The Highland reference library
Roofing, in plain language.
An illustrated roofing glossary. Get to know the parts above your head, the details in your quote, and the words your roofer uses.
259 terms · A–Z
Open a term for related words & drawingsA
Air barrierA continuous layer or connected system that limits air leakage through the building enclosure. Its joints and penetrations matter because moving air can carry heat and moisture into a roof assembly.Ventilation & moisture
Also found as: Air control layer, Air sealing
Air leakageUncontrolled movement of air through gaps in the building enclosure. Warm indoor air leaking into a cold roof space can carry moisture and contribute to condensation.Ventilation & moisture · Illustrated
Also found as: Air infiltration, Air exfiltration, Attic air leaks
Algae discolourationDark staining caused by biological growth on a roof surface, often seen on shingles. Appearance alone does not establish a leak or structural damage.Problems & maintenance · Illustrated
Also found as: Algae discoloration, Roof algae, Black roof streaks
Aluminium roofingRoofing made from aluminium, a lightweight metal that does not form iron rust. Alloy, finish, support and compatibility still matter, especially in demanding exposure conditions.Metal roofing
Also found as: Aluminum roofing
Architectural metal panelA metal roof panel generally intended to be installed over a supporting deck. This term alone does not establish a product's span capacity or minimum slope.Metal roofing
Also found as: Non-structural metal panel
Architectural shingleAn asphalt shingle built with laminated layers to create a thicker, more dimensional appearance. Its rating and warranty depend on the specific product and roof assembly.Other roof materials · Illustrated
Also found as: Laminated shingle, Dimensional shingle
Asphalt shingleA roofing unit typically made with a fibreglass mat, asphalt and protective mineral granules. Shingles overlap to shed water and require a suitable slope and underlayment.Other roof materials · Illustrated
Also found as: Composition shingle, Fibreglass shingle, Fiberglass shingle
AtticThe space between the upper-storey ceiling and the roof above it. Its insulation, air sealing and ventilation arrangement influence roof moisture and heat loss.Roof anatomy & shapes · Illustrated
Also found as: Roof space, Loft space
Attic ventilationAir movement through a vented attic to help manage heat and moisture. It works with insulation and air sealing; it cannot compensate for uncontrolled indoor air leaks into the attic.Ventilation & moisture · Illustrated
Also found as: Roof ventilation
B
Backpan flashingFlashing behind the uphill side of a chimney, skylight curb or similar obstruction. It receives runoff from above and directs water around the sides.Flashing & details · Illustrated
Also found as: Back pan, Back-pan flashing, Back flashing
Backwater lapAn overlap arranged so that water can run into the joint instead of over it. Correct sequencing of roof layers and flashing helps avoid this vulnerable condition.Problems & maintenance
Also found as: Reverse lap, Negative lap
BallastStone or pavers used by some low-slope roof systems to hold components in place or protect them. The added weight and wind resistance need to suit the designed assembly.Other roof materials · Illustrated
Also found as: Roof ballast, Ballasted roof
Base flashingThe portion of a flashing assembly that connects the roof surface to a vertical wall or projection. A counterflashing or other termination protects its upper edge.Flashing & details · Illustrated
Also found as: Roof base flashing
Base metalThe underlying sheet metal before protective metallic or paint coatings are considered. Steel, aluminium, copper and zinc have different weights, movement and compatibility requirements.Metal roofing
Also found as: Metal substrate
BattenA strip of wood or metal installed as a support or fixing base for roofing. Some metal, tile and other systems use battens; others require a continuous deck.Structure & layers · Illustrated
Also found as: Strapping, Roof lath
BirdsmouthA notch in a rafter that provides a seat on the wall's top plate. The cut and remaining rafter depth must suit the framing design.Structure & layers · Illustrated
Also found as: Bird's mouth, Birdsmouth cut, Rafter seat cut
BlisteringRaised bubbles in a roofing membrane, coating or shingle surface. Trapped moisture, air, adhesion problems or material conditions can contribute; diagnosis depends on the roof type.Problems & maintenance · Illustrated
Also found as: Roof blisters
BlockingShort pieces fitted between framing members, or solid backing provided at an attachment point. Blocking can support deck edges, stabilize framing or provide a fastening base.Structure & layers · Illustrated
Also found as: Roof blocking, Nailer
Box gutterA broad, box-shaped drainage trough, often built into a roof edge or between roof sections. Its lining, outlets and overflow provision form part of the roof drainage design.Drainage · Illustrated
Also found as: Built-in gutter, Internal gutter, Concealed gutter
BucklingAn unwanted ridge, bend or distortion in roofing or its substrate. Movement, moisture, attachment or an uneven deck may be involved, so the underlying cause matters before repairs.Problems & maintenance · Illustrated
Also found as: Roof buckles
Built-up roofingA membrane roof assembled from multiple reinforcing plies and layers of bituminous material. The finished surface may use aggregate, a cap sheet or another approved protection layer.Other roof materials · Illustrated
Also found as: BUR, Tar and gravel roof
BundleA packaged quantity of shingles. Coverage varies with the product, so a bundle is not a fixed roof area and is not the same as a roofing square.Installation & measurements · Illustrated
Also found as: Shingle bundle
Butyl tapeA preformed, tacky sealing strip used in certain panel laps and flashing joints. It is compressed within the intended joint and must be compatible with the roof system.Installation & measurements · Illustrated
Also found as: Butyl sealant tape, Mastic tape
C
Cap sheetThe upper sheet in certain multi-layer membrane roof systems. It provides the exposed weathering surface and may have a mineral-granule finish.Other roof materials · Illustrated
Also found as: Roofing cap sheet
Capillary actionWater movement through a narrow gap, including upward or sideways movement against gravity. Panel laps and joints may use specific shapes, breaks or sealants to interrupt this path.Problems & maintenance
Also found as: Capillarity, Capillary draw
Capillary grooveA small formed channel at a sheet-metal overlap that interrupts the close contact through which water can wick. It is one feature of a complete lap detail.Metal roofing · Illustrated
Also found as: Anti-capillary groove, Anti-siphon groove, Capillary break
Cedar shakeA wood roofing unit traditionally split to produce a textured surface, sometimes with a sawn back. Its installation and ventilation requirements differ from those of other roof coverings.Other roof materials · Illustrated
Also found as: Wood shake
Cedar shingleA sawn, tapered wood roofing unit with a more uniform surface than a traditional split shake. Grade, exposure and moisture management affect its service life.Other roof materials · Illustrated
Also found as: Wood shingle
Chalk lineA chalk-coated string snapped against a surface to leave a straight layout mark. Roofers use layout lines to keep courses, panels or fastening rows aligned.Installation & measurements · Illustrated
Also found as: Snap line, Chalkline
ChalkingA powdery residue that develops as a paint coating weathers. Chalking is different from colour fading, and coating warranties may treat the two separately.Problems & maintenance
Also found as: Paint chalking
Chimney flashingThe coordinated flashing around a chimney, which may include front, side and back pieces plus counterflashing. Larger uphill obstructions may also need a cricket to divert water.Flashing & details
Also found as: Chimney apron
Clay tileA fired-clay roofing unit available in curved or flat forms. Tiles shed water through their arrangement and laps, while the supporting roof and underlayment provide additional functions.Other roof materials · Illustrated
Also found as: Terracotta tile
CleatA metal fastening strip or tab that engages a folded edge of flashing or roofing. It can secure an edge while concealing fasteners or allowing specified movement.Installation & measurements
Also found as: Continuous cleat, Metal cleat
Closed valleyA valley where the roof covering conceals the central lining. With asphalt shingles, different cut or woven arrangements are possible only where the product instructions permit them.Flashing & details
