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Roofing Glossary & Information

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Roofing Glossary

roofing glossary section 'A' roofing glossary section 'B' roofing glossary section 'C' roofing glossary section 'D' roofing glossary section 'E' roofingglossary section 'F' roofing glossary section 'G' roofing glossary section 'H' roofing glossary section 'I' roofing glossary section 'J' roofing glossary section 'K' roofing glossary section 'L' roofing glossary section 'M' roofing glossary section 'N' roofing glossary section 'O' roofing glossary section 'P' roofing glossary section 'Q' roofing glossary section 'R' roofing glossary section 'S' roofing glossary section 'T' roofing glossary section 'U' roofing glossary section 'V' roofing glossary section 'W' roofing glossary section 'X' roofing glossary section 'Y' roofing glossary section 'Z'

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Air Barrier: Materials used in building construction to limit or prevent the uncontrolled passage of air into and out of the structure.

Algae Discoloration:  A type of roof discoloration caused by algae, also known as fungus growth.

Aluminum: A non-rusting malleable metal sometimes used for metal roofing and/or flashing.

American Method: The application of very large individual shingles with the long dimension parallel to the rake and applied with a 3/4-inch space between adjacent shingles.

Apron Flashing: A horizontal flashing installed where the top end of a roof slope meets a vertical projections, such as a c chimney or parapet wall. Usually metal.

Asphalt:  A cementitious material (usually black or dark brown) in which the predominant constituents are bitumens found in a natural state or left as a residue after evaporating or otherwise processing crude oil or petroleum.  Asphalt is usually refined to conform to the following roofing grade specifications:

  • Dead Level Asphalt: roofing asphalt conforming to the requirements of ASTM D312, Type I
  • Flat Asphalt: roofing asphalt conforming to the requirements of ASTM D312, Type II
  • Steep Asphalt: roofing asphalt conforming to the requirements of ASTM D312, Type III
  • Special Steep Asphalt: roofing asphalt conforming to the requirement of ASTM D312, Type IV
  • Waterproofing Asphalt: a waterproofing asphalt conforming to the requirement of ASTM D449, Types I, II, and III

Asphalt Shingle: A shingle manufactured by coating a reinforcing material like paper-felt or fiberglass mat with an asphalt based coating.

Asphalt Roofing Cement: Asphalt based cement used to bond roofing materials. Also called flashing cement or mastic, and should conform to ASTM D4586.

ASTM: American Society for Testing and Materials - a voluntary organization concerned with development of consensus standards, testing procedures and specifications.

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Back Surfacing:  Fine mineral material applied tot he back side of shingles to keep them from sticking.

Balanced System:  A ventilation system where 50% of the required ventilating area is provided by vents located in the upper portion of the roof with the balance provided by under eave or soffit vents.

Barrel Vault:  A building profile featuring a rounded profile to the roof on the short axis but with no angle change on a cut along the long axis.

Base Flashing: The portion of flashing attached to or resting upon the deck with the purpose of directing the flow of water onto the roof covering. Piles or strips of roof membrane material used to close off and/or seal a roof at the horizontal-to-vertical intersections, covers the edge of the field membrane and extends up the vertical surface.

Base Ply: The bottom or first ply in a built up or polymer-modified bitumen roof system when additional plies are to subsequently installed.

Base Sheet: An impregnated, saturated or coated felt placed as the first ply in some low-slope roof systems.

Batten: (1) Cap or cover; (2) in a metal roof, a metal closure set over, or covering the joint between adjacent metal panels. (3) In a steep sloped roof system a strip of wood or metal usually set in or over the structural deck that is used to elevate and/or attach a primary roof covering. (4) In a Single-ply membrane roof system, a narrow plastic or metal bar that is used to fasten or hold the roof membrane and/or base flashing in place.

Bitumen: (1) Class of amorphous black or dark-colored, (solid, semi-solid or viscous) cementitious substances, natural or manufactured and composed primarily of high-molecular-weight hydrocarbons, soluble in carbon disulfide. Found in asphalts, tars, pitches, and asphaltites; (2) a generic term used to denote any material composed principally of bitumen, typically asphalt or coal tar.

Blanket Insulation: Fiberglass or other compressible fibrous insulation.

Blisters:  Bubbles that may appear on the surface of asphalt roofing after installation.

