Plain-English definitions of roofing, ventilation, and insurance terms you’ll see in estimates, inspection reports, and claim paperwork. Each term links to a longer guide where we have one.
Architectural shingle · Three-tab shingle · Class 4 impact-resistant shingle · Wind uplift rating · Underlayment · Ice and water barrier · Ice dam · Roof deck (decking) · Drip edge · Flashing · Chimney flashing · Valley · Ridge vent · Soffit and fascia · Attic ventilation · Roofing square · Roof pitch · Tear-off · Overlay (roof-over) · Hail damage (bruising) · Workmanship warranty · Manufacturer warranty · TPO and EPDM · ACV and RCV · Recoverable depreciation · Insurance supplement · Roofing permit · Illinois roofing license
Architectural shingle
An asphalt shingle made of two or more bonded layers, giving a thicker, dimensional look than a flat three-tab shingle. Most residential replacements in Illinois today use architectural shingles. Read the full guide.
Three-tab shingle
A single-layer asphalt shingle cut into three equal tabs. It is flatter and usually carries a shorter warranty and lower wind rating than an architectural shingle. Read the full guide.
Class 4 impact-resistant shingle
A shingle that passed the UL 2218 impact test at its highest level (Class 4), in which a 2-inch steel ball is dropped onto the same spot twice without cracking the shingle. Some insurers offer premium discounts for them. Read the full guide.
Wind uplift rating
A shingle's tested resistance to being lifted by wind, stated as a wind speed or test class. The rating only applies when the shingle is installed to the manufacturer's nailing instructions. Read the full guide.
Underlayment
The water-resistant layer installed over the roof deck and under the shingles. Synthetic underlayment is lighter and more tear-resistant than traditional asphalt-saturated felt. Read the full guide.
Ice and water barrier
A self-adhering membrane installed at eaves, valleys, and around penetrations to stop water that backs up under shingles, such as behind an ice dam, from reaching the deck. Read the full guide.
Ice dam
A ridge of ice that forms at the roof edge when heat from the house melts snow higher up and the water refreezes at the colder eave. Water trapped behind it can leak into the home. Read the full guide.
Roof deck (decking)
The plywood or OSB (oriented strand board) sheathing nailed to the rafters that the rest of the roof is built on. Damaged or soft decking is usually replaced during a tear-off. Read the full guide.
Drip edge
Metal flashing installed along roof edges that directs water off the roof and into the gutter instead of behind the fascia. Read the full guide.
Flashing
Metal pieces that seal joints where the roof meets walls, chimneys, skylights, and vents. Step flashing, counter flashing, and valley flashing are common types. Read the full guide.
Chimney flashing
The flashing system around a chimney, usually step flashing tucked under shingles plus counter flashing set into the masonry, which keeps water out of the joint. Read the full guide.
Valley
The inside angle where two roof slopes meet. Valleys carry a large share of the roof's water, so they are a common place for leaks.
Ridge vent
An exhaust vent running along the roof's peak that lets warm, moist attic air escape. It works with intake vents lower on the roof. Read the full guide.
Soffit and fascia
The soffit is the underside of the roof overhang, often vented for attic intake air; the fascia is the vertical board along the roof edge where gutters attach. Read the full guide.
Attic ventilation
The balance of intake and exhaust vents that moves air through the attic, reducing heat and moisture that can shorten shingle life and cause ice dams. Read the full guide.
Roofing square
A unit of roof area equal to 100 square feet. Roofing estimates and material orders are usually priced per square. Read the full guide.
Roof pitch
The steepness of a roof, written as inches of rise per 12 inches of run (for example, 6/12). Pitch affects which materials can be used and how much labor the job takes. Read the full guide.
Tear-off
Removing the existing roofing down to the deck before installing the new roof. It allows the deck to be inspected and repaired. Read the full guide.
Overlay (roof-over)
Installing new shingles over an existing layer instead of tearing it off. It is cheaper upfront but hides deck problems and can limit manufacturer warranty coverage. Read the full guide.
Hail damage (bruising)
Impact damage from hail that knocks granules loose or softens the shingle mat, sometimes visible only as dark spots. It can shorten a roof's life even without an immediate leak. Read the full guide.
Workmanship warranty
A contractor's own warranty covering installation errors. Trill Roofing's workmanship warranty is 5 years. Read the full guide.
Manufacturer warranty
The shingle maker's warranty on its materials. Enhanced manufacturer warranties, such as GAF's System Plus, require a complete system and a certified installer. Trill Roofing is a GAF Certified Contractor. Read the full guide.
TPO and EPDM
Single-ply membranes used on low-slope and flat commercial roofs. TPO is a white thermoplastic membrane with heat-welded seams; EPDM is a black synthetic rubber membrane. Read the full guide.
ACV and RCV
Insurance terms. Actual cash value (ACV) pays a roof's replacement cost minus depreciation; replacement cost value (RCV) pays the full cost to replace it. Your policy determines which applies. Read the full guide.
Recoverable depreciation
On an RCV policy, the amount an insurer holds back from the first claim payment and releases after the work is completed and documented. Read the full guide.
Insurance supplement
A request to the insurer to add items missed in the original claim estimate, such as damaged decking found during tear-off, supported by photos and documentation. Read the full guide.
Roofing permit
Local approval required for many roof replacements. Requirements vary by municipality in Madison County. Read the full guide.
Illinois roofing license
Roofing contractors in Illinois must be licensed by the Department of Financial and Professional Regulation (IDFPR). Trill Roofing owner Andy Pfleger holds license #104.020330.