Glossary of Terms

Terms to help you reference and better understand the metal industry

Metal Glossary of Terms

Terminology & Useful Phrases


Aluminum: A rust-resistant metal sometimes used for metal roofing; it’s also 100% recyclable. 

Anti-Siphon Groove: A channel on a panel’s edge that prevents the suction effect and fluid transfer between materials. 

Architectural Roofing: Metal roofs that don’t bear weight and need a solid surface for installation. 



Base Ply: The lowest part of roofing in a roof system. 

Batten: (1) A cap or cover; (2) in a metal roof: a metal closure covering the joint between adjacent metal panels; (3) wood: a strip of wood elevating and attaching a primary roof covering. 

Bead Mastic: An adhesive sealant for standing seam panels to protect from moisture. 

Bonderized: Bare steel coated with an anticorrosive solution, used in construction; can be painted post-installation. 

Box Rib: A wide rib on a metal roofing or siding panel, ranging from 2” to 6” between ribs. 

Butyl Tape Sealant: Used to seal shaped joints for a water and air-tight seal. 



CAD: Computer Aided Drafting (CAD) is design software producing construction drawings. 

Camber: Curved coil edge that curves slightly from side to side. 

Cap Flashing: Covers upper edges of base flashing, wall flashing, or primary flashing; usually metal. 

Chalking: Whitish residue on painted metal surfaces over time due to paint degradation. 

Cladding: Exterior wall material. 

Class A, B, and C Fire Ratings: Indicate roofing system resistance to fires from outside the building. 

Cleat: Material elevating or protecting finish material. 

Clip: Formed metal securing two metal pieces or metal roofing. 

Closed Valley: A valley with a cover that can trap debris, causing water issues. 

Coatings: Painted finishes on metal building panels. 

Coil Coating: Continuous paint application to both sides of a moving metal strip. 

Cold Roof: Ventilated roof system carrying heat away to reduce cooling loads. 

Column Wrap: Formed metal enclosing a wood or steel column. 

Combustible: Materials capable of burning. 

Concealed Fastener: Hidden fastening clip system. See Clip. 

Condensation: Effect when warm moist air hits a cool surface; ventilation and insulation prevent it. 

Cool Roof: Describes roofs with high reflectivity through light colors or reflective pigments. 

Copper: Natural weathering metal used in roofing. 

Corner Trim: Formed metal enclosing corners of a metal panel; typically vertical. 

Cornice: Decorative trim along the top of a wall or below the roof. 

Corten A606: Weathering metal rusting over time for a weathered look. 

Counterflashing: Metal applied to shed water off a surface. 

Coverage: Surface area covered by a specific material quantity. 

Cricket: Ridge structure preventing snow and ice accumulation around chimneys. 

Cupola: Small structure on a building’s ridge for ventilation or decoration. 

Curb: Accessory for mounting additions on a sloped roof. 



Decking: Surface over roof framing to apply roofing; typically plywood. 

Door Trim Wrap: Formed metal enclosing a window frame for protection and aesthetics. 

Dormer: Window unit projecting through a roof’s sloping plane. 

Downspout: Vertical pipe carrying runoff water from a rain gutter to the ground. 

Drip Cap: Formed metal above door and window openings diverting moisture. 

Drip Edge: Metal on the eave directing water away. 



Eave: Roof edges projecting beyond a building’s side. 

Electrolysis: Direct electric current through an ionic substance causing chemical reactions. 

Endwall Trim: Separates and protects different surfaces’ transition from a wall to a roof or siding. 



Fading: Lightening of initial color. 

Fascia: Vertical or steeply sloped roof or trim at a building’s perimeter; waterproofs interior. 

Fasteners: Mechanical fastening devices; nails, screws, etc., to secure roof components. 

Field Forming: Materials formed at the job site. Also referred to as on-site rollforming. 

Finishes: Surface coating for metal panels. 

Fire Resistance: Material or assembly property preventing excessive heat passage during fires. 

Fixed Clip System: Anchored metal component securing metal pieces or shingles. 

Flange: Metal edge typically 90 degrees perpendicular to the bent shape. 

Flashings: Thin metal to waterproof roof perimeter and protrusions. 

Floating Clip System: Anchored metal component securing metal pieces, allowing thermal movement. 

Foam Closure: Extruded foam preventing wind, insect, and moisture damage. 



Gable: Roof edge from eave to ridge. 

Galvalume®: Coating over metal composed of aluminum zinc for corrosion protection. 

Galvanic Action: Electrolytic reaction between dissimilar metals in the presence of an electrolyte. 

Galvanized Steel: Carbon steel with a zinc protective coating. 

Gauge(s): Standard measure of steel and steel panels thickness. 

Gutter: Channeled component along a roof’s downslope to convey runoff water. 



