Whether you are getting a free roof estimate, reading an inspection report, or comparing materials, roofing terminology can be confusing. This glossary defines 80+ roofing terms in plain English so you can make informed decisions about your home.
A
Algae Resistance
A property of shingles treated with copper or zinc granules that inhibit the growth of blue-green algae. Algae causes dark streaks on roofs and is common in humid climates. Most premium asphalt shingles now include algae-resistant granules.
Architectural Shingles
Also called dimensional or laminated shingles. These are multi-layered asphalt shingles that create a textured, three-dimensional appearance on the roof. They are thicker, more durable, and longer-lasting than three-tab shingles. Most roof replacements today use architectural shingles.
Asphalt Shingles
The most common residential roofing material in the United States. Asphalt shingles consist of a fiberglass mat coated with asphalt and topped with ceramic granules for UV protection and color. They typically last 20-30 years and are available in three-tab and architectural styles. See our guide on the best roofing materials for Central Valley heat.
Attic Ventilation
The system of intake and exhaust vents that allows air to circulate through the attic space. Proper ventilation prevents heat buildup in summer and moisture accumulation in winter. Poor ventilation is the number one cause of premature shingle failure and voided warranties.
B
Blistering
Bubbles or raised areas on the surface of asphalt shingles caused by trapped moisture or manufacturing defects. Minor blistering is cosmetic, but severe blistering can expose the underlying mat and lead to leaks. Blistering is often covered under manufacturer warranties.
Boot (Pipe Boot)
A pre-formed flashing component that fits around plumbing vent pipes where they penetrate the roof. Boots are typically made of rubber, neoprene, or metal and are a common source of leaks when they crack or deteriorate. They should be inspected during every roof inspection.
Built-Up Roofing (BUR)
A traditional flat roofing system consisting of alternating layers of bitumen (asphalt or tar) and reinforcing fabric. Multiple layers create a thick, durable membrane. BUR has been used for over 100 years and is still common on commercial buildings.
C
Cap Sheet
The top layer of a built-up or modified bitumen roof system. It is typically a granule-surfaced membrane that provides UV protection and weather resistance. The quality of the cap sheet significantly affects the lifespan of a flat roof.
Caulk (Roofing Sealant)
A flexible waterproof compound used to seal joints, gaps, and small penetrations on a roof. Roofing caulk is formulated to withstand UV exposure and temperature extremes. It should not be used as a substitute for proper flashing installation.
Chalk Line
A straight reference line snapped onto the roof deck using a chalk-covered string. Roofers use chalk lines to ensure shingles are installed in straight, even rows. Proper alignment prevents water intrusion and gives the roof a clean appearance.
Class A Fire Rating
The highest fire-resistance rating for roofing materials as defined by UL 790 testing standards. Class A materials can withstand severe fire exposure. Asphalt shingles, metal roofing, tile, and concrete all carry Class A ratings. California building codes require Class A roofing in many areas.
Closed Valley
A valley installation method where shingles from both roof planes overlap across the valley center, completely covering the metal flashing beneath. This creates a cleaner appearance but can trap debris. Compare with open valley.
Coating (Roof Coating)
A liquid-applied membrane that creates a seamless protective layer over an existing roof surface. Coatings extend roof life, improve energy efficiency, and can meet Title 24 cool roof requirements. See our page on roof coating services.
Collar (Pipe Collar)
See Boot. A collar is another term for the flashing component that seals around roof penetrations such as plumbing vents.
Condensation
Moisture that forms when warm, humid air meets a cool surface inside the attic or roof assembly. Chronic condensation leads to mold, wood rot, and insulation damage. Proper attic ventilation and vapor barriers prevent condensation problems.
Cool Roof
A roofing system designed to reflect more sunlight and absorb less heat than a standard roof. Cool roofs use reflective materials, coatings, or light-colored membranes to reduce cooling costs by 10-30%. California Title 24 requires cool roofing on most projects in the Central Valley.
Counter-Flashing
Metal flashing embedded into a masonry wall or chimney that overlaps the base flashing below. Counter-flashing creates a two-piece waterproofing system that allows for thermal movement without breaking the seal. It is critical around chimneys and parapet walls.
Course
A single horizontal row of shingles or roofing material. Shingles are installed in overlapping courses from the eave to the ridge. Each course covers the nailing zone of the course below it.
Cricket (Saddle)
A small peaked structure built behind a chimney or other roof obstruction to divert water around it. Without a cricket, water pools behind the chimney and causes leaks. Building code requires crickets behind chimneys wider than 30 inches.
