that allow fresh air into the attic space.
Attic Ventilation — The system of intake (soffit) and exhaust (ridge) vents that keeps the attic at a consistent temperature. Proper ventilation prevents ice dams in Eastern WA and moisture damage in Western WA.
Common Problem Terms
Moss — Green plant growth that thrives on damp, shaded roof surfaces in Western Washington. Moss roots can lift shingles and trap moisture against the roof surface.
Algae — Dark streaks (often black or green) on shingles caused by Gloeocapsa magma bacteria. Common in humid Western WA climates.
Ice Dam — A ridge of ice that forms at the eave when heat escaping from the attic melts snow on the upper roof, which then refreezes at the cold eave edge. A major problem in Eastern WA.
Ponding — Standing water on flat or low-slope roofs. If water doesn't drain within 48 hours, it indicates a drainage problem.
Granule Loss — The shedding of the small ceramic particles on asphalt shingles. Some loss is normal on new roofs; excessive granules in gutters indicate shingle deterioration.
Cupping/Curling — Shingle edges that bend upward (cupping) or downward (curling), usually due to age, moisture, or ventilation problems.
Contractor & Process Terms
Tear-Off — Removing all existing roofing material down to the deck before installing new roofing. Washington codes generally limit roofs to a maximum of two layers.
Overlay — Installing new shingles directly over existing ones. Less expensive than tear-off but not always advisable — most Washington contractors recommend tear-off for best results.
Square — A unit of measurement equal to 100 square feet of roof area. Roofing materials and labor are typically priced per square.
Pitch (Slope) — The steepness of the roof, expressed as a ratio (e.g., 6/12 means the roof rises 6 inches for every 12 inches of horizontal run).
WA L&I License — Washington State Department of Labor & Industries contractor registration. All roofing contractors in WA must be registered, bonded, and insured through L&I.
Knowing these terms puts you on equal footing with any roofing contractor. When you understand what they're talking about, you can ask better questions, compare estimates more effectively, and ensure the work meets Washington's building standards.
Frequently Asked Questions
What is the most important roofing term to know?
Underlayment — it's the hidden waterproof layer between your shingles and roof deck. In Washington's wet climate, quality underlayment is the difference between a roof that lasts and one that leaks prematurely.
What does 'per square' mean in roofing?
One roofing 'square' equals 100 square feet. When a contractor quotes $350 per square, they mean $350 for every 100 sq ft of roof area.
Construction Journalist & Technical Editor
12 years covering the construction and home improvement industry. Former editor at Pacific NW Building magazine with deep expertise in WA building codes and permit processes.
