Roofing Terms & Architectural Glossary

Also known as dimensional or laminated shingles. Premium asphalt shingles composed of multiple bonded fiberglass layers, providing deep shadow lines mimicking natural slate or wood shakes and resisting winds up to 130 mph.

The unconditioned space directly beneath the roof framing and above the uppermost ceiling. Proper attic ventilation is critical to manage temperature, prevent moisture condensation, and avoid ice dams.

An angled notch cut into the bottom edge of a common rafter that allows it to seat flat and securely across the horizontal top plate of an exterior load-bearing wall.

A standardized package of shingles sold by manufacturers. For standard architectural and 3-tab shingles, exactly three bundles cover one roofing square (100 square feet) of roof surface area.

The top hail resistance rating established under UL 2218, certifying that shingles can survive consecutive impacts from a 2-inch steel ball dropped from 20 feet without cracking the backing mat.

The highest fire-resistance rating recognized by ASTM E108 and UL 790. Materials with Class A ratings provide severe fire protection against exterior flame exposure and do not propagate flame spread.

A horizontal lumber framing tie connecting opposing rafters within the upper third of the roof height. Collar ties prevent rafters from separating at the ridge during high uplift winds.

A secondary metal flashing strip embedded into a masonry mortar joint or wall reglet that hangs downward over the base or step flashing to prevent driving water infiltration.

A small elevated ridge structure constructed on the high-side roof deck behind a wide chimney or roof penetration to divert rainwater and debris around the structure.

The permanent static weight of all structural building materials supported by the roof framing, including trusses, rafters, plywood sheathing, underlayment, and roof coverings (expressed in lbs/sq ft).

A structural roof projection containing a vertical window that extends outward from the sloping roof surface. Dormers enhance natural light and living space but add hips, valleys, and flashing complexity.

A corrosion-resistant L- or T-shaped metal flashing strip installed along eaves and rake edges. Mandated by IRC R905.2.8.5 to direct water runoff directly into gutters without saturating the fascia board.

The horizontal lower perimeter of a roof that overhangs the exterior walls, typically housing the soffit intake vents and gutter catchment system.

A heavy-duty vulcanized synthetic rubber elastomeric membrane widely specified on flat and low-slope roofs (0.25:12 to 2:12 pitch) known for exceptional resistance to UV radiation and thermal shock.

The portion of a roofing shingle, slate, or tile exposed to the weather and left uncovered by the overlapping course above it. Standard architectural shingles feature a 5-5/8 inch exposure.

The flat vertical wooden, composite, or aluminum board attached to the rafter tails along the eave line, serving as the structural mounting surface for gutters.

Galvanized steel, copper, or aluminum sheet metal formed and installed to divert water away from roof junctions, valleys, chimneys, vent pipes, and vertical sidewalls.

A traditional dual-pitch roof design featuring two sloping roof planes that ascend to meet at a central horizontal ridge, creating triangular gable end walls.

A classic barn roof characterized by two distinct slopes on either side of the ridge, where the lower slope is dramatically steeper than the upper slope to maximize upper loft headroom.

The diagonal framing lumber spanning from the exterior wall corner to the ridge board at the junction where two adjacent sloping roof planes form an external hip ridge.

A four-sided roof structure where all planes slope downward toward the exterior eaves without vertical gables, offering superior aerodynamic stability in hurricane-prone zones.

A self-adhering, polymer-modified bitumen membrane applied directly to roof decking along eaves, valleys, and rakes. Required by IBC 1507 to seal around fastener shanks and prevent ice-dam leaks.

A shortened rafter that connects a wall plate to a hip rafter (hip jack), a ridge to a valley rafter (valley jack), or a hip to a valley (cripple jack).

The temporary, transient load placed upon a roof during maintenance, inspection, or construction by personnel, tools, and temporary equipment (distinct from environmental snow or wind loads).

A French curb-style four-sided roof featuring a double slope on each side, where the lower pitch is nearly vertical and incorporates dormer windows, creating a full living story.

The unobstructed open cross-sectional area through which air can pass freely through a soffit, gable, or ridge vent. Governed by the 1:150 or 1:300 balanced ventilation building code ratio.

An engineered structural wood panel manufactured by compressing cross-oriented wood strands with waterproof exterior adhesives. The most common modern residential roof decking.

The horizontal extension of the roof structure that extends past the exterior wall framing, shielding windows and siding from rainfall.

The incline or steepness of a roof plane, expressed as the number of inches of vertical rise per 12 inches of horizontal run (e.g., a 6/12 pitch rises 6 inches for every 12 inches horizontal).

A heavy-duty structural wood panel made of thin cross-laminated veneer sheets bonded with waterproof exterior glue. A premium alternative to OSB for roof sheathing.

A horizontal structural beam installed perpendicular to rafters or roof trusses, supporting roof decking or metal standing-seam panels in post-frame and commercial construction.

Polyvinyl Chloride single-ply thermoplastic membrane engineered for flat roofs. Known for heat-welded watertight seams, chemical resistance, and Class A fire performance.

An inclined framing member spanning from the exterior wall plate to the central ridge beam, directly supporting the roof deck sheathing and dead loads.

The sloped outer edge of a gable roof plane extending upward from the eave overhang to the ridge apex.

The highest horizontal line formed where two opposing sloping roof planes meet at the top of the roof frame.

Pre-formed specialty shingles or fabricated metal caps installed over the apex ridge and hip lines to seal joints and prevent wind-driven rain penetration.

A continuous low-profile exhaust vent installed along the entire length of the horizontal roof ridge to release hot, humid attic air through natural convective stack effect.

The universal unit of measurement in North American roofing, equal to exactly 100 square feet of surface area. All contractor labor, shingles, and underlayments are priced by the square.

A single-plane sloping roof design with no ridge or opposing slope. Common on modern home additions, porches, and contemporary architectural residences.

A geometric multiplier calculated as sqrt(1 + (Rise/Run)^2) used to convert a flat horizontal building footprint area into the true three-dimensional sloped roof surface area.

The horizontal underside of the eave overhang between the fascia and the exterior wall plane, typically fitted with perforated vents to draw cool outdoor air into the attic.

The initial continuous course of specialized self-sealing shingles installed along eaves and rakes beneath the first decorative shingle row to ensure high-wind adhesion.

Individual L-shaped metal flashing sections installed at each shingle course where a sloped roof plane terminates against a vertical wall, chimney, or dormer.

A single-ply reflective white roofing membrane composed of ethylene propylene rubber and polypropylene, recognized for high solar reflectance and energy-efficient cooling.

A factory-engineered structural framework composed of timber or steel members connected in rigid triangles to span long distances without requiring interior load-bearing walls.

A water-resistant synthetic woven polymer or asphalt-saturated felt sheet installed directly over the wood deck sheathing before applying primary roof coverings.

The internal V-shaped channel formed where two sloping roof surfaces intersect, carrying the highest concentration of runoff. Requires heavy flashing and ice barrier membrane.

The percentage allowance (typically 10% to 20%) added to the net roof surface takeoff to account for starter courses, ridge caps, valley cuts, hip angles, and installer trimming.