MI Roofing Contractor cheat sheet

Slope = rise ÷ run, expressed as rise per 12 horizontal units; a 4:12 roof rises 4 inches for every 12 inches of run.

Pitch multiplier for rise r per 12 = √(12² + r²) ÷ 12; sloped roof area ≈ plan area × pitch multiplier.

Roofing squares = roof area in square feet ÷ 100; order bundles, underlayment, and accessories by squares plus waste.

Asphalt shingles are limited to slopes of 2:12 or steeper; 2:12 to 4:12 requires double underlayment, and slopes below 2:12 require a low-slope membrane.

Attic ventilation net free area is at least 1/150 of attic floor area; 1/300 is permitted with a vapor retarder and balanced intake and exhaust.

Ice barrier membrane at eaves extends at least 24 inches inside the exterior wall line in cold climates.

Low-slope membranes include EPDM, TPO, PVC, and modified bitumen; steep-slope coverings include asphalt shingles, metal, tile, and wood shakes.

Balanced ventilation uses about 50% intake at soffits and 50% exhaust at ridge or static vents.

Asphalt shingles consist of a fiberglass mat, asphalt coating, and mineral granules; the mat provides tensile strength and granules shield asphalt from UV.

Underlayment is No. 15 asphalt felt or a synthetic membrane; ice-and-water shield is self-adhering and used at eaves, valleys, and vulnerable edges.

Roofing nails are typically 11–12 gauge with heads at least 3/8 inch; fastener length must penetrate the deck at least 3/4 inch or through the sheathing.

Drip edge is corrosion-resistant metal at eaves and rakes; at eaves it goes under the underlayment, and at rakes it goes over the underlayment.

Step flashing is L-shaped metal installed at sidewalls and chimneys in courses that overlap the shingle course and the one below.

Valley flashing may be open metal, closed-cut, or woven; open metal valleys are required by some covering manufacturers and carry high runoff.

Galvanic corrosion occurs when dissimilar metals contact moisture; aluminum, copper, and galvanized steel must be separated or matched compatibly.

Low-slope single-ply membranes are seamed by adhesive, tape, or heat welding; seam strength and compatibility with cleaners matter.

Deck sheathing must be sound, properly fastened, and free of large gaps; replace deteriorated panels before installing underlayment.

Asphalt felt underlayment laps 2 inches on sides and 4 inches at ends; upper courses overlap lower courses to shed water downslope.

Ice-and-water shield is installed at eaves before underlayment and extends at least 24 inches inside the warm wall line.

At eaves, drip edge is installed under the underlayment; at rakes, drip edge is installed over the underlayment.

Starter strip is installed along eaves and rakes before the first full shingle course to seal edges and improve wind resistance.

Fasteners for asphalt shingles are driven flush, not overdriven, and placed per manufacturer; high-wind areas often require six nails per shingle.

Step flashing is woven with each shingle course at walls; counterflashing covers the top edge and is embedded in the wall.

Valley flashing is installed before field shingles and must extend under shingles on both sides of the valley.

Ridge and hip caps cover the peak and intersections; they are fastened per manufacturer and overlapped to shed water.

Replacement is favored when shingles are brittle, granule loss is widespread, leaks are multiple, or decking is soft; isolated damage may be repaired.

Repair areas must integrate new underlayment and flashing with existing layers so water still sheds downslope.

Leak diagnosis starts uphill of the stain and checks penetrations, valleys, wall intersections, chimneys, and fasteners first.

Ice dams are addressed by air sealing, added insulation, and ventilation; roof-side measures include ice barrier and eave flashing.

Emergency tarping must secure the cover without creating new holes; remove or replace the tarp before permanent repair.

Overlaying new shingles over old is limited by code and manufacturer; tear-off is required when existing layers are damaged or exceed allowed layers.

Flashing repairs often require removing shingles around the penetration, replacing the boot or step flashing, and resealing only as a secondary measure.

Tear-off waste weight varies by covering; asphalt shingles are heavy, so dumpster size and load limits must be planned.

The Michigan Residential Code governs one- and two-family dwellings and townhouses; the Michigan Building Code governs commercial and multi-family construction.

A permit is generally required for roof replacement or alteration; ordinary repairs may be exempt, and the local authority having jurisdiction makes the final determination.

Inspections commonly cover deck condition, underlayment, flashing, and final roof covering; required inspection stages vary by jurisdiction.

Asphalt shingle attachment must follow the manufacturer's printed instructions and code requirements for wind resistance.

Ice barrier is required at eaves where the average January temperature is 25°F or lower; most Michigan locations meet this threshold.

Attic ventilation must provide net free area per code; intake and exhaust vents must be balanced and unobstructed by insulation.

Michigan does not issue a separate roofing license; residential contractors generally need a Residential Builder or Maintenance and Alteration Contractor license.

Permit applications commonly require proof of license and certificate of insurance for the contractor and subcontractors.

Energy code provisions address insulation, air sealing, and duct sealing in the attic, which affect roof performance and ice-dam risk.

Break-even revenue = fixed overhead ÷ gross margin percentage; it is the sales level at which profit is zero.

Markup = margin ÷ (1 − margin); a 25% margin equals a 33.3% markup on cost.

Labor burden = payroll taxes + workers compensation + insurance + benefits; add it to base wage to get true labor cost per hour.

Gross profit = revenue − direct job costs; net profit = gross profit − overhead.

Job costing compares actual labor, material, equipment, and subcontractor costs against the estimate for each project.

Overhead includes office rent, vehicles, insurance, marketing, and management salaries; it is not charged directly to a single job.

Cash flow improves when deposits, progress billings, and final payments are tied to defined project milestones.

Accounts receivable days = (accounts receivable ÷ annual credit sales) × 365; lower days indicate faster collection.

Roof takeoff quantities include field area in squares, eave and rake length, valleys, ridges, penetrations, and flashing linear feet.

Waste factor is added to field quantities; common shingle waste is 10% to 15%, higher for complex roofs with many hips and valleys.

Squares = measured roof area ÷ 100; bundle coverage varies by shingle type and must be confirmed from the manufacturer's label.

A written contract should define scope, price, payment schedule, change-order procedure, warranty, and cancellation rights.

Change orders should be written and signed before extra work begins; they should state price and schedule impact.

Construction lien rights depend on statutory notices and recording deadlines; missing a deadline can waive the lien.

Workmanship warranties cover installation defects, while manufacturer warranties cover material defects; both have exclusions and duration limits.

Bids should state inclusions and exclusions, such as deck replacement, permits, dumpster, and ice-and-water shield.

OSHA construction fall protection is required at 6 feet or more above a lower level; options include guardrail systems, safety nets, and personal fall arrest.

Personal fall arrest systems use a full-body harness, lanyard, and anchor rated at 5,000 pounds per worker or designed by a qualified person.

Extension ladders are set at about a 4:1 angle and extend 3 feet above the landing; they must be secured against movement.

Scaffold guardrails are typically 42 inches high with a midrail at about 21 inches and toe boards; fall protection is required at 10 feet.

Roof edge protection may include guardrails, warning lines, or safety monitors depending on the task and fall distance.

MIOSHA construction safety standards follow federal OSHA requirements for fall protection, ladders, scaffolds, and training.

Workers must be trained on fall hazards, equipment inspection, and rescue procedures before using personal fall arrest.

High winds, lightning, and wet roofs increase fall and material-handling hazards; materials must be secured against wind uplift.