Also found as: Closed-cut valley, Woven valley
Closure stripA shaped piece used to close gaps between a profiled roof panel and a trim or adjoining surface. Solid and ventilated closures serve different purposes and are not interchangeable.Flashing & details · Illustrated
Also found as: Foam closure, Profile filler, Vented closure
CoatingA protective or decorative layer on a roofing material. Metallic coatings and paint systems do different jobs; coating type, thickness and exposure suitability affect long-term performance.Metal roofing · Illustrated
Also found as: Roof finish, Paint finish
Collar tieA horizontal member joining opposing rafters near the ridge to resist their separation. It serves a different purpose from a lower rafter tie that restrains outward wall thrust.Structure & layers · Illustrated
Also found as: Collar ties
Concealed fastenerA fixing covered by the next panel, a seam or another roof component. It reduces exposed fixing points, but the complete roof still depends on correct seams and flashing.Metal roofing · Illustrated
Also found as: Hidden fastener, Secret fix
Concrete tileA roofing unit made from a cement-based mixture. Shape, finish, weight and fastening vary, and the roof structure must be suitable for the specified load.Other roof materials · Illustrated
Also found as: Cement tile
CondensationLiquid water formed when moist air or water vapour encounters conditions cold enough for it to condense. On or beneath a roof, it can resemble a rain leak but needs a different diagnosis.Ventilation & moisture
Also found as: Roof sweating, Condensate
Cool roofA roof surface designed to reduce solar heat absorption through suitable reflectance and emittance. Its effect on annual energy use depends on the climate and building, including heating needs.Performance & warranties
Also found as: Reflective roof
CopingA protective cap on the top of a parapet or other wall. It sheds water and needs joints and attachments that accommodate movement and resist wind.Flashing & details · Illustrated
Also found as: Parapet cap
Copper roofingRoofing made from copper sheet, which develops a changing surface patina over time. Its runoff and contact with other metals require careful detailing to avoid staining or corrosion.Metal roofing
Also found as: Copper roof
CorrosionDeterioration of a metal through reaction with its environment. Coating damage, persistent moisture and incompatible metals can accelerate it; the remedy depends on the metal and cause.Problems & maintenance
Also found as: Metal corrosion, Rust
Corrugated metalSheet metal formed with repeated waves or ribs. Corrugation stiffens the sheet; roofing performance also depends on the exact profile, laps, fasteners and slope.Metal roofing · Illustrated
Also found as: Corrugated roofing
Counter-battenA strip installed across or beneath another set of battens to create a second support direction or a drainage and ventilation space. Its arrangement depends on the roof system.Structure & layers · Illustrated
Also found as: Counterbatten, Counter strapping
CounterflashingFlashing that covers the upper edge of base or step flashing at a wall or chimney. It protects that junction while allowing the lower flashing to do its drainage job.Flashing & details · Illustrated
Also found as: Counter flashing
CourseA horizontal row of shingles, tiles or other individual roof units. Courses are laid with the specified exposure, offsets and overlaps for that roofing product.Installation & measurements · Illustrated
Also found as: Roofing course
Cover boardA rigid board above insulation and below a membrane in some roof assemblies. It can provide a suitable bonding surface and improve resistance to certain construction or service stresses.Structure & layers · Illustrated
Also found as: Roof coverboard
CoverageThe usable roof area or width covered after required overlaps and interlocks are accounted for. A panel's effective coverage is usually smaller than its overall manufactured dimensions.Installation & measurements
Also found as: Effective coverage, Net coverage, Cover width
CricketA small raised roof form that diverts water around the uphill side of a chimney or another obstruction. Its size and shape depend on the obstruction and roof layout.Roof anatomy & shapes
Also found as: Saddle
Cross-gable roofTwo or more gable roof sections meeting at an angle. Where the sections intersect, valleys often form and concentrate runoff.Roof anatomy & shapes · Illustrated
Also found as: Cross gable
CurlingLifting or turning of shingle edges or corners. It can arise from ageing or other material and installation conditions and may make the roof more vulnerable to wind and water.Problems & maintenance · Illustrated
Also found as: Shingle curl, Cupping
D
Dead loadThe permanent weight of the roof assembly and other fixed building components. Replacing one roof material with another may change this load on the structure.Performance & warranties
Also found as: Permanent load
Dead valleyA nearly level area where roof sections converge and runoff can collect. It needs a drainage and waterproofing detail suited to its actual slope and water exposure.Flashing & details · Illustrated
Also found as: Flat valley
Deck replacementRemoval and replacement of damaged or unsuitable roof sheathing. The extent may only become clear after tear-off, so the quote should explain how additional deck work is handled.Installation & measurements · Illustrated
Also found as: Re-decking, Sheathing replacement
DeflectionBending or movement of a structural member under load. Excessive deflection can affect roofing, connections and drainage even before a member reaches its strength limit.Performance & warranties
Also found as: Roof deflection, Sagging
Dew pointThe temperature at which air with a given moisture content becomes saturated and condensation can begin on a surface. Higher indoor moisture can increase the risk at cold roof surfaces.Ventilation & moisture
Also found as: Dewpoint
Dissimilar metalsDifferent metals that may react when electrically connected in the presence of moisture. Even runoff from one metal onto another can create compatibility problems, so contacts and drainage paths need checking.Problems & maintenance
Also found as: Galvanic corrosion, Bimetallic corrosion
DormerA projection through a sloping roof, usually containing a window. A dormer adds its own roof edges, wall junctions and flashing details to the main roof.Roof anatomy & shapes · Illustrated
Also found as: Roof dormer
Double-lock seamA standing seam closed with two successive folds of the panel edges. The finished joint, sealant and installation requirements depend on the particular metal roof system.Metal roofing · Illustrated
Also found as: Double-fold seam, Double locked seam
DownspoutA pipe that carries water from a gutter or roof outlet toward the ground or a drainage system. Its discharge location should suit the property's drainage plan.Drainage · Illustrated
Also found as: Leader, Rainwater pipe, Downpipe
Downspout elbowA bent fitting that changes a downspout's direction, such as around an overhang or at ground level. Its size and connection must suit the drainage system.Drainage · Illustrated
Also found as: Downpipe elbow, Downspout bend
Downspout extensionA continuation at the bottom of a downspout that directs water to an appropriate discharge point. Length and direction should account for grading, walkways and neighbouring property.Drainage · Illustrated
Also found as: Rainwater extension
DrainageThe planned route for water to leave a roof and move away from the building. Roof slopes, valleys, gutters, outlets and ground-level discharge all contribute.Drainage · Illustrated
Also found as: Roof drainage
Drip edgeAn edge flashing that guides water clear of the roof deck and edge components. Its shape and position help direct runoff into the intended drainage path.Flashing & details · Illustrated
Also found as: Eave flashing, Drip flashing
E
EaveThe lower edge of a sloping roof, usually extending beyond the outside wall. Rainwater leaves the roof here and may enter an eavestrough.Roof anatomy & shapes · Illustrated
Also found as: Eaves
EavestroughA channel along a roof eave that collects runoff and carries it to an outlet. This is the common Canadian term for a rain gutter.Drainage · Illustrated
Also found as: Gutter, Rain gutter, Eaves trough
End lapThe overlap where the end of one roofing sheet or membrane length meets another along the drainage direction. Correct orientation and sealing keep water moving over, rather than into, the joint.Installation & measurements · Illustrated
Also found as: Endlap, End overlap
EPDMEthylene propylene diene monomer: a synthetic rubber roofing membrane commonly used on low-slope roofs. Seams and details use compatible joining materials specified for the system.Other roof materials · Illustrated