Curbing
A raised frame installed on a flat roof to support mechanical equipment such as HVAC units. Curbing elevates equipment above the roof membrane and provides a surface for flashing to seal against. Proper curbing prevents leaks around rooftop equipment.
Curling
A common shingle defect where the edges turn upward (cupping) or downward (clawing). Curling is caused by age, poor ventilation, improper installation, or moisture absorption. Curled shingles are vulnerable to wind damage and indicate the roof is nearing end of life. See signs you need a new roof.
D
Deck (Roof Deck)
The structural surface that the roofing system is installed on, typically made of plywood or oriented strand board (OSB) sheets nailed to the rafters. The deck must be sound, dry, and properly nailed before any roofing material is applied. Damaged decking is often discovered during a roof replacement.
Dormer
A structural extension that projects from a sloped roof, typically containing a window. Dormers add light and living space but create additional joints and valleys that require careful flashing. They are common leak points if not properly sealed.
Downspout
The vertical pipe that carries rainwater from the gutter down to the ground or drainage system. Downspouts should discharge water at least 4-6 feet away from the foundation. Clogged downspouts cause water to back up into the gutters and overflow against the fascia.
Drip Edge
An L-shaped metal strip installed along the eaves and rakes of a roof. Drip edge directs water away from the fascia board and into the gutter. It prevents water from wicking back under the roofing material and is required by building code on most roof installations.
E
Eave
The lower edge of a roof that overhangs the exterior wall. Eaves protect the walls from rain and provide shade. The eave is where gutters are typically installed and where ice dams can form in colder climates.
EPDM (Ethylene Propylene Diene Monomer)
A synthetic rubber membrane used primarily on flat and low-slope roofs. EPDM is black, durable, and relatively inexpensive. It is installed in large sheets that are either glued, mechanically fastened, or ballasted. EPDM is less common in California than TPO because it absorbs rather than reflects heat.
Exposure
The portion of a shingle or roofing material that is visible and exposed to the weather after installation. The standard exposure for architectural shingles is approximately 5.625 inches. Incorrect exposure voids the manufacturer warranty.
F
Fascia
The vertical board that runs along the lower edge of the roof, mounted to the ends of the rafters. Fascia supports the bottom row of roof tiles and the gutter system. It is typically made of wood, aluminum, or composite material and should be inspected for rot during any roof project.
Felt Paper (Tar Paper)
A traditional roofing underlayment made from organic or fiberglass mat saturated with asphalt. Available in 15-pound and 30-pound weights. Felt paper has largely been replaced by synthetic underlayment on modern roof installations due to the latter's superior tear resistance and longevity.
Flashing
Thin pieces of metal (typically aluminum, galvanized steel, or copper) installed at joints, valleys, walls, chimneys, and penetrations to prevent water infiltration. Flashing is one of the most critical components of a roof and one of the most common sources of leaks when improperly installed. See our gutters and flashing page.
Flat Roof
A roof with a slope of less than 2:12. Despite the name, flat roofs always have a slight pitch to allow water drainage. Common flat roof materials include TPO, EPDM, built-up roofing, and modified bitumen. See our comparison of flat roof vs. pitched roof costs.
G
Gable
The triangular portion of a wall between the edges of intersecting roof pitches. Gable roofs are the most common roof shape in residential construction. Gable vents are sometimes installed in the gable wall to provide attic ventilation.
Granules
Small, crushed rock particles embedded in the surface of asphalt shingles. Granules provide UV protection, color, and fire resistance. Granule loss is normal as shingles age, but excessive granules in your gutters indicate the shingles are deteriorating. See signs you need a new roof.
Gutter
A channel installed along the eave of a roof to collect and direct rainwater to downspouts. Gutters protect the foundation, siding, and landscaping from water damage. They must be properly sized, pitched, and maintained to function correctly. See our gutter installation guide.
H
Hip
The external angle formed where two sloping roof planes meet. A hip roof has slopes on all four sides, making it more aerodynamic and wind-resistant than a gable roof. Hip ridges require special cap shingles and careful flashing.
Hip Roof
A roof design where all four sides slope downward from the ridge to the eaves. Hip roofs are more stable in high winds than gable roofs and are common in areas prone to storms. They require more material and labor to install.
I
Ice and Water Shield
A self-adhesive waterproof membrane applied to vulnerable areas of the roof deck, including valleys, eaves, and around penetrations. It provides an extra layer of protection against water infiltration from ice dams or wind-driven rain. Required by code in most jurisdictions along eaves and valleys.
