Metal & Roofing Glossary

  • Aluminum: A non-rusting metal sometimes used for metal roofing and flashing. It is 100% recyclable.

  • Anti-Siphon Groove: A continuous channel formed into a panel’s edge to create a break in the panels. This prevents the suction effect and the transfer of fluid between materials.

  • Architectural Roofing: Metal roofing systems that are non-weight bearing.  It must be installed over a solid surface. 


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

  • Batten: (1) A cap or cover; (2) in a metal roof: a metal closure set over, or covering the joint between, adjacent metal panels; (3) wood: a strip of wood usually set in or over the structural deck, used to elevate and/or attach a primary roof covering.

  • Bead Mastic: An adhesive sealant used for standing seam panels to protect the roofing system from moisture and water. 

  • Bonderized: A bare metal coated product protected with an anti-corrosive solution.

  • Box Rib: A wide rib on a metal roofing or siding panel. Can vary in size throughout the metal industry ranging from 2” to 6” between ribs.

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


  • CAD: Computer Aided Drafting (CAD) is a design software that produces drawings to represent construction details.

  • Cap Flashing: Used to cover or shield the upper edges of the membrane base flashing, wall flashing, or primary flashing; usually composed of metal.

  • Cladding: A material used as the exterior wall enclosure of a building.

  • Class A, B and C Fire Ratings: Fire-resistance ratings were established for roofing per American Society for Testing and Materials(ASTM) and UL tests. These indicate the resistance of a roofing system to fires originating from sources outside the building.

  • Cleat: A piece of material typically used to elevate a finish material and/or used to protect that material during transport.

  • Clip: A formed metal component anchored to the building substrate to secure two pieces of metal to each other, or to secure metal shingles or standing seam roofing.

  • Closed Valley: A valley that has an integral cover over the area where the shingles meet the adjoining roof planes. In many cases, this cover creates a trap for debris such as leaves, ice, and snow to gather and clog the valley system, causing water to overflow underneath the roofing system.

  • Coatings: The painted finishes on metal building panels.

  • Coil Coating: A term used to describe the continuous process in which paint is applied to both sides of a moving strip of metal. The process usually includes cleaning, chemical pre-treatment, primer, and topcoat.

  • Cold Roof: A roof system that has ventilation between the roof deck and metal roofing panel to help carry heat away from the structure and reduce cooling loads.

  • Combustible: Materials capable of burning.

  • Condensation: The effect that occurs when warm moist air hits a cool surface. Ventilation, insulation, and vapor barriers are the important areas to focus on, in order to avoid condensation in roof systems.

  • Concealed Fastener: A fastening clip system that is hidden beneath the metal panels. See Clip.

  • Cool Roof: A term describing roofs that have high reflectivity achieved either through light colors or reflective pigments.

  • Copper: A natural weathering metal used in roofing.

  • Cupola: A small structure added to a building’s ridge for ventilation or as a decorative accent.

  • Corner Trim: A formed piece of metal used to enclose the corners of a metal panel; typically placed vertically.

  • Cornice: A building’s decorative trim that runs along the top of a wall or just below the roof. 

  • Counterflashing: A formed piece of metal that is applied to a wall, curb, pipe, rooftop unit, or other surface to shed water off the wall and onto the roof surface.

  • Coverage: The surface area covered by a specific quantity of a particular material.

  • Cricket: A ridge structure constructed at the back of a chimney to prevent accumulation of snow and ice, and to deflect water around the chimney.

  • Column Wrap: A formed metal panel to enclose a wood or steel column.

  • Cupola: A decorative fixture atop a roof ridge that brings light and air into a dark attic space.  Oftentimes, they have a weathervane at the top which displays wind direction.