Also found as: Rubber roofing, Ethylene propylene diene monomer
Exhaust ventAn opening that lets air leave a vented attic or roof space, often near the highest point. Its placement and capacity should suit the intake and roof geometry.Ventilation & moisture · Illustrated
Also found as: Attic exhaust
Expansion jointA designed separation that allows parts of a building or roof to move independently while maintaining weather protection. It is different from an ordinary panel overlap.Installation & measurements
Also found as: Movement joint
Exposed fastenerA fixing that passes through the visible face of a roof panel. Many metal systems use screws with sealing washers; placement, tightening and inspection follow the system's instructions.Metal roofing · Illustrated
Also found as: Through-fastened, Face-fastened, Screw-down roof
ExposureThe portion of a shingle, tile or shake left visible after the next course is installed. It affects water shedding and coverage and must match the product's installation requirements.Installation & measurements
Also found as: Shingle exposure, Reveal
F
FadingA change in a roof finish's colour with weathering and sunlight exposure. The amount and rate depend on the coating, colour and environment.Problems & maintenance
Also found as: Colour fade, Color fade
FasciaThe vertical finishing board or metal-covered face along the roof edge, often behind the eavestrough. It covers rafter ends and may provide a fixing surface for gutter hardware.Drainage · Illustrated
Also found as: Fascia board, Fascia cover
FastenerA screw, nail or other fixing that secures roof components. Material, length, diameter, embedment and placement must be compatible with the substrate and roofing system.Installation & measurements · Illustrated
Also found as: Roofing screw, Roofing nail
Fastener back-outA screw or nail gradually moving out of its intended seated position. It can loosen a component or compromise a seal and should be assessed along with substrate and movement conditions.Problems & maintenance · Illustrated
Also found as: Loose roof screw, Screw back-out, Nail pop
Finish warrantyCoverage for specified performance of a coating, such as defined limits on fading, chalking or film failure. It does not automatically cover leaks, dents or installation defects.Performance & warranties
Also found as: Paint warranty, Coating warranty
Fire classificationA rating describing a roof covering or assembly's performance in a specified fire test. A Class A external-fire classification is not a claim that the whole building is fireproof.Performance & warranties
Also found as: Fire rating, Class A roof, Class A fire
Fixed clipA panel clip used to restrain movement at a specified location. Its relationship to sliding connections and the panel's movement allowance is part of the roof system design.Metal roofing · Illustrated
Also found as: Fixed panel clip
FlangeA projecting edge or flat rim on a roof component, used for attachment or a weathering connection. A pipe boot, for example, has a flange that connects to the roof surface.Installation & measurements · Illustrated
Also found as: Flashing flange
FlashingMaterial shaped or installed to keep water out at roof joints, edges and openings. It must direct water onto the correct downstream surface, with suitable overlaps and movement allowance.Flashing & details · Illustrated
Also found as: Roof flashing
Flat roofThe everyday name for a roof that looks nearly level. A well-designed flat roof still has a drainage strategy, commonly using a small slope to drains or scuppers.Roof anatomy & shapes · Illustrated
Also found as: Flat roofing
G
GableThe roughly triangular part of a wall beneath the end of a two-sided pitched roof. The gable is the wall shape; the gable roof is the roof above it.Roof anatomy & shapes · Illustrated
Also found as: Gable end
Gable roofA roof with two sloping sides that meet along a ridge. The ends form gables. It is a simple shape, although additions can create more complex valleys and intersections.Roof anatomy & shapes · Illustrated
Also found as: Peaked roof
Gable ventA ventilation opening in a gable wall. Whether it is appropriate alongside other vents depends on the intended airflow strategy for the attic.Ventilation & moisture · Illustrated
Also found as: Gable louvre, Gable louver
GalvalumeA trade name commonly used for steel with an aluminium-zinc alloy coating. The metallic coating protects the steel; a painted finish, when present, is a separate coating layer.Metal roofing
Also found as: Aluzinc, Aluminum-zinc coated steel
Galvanized steelSteel protected by a zinc coating. Zinc helps resist corrosion, but cut edges, coating damage, incompatible materials and the exposure environment still need consideration.Metal roofing
Also found as: Galvanised steel, Zinc-coated steel
Gambrel roofA roof with two slopes on each of two sides: a gentler upper slope and a steeper lower slope. Often associated with barns, it creates more space beneath the roof.Roof anatomy & shapes · Illustrated
Also found as: Barn roof
GaugeA numbering convention used to describe sheet-metal thickness. For a given metal and gauge standard, a lower number usually means thicker sheet; compare stated thicknesses when evaluating different products.Metal roofing · Illustrated
Also found as: Metal gauge, 24 gauge, 26 gauge, 29 gauge
Granule lossShedding of the mineral particles on asphalt shingles. Some loose granules can be normal, while widespread bare areas or a change after a storm deserves closer assessment.Problems & maintenance
Also found as: Shingle granule shedding
GranulesMineral particles on the surface of asphalt shingles and some other roofing products. They provide colour and help protect the underlying material from sunlight and weathering.Other roof materials · Illustrated
Also found as: Shingle granules
Green roofA roof assembly that supports vegetation above waterproofing, with suitable root protection, drainage and growing medium. Its saturated weight and maintenance needs must be included in the design.Other roof materials · Illustrated
Also found as: Vegetated roof, Living roof
Gutter end capA fitted closure at the end of an eavestrough run. Its joint and seal keep collected rainwater moving toward the outlet rather than escaping through the open end.Drainage · Illustrated
Also found as: Eavestrough end cap, Gutter stop end
Gutter guardA cover or screen intended to reduce debris entering an eavestrough. It can reduce some cleaning work, but does not remove the need to inspect gutters and outlets.Drainage · Illustrated
Also found as: Leaf guard, Gutter screen
Gutter hangerA bracket or other support that secures an eavestrough to the building. Type, spacing and fastening need to suit the gutter, substrate and expected water, snow and ice loads.Drainage · Illustrated
Also found as: Hidden hanger, Gutter bracket
Gutter slopeThe gradual fall along an eavestrough toward its outlet. The required fall depends on the drainage layout and system; it differs from the roof's slope.Drainage · Illustrated
Also found as: Gutter fall, Gutter pitch, Eavestrough slope
H
HeadlapThe overlap at the upper end of a roofing unit beneath units in higher courses. Required headlap helps prevent water from travelling through the assembled roof covering.Installation & measurements · Illustrated
Also found as: Head lap
Headwall flashingFlashing at the upper end of a roof where it meets a wall across the slope. It bridges the roof-to-wall junction and directs water onto the roofing below.Flashing & details · Illustrated
Also found as: Endwall flashing, Apron flashing
HemA folded-back edge in sheet metal. It can stiffen or finish an edge or form part of an interlock; the fold's purpose depends on the detail.Installation & measurements · Illustrated
Also found as: Hemmed edge
High-temperature underlaymentAn underlayment rated for the temperatures expected beneath a hot roof covering, often metal. The manufacturer's stated rating and compatibility determine where it can be used.Structure & layers · Illustrated
Also found as: High temp membrane
HipThe outward-facing, sloping junction where two roof planes meet. It runs down from a ridge or peak toward an outside corner, rather than collecting water like a valley.Roof anatomy & shapes · Illustrated
Also found as: Hip line
Hip capThe covering over an outward sloping roof intersection. It protects the joint between the adjacent roof planes and must connect correctly to ridge and eave details.Flashing & details · Illustrated
Also found as: Hip capping
Hip roofA roof that slopes down on every side, typically with no vertical gable ends. Its outside roof intersections are hips, which need their own caps or finishing details.Roof anatomy & shapes · Illustrated
