Roofing Glossary: Slate, Tile, Metal, Enviroshake and Commercial Terms

Jump to: Metal roofing · Copper · Slate · Tile · Shake and synthetic · Commercial and flat roofs · Roof anatomy and general terms

Metal roofing

Standing seam

A metal roof made of long vertical panels joined at raised seams that stand above the flat of the panel. The fasteners are hidden under the seam on clips, so no screws pierce the weather surface. Standing seam handles thermal movement well and can go on lower slopes than screw-down panels. More: Standing seam

Snap-lock standing seam

A standing seam profile whose seams snap together by hand, with no seaming tool. It installs quickly and suits most homes and many commercial roofs at moderate pitches. Very low slopes and very long runs usually call for a mechanically seamed panel instead. More: Snap-lock standing seam

Mechanically seamed standing seam

A standing seam panel whose seams are folded closed on the roof with a powered seaming machine, either once (single lock, 90 degrees) or twice (double lock, 180 degrees). The folded seam resists water better at low slopes and holds well in high winds. More: Mechanically seamed standing seam

R-panel

An exposed-fastener steel panel with tall trapezoidal ribs, usually on 12-inch centers, screwed through the face into purlins or decking. It is the workhorse of North Texas shops, barns and warehouses because it is strong, economical and fast to install. More: R-panel

PBR panel

Short for purlin bearing rib. A PBR panel looks like R-panel but has an extra leg at the side lap that rests on the purlin, which supports the overlap and helps the lap seal. It is common on pre-engineered metal buildings. More: PBR panel

Corrugated metal

Metal panel with a rounded, wavy profile, one of the oldest metal roof shapes. It is used on barns, ag buildings, carports and as a design look on modern homes. Like R-panel, it is fastened with exposed screws through the panel. More: Corrugated metal

Exposed-fastener roof

Any metal roof attached with screws driven through the face of the panel, each sealed with a rubber washer. It costs less than standing seam, but the washers age in the sun, so the screws need periodic inspection and eventually a re-screw. More: Exposed-fastener roof

Concealed-fastener clip

The small steel bracket that holds a standing seam panel to the deck. It hooks into the seam and is screwed to the roof below it, so no fastener is exposed. Floating clips let the panel slide as it expands and contracts. More: Concealed-fastener clip

Gauge

The thickness rating of sheet steel: the lower the number, the thicker the metal. Most quality residential and commercial steel roofs are 24 or 26 gauge. Thicker steel resists denting and oil canning better and can span farther between supports. More: Gauge

Roll former

A machine that bends flat coil steel into a finished roof panel profile as it runs through a series of rollers. Running a roll former on site or in our own shop lets panels be cut to the exact length of each roof run, with no end laps. More: Roll former

Oil canning

Visible waviness in the flat part of a metal panel, caused by stresses in the coil, the forming process, installation or thermal movement. It is usually cosmetic. Heavier gauge, striations or ribs in the flat, and careful installation help reduce it. More: Oil canning

Galvalume

Steel coated with an aluminum and zinc alloy that protects it from corrosion. Most painted metal roofing is built on a Galvalume or galvanized steel base, with the paint system on top. Bare Galvalume panels are also used on shops and barns. More: Galvalume

PVDF (Kynar) finish

A paint system based on polyvinylidene fluoride resin, often sold under the Kynar 500 name. It holds color and resists chalking in strong sun better than standard polyester paints, which matters on a Texas roof. Finish warranties are set by the panel maker. More: PVDF (Kynar) finish

Stone-coated steel

Steel roof panels pressed into the shape of shingles, shakes or tile and coated with stone granules bonded to the metal. They give a traditional look with the strength of steel and are popular on homes where an HOA prefers a non-metal appearance. More: Stone-coated steel

Metal retrofit

A new metal roof installed over an existing roof, usually on sub-framing attached through the old roof into the structure. It avoids a tear-off, keeps the building open and can add insulation space. Code and a moisture check decide whether it is allowed. More: Metal retrofit

Purlin

A horizontal structural member, usually a steel Z or C shape on metal buildings, that runs across the rafters and supports the roof panels. Purlin spacing determines what panel and gauge will span safely and where screws must land. We check purlin size and spacing before recommending a panel. More: Purlin

Stitch screw

A short screw that fastens two metal panels together at the side lap, between the purlins, instead of into the structure. Stitch screws keep laps tight so wind cannot lift and open them, which is a common leak point on older metal roofs. More: Stitch screw

Condensation control

The insulation, vapor retarder and ventilation that keep warm, humid indoor air from reaching cold roof panels and dripping. In shops and barndominiums, drips on cool mornings with no rain are usually condensation, not a roof leak. On a retrofit, the new sub-framing leaves room to add insulation. More: Condensation control

