Ontario Roofing Material Calculator

Roofing Material Calculator
🏠 Materials + cost sanity check Bundles • rolls • pieces • boxes

Roofing Material Calculator

Roofing estimates go sideways when someone forgets the boring parts: starter, ridge cap coverage, drip edge, ice & water, valleys, and nails. This calculator gives you a fast materials list and a budget-level materials total so you can order smarter and avoid those “we’re short one roll” roof moments.

Jump to the calculator See the FAQ

What this calculator helps you do

  • Estimate shingles (squares → bundles + waste).
  • Catch the extras (starter, ridge cap, drip edge, ridge vent).
  • Budget materials by editing Ontario-friendly unit prices.
  • Order smarter (fewer last-minute runs… and fewer arguments).

Use this for estimating and ordering. Final details still depend on manufacturer instructions and your inspector.

Before you hit “Calculate”

Have these ready

  • Roof footprint area (or roof surface area if you already measured it)
  • Total eave + rake lengths (for starter + drip edge)
  • Ridge/hip lengths (for ridge cap + ridge vent)
  • Valley length (if any) + how aggressive you want ice & water

Complicated roofs (multi-levels, lots of valleys, dormers) can eat waste for breakfast. Bump waste % accordingly.

Roofing Material Calculator

Wrapped for page layout — calculator styles isolated

Calculator Same page framework as your Snow Loads calculator.

🧮 Roofing Material Calculator

Estimate quantities and budget-level material costs for an asphalt shingle roof: shingles, starter, ridge/hip caps, synthetic underlayment, ice & water, drip edge, valley metal, ridge vent, nails, and an optional deck replacement allowance.

Roof Inputs

If you measured sloped roof area already, choose “Yes”. Otherwise use footprint area + pitch.
Plan view area (not sloped). We multiply by pitch factor to estimate surface area.
Pitch factor = √(1 + (rise/run)²). This converts footprint to sloped area.
Use this for complex roofs where you already measured the sloped surface.
Simple gable: 8–10%. Cut-up roofs: 12–18%.
Affects nails estimate only. Always follow manufacturer instructions.

Edges & Lines

Starter + drip edge + ice & water at eaves.
Gable edges. Hip roofs may be near zero.
Ridge cap + ridge vent.
Leave 0 for gable roofs.
Valley metal + membrane allowance.
Ventilation depends on intake + exhaust. See FAQ for basics.
Simple estimate. Real requirement depends on details and overhang/wall line.
Adds a valley membrane allowance (useful for budgeting).

Unit Prices (editable)

Change to match your supplier. Default coverage is below.
Common architecturals are ~33.3 sq.ft./bundle (3 bundles = 1 square).
Useful for budgeting when you don’t know the deck condition until you strip it.
% of base roof area (before waste).
Set this to OSB/plywood pricing you’re seeing today.

✅ Results

Estimated Materials Total (CAD)
$0
Before tax / labour • edit unit prices as needed
Roof area used
0 sq.ft.
—
Squares
0.0
—
Item Qty Unit Cost
⚠️ Estimating Disclaimer

This tool is for ordering/budget planning. Final quantities depend on manufacturer instructions, flashing details, roof geometry, and site conditions. Always follow the shingle system spec for eaves/valleys/fasteners and local inspection requirements.

What drives roofing quantities (the stuff people forget)

Roofing is details, not just “squares”

Most “quick quotes” only look at roof area. But your materials list swings hard based on edges and lines: eaves + rakes drive starter and drip edge, ridge/hips drive cap, valleys drive both metal and membrane, and your waste factor climbs fast once the roof gets chopped up.

If you’re budgeting in Ontario, don’t ignore ice dam protection. Whether it’s one course or two courses at the eaves, that membrane cost can be the difference between a clean estimate and a “why are we $600 over?” conversation.

Roofing FAQ (quick answers)

Common homeowner + contractor questions

How many bundles are in a “square”? +

Most architectural shingles are 3 bundles per square (a square = 100 sq.ft.). That’s why the default coverage is ~33.3 sq.ft. per bundle.

What waste % should I use? +

Simple gable roofs often land around 8–10%. Cut-up roofs with valleys, dormers, and multiple planes are commonly 12–18%.