Also found as: Hipped roof
Hydrokinetic roof systemA water-shedding roof system that relies on slope and drainage to move water off the surface. It is not intended to function as a basin holding standing water.Metal roofing
Also found as: Water-shedding system
Hydrostatic roof systemA roof system designed to resist water penetration under specified water-head conditions. This describes a tested system and its details, not an assumption that any metal seam is watertight.Metal roofing
Also found as: Water-barrier metal roof
I
Ice and water membraneA self-adhering waterproofing underlayment used in vulnerable areas such as eaves and valleys. Coverage, laps and compatibility matter; it does not eliminate the causes of ice dams.Structure & layers · Illustrated
Also found as: Ice and water shield, Ice & water shield, Ice barrier, Peel and stick, Self-adhered membrane
Ice damA ridge of ice, often near an eave, that can trap meltwater behind it. Heat loss, snow cover and freezing conditions contribute; insulation, air sealing and drainage details all matter.Problems & maintenance · Illustrated · Animated
Also found as: Ice damming
Ice dam protectionThe combined measures used to limit ice-dam damage, including suitable underlayment and roof details plus control of heat and air leakage. A membrane alone does not prevent ice from forming.Problems & maintenance
Also found as: Ice dam prevention
Impact resistanceResistance to damage from impacts under a stated test method. A rating describes test performance; it does not promise that a roof will never dent, crack or suffer hail damage.Performance & warranties
Also found as: Hail resistance, Class 4 impact
Intake ventAn opening that admits outdoor air into a ventilation path, commonly near the eaves. Intake needs an unobstructed path to the intended exhaust openings.Ventilation & moisture · Illustrated
Also found as: Air intake
InterlockA shaped connection where neighbouring roofing units engage each other. It can help align and secure the covering, but does not replace required fasteners or flashing.Installation & measurements
Also found as: Interlocking panels
K
Kick-out flashingA diverter at the bottom of a roof-to-wall junction that sends runoff away from the wall and into the gutter or another intended drainage path.Flashing & details
Also found as: Kickout flashing, Diverter flashing
L
Live loadA variable load considered in structural design, such as certain maintenance or occupancy loads. Snow, wind and other environmental loads are evaluated under their applicable design provisions.Performance & warranties
Also found as: Roof live load
Low-slope roofA roof with a relatively shallow incline, where water drains more slowly. Material suitability and minimum slope are system-specific; a steep-slope panel cannot automatically be used here.Roof anatomy & shapes · Illustrated
Also found as: Low pitch roof
M
Mansard roofA roof with a steep lower slope and a gentler upper portion on all four sides. The steep lower portion can enclose usable upper-storey space.Roof anatomy & shapes
Also found as: French roof
Mechanically seamed roofA metal roof whose panel seams are folded together with a seaming tool or machine. The specified fold and sealant details determine the finished seam configuration.Metal roofing
Also found as: Mechanical seam, Field-seamed roof
Metal roofingA roof covering made from metal panels, shingles or tiles. Profile, base metal, coating, fastening and seam design all affect appearance, installation and suitability for a particular roof.Metal roofing · Illustrated
Also found as: Steel roofing, Metal roof
Metal shingleA relatively small metal roofing unit, often interlocking with surrounding units. It can resemble slate, wood or other shingles while using a metal substrate.Metal roofing · Illustrated
Also found as: Metal shingles
Metal tileA formed metal panel shaped to resemble rows of traditional roof tiles. Panel dimensions, fastening and overlap details are specific to the chosen profile.Metal roofing · Illustrated
Also found as: Tile-profile metal roofing, Modular metal tile
Minimum slopeThe shallowest roof incline permitted for a particular covering and its specified details. Seam design, laps, underlayment and exposure conditions can affect the applicable requirement.Installation & measurements
Also found as: Minimum roof pitch, Minimum roof slope
Modified bitumenAsphalt-based roofing modified with polymers, commonly supplied in reinforced sheets. Systems may be self-adhered, cold-applied, mechanically attached or heat-applied, according to their specifications.Other roof materials · Illustrated
Also found as: Mod-bit, SBS roofing, APP roofing
MossSmall plants that form raised growth on damp roof surfaces. Moss can retain moisture and interfere with shingle edges or drainage; cleaning methods must suit the covering.Problems & maintenance · Illustrated
Also found as: Roof moss, Moss growth
N
Nail flangeAn integral strip along a panel edge used for direct attachment beneath the adjoining panel. Despite the name, some systems use screws and slotted holes to accommodate movement.Metal roofing · Illustrated
Also found as: Nail strip, Fastening flange, Nail-strip standing seam
Net free ventilating areaThe actual open area available for airflow through a vent after accounting for screens, louvers and other obstructions. Use the manufacturer's value when planning ventilation capacity.Ventilation & moisture
Also found as: NFVA, NFA, Net free area
Non-prorated warrantyCoverage that does not reduce the specified benefit on an age-based schedule during the stated period. Other exclusions, limits and uncovered costs may still apply.Performance & warranties
Also found as: Non prorated warranty
O
Oil canningVisible waviness in a broad metal surface, often most noticeable as light changes. It can be an appearance characteristic rather than evidence of a leak; assess the cause and applicable product criteria.Problems & maintenance · Illustrated
Also found as: Panel waviness, Metal rippling
Open valleyA valley detail with an exposed central drainage channel between the adjacent roof coverings. The visible lining carries concentrated runoff down the roof.Flashing & details · Illustrated
Also found as: Exposed valley
OSBOriented strand board: an engineered panel made from bonded wood strands. Rated OSB can serve as roof sheathing when its specification and installation suit the assembly.Structure & layers · Illustrated
Also found as: Oriented strand board
OutletThe opening and fitting that connects an eavestrough to a downspout. Its location and capacity influence how quickly the gutter can drain.Drainage · Illustrated
Also found as: Drop outlet, Gutter outlet
Overflow drainageA secondary route for water to escape if the main roof drainage is blocked or overwhelmed. It may use separate drains or scuppers at a designed elevation.Drainage
Also found as: Secondary drainage, Overflow scupper
OverhangThe part of a roof that extends beyond an exterior wall. It can help shelter the wall and forms the area where fascia and soffit are often installed.Roof anatomy & shapes · Illustrated
Also found as: Roof overhang
P
Panel clipA small connector that secures a metal panel to its support, often inside a seam. Fixed or sliding clips are selected to suit the system's load and movement requirements.Metal roofing · Illustrated
Also found as: Roof clip
Panel panThe broad surface between raised ribs or seams on a metal roof panel. Flat pans can show visible waviness; small ribs or striations may change how light reflects across them.Metal roofing · Illustrated
Also found as: Flat pan
Panel profileThe cross-sectional shape of a roofing panel, including ribs, seams or tile-like steps. Profile affects how panels join and how the finished roof looks.Metal roofing · Illustrated
Also found as: Roof profile
Panel ribA raised lengthwise feature formed into a metal panel. Depending on the profile, ribs add stiffness, define the appearance or form part of the panel connection.Metal roofing · Illustrated
Also found as: Major rib, Minor rib
ParapetA wall that extends above the roof edge, common on low-slope buildings. The top needs weather protection and the roof-to-wall junction needs a continuous waterproofing detail.Roof anatomy & shapes · Illustrated
Also found as: Parapet wall
PatinaA surface layer that develops as a metal weathers, especially copper or zinc. It changes the colour and can be protective; its appearance varies with exposure and time.Problems & maintenance
Also found as: Metal patina
PenetrationAn opening through a roof for a pipe, vent, skylight or other equipment. Each opening needs a compatible flashing detail and must accommodate water flow and movement.Flashing & details · Illustrated
