Roofing & Gutters Glossary

Common residential roof covering made from a fiberglass mat saturated with asphalt and topped with mineral granules. “Architectural / dimensional” are thicker, multi-layer profiles; “3-tab” is thinner and flat.

A skylight with two molded acrylic domes—an inner and outer layer—to reduce condensation and improve insulation. Often seen on older flat roofs; modern alternatives include double-glazed glass units.

Perforated metal or formed closure at the eave of tile roofs that blocks birds and debris while allowing airflow. Also helps the first course of tiles sit correctly.

Plywood with a C-grade face and D-grade back veneer; “X” indicates exterior-grade glue. A common roof sheathing panel when properly fastened and dried-in promptly.

Cement-based tiles in profiles like “S,” “flat,” or “shake.” Durable but heavy; the structure must be rated for the load. Often reused during lift-and-lay when underlayment is replaced.

Skylight set over a site-built or factory curb that rises above the roof surface. Useful on flat roofs and for re-roofing because the curb flashing integrates with new membranes or shingles.

Skylight frame mounts directly to the roof deck (no separate curb). Lower profile; requires manufacturer flashing kits and careful integration with shingles or tile.

Vertical finishing board at the roof edge where gutters attach. Protects rafter tails and provides a straight line for drip edge and gutters.

Channels that capture roof runoff and carry it via downspouts (leaders). Common profiles include K-style and box. Proper sizing, slope, and outlets prevent overflow at valleys and eaves.

Concrete tiles manufactured to lower weight per square (often used in reroofs where structure didn’t account for standard weight). More fragile; walk paths and handling matter.

Engineered wood panel made from compressed strands with adhesive. Performs well when kept dry and properly ventilated; edges are sensitive to prolonged moisture before dry-in.

Ends of the roof rafters that extend to the eave. Often covered by fascia; rot at tails is common where gutters overflow or fascia/soffit aren’t sealed.

Decking made of boards installed with gaps, typical under old wood shakes. If shingles were later installed over it, additional sheathing is needed for proper nailing and ventilation.

Boards with rabbeted edges that overlap to create a relatively tight surface. Used as roof or wall decking on older homes; not the same as skip sheathing.

Local term sometimes used for the decorative board at gable edges (barge board) or fascia detail casting a “shadow line.” Provides finish and helps shed water from the edge.

Diverter flashing installed where a roof edge meets a wall near the eave. “Kicks” water away from the siding and into the gutter—critical to stop wall rot and stucco staining.

Formed metal pan used at headwalls, chimneys, and low-slope transitions with tile. Creates a trough to capture and redirect water beneath tiles where standard step flashing isn’t enough.

Single-ply white membrane for flat roofs. Seams are hot-air welded. Reflective, lightweight, and usually installed over insulation or a recover board on commercial and residential flats.

Asphalt membrane reinforced with mat and polymers, heat-fused at seams. Rugged and repair-friendly; requires fire-safe practices and skilled installers.

Boards milled with a tongue on one edge and a groove on the other that interlock to create a tight deck. Found under older roofs and patio covers.

Formed flashing installed where two roof planes meet (valley). Types include open (exposed metal, often W-valley) and closed (shingles or tile overlay). Directs high volumes of water safely downslope.

Thicker, split wood roof material (commonly cedar). Often installed over skip sheathing. Aging shakes are a frequent source of leaks and can hide deck issues under later shingle overlays.

Foam, mortar, or formed closures used to seal tile edges at ridges, hips, and eaves against wind-driven rain and pests while allowing ventilation where required.