MI General Contractor cheat sheet

Michigan adopts the International Residential Code (IRC) with Michigan amendments as the Michigan Residential Code (MRC); the current edition is enforced by local building departments.

Stairway requirements: minimum clear width 36 in., maximum riser height 7-3/4 in., minimum tread depth 10 in., minimum headroom 6 ft 8 in., and handrail height 34–38 in. above nosing.

Guardrails required on porches, balconies, and decks more than 30 in. above grade; guard height minimum 36 in.; baluster spacing must not allow a 4-in. sphere to pass.

Egress: every sleeping room must have at least one operable emergency escape and rescue opening with a minimum net clear opening of 5.7 sq ft (5.0 sq ft at grade), minimum width 20 in., minimum height 24 in., and sill height not more than 44 in. above floor.

Ceiling height: habitable rooms, hallways, and bathrooms require a minimum 7 ft ceiling height; exceptions allow beams and ducts to project not more than 6 in. below the required height.

Lighting and ventilation: habitable rooms must have aggregate glazing area not less than 8% of floor area and openable area not less than 4% of floor area, unless mechanical ventilation is provided.

Smoke alarms required in each sleeping room, outside each sleeping area, and on each story; carbon monoxide alarms required outside sleeping areas where fuel-burning appliances or attached garages exist.

Foundation drainage: footing drains or approved drainage system required where groundwater conditions exist; exterior foundation walls must be dampproofed or waterproofed per MRC Chapter 4.

Michigan residential builders must be licensed under the Michigan Occupational Code (PA 299 of 1980); a residential builder license covers construction of detached one- and two-family dwellings and attached garages.

Maintenance and alteration (M&A) license covers remodeling, repair, and improvement of residential structures; it does not authorize new construction of a dwelling.

License applicants must pass the Michigan Residential Builders exam and meet experience or education requirements; licenses renew every 3 years with continuing education.

Written contracts for residential construction over $600 must be in writing and include the licensee's name, license number, scope of work, and total price; the Michigan Homeowner Construction Lien Recovery Fund notice must be provided.

Michigan's Right to Cure law (MCL 600.2962) requires a homeowner to give written notice and allow 60 days to cure a construction defect before filing suit.

Lien law: a construction lien must be recorded within 90 days after the last furnishing of labor or materials; a Notice of Furnishing must be provided to the owner and general contractor within 20 days after first furnishing.

Michigan sales and use tax: contractors are consumers of materials they install and pay 6% sales tax on materials; subcontractors are not taxed separately on the same materials.

Business entity: licensed builder must notify the state within 30 days of a change of address, name, or business entity; failure can result in license suspension.

Scale conversion: at 1/4 in. = 1 ft, 1 in. on the drawing equals 4 ft; at 1/8 in. = 1 ft, 1 in. equals 8 ft; always verify the stated scale on the title block.

Board feet formula: (thickness in inches × width in inches × length in feet) ÷ 12 = board feet.

Concrete volume: length × width × depth in feet = cubic feet; divide by 27 to convert to cubic yards; add 5–10% waste for slab and footing estimates.

Roof pitch and area: roof area = horizontal footprint area ÷ cos(roof angle); for a 6/12 pitch, the multiplier is approximately 1.118.

Critical path method (CPM): the critical path is the longest sequence of dependent activities; any delay on the critical path delays project completion; float = late start − early start.

Quantity takeoff: measure linear feet for walls, square feet for flooring and drywall, and cubic yards for concrete; include openings deductions per plan notes.

Schedule sequencing: typical residential order is site work → foundation → framing → roofing → rough-in MEP → insulation → drywall → finishes → final inspection.

Plan symbols: door swing shown as arc, window as double line in wall, section cuts marked with arrows and letters; north arrow and datum noted on site plan.

Footing depth: minimum 12 in. below undisturbed grade or below frost line; Michigan frost depth varies by region (typically 42–48 in. in lower peninsula), so footings must extend below local frost line.

Concrete mix: standard foundation walls use 2,500–3,000 psi; slabs on grade 2,500 psi; air-entrained concrete (5–7% air) required for exterior flatwork in freeze-thaw climates.

Slump test per ASTM C143: typical target slump for foundation concrete is 4–6 in.; slump exceeding specification may indicate excess water and reduced strength.

Curing: concrete must be kept moist and at temperatures above 50°F for at least 7 days; cold-weather concreting requires heated enclosures or accelerators.