Also found as: Roof penetration
Pipe bootA flashing unit with a flexible collar that seals around a pipe passing through the roof. The flange, material and installation must suit the panel profile, pipe and service temperature.Flashing & details · Illustrated
Also found as: Vent boot, Pipe flashing, Roof boot
Plumbing ventA pipe that connects a plumbing drainage system to outside air, often through the roof. It is separate from an attic ventilation outlet and requires its own roof flashing.Flashing & details · Illustrated
Also found as: Vent stack, Soil stack, Stink pipe
PlywoodA wood panel made from thin layers bonded with the grain in alternating directions. Roof use requires the right panel grade, thickness, support spacing and fastening.Structure & layers · Illustrated
Also found as: Plywood decking
Ponding waterWater that remains in a low area of a roof after runoff should have drained. Its significance depends on duration, depth and the roof system, and it can indicate a drainage or deflection issue.Problems & maintenance · Illustrated
Also found as: Standing water, Roof ponding
Product warrantyThe manufacturer's written coverage for specified product defects or performance. Duration alone does not explain exclusions, installation conditions, remedies or the cost of labour.Performance & warranties
Also found as: Material warranty, Manufacturer warranty
Prorated warrantyA warranty whose available benefit decreases according to a stated schedule. The reduction may affect material value or another remedy, so the written calculation matters.Performance & warranties
Also found as: Pro-rated warranty, Proration
PurlinA horizontal structural member that supports roof panels or other roof framing. Its size, span and spacing must match the panel system and required loads.Structure & layers · Illustrated
Also found as: Roof purlin
PVCPolyvinyl chloride: a thermoplastic roofing membrane commonly installed with hot-air-welded seams. Formulation, reinforcement and compatibility with adjacent materials vary by product.Other roof materials · Illustrated
Also found as: Polyvinyl chloride roofing
PVDFPolyvinylidene fluoride: a resin used in some factory-applied architectural paint systems. Finish performance depends on the complete coating formulation, application and exposure, rather than the acronym alone.Metal roofing
Also found as: Fluoropolymer finish, Polyvinylidene fluoride
R
R-valueA measure of thermal resistance: a higher value means greater resistance to heat flow for the stated material or assembly. Gaps, compression and thermal bridges can reduce installed performance.Performance & warranties
Also found as: R value, Thermal resistance
Radiant barrierA low-emissivity surface designed to reduce radiant heat transfer when it faces an appropriate air space. It is not a substitute for the required insulation or moisture-control layers.Ventilation & moisture
Also found as: Reflective foil
RafterA sloping structural member that supports the roof deck. Rafters carry loads toward the building's supporting walls or other structural members.Structure & layers · Illustrated
Also found as: Roof rafter
Rafter tailThe end of a rafter extending beyond the exterior wall. It helps form the roof overhang and may be exposed or concealed behind fascia and soffit.Structure & layers · Illustrated
Also found as: Rafter tails
Rafter tieA horizontal connection between opposing rafters near their lower ends that resists outward thrust on the walls. Some ceiling joists perform this role in conventional roof framing.Structure & layers · Illustrated
Also found as: Rafter ties, Ceiling tie
Rain chainA linked chain or series of cups that guides water down from a gutter outlet. Wind, freezing and splash at the bottom affect whether it suits a particular location.Drainage · Illustrated
Also found as: Rain chains
RakeThe sloping edge at the gable end of a roof. Unlike the eave, it runs uphill toward the ridge. Rake trim protects and finishes this edge.Roof anatomy & shapes · Illustrated
Also found as: Verge, Gable edge
Rake trimA finishing and weather-protection piece along the sloping edge of a gable roof. Metal roofing systems use profile-specific edge details and fastening arrangements.Flashing & details · Illustrated
Also found as: Gable trim, Barge flashing, Verge trim
Re-roofingWork that replaces or renews a roof covering, either through removal and replacement or an allowable recover system. A written scope should identify which approach is proposed.Installation & measurements
Also found as: Reroofing, Roof replacement
RegletA groove or receiver in a wall used to secure the edge of counterflashing. The connection and its seal must prevent water from getting behind the flashing.Flashing & details · Illustrated
Also found as: Flashing reglet
Relative humidityThe amount of water vapour in air compared with what it can hold at the same temperature, expressed as a percentage. It changes as air warms or cools.Ventilation & moisture
Also found as: RH, Indoor humidity
RidgeThe highest horizontal line where two sloping roof planes meet. A ridge cap covers this junction; a ridge vent, when used, lets air escape beneath the cap.Roof anatomy & shapes · Illustrated
Also found as: Roof peak
Ridge beamA structural beam supporting the upper ends of rafters. It carries roof loads to its supports; its size, connections and supporting load path require structural design.Structure & layers · Illustrated
Also found as: Structural ridge
Ridge boardA board at the roof peak that aligns opposing rafters and provides a connection surface. It does not perform the load-carrying role of a structural ridge beam.Structure & layers · Illustrated
Also found as: Ridgeboard
Ridge capThe covering over the horizontal junction at the top of a pitched roof. It may work with closures or a ridge ventilation system, depending on the assembly.Flashing & details · Illustrated
Also found as: Ridge capping
Ridge ventA ventilation outlet along the ridge of a vented roof. It uses a protected opening beneath the ridge cap and needs suitable intake air to work as intended.Ventilation & moisture · Illustrated
Also found as: Continuous ridge vent
Rigid insulationInsulating boards made from materials such as polyisocyanurate, polystyrene or mineral wool. Their location and moisture, load and fire characteristics must suit the whole roof assembly.Structure & layers · Illustrated
Also found as: Insulation board, Polyiso, EPS, XPS
RiseThe vertical height change used in a roof slope measurement. It is paired with a horizontal run, not the length measured along the sloping roof surface.Installation & measurements · Illustrated
Also found as: Roof rise
Roll formingShaping sheet metal by passing it through a sequence of rollers. Roofing panels can be roll-formed in a factory or, with appropriate equipment, near the job site.Metal roofing
Also found as: Roll-forming, Site-formed panels
Roof angleThe incline of a roof measured in degrees above horizontal. A 6:12 rise-to-run slope is about 26.6 degrees; the degree value is different from the rise-per-12 number.Installation & measurements · Illustrated
Also found as: Roof angle in degrees, Pitch angle
Roof assemblyThe complete combination of structure, deck, insulation, air and vapour control, underlayment and roof covering, as applicable. Performance depends on how these parts work together.Structure & layers · Illustrated
Also found as: Roof system, Roof build-up
Roof cementA thick asphalt-based compound used in specified roofing or flashing details. Compatibility and intended application matter; spreading cement over a leak does not establish its cause.Other roof materials · Illustrated
Also found as: Roofing cement, Roofing mastic, Asphalt roof cement, Plastic cement
Roof coveringThe outer weather-exposed material, such as metal panels, shingles or a roofing membrane. It is one component of the roof assembly, rather than the entire roof.Structure & layers · Illustrated
Also found as: Roof cladding
Roof curbA raised frame around a roof opening that supports equipment or a skylight. Waterproofing turns up the curb and must connect properly to the unit above.Flashing & details · Illustrated
Also found as: Equipment curb, Skylight curb
Roof deckThe surface that supports the roof covering or the layers beneath it. In houses, it is commonly plywood, oriented strand board or boards fastened to the framing.Structure & layers · Illustrated
Also found as: Decking, Roof sheathing
Roof drainAn outlet that carries water from a low-slope roof into a drainage pipe. The drain connection, surrounding slope and debris protection must work with the waterproofing membrane.Drainage · Illustrated
Also found as: Internal roof drain