  • Decking: The surface installed over the roof framing to which the roofing is applied; typically plywood. It is the roof’s initial layer, which does not come in contact with moisture. There are four main types of decking commonly used on residential roofing projects:
    Plywood: Plywood is strong, durable, and light. It comes in many grades with ratings from A to D. Use only exterior grade plywood for decking. The thickness of plywood depends on the spacing of the rafters.
    OSB: Oriented strand board (OSB) is cheaper than plywood, but not as strong as plywood, and does not hold nails as well as plywood. One side has a slip resistant coating and should be placed facing up.
    Tongue & Groove 2-by-6: If a roof will be seen from the inside (no ceiling installed), tongue and groove is used. It is a wood decking that provides great insulation without additional rigid roof insulation in moderate climates. Also, the boards can be painted or stained on the inside to match the interior.

  • Door Trim Wrap: A formed metal piece used to enclose the exterior frame of a window for added protection and aesthetics.

  • Dormer: A framed window unit projecting through the sloping plane of a roof.

  • Downspout:  A vertical pipe used to carry runoff water from a rain gutter to the ground or storm water runoff system.  

  • Drip Cap:  A formed piece of metal used above door and window openings to divert moisture around the opening.

  • Drip Edge:  A piece of metal placed on the eave of a roof to protect the underlayment and eave of the roof and direct water in the proper direction.

  • Drip Stop:  An internationally patented condensation control membrane.  It is pre-applied to panel, designed to trap moisture in specially designed pockets in the membrane.  This material holds moisture until conditions go back below the dew point, & is then released back into the air in the form of normal humidity.


  • Eave: The edges of the roof which overhang the face of a wall and, normally, extend beyond the side of the building.

  • Electrolysis: The passing of a direct electric current through an ionic substance that is either molten or dissolved in a suitable solvent, producing chemical reactions at the electrodes and separation of materials.

  • Endwall Trim: Used to separate and protect the transition of different surfaces from the end of a wall to a roof or siding plane.


  • Fading: Any lightening of the initial color.

  • Fascia: A vertical or steeply sloped roof or trim located at the perimeter of a building. Typically, it is a border for the low-slope roof system that waterproofs the interior portions of the building.

  • Fasteners: A wide variety of mechanical securement devices and assemblies, including nails, screws, cleats, clips, and bolts, which may be used to secure various components of a roof assembly.

  • Field Forming: Used when the materials can be formed at the job site.

  • Finishes: A surface coating used to coat the surface of metal panes.

  • Fire Resistance: The property of materials or their assemblies that prevents or retards the passage of excessive heat, hot gases or flames under conditions of use.

  • Fixed Clip System: A formed metal component anchored to the building substrate used to secure two pieces of metal to each other or to secure metal shingles or standing seam roofing.

  • Flange: A metal edge that is typically 90 degrees perpendicular to the bent shape.

  • Flashings: A thin piece of metal used to help waterproof the perimeter and protrusions in a roofing system, such as vent pipes, chimneys, adjoining walls, dormers and valleys.
    Plumbing vent flashing (collar/boot): Plumbing vent flashing prevents rainwater from running into holes cut for pipes in the roof. This flashing is sold according to the size of the vent pipe and the roof angle. Roofing material is installed over the flashing.
    Step flashing: Flashing application method used where a vertical surface meets a sloping roof plane, (example: chimney).
    Valley flashing: This flashing is used in open valleys of the roof. Most often leaks are found in the valley flashings due to flashing that is nailed to tightly to the decking or panels that are not trimmed far enough off the flashing.

  • Floating Clip System: A formed metal component anchored to the building substrate used to secure two pieces of metal to each other, or to secure metal shingles or standing seam roofing but can move with the metal’s expansion to allow for thermal movement.

  • Foam Closure: An extruded foam piece formed from neoprene or polyethylene and conforms to the uniform bends of a metal panel to prevent wind, insect, and moisture damage.


  • Gable: The edge of the roof that runs from the eave to the ridge. (Also referred to in shingle roofing as the “Rake”)

  • Galvalume®: A coating, used over metal, that is composed of aluminum zinc for corrosion protection.

  • Galvanic Action: – An electrolytic reaction between dissimilar metals in the presence of an electrolyte.

  • Galvanized Steel: A carbon steel with a protective alloy consisting primarily of zinc on both sides of the steel. Various grades are available based upon the thickness of the coating. G90 is suggested for residential applications.