Blocking: (1) Section of wood built into a roof assembly and can be preservative-treated. Usually attached above the deck and below the membrane, or flashing. It is use to stiffen the deck around an opening and act as a stop for insulation, to support a curb or to serve as a nailer for attachment of the membrane and/or flashing; (2) Wood cross members installed between rafters or joists to provide support at cross-joints between deck panels.

Boot: (1) a covering made of flexible material that may be preformed to a particular shape, used to exclude dust, moisture, etc. from around a penetration; (2) A flexible material used to form a closure and sometimes installed at inside and outside corners.

Brands: Airborne burning embers released from a fire.

Bridging:  A method of reroofing with metric-sized shingles.

Building Code: The minimum construction requirements established usually by national organizations and adopted in whole or in part by local governing authorities.  Building codes control design, construction, quality of materials, use and occupancy, location and maintenance of buildings or structures within the area for which the code was adopted and assigned.

Built-up Roof (BUR): A continuous semi-flexible roof membrane consisting of multiple plies of saturated felts, coated felts, fabric or mats assembled in place with alternate layers of bitumen and surfaced with mineral aggregate, bituminous materials, a liquid-applied coating or a granule-surfaced cap sheet. A flat or low-slope roof consisting of multiple layers of asphalt and ply sheets.

Bundle: A package of shingles. There are 3, 4, or 5 bundles per square.

Butt Edge: The lower edge of the shingle tabs.


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Cap Flashing: The portion of the flashing that is attached to a vertical surface to prevent water from migrating behind the base flashing.

Capping: A cover used at the top of a gap for weatherproofing.

Cap Sheet:  A sheet, usually granule-surfaced, used as the top ply of some built-up or polymer-modified bitumen roof membranes and/or flashings.

Caulk, caulking: (1) The physical process of sealing a joint, or juncture with mastic or asphalt cement to help weatherproof and prevent leaks.

Chalk line:  A line made on the roof by snapping a taut string or cord dusted with chalk. Used for alignment purposes.

Channel Flashing: In steep-sloped roof construction, a type of flashing used at roof-to-tall junctures and other roof-to-vertical plane intersections where an internal gutter is needed to handle runoff. Commonly used with profile tile.

Class "A": The highest fire-resistance rating for roofing as per ASTM E108. Indicates roofing is able to withstand severe exposure to fire originating from sources outside the building.

Class "B": Fire-resistance rating that indicates roofing materials are able to withstand moderate exposure to fire originating outside the building.

Class "C": Fire-resistance rating that indicates roofing materials are able to withstand light exposure to fire originating outside the building.

Cleat: A continuous metal strip, or angled piece, used to secure metal components.

Clerestory: (1) An upward extension of enclosed space created by carrying a setback vertical wall up and through the roof slope; (2)  Two intersecting shed roofs on different planes.

Clip: A non continuous metal component or angle piece used to secure a metal panel to a substrate of two or metal components together.

Closed Cut Valley: A method of valley treatment in which the shingles from one side of the valley extend across the valley, while shingles from the other side are trimmed two inches from the valley centerline. The valley flashing is not exposed.

Coating: A fluid material applied in the field as a film to the roof surface to provide weather protection to the original roof substrate.

Cold-Applied: Designed for or capable of being applied without heating as contrasted to hot-applied. Cold-applied materials are furnished in liquid state, whereas hot-applied materials are furnished as solids that must be heated to liquefy before application.

Collar: Pre-formed flange placed over a vent pipe to seal the roof around the vent pipe opening. Also called a vent sleeve.

Concealed Nail Method: Application of roll roofing in which all nails are driven into the underlying course of roofing and covered by a cemented overlapping course. Nails are not exposed to the weather.

Condensation: The change of water from vapor to liquid when warm, moisture-laden air comes in contact with a cold surface.

Cool Roof: A roof system that uses products made of highly reflective and emissive materials for its top surface. Cool roof surfaces can remain at markedly lower temperatures when exposed to solar heat in service than surfaces of roofs constructed with traditional non-reflecting roofing products.

Coping: The covering piece on top of a wall exposed to the weather, usually made of metal, masonry or stone.

Cornice: The decorative horizontal molding or projected roof overhang.

Counter-Battens: Vertical wood or metal strips installed on steep-slope roofs over which horizontal battens are secured. The  primary roof covering is attached or secured to these horizontal battens.

Counter -Flashing: That portion of the flashing attached to a vertical surface to help prevent water from migrating behind the base flashing.