Roof inspectionA condition assessment of the covering, details and accessible related components. A useful report distinguishes observed defects from suspected hidden conditions and explains any limits to access.Problems & maintenance
Also found as: Roof assessment
Roof leakUnwanted water entry through or around a roof assembly. The indoor stain may be some distance from the entry point because water can travel along framing or other layers.Problems & maintenance
Also found as: Water ingress, Roof leakage
Roof maintenancePlanned checks and care that keep drainage paths clear and identify deterioration early. The roof material, surroundings and manufacturer instructions determine suitable methods and inspection needs.Problems & maintenance
Also found as: Roof care, Preventive maintenance
Roof pitchHow steep a roof is. In everyday roofing discussions, a 6:12 pitch means 6 units of rise for every 12 units of horizontal run. Strictly, pitch can mean rise divided by the full span, so confirm which notation is intended.Installation & measurements · Illustrated
Also found as: Pitch, Roof steepness
Roof planeOne continuous, generally flat surface of a roof. A simple gable roof has two main planes; a complex roof has many, each affecting measurements and panel layout.Roof anatomy & shapes · Illustrated
Also found as: Roof face, Roof facet
Roof slopeThe amount a roof rises for a given horizontal run. A 6:12 slope rises 6 units for every 12 units horizontally. Minimum slope is set by the roofing system and applicable requirements.Installation & measurements · Illustrated
Also found as: Slope, Rise over run, 6/12, 6:12
Roof ventA roof-mounted outlet used to ventilate an attic or roof space. It is different from a plumbing vent or a duct that exhausts a bathroom or kitchen directly outdoors.Ventilation & moisture
Also found as: Box vent, Static vent, Turtle vent
Roof-overInstallation of a new covering over an existing roof. Suitability depends on the existing condition, weight, fastening, moisture design, product instructions and local requirements.Installation & measurements
Also found as: Overlay, Recover, Roof recover
Roofing feltA sheet underlayment traditionally made with asphalt-saturated fibres. It provides a secondary layer beneath the roof covering; it is not intended to be the finished exposed roof.Structure & layers · Illustrated
Also found as: Felt paper, Tar paper
Roofing squareA roofing measurement equal to 100 square feet of roof surface. It describes area, not a package count; bundles and panels cover different amounts depending on the product.Installation & measurements
Also found as: Square, Squares
RotDecay of wood caused by fungi under persistently favourable moisture conditions. Replacing affected decking should be accompanied by finding and correcting the moisture source.Problems & maintenance
Also found as: Wood decay, Deck rot
RSIThermal resistance expressed in metric SI units, commonly used in Canadian specifications. It describes the same physical property as imperial R-value but uses a different numerical scale; compare values in matching units.Performance & warranties
Also found as: Metric R-value, SI thermal resistance
RunThe horizontal distance used in a roof slope measurement. For a simple symmetrical gable, the run from eave to ridge is approximately half the full structural span.Installation & measurements · Illustrated
Also found as: Roof run
S
ScupperAn opening through a parapet or roof-edge wall that lets water drain out. Scuppers can form part of the primary or overflow drainage system, depending on the design.Drainage · Illustrated
Also found as: Roof scupper
SealantA material applied to a joint to resist water or air entry. Compatibility, joint preparation and movement capacity matter; surface sealant alone is not a replacement for proper flashing.Installation & measurements · Illustrated
Also found as: Roof caulk, Caulking
Sealing washerA compressible seal used with certain exposed roofing screws. It must seat correctly without being crushed; the wrong material or tightening can create a future leak point.Installation & measurements · Illustrated
Also found as: Bonded washer, EPDM washer, Neoprene washer
Seam clampA connector that grips a compatible standing seam, often without piercing the panel. Clamp model, seam profile and tested capacity determine whether it suits snow retention or other attachments.Problems & maintenance · Illustrated
Also found as: Standing seam clamp, Non-penetrating clamp
Seam sealantA compatible sealing material placed in a roof seam according to the system detail. Whether it is required, and where it belongs, depend on the seam design and exposure.Installation & measurements · Illustrated
Also found as: Seam sealer
Seaming machineA powered tool that travels along a metal panel joint and folds its edges into the specified seam. Its rollers and settings must match the panel system.Metal roofing · Illustrated
Also found as: Roof seamer, Electric seamer
Self-sealing stripA factory-applied adhesive band on an asphalt shingle that bonds overlapping shingles under suitable conditions. Sealing depends on the product, weather and installation.Other roof materials · Illustrated
Also found as: Seal-down strip, Shingle sealant strip
Service lifeThe period a roof remains useful under its actual conditions and maintenance. It is an estimate of performance over time and is different from a warranty term.Performance & warranties
Also found as: Roof lifespan, Life expectancy
Shed roofA roof with one sloping plane. It may cover a whole building, a porch or an addition. Its shallowest allowable slope depends on the chosen roofing system.Roof anatomy & shapes · Illustrated
Also found as: Mono-pitch roof, Skillion roof, Lean-to roof
Shingle tabThe exposed section below a cut-out in a strip shingle. Traditional three-tab shingles have three such sections; other shingle designs create their pattern differently.Other roof materials · Illustrated
Also found as: Tab, Shingle tabs
Side lapThe overlap between adjacent roofing sheets or units along their sides. Its arrangement, sealing and fastening depend on the material, profile and roof conditions.Installation & measurements · Illustrated
Also found as: Sidelap, Side overlap
Sidewall flashingFlashing where a sloping roof meets a wall running up the slope. Shingle roofs often use step flashing; metal systems may use a continuous, system-specific detail.Flashing & details
Also found as: Side wall flashing
Single-ply membraneA roof waterproofing system based on one principal membrane layer. Common types include EPDM, TPO and PVC, with different attachment methods and seam treatments.Other roof materials · Illustrated
Also found as: Single ply roofing
SkylightA glazed opening in a roof that brings daylight inside. The unit, flashing kit and underlayment detail must match the roof material, slope and installation type.Flashing & details · Illustrated
Also found as: Roof window
Slate roofingRoofing made from thin pieces of natural stone. Slate is durable but relatively heavy, so the supporting structure, flashing and fastening need to suit the system.Other roof materials · Illustrated
Also found as: Natural slate
Sliding clipA panel connection that permits controlled movement as metal expands and contracts. Movement may occur within a multi-piece clip or at its engagement with the panel.Metal roofing · Illustrated
Also found as: Floating clip, Expansion clip
Slope factorA multiplier converting the horizontal projected area of a roof plane into its sloping surface area. A 6:12 slope has a factor of about 1.118, before any waste allowance.Installation & measurements · Illustrated
Also found as: Roof slope factor, Pitch multiplier
Slope transitionThe junction where a roof changes from one slope to another. A transition flashing or other specified detail carries water across the change without creating a vulnerable reverse lap.Flashing & details
Also found as: Pitch break, Transition flashing
SMPSilicone-modified polyester: a type of resin system used in factory-applied metal coatings. Colour, gloss retention and warranty terms vary among products.Metal roofing
Also found as: Siliconized modified polyester, Silicone modified polyester
Snap-lock seamA standing seam connection designed to engage by snapping adjacent panel edges together. It differs from a mechanically folded seam and has its own slope and installation limits.Metal roofing · Illustrated
Also found as: Snap lock
Snow guardAn individual roof-mounted device used as part of a snow-retention layout. Quantity, attachment and placement need to suit the roof and design loads; a few decorative pieces are not an engineered system.Problems & maintenance · Illustrated
Also found as: Snow stop, Snow cleat
