Glossary of Terms

The following is a list of terms (or phrases) commonly used within the Roofing Industry. Each term is accompanied by a short definition. If you are still unsure of a specific term, please don’t hesitate to ask your local Westman Steel Sales Representative to clarify!

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30 lb felt – was the standard underlayment for quality metal roofing systems and is still used but has been replaced in many areas by the newer synthetic underlayments. It is typically made of a polyester fleece and infused with tar.

Architectural Roofing – are metal roofing systems that are non-weightload bearing and must be installed over solid decking rather than battens or purlins. Also called “Non-Structural Systems”.

Butterfly Roof – A type of roof formed by two gables that pitch sharply from either side toward the center to resemble a butterfly’s wings.

Class A, B and C Fire Ratings – Fire-resistance ratings were established for roofing per ASTM and UL tests. These indicate the resistance of a roofing system to fires originating from sources outside the building.

Clip – is a small metal component used to secure two pieces of metal to each other or to secure metal shingles or standing seam to solid decking.

Coatings – Below are descriptions of the available metal coatings used in the metal roofing industry.

  • Kynar 500 and Hylar 5000 – are trade names for polyvinylidene (PVDF) paint finishes that provide very strong longevity and durability including fade and chalk resistance that leads the coatings industry. Kynar 500 is produced by Arkema Chemicals, and Hylar 5000 is produced by Solvay Solexis.
  • Stone Coated – is metal roofing made from zinc or aluminum coated steel that is then coated with the same granules as composition shingles. It is attractive but faces similar problems of streaking, granule loss, and organic growth as traditional composition shingles – DECRA.
  • Siliconized Polyester – also known as Siliconized Modified Polyester, is 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 where price is of greater concern than performance.

Coil Coating – is 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 – is a roof incorporating “above sheathing ventilation” in order to help prevent hot spots on the roof and subsequent wintertime ice dams.

Cool Roofing – are roofs that have high reflectivity achieved either through light colors or reflective pigments. Cool roofing can also refer to roof systems which have integral ventilation to help carry heat away from the structure and reduce cooling loads.

Combination Roof – A combination of two or more roof types.

Condensation – occurs when warm moist air hits a cool surface. This can occur in or on poorly designed roof assemblies. Ventilation, insulation, and vapor barriers are the keys to avoiding condensation in roof systems.

Course – is a row of metal shingles running the length of the roof.

Cricket – is a peaked “saddle” constructed at the back of a chimney to prevent accumulation of snow and ice and to deflect water around the chimney.

Decking – is the surface installed over the supporting framing members to which the roofing is applied.


1. is a framed window unit projecting through the sloping plane of a roof.

2. A structural element that protrudes from the sloping plane of the roof surface.

Drip Edge – is 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, often into the gutter or eaves trough. In some instances a Drip Edge and starter strip can be incorporated in the same component.

Dutch Gable – Is a combination of a Hip roof with a small Gable at the top and a sloping roof below.

Eave – is the very edge of the roof at the bottom (downhill) of a roof plane.

Fascia – caps the perimeter of the gables and eaves of the roof, can then be used to hang gutters along the eaves.

Flashings – are components used to help waterproof the perimeters and protrusions in a roofing system.

Flat Roof – A type of roof that has no slope and may terminate with or without eaves.

Gable – is the edge of the roof that runs from the eave to the ridge; some within the industry also refer to this as the Rake. The upper portion of a sidewall that comes to a triangular point at the ridge of a sloping roof.

Gable Roof – A type of roof containing sloping planes of the same pitch on each side of the ridge. A gable roof typically contains a gable at each end.

Galvalume steel – is carbon steel with a protective alloy consisting primarily of aluminum on both sides of the steel. AZ50 grade is suggested for painted product while AZ55 is suggested for product with clear acrylic coating.

Galvanized steel – is 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.

Gambrel roof – A type of roof containing two sloping planes of different pitch on each side of the ridge. The lower plane has a steeper slope than the upper. A gambrel roof usually contains a gable at each end, just like a standard gable roof.

Gazebo Roof – Often Hexagonal or Octagonal but usually symmetrical in their design.

Hip – is the inclined external angle formed by the intersection of two sloping roof planes. Runs from the ridge to the eaves.

Hip Roof – is a type of roof containing sloping planes on each side. A type of roof containing sloping planes of the same pitch on each of four sides. A hip roof contains no gables.

Ice and Water Shield – is a self-adhering membrane, 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. Building codes will require this in certain areas.

Ice Dam – is when snow melts on an upper section of a roof surface and then refreezes at the eaves where the roof surface is colder. This causes water to back up, causing leaks into the roofing system. Ice damming is controlled through attic insulation and ventilation.

Jerkinhead Roof – Consists of a Gable Roof with a truncated Hip Roof section at the top to reduce the height of the Gable.

Lean-to Roof – A roof with one slope only that is built against a higher wall.

M-Shaped Roof – A type of roof similar to a double-pitched roof except that it rests on two load bearing walls only. It also features a central gutter at a right angle to the front facade.

Mansard roof – A type of roof containing two sloping planes of different pitch on each of four sides. The lower plane has a much steeper pitch than the upper, often approaching vertical. It contains no Gables.

Master Flash – are also called “Dektites” and refer to metal and/or neoprene flashings used to seal around plumbing pipes, round vents, conduits, and other roof penetrations.

Pitch – is the slope of the roof plane, referred to as the height of rise over length of run, ie: 3:12. Steep slope refers to any pitch great than 3:12 and very low slope refers to any pitch less than 1.5:12. Most metal roofs can be installed on roof pitches of 4:12 or greater though many systems can be installed on shallower roofs.

Pyramid Hip Roof – A type of roof where all four sides come to a point at the roof peak.

Ridge – is the very top section of the roof running the length of the roof, where the two roof slopes come together.

Ridge or Hip Caps – are 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 – is 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.

Roof Framing Styles – Gable, hip, and barn style roofs are only a few of the possible shapes and designs a roof can take. For more information and examples please visit:

Saltbox Roof – A type of roof with asymmetrical roof faces. The asymmetry produces one facade that is two stories high dropping to a single story. A saltbox roof contains a gable at each end.

Sealant – is used most commonly to act as a sealant of joints or cracks to help prevent leaks. The higher grade sealants are usually butyl or polyether chemistry. Sealants should be used for aesthetic reasons as well as for redundant lines of defense against water intrusion. They should never be the sole line of defense. Also, sealants are not designed to be adhesives.

Shed Roof – A type of gabled roof with a single roof face falling away from the main building

Skillion Roof – A Skillion Roof slopes from one side of the building to the other in a single span and no ridge. As a result the external walls are of varying heights.

Snow Guards – are used in snow country to help break apart snow so it does not leave the roof surface in large pieces and harm people or property. An enhanced variation of these consists of Snow Fences. 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.

Square – refers to enough product to cover approximately 100 square feet of the roof.

Starter Strip – is used to begin the attachment of many metal roofing systems. It is used at the eave (bottom) of the roof on many metal shingle systems and on the left hand edge of the roof on many standing seam systems.

Step Flashing – is a method of flashing commonly used with standard roofing shingles and some other materials. Step flashing is generally not advised with metal roofing which usually uses continuous lineal flashings for greater life and watertightness.

Underlayment – is 30 lb felt or synthetic sheet installed on the roof deck below the roofing material. This is required by code beneath all metal roofs, even if the old shingles are left in place.

Valley – is the internal angle formed by the intersection of two sloping roof planes to provide water runoff. Refer to the glossary terms for Closed and Open Valley.