Course: A row of shingles or roll roofing running the length of the roof.

Coverage: Amount of weather protection provided by the roofing material. Depends on number of layers of material between the exposed surface of the roofing and the deck (single coverage, double coverage, etc.).

Cover Board: An insulation board used over closed cell plastic foam insulation to prevent blistering when used in conjunction with hot bituminous membranes. Suitable cover-board insulations are glass-faced siliconized gypsum board, fiberglass board, perlite board, wood fiberboard or mineral fiberboard. Cover boards are also recommended between polyisocyanurate insulation and single-ply membranes to protect the polyisocynurate.

Cricket: A peaked saddle construction at the back of a chimney to help prevent accumulation of snow and ice to deflect water around the chimney.

Curb: A raised member used to support roof penetrations such as skylights, mechanical equipment, hatches, etc., above the level of the roof surface; a raised roof perimeter relatively low in height.

Cutout: The open portions of a strip shingle between the tabs.

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Damper: An adjustable plate for controlling drafts.

Damp Proofing: Treatment of a surface or structure to resist the passage of water in the absence of hydrostatic pressure.

Deck:  A structural component of the roof of a building. The deck must be capable of safely supporting the design dead and live loads, including the weight of the roof system, and the additional live loads required by the governing building codes and provide the substrate to which the roof or waterproofing system is applied. Decks are either noncombustible, (e.g., corrugated metal, concrete or gypsum) or combustible (e.g., wood plank or plywood).

Double Coverage: Application of asphalt roofing such that the lapped portion is at least two inches wider than the exposed portion, resulting in two layers of roofing material over the deck.

Downspout:  A vertical pipe or conduit used to carry runoff water from a gutter away from the structure; also called a conductor or leader.

Drain: An outlet or other device used to collect and direct the flow of runoff water from a roof area.

Drip Edge: A non-corrosive, non-staining material used along the eaves and rakes to allow water run-off to drip clear of underling construction.

Drip Edge: A noncorrosive, non-staining material used along the eves and rakes to allow water runoff to drip clear of underlying construction.

Dutch-Lap Method:  Application of very large individual shingles with the long dimension parallel to the eaves. Shingles are applied to overlap adjacent shingles in each course as well as the course below.

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Eave:  The part of the roof that meets or overhangs the walls of the building. The lowest edge that extends beyond the exterior wall.

Eaves Flashing: Additional layer of roofing material applied at the eaves to help prevent damage from water back up.

Edging Strips: Boards nailed along eaves and rakes after cutting back existing wood shingles to provide secure edges for reroofing with asphalt shingles.

Edge Venting: The practice of providing regularly spaced or continuously protected (louvered or otherwise shielded) openings along a roof edge or perimeter, used as part of a ventilation system to dissipate heat and moisture vapor.

Ell: An extension of a building at right angles to its length.

EPDM: Ethylene propylene diene M-class rubber, also called ethylene propylene diene terpolymer.  A terypolymer of ethylene, propylene and diene with the residual unsaturated portion of the diene in the side chain to provide for vulcanization. It is a thermosetting synthetic elastomer. EPDM is the acronym for 'ethylene propylene diene M-class rubber', which is a name assigned to this material within the classification established in ASTM D1418.

Expansion Joint: A structural separation between two building elements that allows free movement between the elements without damage to the roof or waterproofing system.

Exposed Nail Method: Application of roll roofing in which all nails are driven into the cemented, overlapping course of roofing. Nails are exposed to the weather.

Exposure I Grade Plywood: Type of plywood approved by the American Plywood Association for exterior use.


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Fascia: A flat board that runs along the eaves of a roof, typically capping the ends of the roof rafters to give the roof edge a more finished look and to provide a base for attaching gutters.

Fastener: Any of a wide variety of mechanical securement devices and assemblies, including nails, staples, screws, cleats, clips and bolts, that may be used to secure various components of a roof assembly.

Feathering Strips: Tapered wood filler strips placed along the butts of old wood shingles to create a level surface when reroofing over existing wood shingle roofs. Also called horsefeathers.

Felt: A fibrous material, saturated with asphalt and used as an underlayment or sheathing paper.

Fiberglass Mat: Blanket or rigid board insulation composed of glass fibers bound together, faced or unfaced, used to insulate roofs and walls.