Heat Tape: Electric cable melting snow near a roof’s eaves. 

Hem: Formed edge of a metal panel where the metal is bent 180 degrees. 

Hip Caps: See Ridge Caps. 

Hip Roof: Roof containing sloping planes on each side. 

Hip: Inclined external angle formed by two sloping roof planes; runs from ridge to eaves. 

Hot Roof: Sealed, unvented attic with closed cell urethane foam insulation. 



Ice and Water Shield: Self-adhering material for heavy rain and snow areas. 

Ice Dam: Mass of ice forming at the transition from a warm to a cold roof surface. 

Impact Resistance: Roofing material’s resistance to damage from falling objects, foot traffic, etc. 

Insulation: Material designed to reduce heat flow into or out of a building. 

Interlocking: Folding and bending metal shapes over each other to lock them together. 



Joist: A horizontal supporting member typically used in roof framing. 

Jamb Flashing: Flashing used to seal and protect the sides of a door or window opening. 




Kickout Flashing: A specialized flashing used to direct water away from a roof-to-wall intersection, preventing water infiltration into the wall assembly. 

Kneewall: A short wall that is typically not full height, often found in attic spaces or on the upper floor of a building. 

Kynar®: A type of high-performance coating commonly used in metal roofing systems, known for its durability, weather resistance, and color retention. 

Kerf: A narrow cut or groove made in a material, often seen in the context of creating a space for sealing or fastening elements in roofing. 



LEED: Leadership in Energy and Environmental Design; ecology-oriented building certification. 

Lap Seam: A type of seam where one roofing component overlaps another, creating a watertight joint. 

Leak Barrier: A protective material installed in vulnerable areas of the roof, such as valleys and penetrations, to prevent water penetration in case of a leak. 

Louvers: Openings with slanted slats designed to allow for ventilation while preventing the entry of water, snow, or debris. 

Low-Slope Roofing: Roofing systems with a pitch less than 3:12, where water drainage may be slower, requiring varied materials and installation methods. 



Mastic: Thick bituminous-based adhesive applied to metal panels or substrates. 

Membrane: Thin pliable sheet of material. 

Metal Roof Panel: Sheet-metal product with installed weather exposure less than 3 square feet. 

Mansard Roof: A style of roof characterized by two slopes on each of its sides, with the lower slope being steeper than the upper slope. This design allows for additional living space or storage within the attic. 

Metallic Paint: A paint finish that, due to its properties, mimics natural steel, aluminum, zinc, or copper in its finish. This is often created through a high gloss, reflective finish used together with a naturally occurring metal color. 



Non-Structural Systems: See Architectural Roofing. 

Non-Vented Ridge Cap: Single sheet metal ridge without vented material below. 

Nesting: The practice of stacking or arranging roofing materials, such as shingles or tiles, in a way that interlocks and provides a secure and weather-resistant covering for the roof. 

Nailer: A piece of wood or metal used to provide a secure base for attaching roofing materials, such as shingles or tiles, to the roof deck. 




Oil Canning: Visible waviness in metal panels; elastic buckling. 

Open Purlin: Roof structure with wood members instead of panel sheathing. 

Open Valley: Valley design allowing water and debris to flow on top of roofing systems. 



Pancake Head Screw Fasteners: Flat-headed screws with a low-profile appearance. 

Panel Profile: Shape metal panels are formed into; determines how panels fit and connect. 

Pipe Flashings: See Pipe Jacks. 

Pipe Jacks: Metal and/or neoprene flashing to seal around plumbing pipes, vents, and conduits. 

Pitch: Slope of the roof plane. 

Pliability: Material property of being flexible or moldable. 

Portable Rollforming Machine: Smaller metal rollformer for easy transport. 

Portable Seamless Gutter Machine: Transportable machine for onsite seamless gutter rollforming. 

Pre-Painted Coil: Metal coil with a factory-applied paint coating. 

Prow Gable: Formed edge metal at the front of a gable roof. 

Purlin: Horizontal beam along the roof length, resting on a main rafter. 

PVDF: Polyvinylidene (PVDF) paint finishes for longevity, durability, fade, and chalk resistance. 



Rake: Outside edge of a gable running with the roof’s pitch. 

Rib: Longitudinal raised profile providing panel bending strength. 

Ribbed Panel: Panel with ribs forming a trapezoidal void at the side lap. 

Ridge Caps: Accessories covering the inclined angle formed by two sloping roof planes. 

Ridge Vent: Vent integrated into the ridge flashing for effective attic ventilation. 

Ridge: Very top section where two roof slopes meet. 

Rollforming: Process of feeding metal through rollers to shape it. 

Roof Assembly: Interacting roof components; deck, vapor retarder, insulation, and roof covering. 