Impact Resistance
A shingle's ability to withstand damage from hail and falling debris, rated on a scale from Class 1 to Class 4. Class 4 shingles can withstand a 2-inch steel ball dropped from 20 feet. Impact-resistant shingles may qualify for insurance discounts in hail-prone areas.
J
Joist
A horizontal structural member that supports the ceiling below the attic and sometimes the roof deck above. Joists transfer loads to the walls and foundation. They are distinct from rafters, which are the sloped structural members that form the roof pitch.
K
Kick-Out Flashing
A specialized piece of flashing installed where a roof edge meets a sidewall, directing water into the gutter instead of behind the siding. Missing kick-out flashing is a common cause of hidden water damage inside exterior walls. Building code now requires kick-out flashing in most jurisdictions.
L
Laminated Shingles
See Architectural Shingles. Laminated shingles are made by bonding two or more layers of shingle material together, creating a thicker, more dimensional product.
Leak Barrier
See Ice and Water Shield. A self-adhesive membrane installed on the roof deck in areas prone to water intrusion.
Low-Slope Roof
A roof with a pitch between 2:12 and 4:12. Low-slope roofs require different materials and installation methods than steep-slope roofs. Standard asphalt shingles cannot be used below a 2:12 pitch. Modified bitumen and single-ply membranes are common choices for low-slope applications.
M
Mansard Roof
A four-sided hip roof with two slopes on each side. The lower slope is steeper than the upper slope. Mansard roofs maximize usable attic space and are common on French-style and commercial buildings. They require careful waterproofing at the slope transition.
Membrane
A continuous waterproof sheet used to cover flat or low-slope roofs. Common membrane materials include TPO, EPDM, and PVC. Membranes can be mechanically attached, fully adhered, or ballasted. See our flat roofing services.
Metal Roofing
A roofing system made from steel, aluminum, copper, or zinc panels or shingles. Metal roofs last 40-70 years, reflect solar heat, and are highly wind-resistant. They are increasingly popular in the Central Valley for energy efficiency and longevity. See our metal roofing services and our comparison of metal roofing vs. asphalt shingles.
Modified Bitumen
A flat roofing material made from asphalt modified with rubber or plastic polymers (SBS or APP) for improved flexibility and durability. Modified bitumen is applied in rolls that are torch-welded, cold-adhered, or self-adhered to the roof deck. It is a common choice for commercial roofing projects.
N
Nail Pop
A condition where a roofing nail works its way up through the shingle due to thermal expansion, improper nailing, or decking movement. Nail pops create bumps in the shingle surface and can puncture through, causing leaks. They are a common finding during roof inspections.
Nailing Pattern
The specific number and placement of nails required for each shingle. Manufacturer specifications typically require 4-6 nails per shingle, placed in designated nailing zones. High-wind areas require additional nails. Improper nailing is the most common installation defect and can void the warranty.
O
Open Valley
A valley installation method where the metal flashing is left exposed between the shingle courses on each side. Open valleys allow water and debris to flow freely and are easier to maintain than closed valleys. They are the preferred method in areas with heavy rainfall or debris.
OSB (Oriented Strand Board)
An engineered wood panel made from compressed wood strands bonded with adhesive. OSB is the most common roof decking material, having largely replaced plywood due to lower cost. It performs well when kept dry but swells and deteriorates when exposed to prolonged moisture.
Overhang
The portion of the roof that extends beyond the exterior wall of the building. Overhangs protect walls and foundations from rain and provide shade. Typical residential overhangs range from 12 to 24 inches.
P
Parapet
A low wall that extends above the roof edge, common on commercial buildings and flat-roofed homes. Parapets require cap flashing and proper drainage to prevent water from pooling behind them. They are frequent leak sources when the coping or flashing fails.
Penetration
Any object that passes through the roof surface, including plumbing vents, exhaust fans, skylights, chimneys, and satellite dishes. Every penetration requires proper flashing and sealing. More penetrations mean more potential leak points.
Permit (Roofing Permit)
A building permit required by most California cities and counties before roof work can begin. Permits ensure the work meets building code and is inspected for compliance. See our guide on California roofing permit requirements.
Pitch
The steepness of a roof, expressed as a ratio of vertical rise to horizontal run. A 6:12 pitch rises 6 inches for every 12 inches of horizontal distance. Pitch affects material choices, installation methods, drainage, and cost. Steeper pitches shed water faster but are more expensive to work on.