Fire-retardant-treated (FRT) Plywood: Plywood that has been impregnated under pressure with mineral salts; in the event of fire, the burning wood and salts emit noncombustible gases and water vapor instead of the usual flammable vapors.

Flashing:  Pieces of metal or roll roofing used to prevent seepage of water into a building around any intersection of projection in a roof such as vent pipes, chimneys, adjoining walls, dormers and valleys. Galvanized metal flashing should be minimum 26-gauge.

Free-tab Shingles:  Shingles that do not contain factory applied strips or spots of self-sealing adhesive.

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Gable: 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 a sloping plane on each side of a single ridge  with a gable at each end.

Gambrel:  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. Features a gable at each end.

Gauge:  A metal thickness measurement; a smaller number indicates a thicker metal.

Glass Felt: Glass fibers bonded into a sheet with resin and suitable with resin and suitable for impregnation with asphalt in the manufacture of bituminous waterproofing, roof membranes and shingles.

Granules:  Ceramic coated, colored crushed rock that is applied to the exposed surface of asphalt roofing products.

Gravel Stop: A flanged device, frequently metallic, designed to prevent loose aggregate from washing off the roof and to provide a continuous finished edge for the roofing.

Gutter: The trough that channels water from the eaves to the downspouts.

Gypsum Board Panels:  Cementitious board stock with noncombustible core primarily comprised of gypsum that is commonly used as a barrier board, thermal barrier or cover board in a roof assembly.

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Hand Tabbing: A method of spot-applying asphalt-based adhesive to shingles for securement and wind resistance, also called 'hand-sealing'.

Head Lap:  Shortest distance from the butt edge of an overlapping shingle to the upper edge of a shingle in the second course below. The coverage portion of the top lap of strips shingles.

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

Hip Roof: A type of roof containing sloping planes of the same pitch on each of four sides.  Contains no gables.

Hip Shingles:  Shingles used to cover the inclined external angle formed by the intersection of two sloping roof planes. 

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Ice Dam: Condition formed at the lower roof edge by the thawing and refreezing of melted show on the overhang. Can force water up and under shingles, damaging walls and causing leaks.

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

Interlayment:  A felt, metal or membrane sheet material used between courses of steep sloping roofing to improve the weather and water-shedding characteristics of the primary roof covering during times of wind-driven precipitation; typically used with wood shakes.

Interlocking Shingles: Individual shingles that mechanically fasten to each other to provide wind resistance.

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Joist: Any of the small timbers, metal or wood beams arranged parallel to one another and spanning from wall to wall to support a floor, ceiling or roof of a building.

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Kick-Out Flashing (diverter): A metal flashing detail installed at the eave end of a roof-to-wall transition designed to direct runoff away from the wall or wall cladding.

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Laminated Shingles: Strip shingles containing more than one layer of tabs to create extra thickness. Also called architectural or dimensional shingles.

Lap: To cover the surface of one shingle or roll with another.

Lap Cement:  An asphalt based cement used to adhere overlapping plies of roll roofing.

Lead:  A soft, malleable, naturally weathering heavy metal; has low meeting point and a high coefficient of thermal expansion.

Low Slope Application: Method of installing asphalt shingles on roof slopes between two and four inches per foot.

Low-Slope Roof:  A category of roofs that generally includes weatherproof membrane types of roof systems installed on slopes at/or less than 3:12.

Louver: A slanted opening for ventilation.

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Mansard Roof: A roof built at two pitches, the steeper pitch commencing at the eaves and the flatter pitch finishing at the ridge.

Masonry: Construction, usually set in mortar, of natural building stone or manufactured units, such as brick, concrete block, adobe, glass block, tile, manufactured stone of gypsum block.

Masonry Primer:  An asphalt-based primer used to prepare masonry surfaces for bonding with other asphalt products.

Membrane: A flexible or semi-flexible roof covering or waterproofing whose primary function is to exclude water.

Metal Flashing: See flashing; frequently used as through-wall, step-, cap- or counter flashing.

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

Mildew: A superficial growth produced on organic matter or living plants by fungi.

Mineral Stabilizers: Finely ground limestone, slate, traprock, or other inert materials added to asphalt coatings for durability and increased resistance to fire and weather elements.

Mineral Surfaced Roofing: Asphalt shingles and roll roofing that are covered with granules.

Mold: A surface growth of fungus on damp or decaying matter. The term has no taxonomic significance and is used only in a general sense of visible fungal growth on organic matter.