Copper

Copper roofing

Roofing and flashing made from sheet copper, usually formed into standing seam or flat-seam panels for bay windows, porches, dormers and full roofs. Copper needs no paint, weathers to a natural patina and lasts for generations when the details are right. More: Copper roofing

Patina

The surface layer copper forms as it weathers. New copper turns russet and then brown within months to years, and the blue-green verdigris develops over a much longer time. In drier climates like North Texas the green can take decades or stay patchy. More: Patina

Copper weight (16 oz, 20 oz)

Copper sheet for roofing is specified by weight per square foot rather than gauge. 16-ounce cold-rolled copper is the common choice for roofing and flashing, and 20-ounce is used where more stiffness or durability is wanted. ASTM B370 covers copper sheet for building construction. More: Copper weight (16 oz, 20 oz)

Galvanic corrosion

Corrosion that happens when two different metals touch in the presence of water, with the less noble metal eaten away. Copper should not touch steel, galvanized metal or aluminum, and water running off copper can stain or corrode those metals downslope. More: Galvanic corrosion

Slate

Natural slate

A roof made of split stone tiles, usually hung with copper nails over a solid deck. Good slate can last for generations, and its weight and installation method make it a specialty trade. Slate roofs are usually repaired piece by piece rather than replaced. More: Natural slate

S1 slate

The top service-life grade for roofing slate under the ASTM C406 standard, which classes slate as S1, S2 or S3 based on lab tests for absorption, strength and weathering. S1 has the longest expected life. Ask for the grade before buying any slate. More: S1 slate

Slate hook

A small stainless or copper hook nailed to the deck that holds a replacement slate in place without new nails through the slates above. Hooks let a roofer replace a broken slate cleanly. The visible hook is small and becomes hard to see from the ground. More: Slate hook

Headlap

The amount each slate, tile or shingle overlaps the course two rows below it. Headlap keeps water from running between pieces and reaching the deck. Low-slope slate and tile roofs need more headlap than steep ones, so the spec changes with pitch. More: Headlap

Synthetic slate

Roofing made from engineered polymers or rubber and plastic blends, molded to look like natural slate. It weighs far less than stone, so it usually needs no structural changes, and many products carry Class 4 impact ratings. Look and fade resistance vary by brand, so we bring samples. More: Synthetic slate

Tile

Clay tile

Roof tile made from fired clay, in barrel (Spanish or mission), flat and interlocking profiles. Clay holds its color for a very long time and suits Mediterranean, Spanish and estate homes. It is heavy and brittle, so walking on it and repairs take training. More: Clay tile

Concrete tile

Roof tile made from sand, cement and color, molded into flat, S and barrel shapes. It costs less than clay and comes in many profiles. It is heavy, absorbs some water and can fade, so color-through and coated options matter. More: Concrete tile

Barrel tile

A half-round tile laid in alternating up and down courses to form channels, the classic Spanish or mission look. Barrel roofs need bird stops at the eaves and careful flashing at walls and valleys. Clay barrel tile is common on high-end Mediterranean homes. More: Barrel tile

Tile battens

Strips of wood or other material fastened across the roof deck that tiles hang on or are fastened to. Battens hold the tile in line, raise it slightly for drainage, and on many systems let air move under the tile, which helps the underlayment last. More: Tile battens

Tile reset (lift and relay)

A repair where the tiles are carefully removed, the worn underlayment and flashings underneath are replaced, and the same tiles are reinstalled. On tile roofs, the underlayment usually fails long before the tile, so a reset can save sound tile. More: Tile reset (lift and relay)

Bird stop

A closure piece at the eave of a tile roof that blocks the open ends of the tile so birds and pests cannot nest underneath. It also helps support the first course and keeps wind-driven rain from blowing up under the tile. More: Bird stop

Shake and synthetic

Enviroshake

A composite roofing product made to look like cedar shake, built from recycled materials and engineered to resist rot, insects and impact. It gives the look of a real shake roof without the upkeep. We are certified with Enviroshake. It is also made in slate-look and other profiles for different home styles. More: Enviroshake

Synthetic cedar shake

Molded polymer or composite shakes made to look like split cedar. Unlike real wood they do not rot, split or need treatment, and many carry Class A fire ratings and Class 4 impact ratings. Color and texture vary a lot by brand. More: Synthetic cedar shake

Commercial and flat roofs

TPO

Thermoplastic polyolefin, a single-ply white membrane whose seams are heat-welded with hot air. It is the most common new flat roof on North Texas commercial buildings because it reflects sun, welds into one watertight sheet and can carry long manufacturer warranties. More: TPO