Footing width: minimum 12 in. wide for 8-in. foundation wall; footing thickness minimum 6 in.; reinforcement per plan and MRC Table R403.1.

Backfill: do not backfill against foundation walls until concrete has reached sufficient strength (typically 7 days) and wall bracing is in place; use free-draining soil and compact in lifts.

Site drainage: finish grade must slope away from foundation at least 6 in. within the first 10 ft; swales and downspouts must discharge away from footings.

Excavation safety: trenches 5 ft or deeper require protective systems (sloping, shoring, or trench box); spoil piles kept at least 2 ft from trench edge.

Wall stud spacing: 16 in. or 24 in. on center; exterior walls with 2×6 studs at 24 in. o.c. may require additional sheathing or bracing per MRC Table R602.3(5).

Header sizing: use MRC Table R602.7; a 4-ft opening in a bearing wall typically requires a 2×6 or larger header depending on span and load.

Floor joist spans: maximum spans per MRC Table R502.3.1(1); notching allowed only in outer third of span, max depth 1/6 of joist depth; hole diameter max 1/3 of joist depth, not in cantilever.

Wall bracing: braced wall panels required at corners and intervals along exterior walls; minimum 1/4 in. wood structural panel sheathing or let-in bracing per MRC R602.10.

Roof framing: ridge board minimum 1 in. nominal thickness and depth not less than cut end of rafter; collar ties required in upper third of attic space for rafters without ceiling ties.

Engineered lumber: LVL, LSL, and glulam beams must be installed per manufacturer's specifications; no field cutting or notching unless approved by the manufacturer.

Fasteners: nails in withdrawal must penetrate at least 1-1/2 in. into receiving member; use galvanized or stainless fasteners for treated lumber and exterior applications.

Stair stringers: minimum 2×10 nominal; not more than 1/3 of stringer depth may be cut at any point; stringers spaced not more than 16 in. o.c. for 2×10.

Asphalt shingle installation: minimum roof slope 2:12 for shingles; slopes 2:12 to 4:12 require double underlayment; slopes below 2:12 require low-slope roofing membrane.

Ice dam protection: in Michigan, ice barrier membrane required at eaves extending from eave edge to a point at least 24 in. inside the exterior wall line.

Attic insulation: Michigan energy code (based on IECC) requires R-49 to R-60 in attics depending on climate zone (Zone 5/6); verify local amendments.

Vapor retarder: Class I or II vapor retarder required on warm side of insulation in walls; in cold climates, use kraft-faced or 6-mil poly with proper sealing.

Roof ventilation: minimum 1 sq ft of net free ventilation per 150 sq ft of attic floor area; if balanced intake/exhaust, ratio may be 1:300.

Flashing: step flashing required at sidewalls, headwall flashing at chimneys, and pan flashing at skylights; all flashing must be installed before roofing.

Windows and doors: flashing must integrate with weather-resistive barrier (WRB) in shingle-lap fashion; sill pan required at exterior doors and windows per MRC R703.4.

Roof sheathing: minimum 7/16 in. OSB or 1/2 in. plywood for shingle roofs; panels must be gapped 1/8 in. at edges for expansion.

OSHA fall protection: required at 6 ft or more above lower level in construction; guardrails, safety nets, or personal fall arrest systems must be used.

Scaffold safety: scaffolds must be erected on firm footing, plumb and square, with guardrails and toe boards; maximum height 4 times the minimum base dimension unless tied to structure.

Lead-safe practices: EPA Renovation, Repair, and Painting (RRP) rule requires certified firms and renovators when disturbing painted surfaces in pre-1978 housing; Michigan enforces the rule.

Asbestos: Michigan OSHA and EPA NESHAP regulations require inspection and notification before demolition or renovation that may disturb asbestos-containing materials.

Personal protective equipment: hard hats, safety glasses, and sturdy footwear required on all construction sites; hearing protection when noise exceeds 85 dBA.

Hazard communication: Safety Data Sheets (SDS) must be available for all chemicals on site; employees must be trained on chemical hazards per OSHA HazCom standard.

Excavation and trenching: protective system required for trenches 5 ft or deeper; access ladder within 25 ft of workers in trenches 4 ft or deeper.

Michigan jobsite regulation: building permits must be posted on site; inspections required at foundation, framing, and final stages; stop-work orders may be issued for noncompliance.