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Nailer: Sometimes referred to as blocking; a piece of pieces of dimensional lumber and/or plywood secured to a structure deck or walls that provides a receiving medium for the fasteners used to attach membrane or flashing.

Natural Ventilation: A ventilation system utilizing ventilators installed in openings in the attic and properly positioned to take advantage of natural air flow to draw hot summer or moist winter air out and replace it with fresh outside air.

Nesting: A method of reroofing with new asphalt shingles over old shingles in which the top edge of the new shingle is butted against the bottom edge of the existing shingle tab.

Net Free Vent Area (NFVA):  Area unobstructed by screens, louvers or other materials.

No-Cutout Shingles:  Shingles consisting of a single, solid tab with no cutouts.

Non-Veneer Panel: Any wood based panel that does not contain veneer and carries and APA span rating, such as wafer board or oriented strand board.

Normal-Slope Application: Method of installing asphalt shingles on roof slopes between 4 inches and 21 inches per foot.

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Open Valley: A pipe fitting that directs a downpipe from the gutter, under the eaves soffit and down a wall or the distance from the outlet back to the wall of the structure.

Organic Felt: An asphalt roofing base material manufactured from cellulose fibers.

Oriented Strand Board: A mat-formed panel product with oriented layers resulting in directional properties. OSB is comprised primarily of wood strands bonded with exterior adhesive formulations under heat and pressure. Design capacities are referenced to the primary and secondary structural axes, which typically correspond to the manufacturing machine and cross-machine directions, respectively. The primary direction is often referred to as the strength direction.

Overflow Drainage:: Component(s) in a roof or waterproofing system used to protect it against damage from a water load imposed by blocked or partially blocked primary drainage systems; e.g., overflow scupper, overflow interior drain.

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Pallets: Wooden platforms used for storing and shipping bundles of shingles.

Parapet: A wall on the perimeter of a building that projects above the line of eaves.

Penetration: A projection through the roof, like a vent pipe, roof light or chimney.

Pitch: The angle at which a horizontal section of gutter is tilted in order to force water to flow toward a downspout. Also referred to as the 'gutter slope'.

Ply: The number of layers of roofing (e.g., one-ply, two-ply)

Plywood: A flat panel build up of sheets of wood called veneers, united under pressure by a bonding agent to create a panel with an adhesive bond between plies as strong or stronger than the wood.

Polyisocyanurate Foam: A cellular, unfaced, preformed rigid thermal insulation produced by the polymerization of polyisocyanates in the presence of polyhydroxyl compounds, catalysts, cell stabilizers, and blowing agents; classified in accordance with ASTM C591.

Polyisocyanurate Foam Board: A thermal insulation composed of polyisocyanurate foam with adhered facers; commonly called iso or isoboard; classified in accordance with ASTM C1289.

Polymer-modified Bitumen: A bitumen modified by including one or more polymers; composite sheets consisting of a polymer-modified bitumen, often reinforced with various types of mats or films and sometimes surfaced with films, foils or mineral granules.

Polyvinyl Chloride (PVC): a synthetic thermoplastic polymer prepared from vinyl chloride. PVC can be compounded into flexible and rigid forms through the use of plasticizers , stabilizers, fillers and other modifiers. Rigid forms are used in pipes; flexible forms are used in the manufacture of sheeting and roof membrane materials.

Ponding:  The excessive accumulation of water at low-lying areas on a roof that remains after 48 hours after precipitation under conditions conducive to drying.

Positive Drainage:  The drainage condition in which consideration has been made during design for all loading deflections of the deck and additional roof slope has been provided to ensure drainage of the roof area within 48 hours of precipitation.

Primary Drainage: Drainage devices such as drains or scuppers, that provide for the direct removal of water from a waterproofing system.

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Quick-Setting cement: An asphalt based cement used to adhere tabs or strip shingles to the course below. Also used to adhere roll roofing laps applied by the concealed nail method.

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Racking: A method of asphalt shingle application also referred to as the 'straight-up method', whereby shingle courses are applied vertically up the roof rather than laterally or across and up; requires placing a part of a shingle under product already in place every other course, which may result in a less-than-recommended number of nails being used for fastening.

Rafter: The supporting frame member immediately beneath the deck, sloping from the ridge to the wall plate.

Raggle: A groove or slot often cut in a masonry wall or other vertical surface adjoining a roof for inserting an inset flashing compound such as a reglet.