PVC roofing

A single-ply thermoplastic membrane, like TPO but made from polyvinyl chloride, with heat-welded seams. PVC resists grease and many chemicals, which makes it the usual choice around restaurant exhaust fans and some industrial roofs. It also handles ponding and holds up well on roofs with heavy rooftop equipment and frequent service traffic. More: PVC roofing

EPDM

A synthetic rubber roofing membrane, usually black, installed in large sheets with taped or glued seams. EPDM is tough and flexible and has a long track record. In Texas sun, owners often choose a white membrane instead to keep the building cooler. More: EPDM

Modified bitumen

Asphalt roofing reinforced with polyester or fiberglass and modified with rubber-like (SBS) or plastic (APP) polymers, installed in rolls by torch, hot asphalt, cold adhesive or self-adhesion. It is tough, multi-layer and good under foot traffic. Granulated cap sheets add UV protection, and white or coated caps help reflect the Texas sun. More: Modified bitumen

Built-up roofing (BUR)

A flat roof built from alternating layers of asphalt or coal tar and reinforcing felts, finished with gravel or a cap sheet. Often called tar and gravel. Its several plies give redundancy, and many older commercial buildings still have one. More: Built-up roofing (BUR)

Spray polyurethane foam (SPF)

A roof made by spraying liquid foam that expands into a seamless, rigid, insulating layer, then covering it with a protective coating. Foam can be sprayed thicker in low spots to create slope to the drains. The code requires at least 1/4 inch per foot of slope and a protective coating, which is renewed over the roof's life. More: Spray polyurethane foam (SPF)

Silicone roof coating

A fluid-applied coating that cures into a seamless, UV-stable membrane over a sound existing roof. Silicone tolerates ponding water better than water-based coatings, but almost nothing but silicone will stick to it later. It is covered by ASTM D6694. Wet insulation must be removed first. More: Silicone roof coating

Acrylic roof coating

A water-based elastomeric coating that cures bright white and resists dirt pickup. It works well on metal buildings and roofs that drain quickly, but standing water softens it. It is covered by ASTM D6083 and can be recoated with acrylic or silicone. More: Acrylic roof coating

Urethane roof coating

A polyurethane coating, often used as a tough aromatic base coat with a UV-stable aliphatic or other top coat. Urethane resists foot traffic and impact best among common coatings. Moisture-cured polyurethane coatings are covered by ASTM D6947. Solvent-based products have more odor during application. More: Urethane roof coating

Dry mils

The thickness of a cured coating, measured in thousandths of an inch. Coating warranties are tied to how many dry mils are applied, so a bid should state the thickness or the coverage rate. Crews check wet thickness with a gauge as they apply it. More: Dry mils

NDL warranty

Short for no dollar limit. A manufacturer system warranty that pays the full cost to repair covered leaks for its term, with no cap. It usually requires an approved system, an allowed installer and a manufacturer inspection, and it still has exclusions. More: NDL warranty

Tapered insulation

Rigid insulation boards cut with a built-in slope, laid under a flat roof membrane to move water toward drains and scuppers. It is the standard fix for ponding on low-slope roofs and adds insulation at the same time. The slope is laid out on a plan before the boards are cut. More: Tapered insulation

Cover board

A thin, rigid board installed over the insulation and under the membrane on a flat roof. It protects the insulation from foot traffic and hail, gives the membrane a smooth surface and can improve wind and fire performance. Gypsum and high-density board are common types. More: Cover board

Parapet wall

The short wall that extends above the roof line around many flat commercial roofs. The membrane runs up the inside of the parapet and is capped with metal coping. Parapet flashings and coping joints are some of the most common flat-roof leak points. More: Parapet wall

Scupper

An opening through a parapet wall that lets water drain off a flat roof, usually into a collector box and downspout. Scuppers also serve as overflow drains. Clogged or poorly flashed scuppers cause ponding and leaks. We size and flash them to the membrane so water leaves the roof quickly after heavy storms. More: Scupper

Moisture survey

A check for water trapped inside a roof system, using infrared (thermal) scans, moisture meters and core cuts. On flat roofs it decides whether a coating or recover is possible, because wet insulation has to be removed first. A drone with a thermal camera speeds up the scan on large roofs. More: Moisture survey

Core cut

A small sample cut through a flat roof down to the deck. It shows how many roofs are on the building, what the layers are, and whether the insulation is wet. The hole is patched the same day. Several cores spread across a large roof give a fair picture of the whole system. More: Core cut

Recover (re-cover)

Installing a new roof over an existing one instead of tearing it off. Under the 2021 IBC reroofing rules, a recover generally is not allowed over a water-soaked or deteriorated roof or over two or more existing layers. A moisture survey tells you whether a recover is even an option. More: Recover (re-cover)