  • Gauge(s): The standard measure of thickness of steel and steel panels.

  • Gutter: A channeled component installed along the downslope perimeter of a roof (parallel to the eave) to convey runoff water from the roof to the drain leaders or downspouts.


  • Heat Tape: An electric cable used to help melt snow near the eaves of the roof. This is used to help alleviate ice damming.

  • Hem: The formed edge of a metal panel where the metal is bent 180 degrees back onto itself to help soften the sharp cut metal edge. 

  • Hip: The inclined external angle formed by the intersection of two sloping roof planes. Runs from the ridge to the eaves.

  • Hip Caps: See Ridge Caps.

  • Hip Roof: A type of roof containing sloping planes on each side.

  • Hot Roof: A completely sealed, not vented, attic where the entire interior of which is often sprayed with closed cell urethane foam insulation. 


  • Ice and Water Shield: A self-adhering material layer, specifically designed to be used in heavy rain and snow areas where leaks can be a problem. In most cases you would install ice and water shield on the first three feet of the roof in addition to underlayment.

  • Ice Dam: A mass of ice formed at the transition from a warm to a cold roof surface. Frequently formed by refreezing melted water at the overhang of a steep roof causing ice and water to back up under roofing materials, which may result in roof leaks. Ice damming is controlled through attic insulation and ventilation.

  • Impact Resistance: The ability of a roofing material to resist damage (e.g., puncturing) from falling objects, application equipment, foot traffic, etc. The impact resistance of the roofing assembly is a function of all of its components, not just the membrane itself.

  • Insulation: Any material designed to reduce the flow of heat from or into a building.

  • Interlocking: The process of folding and bending metal shapes over one another to lock them together.

  • Intake Ventilation: The part of a ventilation system used to draw fresh air in. Usually vents installed in the soffit or along the eaves of a building. 


  • Kynar®: See PVDF


  • LEED: Leadership in Energy and Environmental Design (LEED) is an ecology-oriented building certification program run under the auspices of the U.S. Green Building Council (USGBC).

  • Load:  The maximum amount of weight that a roof is designed to take on. Calculated in psf – pounds per square foot.

  • Load Table: A matrix that calculates the allowable uniform live loads on the rooftop.


  • Mastic: A thick bituminous-based adhesive applied to metal panels or substrates.

  • Membrane: Any thin pliable sheet of material.

  • Metal Roof Panel: A sheet-metal product having an installed weather exposure less than 3 square feet per sheet.

  • Metal Drip Edge: This refers to trim, usually gable and eave trim, that has a slight bend at the edge which facilitates water runoff, away from the building.


  • Non-Vented Ridge Cap: A metal ridge formed from a single sheet of steel that does now allow for vented ridge material to be inserted below it.

  • Non-Structural Systems: See Architectural Roofing.


  • Oil Canning: A visible waviness in the flat areas of metal roofing and metal wall panels. In technical terms, oil canning is referred to as elastic buckling (more commonly known as “stress wrinkling”). It can occur in any type of metal panels: steel, aluminum, zinc, or copper.

  • Open Purlin:  A roofing structure where wood members are used in lieu of paneled sheathing or decking.

  • Open Valley: A valley design used to transition water and debris off of a roof slope, carrying the water on top of the roofing systems. These valley systems are designed to not clog with debris such as tree leaves and needles, ice, or snow.


  • Pancake head screw fasteners: A flat headed screw that has a low profile appearance.

  • Pipe Jacks: A metal and/or neoprene flashing used to seal around plumbing pipes, round vents, conduits, and other roof penetrations. 

  • Pipe Flashings: See Pipe Jacks.

  • Pitch: The slope of the roof plane. Steep slopes refer to any pitch great than 3:12 (3:12, or 3/12 meaning a roof will rise 3 inches for every 12 inches of length), and very low slopes refers to any pitch less than 1.5:12. 

  • Pliability: The material property of being flexible or moldable.

  • Pre-Painted Coil: Coil of metal that has received a factory applied paint coating.