Rake: The inclined edge of a sloped roof over a wall from the eave to the ridge.

Random-tab Shingle: Shingles on which tabs vary in size and exposure.

Receiver: A component in a two piece counter flashing that may be surface mounted to a wall, inset into a raggle or embedded behind cladding. It is used for ease of installation and future maintenance and repair or replacement.

Re-Cover: The process of installing an additional roof covering over a prepared existing roof covering without removing the existing roof covering.

Reglet: A sheet-metal receiver for the attachment of counter flashing. A reglet may be surface mounted, inset into a raggle or embedded behind cladding.

Release Tape:  A plastic or paper strip that is applied to the back of self-sealing shingles. This strip prevents the shingles from  sticking together in the bundles and need not be removed for application.

Replacement:  The process of removing the existing roof covering, repairing any damaged substrate and installing a new roof covering; also refereed to as 'tear-off and replacement'.

Reroofing: The process of recovering or replacing an existing roof cover.  See replacement.

Ridge: The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.

Ridge Board: A horizontal board in wood frame construction at the upper end of the common rafters to which the rafters are nailed.

Ridge Capping: A formed metal designed to weatherproof the junction at the apex of opposing roof slopes.

Ridge Course: The last or top course of roofing materials, such as tile, roll roofing, shingles, that cover the ridge and overlaps the intersecting field roofing.

Ridge Shingles: Shingles used to cover the horizontal external angle formed by the intersection of two sloping roof planes.

Riser: The vertical distance from the eaves line to the ridge.

Ridge Vent: A ventilator located at the ridge that allows the escape of warm and/or moist air from the attic area or rafter cavity.

Roll Roofing: Coated felts, either smooth or mineral surfaced that are manufactured in a roll form.

Roof Assembly: An assembly of interacting roof components including the roof deck, vapor retarder -if present, insulation and membrane or primary roof covering designed to weatherproof.

Roof Cement:  A compound used to seal flashings, seal down shingles, and for other small waterproofing jobs.

Roof Curb:  Raised frame used to mount mechanical units such as air conditioning units, exhaust fans, skylights, etc., on a roof.

Roof Mount: A method of installing the gutter attachment directly to the roof, i.e., a rod with a hidden bracket or a roof bar with a fascia bracket.

Roof Slope:  The angle a roof surface makes with the horizontal, expressed as a ratio of the units of vertical rise to the units of horizontal length (sometimes referred to as runs).

Roof System:  A system of interacting roof components. See Roof Assembly.

Roofing Tape: An asphalt saturated tape used with asphalt cements for flashing and patching asphalt roofing.

Run: A length of horizontal section of gutter.

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Saddle: A small tapered/sloped roof area structure that helps to channel surface water to drains; frequently located in a valley. A saddle is often constructed like a small hip roof or pyramid with a diamond-shaped base.

Saddle Strap, Straps: Flat hangers that are nailed into the house to hold the downspouts in place.

Scupper: A drainage device in the form of an outlet through a wall, parapet wall or raised roof edge typically lined with a sheet-metal sleeve.

Seam: A joint formed by mating two separate sections of material. Seams can be made or sealed in a variety of ways, including adhesive bonding, hot-air welding, solvent welding, using adhesive tape and sealant.

Self-adhering Membrane: A membrane 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.

Service Life: The period of time a building component or system will function successfully without replacement or excessive repair assuming reasonable or expected periodic maintenance is performed.

Shed Roof:  A roof containing only one sloping plane. Has no hips, ridges, valleys or gables.

Shingle: A small unit of prepared roofing designed for installation with similar units in overlapping rows or courses on inclines normally exceeding 3:12 slope.

Single Ply Roofing: A roof system in which the principal roof covering is a single layer flexible thermoset or thermoplastic membrane.

Smooth Surfaced Roofing:  Roll roofing that is covered with ground talc or mica instead of granules.

Snow Guard:  A series of devices attached to a roof in a pattern that attempts to hold snow in place, thus preventing sudden snow or ice slides from the roof.

Soffit:  The exposed undersurface of any exterior overhanging section of a roof eave.

Soffit Vent: A manufactured or custom built air inlet source located at the downslope eave or in the soffit of a roof assembly.

Soil Stack:  A sanitation pipe that penetrates the roof; used to vent plumbing fixtures.

Specialty eaves Flashing Membrane:  A self adhering water proofing shingle underlayment designed to protect against water infiltration due to ice dams or wind-driven rain.