Roof anatomy and general terms

Ridge

The horizontal peak where two roof slopes meet at the top. It is capped with ridge shingles, ridge tile or a metal ridge cap, and on many roofs a ridge vent there lets hot attic air escape. Ridge caps take a lot of wind, so loose or cracked caps are a common storm repair. More: Ridge

Hip

The sloped outside corner where two roof planes meet and run down from the ridge to the eave. Hip roofs have slopes on all four sides. Hips are capped like the ridge and are a common place for wind to lift caps. More: Hip

Valley

The inside angle where two roof slopes meet and channel water down together. Valleys carry more water than any other part of the roof, so they are lined with metal or special underlayment and are a common leak point when worn. More: Valley

Eave

The lower edge of the roof that overhangs the walls, where gutters usually hang. Drip edge, starter courses and ice and water underlayment protect the eave, where water collects on its way off the roof. Rotted decking and fascia along the eave are common findings during tear-off on older homes. More: Eave

Rake

The sloped edge of a roof at the end of a gable, running from eave to ridge. Rake edges are finished with drip edge or rake trim to protect the deck edge from wind-driven rain. Wind gets under the rake edge first, so the starter course and fastening there matter on storm-prone roofs. More: Rake

Drip edge

An L-shaped metal flashing installed at the eaves and rakes that directs water away from the fascia and into the gutter. Many building codes require it on shingle roofs, and the City of Denton requires it on asphalt-shingle re-roofs. It also keeps the deck edge from wicking water. More: Drip edge

Fascia

The vertical board along the edge of the roof, behind the gutter, that caps the ends of the rafters. Rotted fascia lets water and pests into the roof edge and usually shows up when the gutters come off during a re-roof. More: Fascia

Soffit

The underside of the roof overhang, between the fascia and the wall. Vented soffits let fresh air into the attic as part of the ventilation system. Damaged soffit lets birds, wasps and rodents into the attic. We replace soffit in wood, aluminum, vinyl or fiber cement. More: Soffit

Step flashing

Small bent pieces of metal woven in with each course of shingles where a roof meets a wall or chimney side. Each piece overlaps the one below to shed water. Missing or reused step flashing is a frequent cause of wall leaks. More: Step flashing

Counterflashing

Metal flashing set into or attached to a wall or chimney that covers the top of the base or step flashing below it. It keeps water from getting behind the flashing while letting the roof and wall move separately. On masonry it is usually set into a cut mortar joint and sealed. More: Counterflashing

Cricket (saddle)

A small peaked structure built on the high side of a chimney or curb to split water around it instead of letting it pond. Codes require crickets behind wider chimneys, and on flat roofs they push water toward drains. A cricket is flashed like a small roof. More: Cricket (saddle)

Dormer

A structure with its own small roof that projects out of a sloped roof, usually with a window. Dormers add light and space but also add valleys, wall flashings and corners that need careful detailing. Copper is a classic dormer roof. More: Dormer

Square

The roofing unit for 100 square feet of roof surface. Roofers measure, order and often price roofs by the square. A 30-square roof covers about 3,000 square feet of roof area, which is more than the home's floor area because of pitch and overhangs. More: Square

Pitch (slope)

How steep a roof is, written as inches of rise per 12 inches of run, such as 6:12. Pitch decides which materials can be used: most shingles need at least 2:12, standing seam can go to 1/4:12, and flat roofs use membranes. More: Pitch (slope)

Self-adhered underlayment

A rubberized asphalt membrane, often called ice and water shield, that sticks directly to the deck and seals around nails. It goes in valleys, at eaves and around penetrations, and high-temperature versions are used under metal and tile. It is a secondary barrier under the roof covering. More: Self-adhered underlayment

Synthetic underlayment

A woven or spun polymer sheet installed over the roof deck under shingles, metal or tile. It is lighter and stronger than old felt paper, resists tearing in wind and lies flatter. It is a secondary barrier, not the roof. More: Synthetic underlayment

Class 4 impact rating

The highest rating under UL 2218, the standard test that drops steel balls on roofing to simulate hail. Class 4 products survive a 2-inch ball without cracking. Texas insurers must offer a premium credit for UL 2218 rated roofs, and each insurer sets the amount. More: Class 4 impact rating

TDI Form PC068

The Texas Department of Insurance form a roofing contractor fills out to certify that an impact-resistant roof was installed, so the homeowner can ask their insurer for the impact-resistant roof credit. We fill it out after every qualifying install. Ask your insurer what credit it gives. More: Texas impact-resistant roof discount guide

Missing a term? Ask us when we inspect your roof. Every inspection comes with a free digital photo report, so you see what we see. More guides: what drives high-end roof costs · TPO vs. mod bit vs. coating · synthetic vs. real slate · all guides.

Product names and standards are as published by their owners and can change. Code references are summaries; your building official has the final word.

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