AZ Roofing Contractor common mistakes
AZ Roofing Contractor · Understand the traps and how to avoid them.
Selecting a roof cover from a price or availability sheet before checking the manufacturer's minimum slope for that product - bidding 3-tab shingles on a 2.5:12 patio roof, or specifying a single-ply membrane on a 1:12 area without the low-slope assembly the membrane requires.
Exam items list cover types (shingle, tile, metal, mod-bit) as if they were interchangeable, and candidates answer from cost or from what they install most, skipping the slope check that drives the whole system choice.
What to do instead
Answer slope first, always. Keep a one-page card listing each cover with its minimum slope, its approved deck types, and its underlayment requirement, and read the slope off the stem before reading the answer choices.
Applying one underlayment rule to every roof - e.g., stating that a single layer of No. 15 felt is adequate on a 3:12 shingle roof, or omitting the eave/valley membrane because 'Arizona doesn't have ice dams.'
Candidates memorize a single sentence ('put felt under shingles') instead of the slope bands, and the slope bands are exactly where the exam puts the distractors.
What to do instead
Build a slope-band table: 2:12 up to 4:12 needs double underlayment (two layers of No. 15 or one of No. 30) under asphalt shingles; 4:12 and steeper takes a single layer; valleys and other specific locations require the membrane regardless of climate. Recite the bands from memory before answering.
Detailing a standing-seam metal roof with fasteners driven through the pan at every purlin, or using fixed clips at every pan, with no allowance for thermal movement.
Nailing patterns learned on shingles get carried over to metal, and candidates picture the panel as rigid rather than as a sheet that grows and shrinks with temperature.
What to do instead
Commit the rule 'fixed and floating' to memory: one fixed clip per panel, slotted or sliding clips elsewhere, fasteners in the pan only for ribbed/exposed-fastener panels per the manufacturer. When an answer choice shows fasteners through the pan of a standing-seam panel, eliminate it first.
Treating TPO and PVC as the same membrane - using TPO cleaner, TPO splice adhesive, or TPO hot-air weld settings on PVC seams, or using contact adhesive on either one.
Both are light-colored single-ply thermoplastics, so candidates group them and assume one seaming method serves both, ignoring that PVC seams can also be solvent welded and TPO cannot.
What to do instead
Memorize a three-row table: TPO = hot-air welded, specific TPO cleaner/primer; PVC = hot-air or solvent welded, PVC-specific cleaner; EPDM = contact adhesive, splice tape, or primer plus tape, never hot-air welded. On the exam, match the cleaner, primer, and weld method to the membrane named in the stem.
Terminating a sidewall with a continuous piece of L-flashing, or running step flashing past the bottom of the wall without a kick-out flashing where the roof meets a gutter or eave.
Step flashing is a small, layered detail that candidates read as one continuous strip, and the kick-out is a detail most installers have never personally bent, so it never appears in the answer they choose.
What to do instead
Draw the layer sequence once and keep it: underlayment, then step flashing woven with each shingle course, then housewrap or building paper laps over the flashing, then counterflashing. Treat 'kick-out flashing at the wall/gutter intersection' as a required element in every wall-flashing question.
Sizing attic ventilation at 1/150 net free area for every roof, or specifying exhaust vents with no matching intake, or intake area far smaller than exhaust area.
One ratio gets memorized and then applied unconditionally, and candidates do not connect the ratio to the conditions (vapor retarder, upper-vent placement) that allow the reduced ratio.
What to do instead
Use the conditional form: baseline 1/150 of the vented ceiling area, reduced to 1/300 only where a vapor retarder is present and roughly half to four-fifths of the vent area is high on the roof. Always balance intake and exhaust at approximately equal net free area and reject any answer offering exhaust-only ventilation.
Labeling every raised, wrinkled, or granule-depleted area on a modified-bitumen or built-up roof as hail damage or storm damage and recommending full replacement, instead of distinguishing blisters, ridging, and thermal splitting from impact damage.
Candidates pattern-match from photographs and memory of insurance work rather than running a diagnostic sequence, and 'replace the roof' feels like the safe answer.
What to do instead
Diagnose before recommending: a blister is hollow and delaminated, ridging follows the felt or ply lines, thermal splitting runs with the slope or along laps, and hail leaves circular impact marks with displaced granules and fractured mat. Write the observed condition and its cause in the answer, and reserve full replacement for widespread saturation or failed deck.
Computing material quantities from the building footprint with no slope multiplier and no waste or accessory allowance - ordering shingle squares only, with no starter, hip/ridge, valley, or drip-edge linear footage.
Footprint dimensions are the numbers printed on the plan, so they get used directly, and accessories are invisible on a plan view where the candidate is already rushing.
What to do instead
Use the fixed sequence: footprint area times the slope multiplier (about 1.03 at 3:12, 1.12 at 6:12, 1.20 at 8:12, 1.30 at 10:12) equals roof area; add waste (about 10 percent for shingles, 5 to 10 percent for tile); then take off ridge, hip, valley, eave, and rake linear footage for the accessory materials and fasteners. Show the takeoff steps in order rather than jumping to a total.
Citing the wrong fall-protection trigger height (10 ft or 4 ft) for construction work, and protecting only the roof edge while ignoring skylights, roof hatches, and other holes.
Height thresholds from general-industry rules, state plan requirements, and the construction standard get mixed together, and the edge is the only hazard that gets pictured.
What to do instead
Anchor on the construction standard: unprotected edges 6 ft or more above a lower level require guardrail, safety net, or personal fall arrest, or a combination of warning line and safety monitor for low-slope roofing; every hole and skylight needs a cover or guardrail regardless of height. When an answer choice gives 10 ft, eliminate it unless the stem is about a different hazard entirely.
Detailing roof drainage from the plan slope alone - no secondary or emergency drainage, no crickets behind large rooftop units, and no check that the slope to drain actually produces flow rather than ponding.
Candidates focus on the primary drain or scupper shown on the detail and forget that codes require a backup path for water when the primary clogs, and that large penetrations divert water around them.
What to do instead
For every low-slope drainage question, check three items: primary drainage, secondary/emergency drainage (a second drain or scupper set above the primary), and crickets or saddles upstream of units and wide penetrations. Verify the specified slope to drain and reject answers that rely on a single drain or on ponding as acceptable.