Square:  A unit used in measuring roof area equivalent to 100 square feet

Standing Seam:  A type of seam between adjacent sheets of materials made by turning up the edges of two adjacent metal panels and then folding or interlocking them in a variety of ways.

Starter Course: The first layer of roofing, applied along a line adjacent to the downslope perimeter of the roof area; with steep slope water-shedding roof coverings, the starter course is covered by the first course.

Starter Sheet:  Felt, ply sheet or membrane strip that is made or cut to a width narrower than the standard width of the roll material and used to start the shingling pattern at a roof edge.

Starter Strip:  Roll roofing or shingle strips applied along the downslope eave line before the first course of roof covering and intended to fill spaces between cutouts and joints of the first course.

Steep-Slope Roofs:  A category of roofing that generally includes water-shedding types of roof coverings installed on slopes exceeding 3:12.

Step Flashing:  Individual pieces of sheet-metal material used to flash walls, around chimneys, dormers and such projections along the slope of a roof. Individual pieces are overlapped and stepped up the vertical surface.

Strip Shingles: Asphalt shingles that are manufactured in strips approximately three times as long as they are wide with or without cutouts.

Structural Panel:  A metal roof panel designed to be applied over open framing rather than a continuous or closely spaced roof deck.

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

Surfacing:  The top layer or layers of a roof covering specified or designed to protect the underlying roofing from direct exposure to the weather.

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Tab: The exposed portion of strip shingles defined by cutouts.

Telegraphing:  A shingle distortion that may arise when a new roof is applied over an uneven surface.

Thermal Stress: The stress due to expansion and contraction that occurs due to changes in temperature.

Three-Tab Shingles:  A single layer shingle having three tabs.

Thermal Resistance (R):  The quantity determined by the temperature difference at steady state between two defined surfaces of a material or construction that induces a unit heat flow rate through a unit area.  A thermal resistance (R) value applies to a specific thickness of a material or construction. Can be added, subtracted, multiplied and divided by mathematically appropriate methods.

Thermoplastic Olefin Membrane (TPO):  A blend of polyproplene and ethylene-propylene polymers, colorant, flame retardants, ultraviolet radiation absorbers and other proprietary substances that may be blended with the TPO to achieve the desired physical properties. The membrane may or may not be reinforced.

Top Lap:  That portion of the roofing covered by the succeeding course after installation.

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UL:  Underwriters Laboratories, LLC.

UL Label:  Label displayed on packaging to indicate the listing for fire and/or wind resistance of asphalt roofing.

Undereave: Underside area of the overhang at the eave of the roof.

Underlayment:  A layer of asphalt-saturated felt (sometimes referred to as tar paper) which is laid down on a bare deck before shingles are installed to provide additional protection for the deck.


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

Valley Boards: A gutter at the bottom intersection of two sloping roofs, also called valley flashing.

Valley Gutter: Timber or profiled metal laid under a valley gutter to support it.

Vapor Retarder:  Any material used to prevent the passage of water vapor.  Material which, when installed on the high-vapor-pressure (warm in the winter) side of a material, retards the passage of moisture vapor to the lower-pressure (cold in winter) side.

Vent: Any outlet for air that protrudes through the roof deck, such as a pipe or stack. Any device installed on the roof, gable or soffit for the purpose of ventilating the underside of the roof deck.

Ventilators:  Devices that eject stale air and circulate fresh air (e.g., ridge, roof, gable, undereave, foundation or rafter vents and vented soffit panels.

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Water-Shedding:   The ability of individual, overlapping components to resist the passage of water without hydrostatic pressure.

Water-Shedding Roof System:  A roof system that depends on gravity for quick drainage via water shedding to prevent water entry into or through the system.

Water and Ice dam Protection Membrane:  A continuous membrane installed under steep-slope roofing materials in areas subject to ice damming or wind-driven rain that prohibits water that gets through roof covering from getting into the structure; ice-and water protection membranes classified by ASTM D1970 must also seal around fasteners.

Waterproofing:  Treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.

Wedge: Wedges are used behind fascia brackets to accommodate for an angled fascia or rafter tail. Wedges range from 7.5 degrees to 45 degrees.

Woven Valley: A method of valley construction in which shingles or roofing from both sides of the valley extend across the valley and are woven together by overlapping alternate courses as they are applied.

