Inspect Existing Roof
1-2 hoursAssess decking condition, identify rot or soft spots, check ventilation, document existing layers, and determine if tear-off or overlay is appropriate.
Advanced3-7 days
Roofing Project
End-to-end roofing project guide covering material estimates, pitch calculations, underlayment, flashing, and safety planning for shingle or metal roofs.
rooferscontractorsexperienced DIYers
Workflow
Measure Roof Dimensions
2-3 hoursMeasure each roof plane length and width, record pitch, note valleys, hips, ridges, and penetrations (vents, chimneys, skylights).
Calculate Materials
1 hourDetermine shingle bundles, underlayment rolls, drip edge, ridge cap, nails, ice-and-water shield, and gutter capacity based on measured area and pitch.
Tear Off Old Roofing
1-2 daysRemove existing shingles and underlayment, inspect and replace damaged decking, install drip edge at eaves and rakes, and dispose of waste properly.
Install Underlayment and Flashing
4-8 hoursLay ice-and-water shield in valleys and at eaves, roll synthetic or felt underlayment, install step flashing at walls, and set pipe boot flashings.
Install Shingles or Roofing Material
1-2 daysInstall starter strip, field shingles from eave upward with correct exposure and nail pattern, cap ridges and hips, and seal exposed nail heads.
Final Flashing and Gutters
4-6 hoursInstall counter-flashing at chimneys, seal all penetrations, hang and pitch gutters, install downspouts, and perform a final walk-through inspection.
Tools Used
- Roof Pitch CalculatorPrimarySupportingReference
Determine roof pitch to assess walkability and select appropriate materials. · Convert rise/run measurements to pitch factor for area calculations. · Confirm nail pattern requirements based on roof slope.
- Square Meters to Square Feet ConverterPrimarySupportingReference
Calculate true roof surface area using pitch multipliers for each plane. · Cross-check total squares (100 sq ft units) for material ordering. · Estimate tear-off waste volume for dumpster sizing. · Calculate underlayment roll count from net roof area plus overlaps. · Verify total catchment area for gutter capacity validation.
- Rafter Length CalculatorSupporting
Verify rafter length and spacing when replacing damaged structural members.
- Shingle CalculatorPrimary
Calculate shingle bundles needed based on roof area and exposure rating. · Track bundle consumption during installation against calculated order.
- Gutter Size CalculatorPrimarySupporting
Size gutters and downspouts based on roof catchment area and rainfall intensity. · Size and position downspouts based on roof drainage area.
- Percentage CalculatorReference
Apply waste factor (10–15%) for complex roof geometries.
Checklist
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Preparation
Underlayment
Installation
Finishing
Reference Materials
Roof Pitch Factor TableTable
Multipliers to convert flat footprint area to actual roof surface area.
| Pitch (rise/run) | Angle (°) | Pitch Factor | Walkability |
|---|---|---|---|
| 4/12 | 18.4° | 1.054 | Easy |
| 6/12 | 26.6° | 1.118 | Moderate |
| 8/12 | 33.7° | 1.202 | Difficult — use roof brackets |
| 10/12 | 39.8° | 1.302 | Steep — safety harness required |
| 12/12 | 45.0° | 1.414 | Very steep — professional only |
Asphalt Shingle Coverage RatesTable
Standard three-tab and architectural shingle bundle coverage.
| Shingle Type | Bundles per Square | Coverage per Bundle | Nails per Shingle |
|---|---|---|---|
| Three-tab (standard) | 3 | 33.3 sq ft | 4 |
| Architectural (laminated) | 3 | 33.3 sq ft | 4 (6 on steep) |
| Ridge cap | — | 25 linear ft per bundle | 2 |
Underlayment TypesStandard
#15 felt: budget option, 36" wide, two layers in valleys. Synthetic: lighter, tear-resistant, better UV exposure tolerance during construction delays. Self-adhering ice-and-water shield: required at eaves in IECC climate zones 5–8.
Flashing RequirementsStandard
Drip edge required at eaves and rakes. Step flashing at roof-to-wall intersections (minimum 100 mm / 4" per step). Counter-flashing at chimneys must extend 100 mm (4") over step flashing. Pipe boots sized to pipe OD with storm collar above.
Check Weather Before Starting
Never tear off more than you can dry-in in one day. Keep tarps ready and monitor hourly forecasts — a surprise rainstorm on exposed decking causes thousands in damage.
Start at the Lowest Eave
Work from the bottom up so each course overlaps the one below. Starter strip overhangs the drip edge by 6–10 mm (1/4–3/8") — more causes cracking, less allows water wicking.
Valley Installation Method
Open metal valleys last longer than woven shingles in heavy snow regions. Closed-cut valleys look cleaner but require precise cuts. Pick one method and use it consistently across the entire roof.
Safety Notes
- OSHA requires fall protection (harness, anchor, lanyard) at heights above 1.8 m (6 ft) — roofs are the leading cause of construction fatalities.
- Never work on wet, icy, or windy roofs — wait for dry conditions with wind below 30 km/h (20 mph).
- Identify and mark overhead electrical service lines before ladder placement and material hoisting.
- Wear soft-soled shoes for traction; hard boots damage shingles and increase slip risk.