AZ Roofing Contractor key terms

The incline of a roof expressed as inches of vertical rise per 12 inches of horizontal run, such as 4:12. Slope determines which roof coverings, underlayments, and fastening methods are permitted.

A roof steeper than roughly 3:12, usually covered with shingles, tile, slate, shakes, or metal panels. Water sheds quickly, so these systems rely on overlapping layers rather than a fully sealed membrane.

A roof with a slope below about 3:12, commonly waterproofed with built-up, modified bitumen, or single-ply membrane rather than shingles. Drainage depends on slope, tapered insulation, drains, and scuppers.

A roof covering made of a fiberglass or organic mat coated with asphalt and surfaced with mineral granules. Products are rated for wind, impact, and fire performance and are installed over underlayment in overlapping courses.

The panel or board layer fastened over rafters or trusses that supports underlayment and the roof covering. Common materials include oriented strand board, plywood, and solid or spaced lumber boards.

A panel of glued, compressed wood strands used as roof sheathing. Roof panels carry span ratings, thickness requirements, and fastener schedules set by the panel manufacturer and the building code.

A sheet material such as asphalt-saturated felt or synthetic fabric laid over the deck beneath the covering. It acts as a secondary weather barrier and keeps the covering from contacting the sheathing.

A self-adhering waterproof sheet installed at eaves, valleys, and other vulnerable spots before the main underlayment. It seals around fasteners to resist water that backs up behind ice dams.

A material that limits how much water vapor moves into the roof assembly, reducing condensation on cold surfaces. Whether it is required, and where it belongs, depends on climate and on how the assembly is vented.

Metal or membrane components that waterproof junctions where the roof meets walls, valleys, curbs, penetrations, and edges. Correct lapping and fastening keep water flowing down and away from the joint.

Small L-shaped pieces of flashing installed in a stair-step pattern where a sloped roof meets a wall or chimney. Each piece is woven with a shingle course so water cannot get behind siding or masonry.

Flashing attached to or embedded in a wall, chimney, or curb that overlaps the top of base flashing to shed water away from the joint. It is often removable so the base flashing can be serviced.

A formed metal strip along eaves and rakes that projects past the deck edge so runoff clears the fascia and siding. It also protects the deck edge and helps direct water into the gutter.

The internal intersection where two sloping roof planes meet. Because it receives water from both planes, it needs a dedicated lining of metal, membrane, or woven shingles.

A small sloped roof built on the uphill side of a chimney or large rooftop unit to push water around the obstruction. It prevents ponding and debris buildup behind the projection.

A raised framed enclosure around a rooftop opening or piece of equipment, flashed into the roof membrane. It keeps water out of the opening while supporting skylights, hatches, or HVAC units.

The first course at the eave, made of shingles laid upside down or of a manufactured strip. It seals the eave edge and covers the joints of the first exposed shingle course.

A horizontal row of shingles, tiles, or shakes running across the roof. Courses are installed from the eave upward, each lapping over the one below it.

The part of a shingle or tile course left uncovered to the weather, set by the manufacturer. Exposure controls headlap, coverage per square, and the finished weight of the roof.

The number, type, and location of fasteners required for each shingle or panel. Fasteners must fall within the manufacturer's nail zone and be driven flush to achieve rated wind resistance.

Specially shaped shingles or tiles bent over hips and along the ridge to cover the intersection of roof planes and close off the top of the roof.

A metal panel system with raised seams joined above the panel surface and fasteners concealed. The raised seams let panels move with temperature changes and improve weathertightness.

Waviness or buckling visible across the flat part of metal panels, caused by forming stresses, uneven framing, or thermal movement. It is usually an appearance problem rather than a leak.

Wood or metal strips fastened over the underlayment or deck to support tile or slate and create a drainage and ventilation gap. They are laid across the slope to carry horizontal courses.

A flexible sheet of synthetic rubber or plastic, such as EPDM, TPO, or PVC, installed in one layer over low-slope roofs and joined by adhesive, tape, or heat welding.

A thermoset synthetic rubber membrane, usually black, seamed with contact adhesive or splice tape. It weathers and resists ozone well, but its seams cannot be heat welded.

A thermoplastic polyolefin membrane, commonly white, with seams joined by hot-air welding. It is chosen for reflectivity and strong welds but is sensitive to heat, oils, and job conditions.

An asphalt sheet reinforced with polyester or fiberglass and modified with SBS or APP polymers for flexibility. It is installed in plies using a torch, hot asphalt, or cold adhesive.

A multi-ply membrane built from alternating layers of bitumen and reinforcing felt. It is usually finished with a flood coat of asphalt and gravel or with a cap sheet.

A roof system formed by spraying mixed resins that expand into a seamless insulating layer. A protective coating is then applied to resist sunlight, traffic, and weather.

Water that remains standing on a roof more than 48 hours after rain. It adds structural load, shortens membrane life, and points to insufficient slope or blocked drainage.

Rigid insulation cut in graduated thicknesses and laid to create slope toward drains or scuppers. It improves drainage and helps eliminate ponding on low-slope roofs.

A venting design in which intake area at the soffits roughly equals exhaust area at the ridge or other high vents, so air moves steadily beneath the roof deck.

A survey technique that reads surface temperature differences to find wet insulation or trapped moisture under a membrane. Results are clearest when the roof is warming or cooling.

A cracked pattern resembling alligator skin on aged asphalt roofing, caused by weathering and loss of oils. It shows the surfacing is brittle and near the end of its service life.

The process of measuring and listing every material and quantity needed for the roof from the drawings and specifications. The takeoff forms the basis of the estimate and the purchase list.

A roofing unit of area equal to 100 square feet. Shingles, underlayment, and membrane quantities are ordered and priced in squares.

Guardrails, nets, or personal fall arrest systems required when workers are exposed to falls from height. Roofing work generally requires protection once the fall distance reaches six feet.

A written authorization required before torch-applying membrane, firing a kettle, or grinding near roofing materials. It documents the fire watch, clearance of combustibles, and precautions taken.