Roof Framing Styles: Gable, hip, and barn style roofs; various roof designs. 

Roof Slope: Incline of the roof expressed as a ratio of vertical rise to horizontal run. 

Run: Horizontal dimension of a slope. 

Run-out Table: Adjustable platform supporting roofing panels as they exit the Rollforming machine. 

R-value: Material’s ability to resist heat flow. 



Sealant: Used to seal joints or cracks to prevent leaks. 

Seam: Side rib where two metal panels connect. 

Self-Adhering Membrane: Material layer adhering to a substrate and itself without additional adhesive. 

Self-Drilling Screw: Fastener drilling and tapping its own hole. 

Self-Tapping Screw: Fastener forming receiving threads when turned into a drilled hole. 

Shed Roof: Roof with only one sloping plane; no hips, ridges, or valleys. 

Slider Clip: Anchored metal component securing two metal pieces, allowing thermal movement. 

Slitting: Cutting a sheet of metal into narrower strips. 

SMP or Siliconized Polyester: Solvent-based system with polyester resin for agricultural metal roofs. 

Snow Break: Prevents large snow pieces from sliding off the roof. 

Snow Guard: See Snow Break. 

Soffit: Enclosed underside of a roof eave’s overhanging section. 

Solar Reflectance: Roof’s ability to reflect solar heat. 

Square: 100 square feet of the roof. 

Standing Seam Roof System: Metal roof with raised, interlocking seams secured by concealed clips. 

Standing Seam: Seam created by turning up two adjacent edges and folding them over. 

Step Flashing: Flashing method used with standard roofing shingles. 

Stone Coated: Metal roofing with zinc or aluminum-coated steel coated with composition shingle granules. 

Striation: Ribs or waves in metal panels to minimize oil canning. 

Structural Roofing: Metal roofing providing structural integrity without decking. 

Substrate: Surface on which roofing or waterproofing membrane is applied. 



Tapering: Making a panel narrower at one end. 

Thermal Block: Insulating material between the metal roof and compressed insulation over purlins. 

Transverse Seam: The seam formed by the joining of metal panels in a direction perpendicular to the length of the panels. 

Tensile Strength: The maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen’s cross-section starts to significantly contract. 

Tin Tab: A small metal tab used in roofing installations, often associated with securing shingles or other roofing materials. 




Underlayment: A secondary waterproofing material installed between the substrate and the roof panels, providing an additional layer of protection. 

UL-2218 Impact Resistance Rating: A test criteria for measuring the impact resistance of roofing materials, rating them on a scale from I to IV, with IV being the highest level of impact resistance. 

Uplift: The force caused by wind deflection at roof edges, peaks, or obstructions, resulting in a drop in air pressure that can lift the roofing material. 

Utility Trim: A metal trim used for functional purposes, such as protecting edges, providing transitions, or enhancing the overall performance of the roofing system. 




Valley: The internal angle formed by the intersection of two sloping roof planes, designed to channel water runoff. 

Vented Ridge Cap: A formed metal piece used at the cap of a ridge that allows the use of a vented material, providing additional ventilation for the attic space. 

Ventilation: The process of allowing air to flow through the roof system, promoting temperature control and preventing moisture buildup. 

Vapor Barrier: A material that inhibits the passage of water vapor, typically used to prevent condensation within the roofing system. 




Wainscot: Horizontal or vertical metal siding at ground level. 

Walk Board: Planks for walking or standing on. 

Walkway Pads: Placed on the roof for foot traffic to minimize damage. 

Wind Uplift: Force caused by wind deflection at roof edges, peaks, or obstructions. 

Window Wraps: Formed metal shapes around a window for trim and protection. 

Wood Fascia: Finished wood trim around a building’s exterior. 



X-Bracing: In structural engineering, X-bracing refers to a system of diagonal braces that form an “X” shape, providing lateral support to a structure. 



Yield Strength: The amount of stress at which a material begins to deform plastically, indicating its ability to withstand applied pressure. 

Yellowing: The process of a material turning yellow over time, which can occur in some roofing products due to exposure to sunlight and environmental factors.  This was common on old paint systems but is often no longer a factor in modern paint systems like SMPs and PVDFs. 

Yield Point: The stress level at which a material begins to deform permanently under load, beyond which it won’t return to its original shape. 




Z Metal: “Z” shaped metal piece transitioning between two different materials. 

Zee or Z Purlin: Cold-formed steel member in a Z shape for construction. 

Zinc: Non-sparking, corrosion-resistant metal used in outdoor applications. 

Zincalume®: Sheet steel with a metallic coating of aluminum, zinc, and silicon alloy. 

Zip-Up UnderDeck: Vinyl rain drainage system extending a deck or patio’s usable space. 

Zinc Trim: See Zinc