Snow loadThe weight of snow and associated conditions that a roof or attachment must be designed to carry. Local climate, drifting and roof geometry influence the required design load.Performance & warranties
Also found as: Roof snow load
Snow railA continuous bar or fence supported above a roof to restrain sliding snow. Its supports and attachments form a load-bearing system that needs a suitable design.Problems & maintenance · Illustrated
Also found as: Snow fence, Snow bar
Snow retentionA designed system that restrains snow on a roof to reduce sudden sliding over entrances, paths or equipment. Selection must account for snow loads, roof slope, panel strength and attachment capacity.Problems & maintenance · Illustrated
Also found as: Snow management, Snow retention system
SoffitThe underside of a roof overhang. It may be solid or vented; a vented soffit can admit air to an attic when there is a clear, connected ventilation path.Drainage · Illustrated
Also found as: Soffit panel
Soffit ventAn intake opening in the underside of an eave. Insulation, paint, debris or an obstructed air path can reduce its useful ventilation area.Ventilation & moisture · Illustrated
Also found as: Eave vent, Soffit intake
Solar reflectanceThe fraction of incoming solar energy a surface reflects. Roof colour and finish influence it, but energy use also depends on insulation, climate and the building's operation.Performance & warranties
Also found as: Reflectivity, Albedo
Solid deckingA substantially continuous roof substrate made from panels or closely fitted boards. It differs from spaced supports and is required by many, but not all, roof coverings.Structure & layers · Illustrated
Also found as: Continuous sheathing, Solid sheathing
SpanThe distance between supports for a structural member, or the full horizontal width across a roof in a pitch calculation. Clarify which meaning is intended in a drawing or quote.Installation & measurements · Illustrated
Also found as: Roof span
Splash blockA shaped pad beneath a downspout outlet that spreads or directs runoff and reduces soil erosion. It is one part of surface drainage, rather than a complete drainage solution.Drainage · Illustrated
Also found as: Splash pad
SRISolar reflectance index: a calculated comparison of surface heating based on reflectance and thermal emittance under standard conditions. It is not a percentage of energy savings.Performance & warranties
Also found as: Solar reflectance index
Standing seamMetal roofing with raised seams between adjacent panels. Many systems conceal their fasteners beneath the seams; seam shape, clip design and slope requirements vary by product.Metal roofing · Illustrated
Also found as: Standing-seam roof
Starter courseThe first specially detailed row at a roof edge. For shingles, it supports and seals the first exposed course; other roof systems may use a different starter component.Installation & measurements
Also found as: Starter strip, Starter shingle
Steep-slope roofA roof inclined enough to use an appropriate water-shedding covering. The boundary between low and steep slope depends on the standard or system being discussed.Roof anatomy & shapes · Illustrated
Also found as: Pitched roof, Steep pitch roof
Step flashingIndividual flashing pieces interwoven with successive shingle courses where a sloping roof meets a wall. Each piece overlaps the one below to guide water back onto the roof.Flashing & details · Illustrated
Also found as: Stepped flashing
Stone-coated steelSteel roofing units finished with bonded mineral granules over protective coating layers. The granulated surface changes appearance and texture; product-specific installation and care still apply.Metal roofing
Also found as: Stone coated metal roofing
StriationA shallow line or crease formed along a metal panel pan. Striations alter its appearance and can make waviness less noticeable; they do not guarantee a perfectly flat surface.Metal roofing · Illustrated
Also found as: Pencil rib, Panel striations
Structural metal panelA panel designed and tested to span between supports under specified loads. Allowable spans, connections and slope limits come from the system's engineering and installation requirements.Metal roofing
Also found as: Structural roofing panel
SubstrateThe surface directly receiving a roofing layer, adhesive or attachment. Depending on the detail, it may be a roof deck, cover board, insulation or another prepared surface.Structure & layers · Illustrated
Also found as: Roof substrate
SwarfSmall metal chips or filings left by cutting and drilling. Loose steel particles can rust and stain a roof finish, so installation cleanup is important.Problems & maintenance · Illustrated
Also found as: Metal filings, Cutting debris, Drilling swarf
Synthetic roofingManufactured roofing that may imitate slate, shake or tile using polymer, rubber or composite materials. Fire, impact and weather performance must be checked for the particular product.Other roof materials
Also found as: Composite roofing, Synthetic slate, Synthetic shake
Synthetic underlaymentA manufactured sheet underlayment, often polymer-based, used beneath roofing. Products differ in traction, fastening, vapour permeability, exposure time and temperature limits.Structure & layers · Illustrated
Also found as: Synthetic roof underlay
T
Tapered insulationInsulation boards made with a changing thickness to create drainage slopes on a low-slope roof. Layout directs water toward drains, scuppers or gutters.Structure & layers · Illustrated
Also found as: Tapered roof insulation
Tear-offRemoval of an existing roof covering before replacement. It exposes underlying materials for inspection and allows damaged decking or unsuitable layers to be addressed.Installation & measurements
Also found as: Roof strip-off, Roof removal
Termination barA strip used to secure the upper edge of a membrane or flashing to a vertical surface. Its fasteners, seal and any counterflashing must follow the system detail.Flashing & details
Also found as: Term bar
Thermal bridgeA path through an assembly that conducts heat more readily than neighbouring insulated areas. Framing and metal connections can create bridges and lower local surface temperatures.Ventilation & moisture
Also found as: Cold bridge, Thermal bridging
Thermal emittanceA surface's ability to release heat as infrared radiation. It is separate from how much sunlight the surface reflects, and both properties affect roof surface temperature.Performance & warranties
Also found as: Emissivity
Thermal movementThermal movement is the expansion and contraction of roofing materials as temperatures change. Long metal panels may require sliding connections and carefully positioned fixed points to accommodate this movement without putting stress on the roof.Installation & measurements · Illustrated
Also found as: Thermal expansion, Expansion and contraction
Three-tab shingleAn asphalt shingle with cut-outs that give the exposed portion three regularly spaced tabs. It typically has a flatter, more uniform appearance than a laminated architectural shingle.Other roof materials · Illustrated
Also found as: 3-tab shingle
TPOThermoplastic polyolefin: a single-ply roof membrane whose seams are typically joined with hot-air welding. Proper welds, attachment and flashing are essential to the finished system.Other roof materials · Illustrated
Also found as: Thermoplastic polyolefin
Transferable warrantyA warranty that can pass to a subsequent owner when its stated conditions are met. Registration, deadlines, fees or reduced coverage may apply depending on the document.Performance & warranties
Also found as: Warranty transfer
TrussAn engineered framework, often triangular, that supports a roof. Its connected members work as a system; altering one member can change the way the entire truss carries loads.Structure & layers · Illustrated
Also found as: Roof truss
Truss chordAn outer member of a roof truss. Top chords follow the roof slopes; the bottom chord usually runs across the base of the truss.Structure & layers · Illustrated
Also found as: Top chord, Bottom chord
Truss webAn internal member joining the chords of a roof truss. Webs help transfer loads through the engineered framework and must not be cut or moved without an approved design.Structure & layers · Illustrated
Also found as: Web member, Truss webs
U
UnderlaymentA protective layer beneath the main roof covering that provides secondary weather protection. Its type, attachment, overlaps and temperature rating must suit the covering and roof conditions.Structure & layers · Illustrated
Also found as: Roof underlay, Roofing underlayment
Unvented roof assemblyA roof designed without a conventional ventilation space beneath the roof deck. Insulation, air sealing and moisture control must be coordinated specifically for this type of construction.Ventilation & moisture
