7.2 Pre-Job Walk-Through, Plans & Details, Permits & Selecting the Roof System
Key Takeaways
A pre-job walk-through checks access, the roof's condition and layers, penetrations, landscaping, loading and tear-off areas, overhead power lines, and safety requirements.
Roof plans show slopes, ridges, hips, valleys, and penetrations, while details show how edges, walls, and penetrations are flashed, and specifications list materials and methods.
Every Michigan shingle-type roof needs an ice barrier from the eave to at least 24 inches inside the exterior wall line, because Michigan's design table marks ice barrier as required.
Roof covering choice depends on minimum slope: asphalt shingles need 2:12, metal shingles and wood shingles or shakes 3:12, slate 4:12, and built-up and membrane systems 1/4:12.
Enhanced manufacturer warranties usually require the manufacturer's specified components, a credentialed installer, and registration within the manufacturer's deadline.
The Pre-Job Walk-Through
PSI's outline lists this task as "Conduct pre-job walk-through to determine access, roof's condition, roof penetrations, landscaping issues, loading and tear-off areas, and safety requirements." A practical checklist:
| Area | Check |
|---|---|
| Access | Driveway width for trucks and dumpsters, overhead wires, gates, and neighbor property. Where ladders, hoists, or a conveyor will go |
| Roof condition | Number of existing layers (probe at a rake or vent), soft spots, sagging, granule loss, curling, rot at eaves, and prior repairs |
| Attic | Ventilation, insulation depth, baffles, bath fans venting into the attic, stains, mold, and daylight at the deck |
| Penetrations | Chimneys (width across the slope decides whether a cricket is needed), skylights, plumbing vents, flues, exhaust fans, satellite dishes, solar |
| Walls and edges | Sidewalls, headwalls, dormers, kick-out locations, drip edge, gutters, and fascia condition |
| Landscaping and property | Shrubs, flower beds, AC condensers, decks, pools, vehicles, and windows under the drop zone |
| Loading and tear-off areas | Where bundles can be staged over framing and at least 6 feet from unguarded edges, and where debris will be dropped |
| Safety | Roof slope and eave height (fall protection method), anchor locations, power-line clearance, skylights and holes, and weather exposure |
| Hazardous materials | Pre-1978 painted trim (lead rules) and suspect asbestos felts or cement shingles |
| Other trades | Chimney repair, gutter replacement, electrical (PV), and HVAC vents that must be done or coordinated before roofing |
Photograph existing conditions, including cracked driveways, dented gutters, and interior stains. This protects both you and the owner.
Reading Plans, Details, and Specifications
- Roof plan: a view from above showing ridges, hips, valleys, slopes (often as a slope triangle such as 6 over 12), overhangs, drains, and penetrations. Dimensions are horizontal projections, so apply a slope factor (Section 7.3).
- Elevations: show eave and ridge heights, which help with fall protection and ladder planning.
- Sections and details: drawn at larger scale to show eave assemblies (drip edge, ice barrier, vents), wall intersections (step flashing, counterflashing), valleys, curbs, and crickets.
- Specifications: product names, ASTM standards, underlayment type and coverage, fastener type and schedule, flashing metal and gauge, and warranty.
- Scale: a roof plan at 1/4 inch = 1 foot means each 1/4 inch on paper equals 1 foot. A 9-inch line is 36 feet.
- Satellite and drone measurement reports: convenient for existing roofs, but verify pitches and key dimensions on site before ordering.
Permits
Obtain the permit the local enforcing agency requires before starting (MRC R105.1). Reroofing is not on the R105.2 exempt list. Keep the permit on site (R105.7), and schedule required inspections. LARA's homeowner guidance recommends that contracts say the contractor will obtain all required permits.
Selecting the Roof System
1. Slope Decides What Is Allowed
| Roof covering | Minimum slope (2015 MRC) |
|---|---|
| Asphalt shingles | 2:12. Double underlayment from 2:12 up to 4:12 (R905.2.2) |
| Clay and concrete tile | 2 1/2:12. Double underlayment from 2 1/2:12 to 4:12 (R905.3.2) |
| Metal roof shingles | 3:12 (R905.4.2) |
| Mineral-surfaced roll roofing | 1:12 (R905.5.2) |
| Slate | 4:12 (R905.6.2) |
| Wood shingles, wood shakes | 3:12 (R905.7.2, R905.8.2) |
| Metal panels | 3:12 lapped without sealant. 1/2:12 lapped with sealant. 1/4:12 standing seam (R905.10.2) |
| Built-up, modified bitumen, single-ply, spray foam, liquid-applied | 1/4:12, or 1/8:12 for coal-tar built-up |
2. Michigan Climate Requirements
- Ice barrier is required statewide on the roof coverings listed in R905.1.2, including shingles, metal shingles, slate, wood shingles, and shakes. It runs from the eave to at least 24 inches inside the exterior wall line, and at least 36 inches up the slope on roofs 8:12 and steeper (Section 8.3).
- Wind: asphalt shingles must be labeled to ASTM D7158 or D3161 classes suited to the wind speed (Section 9.1).
- Snow load and structure: heavy coverings and extra layers need structural confirmation, and engineering above 70 psf.
- Ventilation or unvented design: attic ventilation at 1/150 or 1/300, or an unvented assembly with the required insulation (Chapter 12 and Section 8.5).
- Energy code: ceiling insulation of R-38 in zone 5A and R-49 in zones 6A and 7 when insulation is part of the work (Section 8.5).
3. Owner Needs and Warranties
Discuss appearance, budget, expected service life, noise, hail resistance (UL 2218 Class 4 for impact resistance), reflectivity, and resale. Explain the difference between a manufacturer's standard limited warranty, which usually covers materials and is prorated after an initial period, and an enhanced system warranty. Enhanced warranties generally require:
- the manufacturer's specified accessory components (starter, underlayment, ridge cap, ventilation);
- installation by a contractor the manufacturer has credentialed;
- registration within the manufacturer's stated deadline, often with a fee.
Your own workmanship warranty covers installation errors. Define its term and exclusions in the contract (Section 3.3).
4. Match the Components
Selecting a roof means choosing a compatible system: deck, insulation (if any), underlayment, ice barrier, flashings, drip edge, ventilation, and the covering. The MRC requires materials to be compatible with each other and the building (R904.2) and installed per the manufacturer's instructions (R904.1).
Example Decision
A 1960s ranch in Kent County has a 3:12 roof and two existing shingle layers. The owner wants architectural shingles. At 3:12, shingles are allowed only with double underlayment or a full self-adhered alternative. The two existing layers require a full tear-off (R908.3.1.1). Kent County is climate zone 5A, so ventilation can use 1/300 only through balanced upper and lower vents, not the vapor retarder option (Section 12.1). Include ice barrier, drip edge, and a unit price for deck replacement in the bid.
What is the minimum slope for asphalt shingles under the 2015 Michigan Residential Code, and what is required between that slope and 4:12?
3:12, with a single layer of underlayment
2:12, with double underlayment from 2:12 up to 4:12
4:12, with no exceptions
1/4:12, with a self-adhered membrane
A roof plan drawn at 1/4 inch = 1 foot shows an eave line 11 1/2 inches long. What is the horizontal length of the eave?
23 feet
34 feet
44 feet
46 feet
Which item is part of a proper pre-job walk-through under the PSI roofing outline?
Ordering shingles before measuring the roof
Determining access, roof condition and layers, penetrations, landscaping issues, loading and tear-off areas, and safety requirements
Signing the completion certificate for the lender
Registering the manufacturer's warranty
Sections you finish are checked off in the contents.