Plywood
A wood panel made from thin layers of veneer glued together with alternating grain directions. Plywood was the traditional roof decking material before OSB became dominant. CDX plywood (exposure-rated) is still used when moisture resistance is a priority.
Ponding
Standing water that remains on a flat roof 48 hours after the last rainfall. Ponding indicates inadequate drainage, structural deflection, or improper slope. It accelerates membrane deterioration and adds weight stress to the roof structure.
PVC (Polyvinyl Chloride) Roofing
A single-ply white membrane used on flat and low-slope roofs. PVC is heat-welded at the seams, creating a watertight bond. It is highly reflective, chemical-resistant, and meets cool roof requirements. PVC is commonly used on commercial roofing projects.
R
Rafter
A sloped structural member that extends from the ridge to the eave, forming the framework of the roof. Rafters support the roof deck and transfer the roof load to the walls. In modern construction, prefabricated trusses have largely replaced individual rafters.
Rake
The sloped edge of a roof that runs from the eave to the ridge along the gable end. The rake is finished with trim (rake board) and protected by drip edge. It is vulnerable to wind-driven rain if not properly sealed.
Re-Roofing
Installing a new roof over an existing one, or tearing off the old roof and installing new materials. California allows a maximum of two roofing layers. A full tear-off is recommended when there is underlying damage. See how much a new roof costs.
Ridge
The horizontal line at the top of the roof where two sloping planes meet. The ridge is the highest point of the roof. It is capped with ridge shingles or a ridge vent for ventilation. Proper ridge installation prevents water intrusion at the roof peak.
Ridge Vent
A continuous ventilation device installed along the ridge of the roof. Ridge vents allow hot, moist air to escape from the attic while remaining hidden from view. They work in conjunction with soffit vents to create natural airflow through the attic space.
Roof Inspection
A professional examination of the roof to assess its condition, identify damage, and estimate remaining lifespan. Inspections cover the exterior surface, flashing, ventilation, gutters, and interior attic space. DeHart Roofing offers free roof inspections. See what happens during a roof inspection.
S
Sealant Strip
A factory-applied adhesive strip on the underside of asphalt shingles that bonds each course to the one below when activated by sun heat. This thermal seal prevents wind uplift. Shingles installed in cold weather may not seal properly until warmer temperatures arrive.
Sheathing
See Deck. Sheathing refers to the plywood or OSB panels that form the roof deck.
Single-Ply Membrane
A category of flat roofing materials that are manufactured in large sheets and applied in a single layer. TPO, EPDM, and PVC are the three main types. Single-ply membranes are lightweight, flexible, and available in rolls up to 12 feet wide for fewer seams.
Skylight
A window installed in the roof plane to provide natural light. Skylights require careful flashing and sealing. They are a common source of leaks, especially when curb-mounted rather than deck-mounted. Aging skylight flashing should be replaced during a roof replacement.
Slope
See Pitch. Slope and pitch are often used interchangeably to describe the angle of a roof. Technically, slope is the ratio of rise to run (e.g., 6:12), while pitch is the ratio of rise to span.
Soffit
The finished underside of the roof overhang, connecting the fascia board to the exterior wall. Soffits are often vented with perforated panels to provide attic intake ventilation. Damaged or blocked soffits compromise attic airflow and can lead to moisture problems.
Soffit Vent
Openings in the soffit that allow outside air to enter the attic. Soffit vents serve as intake vents in a balanced ventilation system, working with ridge vents to create continuous airflow. Adequate soffit ventilation is essential for roof longevity and energy efficiency.
Solar Reflectance
A measure of a roofing material's ability to reflect sunlight, expressed as a value between 0 and 1. Higher values mean more sunlight is reflected. Solar reflectance is a key factor in Title 24 cool roof compliance and directly affects cooling costs.
Square
A unit of measurement used in roofing that equals 100 square feet. A typical residential roof ranges from 15 to 35 squares. Roofing materials are priced and ordered by the square, and labor estimates are calculated per square.
Standing Seam
A metal roofing system with vertical panels joined by raised seams that interlock without exposed fasteners. Standing seam roofs are highly weather-resistant, long-lasting, and give a clean modern appearance. They allow thermal expansion and contraction without compromising the seal.
Starter Strip
A row of shingles or a purpose-made adhesive strip installed along the eave before the first full course. Starter strips provide adhesive to seal the first course against wind uplift and fill the gaps between shingle tabs at the roof edge. Skipping the starter strip is a common installation error.
