CA C-39 Roofing Contractor cheat sheet

One roofing square = 100 sq ft of roof surface; 3-tab shingles typically require 3 bundles per square.

Asphalt shingles are limited to slopes of 2:12 or steeper; 2:12 to under 4:12 requires double underlayment.

Slopes of 3:12 or less are low-slope and use membrane or built-up systems; minimum drainage slope is typically 1/4 in per ft.

No. 15 asphalt felt commonly laps 2 in at sides and 4 in at ends; high-temperature underlayments are used under metal and some tile.

Step flashing is woven with each shingle course at sidewalls; kick-out flashing diverts water at roof-wall and eave intersections.

Ventilation: 1 sq ft net free area per 150 sq ft of attic floor; 1 per 300 is allowed with balanced vents and a vapor retarder.

Metal panels require slotted or oversized fastener holes and washers to accommodate thermal movement; clip spacing follows the manufacturer.

Title 24 cool-roof compliance uses CRRC-listed solar reflectance and thermal emittance values for steep-slope and low-slope products.

Roof slope = rise/run, expressed as inches of rise per 12 in of run; a 6:12 roof rises 6 in over 12 in.

Roof area = horizontal footprint area × slope factor, where slope factor = √(1 + (rise/12)²).

Roof live load is commonly 20 psf minimum for residential roofs; dead load includes roofing, sheathing, framing, insulation, and ceiling.

Sheathing thickness and fastener schedule are selected from the span rating and code tables; panel edges need support or approved clips.

H-clips provide edge support between panels but do not replace blocking where code or diaphragm design requires it.

Rafter ties resist outward thrust at the wall plate; collar ties are located in the upper third and help resist rafter separation.

A ridge board is nonstructural; a ridge beam is structural and must be sized by design for rafter loads and deflection.

Trusses may not be cut, notched, or field-modified without approval from the truss manufacturer or a licensed engineer.

Scale conversion: measured drawing length × scale denominator = actual length; verify the stated scale before measuring.

Roof takeoff = footprint area × slope factor + waste; divide total roof area by 100 to get squares.

Waste allowance: roughly 5–10% for simple gable roofs and 10–15% for complex hip, valley, and penetration-heavy roofs.

Bundle count = squares × bundles per square, rounded up; verify coverage on the shingle wrapper because architectural products vary.

Takeoff must include starter strip, ridge/hip cap, drip edge, valley metal, flashing, underlayment, fasteners, and ventilation.

An addendum modifies bid documents before bid opening; a change order modifies the contract after award and requires signature.

Markup = profit ÷ cost; margin = profit ÷ selling price; a 20% markup equals a 16.7% margin.

Specifications govern material quality and workmanship; drawings govern dimensions and locations; conflicts are resolved by RFI before bid.

Cal/OSHA construction fall protection generally applies at 7.5 ft; systems include guardrails, safety nets, and personal fall arrest.

Extension ladders: 4:1 setup ratio and 3 ft extension above the landing; secure the ladder at top and bottom.

Standard guardrail: top rail about 42 in, midrail, and toe boards where required; openings must prevent a fall.

Hot work requires a permit, fire watch, and control of combustibles; keep a fire extinguisher at the roof and kettle.

Personal fall arrest uses a full-body harness and anchor rated 5,000 lb or engineered equivalent, plus a rescue plan.

Asphalt kettles must be covered, temperature-controlled, and separated from combustibles; workers need burn and fume protection.

Roof openings and skylights must be covered or guarded before workers are exposed; covers must support expected loads.

PPE for roofing includes head, eye, hand, and foot protection plus fall protection; housekeeping controls trip and cut hazards.

California requires a contractor license for projects of $500 or more in labor and materials (B&P §7048).

Home improvement down payment cannot exceed 10% of contract price or $1,000, whichever is less (B&P §7159.5).

A preliminary notice generally must be served within 20 days after first furnishing labor or materials to preserve lien rights.

Workers' compensation insurance is required for employees; contractors may need to file certificates or exemptions with CSLB.

Bid bonds are commonly 10% of bid; performance and payment bonds are commonly 100% of contract price.

Change orders should be written and signed before work; they state scope, price, schedule impact, and payment terms.

Conditional lien releases release rights only when payment clears; unconditional releases take effect immediately on signing.

Retainage and prompt-payment deadlines are set by contract and California Civil Code; track invoice dates and waiver deadlines.