Also found as: Unvented attic, Compact roof, Warm roof
V
ValleyThe inward-facing junction between two roof slopes. It collects runoff from both sides, making the valley lining, overlaps and drainage path especially important.Roof anatomy & shapes · Illustrated
Also found as: Roof valley
Valley flashingA lining or formed metal piece that carries water along a roof valley. Its width, overlaps, fastening and relationship to the roof covering depend on the selected system.Flashing & details · Illustrated
Also found as: Valley metal, Valley lining
Vapour barrierA very low-permeance vapour control layer. The term is sometimes used loosely for all vapour retarders, so the actual material rating and intended roof assembly matter.Ventilation & moisture
Also found as: Vapor barrier
Vapour permeanceA measure of how readily water vapour passes through a material at its stated thickness. Greater permeance allows more diffusion; it does not describe air leakage or liquid-water resistance.Ventilation & moisture
Also found as: Vapor permeance, Perm rating, Vapour diffusion
Vapour retarderA material or layer that slows water vapour diffusion. Its permeability and location must suit the climate and assembly; it serves a different function from an air barrier.Ventilation & moisture
Also found as: Vapor retarder, Vapour control layer, Vapor control layer
Ventilation baffleA channel or separator that keeps insulation clear of the airflow path near the eaves. It helps connect soffit intake air to the attic or another designed ventilation space.Ventilation & moisture · Illustrated
Also found as: Rafter vent, Insulation baffle, Air chute
Ventilation channelA continuous air space within a roof assembly. Its purpose and required dimensions depend on the design; an isolated gap with no inlet or outlet is not a working ventilation path.Ventilation & moisture · Illustrated
Also found as: Vent cavity, Air gap
W
Waste allowanceExtra material allowed for cuts, layout, valleys, hips and other installation needs. It depends on roof geometry and the product layout, rather than one universal percentage.Installation & measurements
Also found as: Cutting allowance, Roofing waste
Watertightness warrantyWritten coverage for water penetration under stated conditions. Some roof systems offer it separately; the responsible party, approved assembly, exclusions and remedy must be checked in the actual document.Performance & warranties
Also found as: Weathertightness warranty, Leak warranty
Wet storage stainWhite or grey corrosion deposits that can form on zinc-coated metal when moisture is trapped between closely stacked sheets with little airflow. Severity depends on the exposure.Problems & maintenance · Illustrated
Also found as: White rust, Storage staining
Wind upliftUpward wind forces that can pull roofing and attachments away from their supports. Resistance depends on the tested assembly, fastener layout, substrate and location on the roof.Performance & warranties
Also found as: Uplift resistance, Wind resistance
Wind-driven rainRain pushed sideways or upward by wind. Roof edges, laps, vents and openings need details appropriate to this exposure, rather than relying only on water flowing straight downhill.Problems & maintenance
Also found as: Driven rain
Workmanship warrantyThe installer's written coverage for specified installation defects. The scope, duration and remedy should be stated clearly and distinguished from the manufacturer's product coverage.Performance & warranties
Also found as: Installation warranty, Labour warranty, Labor warranty
Woven valleyA shingle valley with courses from opposing roof slopes interlaced across the junction. Suitability depends on the shingle design and published installation instructions.Flashing & details · Illustrated
Also found as: Interwoven valley
Z
Zinc roofingRoofing made from zinc sheet or a zinc alloy. It develops a protective patina and requires suitable underside moisture management and compatible detailing.Metal roofing
Also found as: Zinc roof
See how the parts fit together.
Select a numbered marker or a name beneath a drawing to explore that part of the roof.
Animated guide
How an ice dam forms
Why ice builds at the eave in a Caledon winter, and why the fix lives in the attic rather than on the roof. A metal roof sheds snow and water readily, but no roof covering can cure a warm attic.
Step 1 of 6
Snow on a cold roof. Snow settles on the roof during a cold spell. Over the heated rooms and over the unheated overhang alike, the roof surface starts out as cold as the outside air.
Conceptual animation · not to scale · details vary by roof and attic
Meet the roofline
Follow the horizontal ridge, sloping rake and lower eave. Where two roof sections turn inward, they form a valley.
Ridge. The highest horizontal line where two sloping roof planes meet. A ridge cap covers this junction; a ridge vent, when used, lets air escape beneath the cap.
Go to term →Conceptual drawing · not to scaleDownload drawing ↓
Beneath the surface
The metal covering sits above protective underlayment, a supporting deck and structural framing. Actual layer arrangements vary by roof system.
Roof covering. The outer weather-exposed material, such as metal panels, shingles or a roofing membrane. It is one component of the roof assembly, rather than the entire roof.
Go to term →Conceptual drawing · not to scaleDownload drawing ↓
Where the water goes
At the eave, the drip edge directs runoff toward the eavestrough. The fascia closes the vertical edge; the soffit finishes the underside.
Drip edge. An edge flashing that guides water clear of the roof deck and edge components. Its shape and position help direct runoff into the intended drainage path.
Go to term →Conceptual drawing · not to scaleDownload drawing ↓
An attic that can breathe
In this vented assembly, outside air enters low at the soffits and exits high at the ridge. Insulation stays clear of the ventilation path.
Soffit vent. An intake opening in the underside of an eave. Insulation, paint, debris or an obstructed air path can reduce its useful ventilation area.
Go to term →Conceptual drawing · not to scaleDownload drawing ↓
The roof meets a wall
The teal pieces show step flashing interwoven with shingle courses. The drawing isolates this layer; a finished wall junction also needs protection over its upper edges, such as counterflashing.
Step flashing. Individual flashing pieces interwoven with successive shingle courses where a sloping roof meets a wall. Each piece overlaps the one below to guide water back onto the roof.
Go to term →Conceptual drawing · not to scaleDownload drawing ↓
Inside a standing seam
Raised panel edges form the seam. A concealed clip connects the panel to its support; the exact seam and movement detail depend on the system.
Standing seam. Metal roofing with raised seams between adjacent panels. Many systems conceal their fasteners beneath the seams; seam shape, clip design and slope requirements vary by product.
Go to term →Conceptual drawing · not to scaleDownload drawing ↓
Four familiar roof shapes
Compare gable, hip, shed and gambrel forms. The shape changes the roof's edges, intersections and detailing needs.
Gable roof. A roof with two sloping sides that meet along a ridge. The ends form gables. It is a simple shape, although additions can create more complex valleys and intersections.
Go to term →Conceptual drawing · not to scaleDownload drawing ↓
Sealing around a pipe
A flexible boot fits around a vent pipe and connects to the roof with a flange. Materials, placement and seals must suit the roof and pipe.
Pipe boot. A flashing unit with a flexible collar that seals around a pipe passing through the roof. The flange, material and installation must suit the panel profile, pipe and service temperature.
Go to term →Conceptual drawing · not to scaleDownload drawing ↓
These drawings explain concepts. Layer arrangements, fasteners and installation details depend on the selected roof system.
A little context goes a long way.
These definitions cover common residential and technical roofing language, with Canadian and US names where helpful. Exact construction details and ratings depend on the roof system.
Reference shelf
For deeper technical reading, explore these industry and building-science resources.
- IKO · roof parts and shingle terminology ↗
- NRCA · technical roofing glossary ↗
- Metal Construction Association · metal roofing fundamentals ↗
- InterNACHI · collar ties and rafter ties ↗
- RCABC · roofing details and terminology ↗
- American Galvanizers Association · wet storage stain ↗
- NZ Metal Roofing Manufacturers · swarf and cut-edge corrosion ↗
- Building Science · understanding air barriers ↗
- Building Science · understanding vapour barriers ↗
- S-5! · snow retention fundamentals ↗