Step Flashing
L-shaped pieces of metal installed in an overlapping pattern where a roof slope meets a vertical wall. Each piece is woven into the shingle courses to create a waterproof barrier. Step flashing prevents water from running down the wall and behind the roofing material.
Storm Damage
Roof damage caused by high winds, hail, falling trees, or heavy rain. Storm damage may include missing shingles, cracked tiles, punctured membranes, or damaged flashing. Most homeowner insurance policies cover storm damage with a deductible. See our storm damage repair services and insurance claim guide.
Synthetic Underlayment
A modern roofing underlayment made from woven or spun polyethylene or polypropylene. Synthetic underlayment is lighter, stronger, more tear-resistant, and longer-lasting than traditional felt paper. It is now the industry standard for most residential roof installations.
T
Tear-Off
The complete removal of existing roofing materials down to the roof deck before installing a new roof. A tear-off allows inspection of the deck for damage and ensures a clean surface for the new installation. It is recommended over a layover when the existing roof has damage or when two layers are already present.
Thermal Emittance
A measure of a roofing material's ability to release absorbed heat, expressed as a value between 0 and 1. Higher values mean the material radiates heat more effectively. Thermal emittance, along with solar reflectance, determines whether a material qualifies as a cool roof.
Three-Tab Shingles
The simplest and least expensive type of asphalt shingle, with three evenly spaced tabs cut into the lower edge to create a uniform, flat appearance. Three-tab shingles are thinner and lighter than architectural shingles and typically last 15-20 years. They are being phased out by most manufacturers.
Tile Roofing
Roofing made from concrete or clay tiles that are extremely durable and long-lasting, often 50-100 years. Tile is popular in California for its heat resistance, fire rating, and aesthetic appeal. Tile roofs are heavier than shingles and require a reinforced roof structure. See our tile roofing services.
Title 24
California's Building Energy Efficiency Standards, which include requirements for cool roofing. Title 24 mandates minimum solar reflectance and thermal emittance values for roofing materials in specific climate zones. Most Central Valley cities fall in climate zones that require cool roof compliance. See our detailed guide on Title 24 cool roof requirements.
TPO (Thermoplastic Polyolefin)
A white single-ply membrane used on flat and low-slope roofs. TPO is heat-welded at the seams, energy-efficient, and meets cool roof requirements. It has become the most popular flat roofing material in California due to its reflectivity and cost-effectiveness.
Truss
A prefabricated structural framework that supports the roof, combining rafters, joists, and bracing into a single unit. Trusses are manufactured off-site and installed as complete assemblies, replacing traditional stick-framing. They distribute loads efficiently and speed up construction.
U
Underlayment
A water-resistant or waterproof barrier installed on the roof deck beneath the finished roofing material. Underlayment provides a secondary line of defense against moisture. Modern installations use synthetic underlayment, which outperforms traditional felt paper in strength, durability, and moisture resistance.
V
Valley
The internal angle formed where two sloping roof planes intersect. Valleys channel large volumes of water and are one of the most vulnerable areas on a roof. They require metal flashing and careful installation to prevent leaks. Valleys can be open (exposed metal) or closed (covered by shingles).
Vapor Barrier
A material that resists the passage of moisture vapor through walls, ceilings, or floors. In roofing, vapor barriers are installed on the warm side of the insulation to prevent moisture from reaching the roof deck. They are critical in climates with significant temperature differentials between indoors and outdoors.
Ventilation
See Attic Ventilation. A balanced ventilation system with intake (soffit) and exhaust (ridge) vents is essential for roof performance, energy efficiency, and shingle longevity.
W
Warranty
A guarantee covering roofing materials and/or installation workmanship. Manufacturer warranties cover material defects; workmanship warranties cover installation errors. As a certified contractor, DeHart Roofing offers manufacturer-backed extended warranties covering both materials and labor. See our roofing warranty guide.
Wind Uplift
The upward force created when wind flows over a roof surface. Wind uplift can peel back shingles, tear membranes, and even lift sections of the roof deck. Proper nailing, sealant strips, and edge detailing resist wind uplift. Shingles rated for high wind zones are tested to withstand sustained winds of 110-130 mph.
Workmanship Warranty
A warranty from the roofing contractor covering installation defects such as improper nailing, bad flashing, or ventilation errors. Standard contractors offer 1-5 years. Certified contractors like DeHart can offer manufacturer-backed warranties that extend coverage to 25-50 years. See our warranty guide for details.