Do I really need starter strip and ridge cap? +

Yes. Starter gives you the correct seal at the eaves/rakes, and ridge cap finishes the ridge/hips. Skipping either is the roofing version of “I’ll tighten that later.”

Is ridge vent always a good idea? +

Ridge vent is great if you also have proper intake (typically soffits). Exhaust without intake doesn’t move air — it just makes a fancy slot.

Why estimate ice & water by eave length × depth? +

It’s a fast budgeting method: you’re effectively covering a strip along the eaves. Real requirements can be more specific (overhangs, wall line, valleys), but this gets you close enough for ordering and cost planning.

Want me to add 20–30 more FAQ items like your electrical/roofing sets? Say the word.

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Roofing Questions People Ask All the Time

Homeowners want to avoid leaks and surprise bills. Contractors want to avoid call-backs and failed inspections. Here are the roofing questions that come up over and over in Ontario—answered in plain English.

1
How do I know if I need a full roof replacement or just a repair?
+
If the roof is leaking from a single, obvious issue (a pipe boot, one valley, a few missing shingles), a repair can be sensible. But if you’re seeing widespread wear, multiple leak points, or the shingles are at end-of-life, repairs become “band-aids on a tire.”
  • Repair-friendly: isolated damage, recent roof, good attic ventilation, no deck rot.
  • Replace-friendly: lots of granule loss, curling, repeated leaks, soft decking, or multiple layers.
Tip: If you’re paying for the same leak twice, it’s not a “repair”… it’s a roof asking for retirement.
2
How long should asphalt shingles last in Ontario weather?
+
“Lifetime” is marketing. Real life depends on ventilation, sun exposure, slope, installation quality, and storm cycles.
  • 3-tab: typically shorter service life.
  • Architectural/laminate: generally longer and more wind-resistant.
  • Bad ventilation can shorten lifespan fast (heat cooks shingles from underneath).
Rule of thumb: The roof system (venting + flashing + deck condition) matters as much as the shingle brand.
3
What are the early warning signs of roof failure (even if it “looks fine”)?
+
Many roofs fail from details—not from the big open field of shingles.
  • Granules in gutters / at downspouts
  • Shingle edges curling, cracking, or lifting
  • Rusty nails in attic, moldy sheathing, damp insulation
  • Stains around chimneys, skylights, valleys, and bathroom fans
Tip: The attic tells the truth. The roof surface often lies.
4
What causes leaks the most: shingles, flashing, valleys, skylights, or vents?
+
Leaks usually start at transitions—anywhere the roof changes direction or gets penetrated.
  • #1 suspects: step flashing at walls, chimney flashing, plumbing boots, skylight curbs
  • Next up: valleys (heavy water flow), missing/incorrect drip edge, poor underlayment laps
Field shingles are the easy part. Details are where the money (and headaches) live.
5
What’s the best way to prevent ice dams and winter leaks?
+
Ice dams are usually a heat-loss + ventilation problem, not a “bad shingle” problem.
  • Air-seal the attic plane (stop warm air leakage)
  • Increase attic insulation (reduce roof melting)
  • Ensure continuous soffit intake + exhaust (ridge/vents)
  • Use proper eave protection membrane (ice & water)
Tip: If your attic is warm in January, your roof is doing double duty as a space heater.
6
Do I really need ice & water shield — and how far up the roof does it go?
+
In Ontario, eave protection is often required for heated roofs and is cheap insurance against ice dam backup.
  • Typical installs are one course (3 ft) or two courses (6 ft) at eaves
  • Valleys and penetrations often get membrane too
Always follow local inspector expectations and the shingle manufacturer’s details.
7
Should I install ridge vent, roof vents, or gable vents—and what happens if it’s “unbalanced”?
+
Balanced ventilation means you have enough intake (soffit) to feed your exhaust (ridge/roof vents). If you only add exhaust, the attic will try to “pull” air from wherever it can—often from the house.
  • Best: soffit intake + ridge exhaust
  • Watch out: mixing ridge vents with large gable vents can short-circuit airflow
8
What’s the difference between 3-tab and architectural shingles?
+
Architectural shingles are thicker, more dimensional, and typically offer better wind performance and longer real-world lifespan. 3-tab is cheaper upfront but often loses the long game.
