6.1 Asphalt Shingle Types, Ratings & Installation

6.1 Asphalt Shingle Types, Ratings & Installation

Quick Answer: Illinois steep-slope asphalt work centers on choosing the right shingle type, verifying ASTM and wind ratings, respecting slope and underlayment limits, and driving the correct number of nails into the manufacturer’s nail line so the roof survives Midwest wind and freeze-thaw cycles.

Asphalt shingles dominate Illinois residential steep-slope roofs. On the CTS exam—roughly 20 Domain 3 questions on the Limited scope and about 35 on Unlimited—you are expected to know product types, rating labels, minimum slopes, and fastening patterns, not just how to swing a hammer.

Three-Tab vs Laminated (Architectural) Shingles

Three-tab (strip) shingles are single-thickness asphalt sheets cut into three tabs. They are lighter, usually lower cost, and historically common on starter and older Illinois stock. Exposure is typically 5 inches; each strip is about 36 inches wide. Because they are thinner, wind uplift resistance depends heavily on correct nailing and seal-strip activation.

Laminated (architectural / dimensional) shingles bond two or more layers into a thicker, shadow-lined appearance. They generally carry higher wind ratings, longer warranties, and better hail resistance—valuable across Illinois, where spring storms and winter ice cycles punish roofs. Most modern Illinois re-roofs specify laminated products.

Exam tip: if a question contrasts “3-tab” with “laminated” or “architectural,” laminated means multi-layer dimensional product—not a different fastener brand.

ASTM and Performance Ratings

Product labels and manufacturer instructions are exam gold. Know what the common standards mean:

Illinois code jurisdictions typically require Class A fire-rated asphalt assemblies on dwellings. Wind rating on the bundle must meet or exceed the design wind speed for the site when the manufacturer’s enhanced nailing pattern is used. Do not assume a “130 mph” label applies if you only drove four nails when six were required for that rating.

Slope Limits and Underlayment

Asphalt shingles are steep-slope products. Manufacturer and code practice in Illinois generally follow this framework:

In Illinois freeze-thaw climates, an ice-and-water shield (self-adhered membrane) is required from the eave upward to at least 24 inches inside the exterior wall line—often farther on wide overhangs—because ice dams force meltwater under shingles. Underlayment alone is not a substitute for that eave ice barrier.

Fastening: Four vs Six Nails

Four nails per strip shingle is the standard pattern for many three-tab and laminated products in normal exposure: one nail about 1 inch from each end and nails spaced along the manufacturer’s nail line (often just below the seal strip / through the common bond area on laminates).

Six nails per shingle is required when:

• The manufacturer’s high-wind or enhanced warranty instructions say so
• Local design wind speed or Illinois code adoption triggers enhanced fastening
• You are installing in known high-wind corridors or on steep slopes where the manufacturer mandates it

Nails must be corrosion-resistant roofing nails with minimum 12-gauge shank and 3/8-inch head (verify manufacturer). Each nail must penetrate the roof deck at least 3/4 inch, or fully through thinner sheathing. Overdriven nails that cut the shingle, or underdriven nails that sit high, both fail inspection and void wind performance.

Nail location matters more than nail count. High-nailing (above the seal strip / outside the nail zone) and low-nailing (into the exposed butt) are classic CTS failure points. On laminated shingles, nails must catch both the common bond and the overlying laminate layer as the instructions show—missing the laminate layer is a frequent Midwest callback after wind events.

Illinois Wind and Freeze-Thaw Considerations

Illinois roofs see repeated freeze-thaw, ice dams, and thunderstorm outflow winds. Practical exam-relevant rules:

1. Seal strips must activate. In cold weather, hand-seal or use manufacturer cold-weather procedures so tabs bond before the first windstorm.
2. Deck must be dry and sound. Wet OSB or cupped plywood leads to fastener withdrawal when ice repeatedly expands in Illinois winters.
3. Match wind rating to fastening. A high wind classification on the wrapper is meaningless without the nail count and placement that earned that rating.
4. Starter and drip edge (covered in 6.2) complete the wind and water path—shingles alone do not seal the eave.

Installation Sequence Snapshot

A code-compliant Illinois asphalt install typically follows this order:

1. Inspect and repair deck; replace damaged sheathing
2. Install drip edge at eaves (under underlayment) and rakes (over underlayment—verify local/manufacturer sequence)
3. Apply ice-and-water barrier at eaves, valleys, and other required locations
4. Install underlayment up the field
5. Snap chalk lines; install starter course
6. Course field shingles with correct exposure and offset
7. Flash penetrations and walls as work progresses (see 6.3)
8. Cap hips and ridges last

Offset patterns (commonly 6-inch or manufacturer-specified racking/offset) prevent stacked cutouts that create water channels. Never install asphalt shingles over existing shingles unless the manufacturer and local Illinois authority specifically allow a second layer and the structure can carry the load.

Exam Focus

Expect Domain 3 items that ask: minimum slope for asphalt; when six nails are required; where the nail line sits; difference between three-tab and laminated; which ASTM number relates to shingles; and why Illinois ice barriers extend inside the wall line. Answer from manufacturer instructions and the principles above—not from “whatever the last crew did.”