Why the vocabulary matters
Roofing estimates are written in a language most homeowners never learned: squares, pitch, step flashing, drip edge, ridge vent. When two estimates use different words, it is hard to tell whether they describe the same roof. This guide explains the parts of a typical Midwest roof from the inside out, then the measurements and warranty words you will see on paper.
The structure: rafters, trusses and decking
Rafters or trusses are the wood framing that forms the roof’s shape. Decking (also called sheathing) is the plywood or OSB nailed over them that everything else is fastened to. Older homes may have plank decking. Soft, rotted or delaminated decking is replaced during a roof replacement.
The water barriers: underlayment and ice and water shield
Underlayment is a water-resistant layer over the decking, today usually synthetic. It is the backup when water gets past the shingles. Ice and water shield is a self-adhering membrane installed in the highest-risk areas: valleys, eaves and around chimneys and vents. In the Midwest it is critical for resisting ice dams.
The edges: drip edge, eaves, rakes and fascia
The eaves are the lower, horizontal edges of the roof where gutters attach. The rakes are the sloped edges at the gable ends. Drip edge is the metal trim along both that directs water into the gutters and protects the deck edge. Fascia is the board behind the gutter, and soffit is the underside of the overhang, often vented.
The joints: valleys, hips and ridges
A valley is where two roof slopes meet in an inward angle; it carries the most water. A hip is where two slopes meet in an outward angle. The ridge is the top horizontal peak. Hips and ridges are covered with hip and ridge cap shingles.
Flashing: where most leaks start
Flashing is metal that seals joints and penetrations. Step flashing is installed piece by piece where a roof meets a wall. Counter-flashing covers the top of step flashing on chimneys. Pipe boots (or vent collars) seal plumbing vents. Failed flashing is among the most common causes of leaks; see our guide on finding the source of a roof leak.
Ventilation: intake and exhaust
Roof ventilation moves air through the attic. Intake vents, usually in the soffits, let cool air in; exhaust vents, such as a ridge vent or box vents, let warm, moist air out. Balanced ventilation helps shingles last, reduces summer heat in the attic and limits winter condensation and ice dams.
The outer layer: shingles and other roof coverings
- Architectural (laminated) shingles: the most common Midwest home roof, layered for a dimensional look.
- 3-tab shingles: flatter, simpler, older style.
- Impact-rated shingles: built to resist hail damage.
- Starter strip: the first course along the eaves and rakes that helps seal against wind.
- Metal roofing: standing seam or panels.
- Low-slope membranes: TPO, EPDM and modified bitumen on flat or nearly flat roofs.
Explore hundreds of shingle colors on our shingle color selector.
Measurements: squares, pitch and layers
A square is 100 square feet of roof area; roofs are measured and priced in squares. Pitch is the steepness, written as rise over 12 inches of run — a 6/12 roof rises six inches every foot. Steeper roofs take more time and safety equipment. Layers refers to how many roofs are stacked on the deck; two layers usually means a bigger tear-off. Waste factor is extra material ordered to cover cuts at valleys, hips and edges.
Paperwork words
- Tear-off: removing the old roof down to the deck.
- Overlay: installing new shingles over old ones (we recommend against it).
- Workmanship warranty: the contractor’s promise about the installation.
- Manufacturer warranty: covers the product; a system warranty covers matched components through a certified contractor.
- Supplement: an additional request to an insurer for items missed in the original claim estimate.
- ACV and RCV: actual cash value and replacement cost value, two ways insurance can value a roof.
Using these words on your estimate
With these terms, you can read any roofing estimate and ask the right questions: Which underlayment? Where does ice and water shield go? Is flashing new or reused? What ventilation is included? How many squares, at what pitch, and how many layers come off? Comparing estimates line by line is the fastest way to see which one actually describes a better roof. Our roof replacement step-by-step guide shows where each part goes during installation.
Ask a roofer who will explain it
John Beal Roofing has been family-run since 1947, and our inspectors walk homeowners through photos and plain-English explanations of what they found. Call 1-800-564-6232 any hour for a free inspection.
Frequently asked questions
What is a roofing square?
A square is 100 square feet of roof area. Roofs are measured and priced by the square.
What is roof pitch?
Pitch is the roof’s steepness, written as inches of rise per 12 inches of horizontal run, such as 6/12.
What is roof flashing?
Flashing is metal installed at joints and penetrations, like walls, chimneys and vents, to direct water away from openings.
What is the difference between underlayment and ice and water shield?
Underlayment covers the whole deck as a backup water barrier; ice and water shield is a self-adhering membrane used in the highest-risk areas such as valleys and eaves.
What does drip edge do?
Drip edge is metal trim at the roof edges that directs water into the gutters and protects the edge of the decking.