  • Prow Gable: The formed edge metal used at the prow or front of a gable roof.

  • Purlin: A horizontal beam along the length of the roof, resting on a main rafter.

  • PVDF: Names for polyvinylidene (PVDF) paint finishes that provide very strong longevity and durability including fade and chalk resistance.


  • R-value: Indicate a material’s ability to resist heat flow.

  • Rafter: The supporting framing member immediately beneath the deck, sloping from the ridge to the eave.

  • Rake: The outside edge of a gable that runs with the slope of the roofs pitch. Trim that goes on these slopes is referred to as “gable or rake trim”. We typically use the term “gable trim.”

  • Retro-fit:  The process of installing a new roof directly over an existing roofing system, without removing the existing system.

  • Rib: The longitudinal raised profile of a panel that provides much of the panel’s bending strength.

  • Ribbed Panel: A panel that has ribs with sloping sides and forms a trapezoidal shaped void at the side lap.

  • Ridge: The very top section of the roof, where the two roof slopes come together. The material that covers this area is called the ridge cap.

  • Ridge Caps: The accessories used to cover the inclined external angle formed by the intersection of two sloping roof planes, either at the ridge or hip.

  • Ridge Vent: An outtake vent for air integrated into the ridge flashing. A ridge vent’s proper performance requires adequate intake vents, usually in the eave soffits of the home. For most homes this is the most effective method for siphoning air out of the attic or other air space.

  • Rise: The vertical distance from the eave’s line to the ridge.

  • Roof Assembly: An assembly of interacting roof components (includes the roof deck, vapor retarder [if present], insulation, and roof covering).

  • Roof Framing Styles: Gable, hip, and barn style roofs are only a few of the possible shapes and designs a roof can take.

  • Roof Slope: The incline of the roof expressed as a ratio of the vertical rise to the horizontal run. (example 3:12, or 3/12 meaning a roof will rise 3 inches for every 12 inches of length).

  • Run: The horizontal distance (of the roof’s slope) from the eaves to a point directly under the ridge.


  • Sealant: Used to seal joints or cracks to help prevent leaks. Sealants should be used for aesthetic reasons as well as for extra lines of defense against water intrusion. Sealants are not designed to be adhesives.

  • Self-Adhering Membrane: A material layer that can adhere to a substrate and to itself at overlaps, without the use of an additional adhesive. The undersurface of a self-adhering membrane is protected by a release paper or film, which prevents the membrane from bonding to itself during shipping and handling.

  • Self-Drilling Screw: fastener that drills and taps its own hole during application.

  • Self-Tapping Screw: A fastener that forms receiving threads when turned into a previously drilled hole.

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

  • Slider Clip: A formed metal component anchored to the building substrate and used to secure two pieces of metal to each other or to secure metal shingles or standing seam roofing. This clip can move as the metal expanse to allow for thermal movement.

  • Slope: The degree of roof incline expressed as the ratio of the rise, in inches, to the run, in feet. Also referred to as “pitch”.

  • SMP or Siliconized Polyester: A solvent-based system with polyester resin. Silicone additives are used to increase resin stability and coating flexibility. Standard polyester finishes are commonly used on agricultural metal roofs.

  • Snow Break: Used in snow country to help break apart snow so it does not slide off the roof in large pieces. On standing seam roofs, these items need to be installed in a way that does not impede movement of the roofing system with thermal expansion and contraction.

  • Snow Guard: See Snow Break

  • Soffit: The enclosed underside of any exterior overhanging section of a roof eave.

  • Solar Reflectance: The ability of a roof to reflect solar heat.  

  • Span: The horizontal distance from eaves to eaves.

  • Square: 100 square feet of the roof.

  • Standing Seam: A seam made by turning up two adjacent edges and folding the upstanding parts over on themselves.

  • Standing Seam Roof System: A type of metal roof that typically has panels run vertically with a raised, interlocking seam which joins one panel to the next. The roof panel system is secured to the roof substructure by concealed clips attached with screws, or panels directly screwed down, to the substructure.

