Roofing Installation and Application Practices
Sequence and detail drive quality
Installation questions test whether you know the order of operations and the fastening pattern. For steep-slope, that means eave protection first, then underlayment, then flashing, then field material, working from the eave upward and from the rake inward. For low-slope, it means substrate prep, then insulation attachment, then membrane, then terminations and flashings.
Know standard fastening schedules: shingle nails placed above the exposure line and below the sealant strip, typically 4 nails per shingle (6 in high-wind zones), with nails driven flush - not overdriven or angled. Know offset patterns (6-inch side lap stagger for three-tab) and starter course requirements. For metal, know clip spacing, panel overlap direction (overlap away from prevailing weather), and allowance for thermal expansion.
Traps: confusing exposure with overlap; thinking more fasteners always help (over-fastening can tear material); installing valley material in the wrong order (woven vs. cut vs. open metal); and forgetting that ice dam protection is required at the eave in cold climates, not just recommended.
Worked example: a 40-foot eave with 36-inch ice barrier, lapped 6 inches horizontally, needs roughly 40 ft of length per course; two courses give 72 inches of coverage, exceeding the typical 24-inch interior warm-wall requirement. Always verify against the local code and manufacturer.
Rule of thumb: every installation decision should be traceable to the manufacturer's written instructions or the adopted code - not to habit.