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Zincalume: Steel sheeting that is protected against corrosion by an aluminum-zinc coating.

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Roof 101

There is no doubt that a solid roofing system is necessary to the health of your home. While you can repair a roof, you can only do so for so long before it will need to be replaced, and the longer you wait, the more expense you can run into as the damage grows regardless of repairs.

Your roof can increase the value of your home, save you time and money, and protect you during inclimate weather.

Choosing Iossi for your roofing needs is a wise decision because roofing is a science, not an art and having a contractor who knows the area, the industry and the best practices will prevent you from having to redo your roof sooner than necessary.

When installing a new roof, there are factors to be aware of such as ventilation. Without proper ventilation your attic area will trap warm, moist air causing a host of problems like wood rot or fungus.  Knowing how much ventilation  is exactly enough, because too much ventilation can be as detrimental as to little, will make your home more energy efficient.

Selecting the right kind of shingles for your home, including its style and the environment will help assure you that you are protected during storms and in the heat of summer.  With so many years of experience, Iossi is able to assess your homes current roof, and explain what would work best for you.

If your roof is not installed properly, you may find that you have wasted a lot of money as well as time.  You want the right products, installed professionally to avoid running into problems a few years down the road.

Some signs that it is time to have your roof professionally done include:

  • Blistering: bubble like or long thin raised areas on the roof are the most common issue in roofing. They occur when a gas, usually water vapor is trapped within the roofing system. Solar heat causes that gas to expand and creates a pressure within the system that pushes the plies apart and results in blisters.
  • Open Laps: When adhesive is not properly used, open laps in the field membrane, especially the flashings, can occur. Sometimes, it is caused in built-up and modified bitumen systems when the bitumen is applied too cold. The laps appear to be closed but open as the roof ages.
  • Splitting: the most common splits occur when a metal accessory is flashed with membrane material and as the temperature changes, metals and membranes expand and contract at different rates. The membrane cannot move as must as the metal and will eventually fatigue and crack. Or the splits can occur in expansion joints. Roofs become more brittle and less resilient as time passes, so temperature changes, activity within the house and outside, and substrate movements can become a problem for a roof that is not able to flex as well as it did when it was new.
  • Punctures can become an issue, especially when caused by the carelessness of people who visit the roof, like window washers, media installation technicians, etc. They can also be caused by debris and may appear as holes or tears.
  • Penetrations, particularly pitch pans, can cause roof failure when the sealer itself, the container in which it sits and the penetration to which the sealant is supposed to adhere to are not done properly. If the penetration is not stabilized any vibration or movement of the penetration can cause the sealant to crack. Other factors that can cause a penetration to be a problem include whether or not it is properly supported, how old it is, and maintenance issues.
  • Wrinkles can occur in the flashings and the membrane, again due to diversity of movement between them, and a wrinkle can become a tunnel for water.
  • Flashings that are not properly secured at the top to prevent the membrane from slipping or forming a funnel, can cause problems.
  • Fasteners and Surfacings can become vulnerable to wind and sun.
  • Abuse and neglect. Thinking that a roof repair can wait, or looking for the cheapest way to repair a problem, can make the problem worse and add additional expense to having it done properly by a professional.

A good roofing system can save you a lot of expense in the long run, and should last a long time.

If you are unsure of whether your roof needs to be updated, contact Iossi for a free quote.

Iossi is always glad to inspect your current roofing system and make recommendations based on their knowledge of the area and their experience with products that have worked well.

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Roofing Care & Maintenance

Roofs need to be maintained and inspected periodically.  Foot traffic should be limited, since it can damage the surface and cause premature failure.  Particularly harsh storms can create problems, however you should not climb onto your roof to inspect it, but should have a professional who can do the inspection without adding to or missing any possible damage.

Inspect your roof twice a year, keep your drains clear and debris off the roof. Address any issues like small punctures and sealant failures right away to avoid having them develop into larger problems.

If you are have questions or reasons to consider a new roof, including noticing that many of your neighbors are suddenly reroofing, since most homes in an area will have been built around the same time, then contact Iossi.

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Our Policy

We put our customers first.


Our Thoughts

We earn our customers trust, it is part of what has kept us a successful business for so many years.  We know the area and we offer products and services that have proven to provide excellent results. 

Contact Us

4374 State Street
Bettendorf, Iowa 52722


Monday-Friday: 8-4
Other times available by appointment