  • Architectural: better look, heavier, usually stronger
  • 3-tab: budget choice, less forgiving in storms
9
How do you estimate bundles/squares and waste so you don’t run short?
+
Roofing is sold in squares (100 sq.ft.) and bundles. Waste depends on roof complexity.
  • Simple gable: 8–10% waste
  • Hip/cut-up: 12–18% waste
  • Don’t forget caps, starter, valleys, and edge metal—those aren’t “included.”
10
Can new shingles go over old shingles, or should everything be stripped?
+
You can sometimes re-roof over an existing layer, but it’s often a false economy. Stripping lets you inspect the deck, fix rot, and install proper underlayment and details.
  • Overlay risks: hides deck issues, adds weight, can worsen ventilation, messy lines at edges
  • Best practice: strip when the roof is old, uneven, leaking, or you want it done once.
11
Do I need drip edge—and does it go under or over the underlayment?
+
Drip edge protects the deck edge and fascia from water tracking back under shingles. Where it goes depends on the edge:
  • Eaves: commonly drip edge goes under underlayment
  • Rakes: commonly drip edge goes over underlayment
Follow the manufacturer detail package and local practice—this is a small detail with a big payoff.
12
What’s the “right” roof pitch for shingles—and what changes on low-slope roofs?
+
Shingles need slope to shed water properly. On lower slopes, you may need special underlayment practices (and sometimes shingles aren’t the best roof covering at all).
  • Low slopes are more vulnerable to wind-driven rain and ice backup.
  • Always check the shingle product’s minimum slope requirement.
13
Which underlayment should I use: synthetic vs felt?
+
Synthetic underlayments are lighter, stronger, and often safer to walk on. Felt is cheaper but tears easier and wrinkles more.
  • Synthetic: better tear resistance, longer exposure ratings, consistent coverage
  • Felt: budget-friendly, but more sensitive to moisture and wrinkles
14
When is ice & water required, and how should it be used at valleys/eaves/penetrations?
+
Treat membrane like the roof’s “seatbelt.” It’s not the whole system, but when something goes wrong, you’ll be glad it’s there.
  • Eaves: protects against ice dam backup
  • Valleys: common to membrane the valley before metal/shingles
  • Penetrations: proper boots/flashing first, membrane as backup detail
15
How should valley flashing be detailed: open vs closed valley?
+
Open valleys shed water fast and are easy to inspect. Closed valleys can look cleaner but are pickier to install correctly.
  • Keep nails away from the valley centerline.
  • Use continuous sheathing and proper valley flashing/membrane.
  • In heavy snow areas, valleys deserve extra respect (and often extra protection).
16
What installation mistakes cause blow-offs and leaks?
+
The greatest hits:
  • High nailing (misses the reinforced zone)
  • Overdriven nails (cuts the shingle)
  • Underdriven nails (holds shingle up, creates leak path)
  • Poor flashing at walls/chimneys, sloppy valleys, bad vent/boot details
Tip: A roof doesn’t leak because it hates you. It leaks because someone rushed the details.
17
How many nails per shingle—4 vs 6—and when do I use 6?
+
Many standard installs are 4 nails/shingle. High-wind zones and some manufacturer requirements call for 6.
  • 4 nails: typical baseline
  • 6 nails: higher wind resistance (more labour + more nails)
Always follow the shingle manufacturer’s nail placement diagram.
18
How do I calculate ridge/hip cap bundles correctly?
+
Cap coverage varies by product and exposure. Don’t guess.
  • Measure ridge + hips in linear feet.
  • Divide by the cap product’s coverage (lin.ft./bundle) and round up.
  • Factor extra if you’re using a thicker cap profile or special vented caps.
19
How do I estimate materials for a “cut-up” roof?
+
Cut-up roofs burn material in three places: waste, starter/caps, and details (valleys, walls, dormers).
  • Bump waste to 12–18% depending on complexity.
  • Expect higher starter and cap usage (more edges, more ridges/hips).
  • Valleys can double up membrane/metal needs.
20
Where do code requirements end and manufacturer instructions begin—and which one wins?
+
  • Code sets minimum safety/performance requirements.
  • Manufacturer instructions protect the warranty and specify how the system must be installed.
If there’s a conflict, your local building official and the product system requirements dictate what you do on site.
Tip: The only thing worse than failing an inspection is “passing” and then getting a leak call-back.