  • Step Flashing: A method of flashing commonly used with standard roofing shingles and other materials. Step flashing is generally not advised with metal roofing.

  • Stone Coated: Metal roofing made from zinc or aluminum coated steel that is then coated with the same granules as composition shingles. 

  • Striation:  Ribs or waves formed into metal panels to minimize oil canning.

  • Structural Roofing: Metal roofing that provides structural integrity to the building and does not require decking for installation. Generally these systems are not advised for residential application because a lack of decking can be a contributing factor to condensation issues.

  • Substrate: The surface upon which the roofing or waterproofing membrane is applied.

  • Substructure: It lies just beneath the metal roof panels. Typically made in two ways – Open Framing of Rafters and purlins, and Solid Decking made of wood, metal or composite materials. Solid Decking examples are OSB and Plywood.


  • Tear off: Removing an existing roof system.

  • Thermal Block: A thermal insulating material that is placed between the metal building roof and the compressed insulation over the purlins.


  • UL-2218 Impact Resistance Rating: A test criteria for measuring the impact resistance of roofing materials. It rates roofing materials on a scale from I to IV with IV being products that withstand the impact test best. Insurance discounts are available to homeowners in some areas who choose Class IV roofs. 

  • Underlayment: A secondary waterproofing material installed between the substrate and the roof panels. Some types may be self-adhering. This is required by code beneath all metal roofs, even if old shingles are left in place.


  •  Valley: The internal angle formed by the intersection of two sloping roof planes to provide water runoff.

  • Vented Ridge Cap: A formed metal piece used at the cap of a ridge that allows the use of a vented material and provides additional ventilation of the attic space in a roofing system.


  • Wainscot: The horizontal or vertical application of metal siding typically installed at the ground level and can run from 36” to 8’-0”. 

  • Wind Uplift: The force caused by the deflection of wind at roof edges, roof peaks or obstructions. This causes a drop in air pressure immediately above the roof surface. This force is then transmitted to the roof surface. Uplift may also occur because of the introduction of air pressure underneath the membrane and roof edges, where it can cause the membrane to balloon and pull away from the deck

  • Window Wraps: Formed metal shapes used around the perimeter of a window as trim and protection. 

  • Wood fascia: Finished wood trim around the exterior of a building to help accent siding and roofing.


  • Z Metal: A “Z” shaped metal piece that provides a transition between two different material.

  • Zinc Panel: A non-sparking, corrosion resistant material that is widely used in outdoor applications. Zinc is highly formable and is known to be environmentally friendly due to its infinite recyclability and low-impact production method.

Substrate Facts

Galvalume coating

  • Galvalume is a hot-dip process in aluminum, zinc and silicon. AZ55
  • 55% aluminum, 43.5% zinc, 1.5% silicon by weight.
  • 80% aluminum, 19% zinc, 1% silicon by volume.
  • Zinc bonds with steel to create a barrier to corrosion caused by moisture.
  • Aluminum is a metal that naturally resists corrosion and reflects heat.
  • Silicon enhances the adhesion of the coating.
  • Galvalume under normal environmental conditions is at least 2-4 times as resistant to corrosion compared to galvanized.
  • Galvalume should not be used in contact with concrete or mortar. The high alkaline content will cause rapid corrosion.
  • Galvalume panels are not warrantied when used in animal containment buildings.
  • Galvalume carries a 25 year 6 month warranty from the steel mill on rust perforation.


  • Galvanized is a hot-dip process in zinc. G100
  • A chemical bond occurs between the zinc and the carbon sheet steel.
  • Galvanized coating is measured in ounces per 100 square feet.
  • G100 has 100 oz. of zinc per 100 square feet; includes both sides.
  • The greater the amount of zinc, the greater the protection against corrosion.
  • Galvanized panels perform better in animal containment buildings than galvalume but still are not warrantied.
  • The zinc in the two substrates actually sacrifices itself to protect the underlying steel from rust when panel damage occurs. Since galvanized has more zinc this phenomenon is more pronounced in galvanized panels. After 10 years this action seems to equalize between the two substrates.