Roofing
Shingles are just the waterproof layer — the underlayment, flashing, and ventilation are what keep your roof from leaking. The roof that failed leaked at the wall junction because the roofer skipped the kick-out flashing.
Project Overview
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What is roofing?
A roof is a multi-layer assembly designed to shed water, resist wind, block UV radiation, and ventilate the attic space. From bottom to top:
**1. Roof deck (sheathing):** OSB or plywood panels (1/2" or 5/8" thick) nailed to rafters or trusses. This is the structural layer that supports all other components. Spacing between sheets (1/8" gap) allows for thermal expansion — tight joints cause buckling in summer heat.
**2. Underlayment (water barrier):** The real waterproofing layer. **Ice and water shield** (rubberized asphalt membrane) is required at eaves (first 3 feet up from edge) and in valleys — it self-seals around nails and prevents ice dam leaks. **Synthetic underlayment** (polypropylene or polyester fabric) or **asphalt felt** (15# or 30#) covers the rest of the deck. Synthetic is stronger, lighter, and doesn't wrinkle when wet — preferred by most contractors. Felt is cheaper but tears easily and degrades in UV (must be covered with shingles within days).
**3. Asphalt shingles:** Fiberglass mat coated with asphalt and ceramic granules. The granules provide UV protection — when they wear off (15-25 years depending on quality), the asphalt deteriorates rapidly. **Architectural shingles** (dimensional, laminated) are thicker and heavier than **3-tab shingles** — better wind resistance (110 mph vs 60 mph), longer warranty (25-50 years vs 15-20 years), and better curb appeal (shadow lines mimic wood shakes). Cost difference: $1-$2 per sq ft installed.
**4. Flashing:** Metal or membrane pieces that divert water at junctions and penetrations. Critical flashings: **Step flashing** (where roof meets a vertical wall — each shingle course gets a piece of flashing tucked under siding and over shingles), **kick-out flashing** (at the bottom of step flashing, diverts water into gutter — without it, water runs behind siding), **valley flashing** (metal channel where two roof planes meet — handles high water flow), **chimney flashing** (base flashing, step flashing, counter-flashing, and cricket/saddle to divert water around the chimney). Flashing failures cause 80% of roof leaks.
**5. Ventilation:** Attic ventilation prevents ice dams (winter) and heat buildup (summer). The rule: 1:300 ratio (1 sq ft of vent per 300 sq ft of attic floor). Split equally between **intake vents** (soffit vents at eaves) and **exhaust vents** (ridge vent, gable vents, or roof vents at peak). Air flows in at soffit, up along underside of roof deck, and out at ridge — this removes moisture and heat. **Ice dams** form when heat escapes through the ceiling, melts snow on the roof, and the melt refreezes at the cold eave — creating an ice barrier that backs water under shingles. The cure is not more ice/water shield (that's a bandaid) — it's better insulation (R-50 in attic) and ventilation (1:300 ratio with baffles to maintain airflow).
**Fastener requirements:** Shingles must be nailed, not stapled (staples pull through in high wind). **6 nails per shingle** in high-wind zones (most of Ontario), placed in the nailing strip (upper third of shingle, above the cutouts). Nailing too high means the shingle below doesn't trap the nail head — the shingle lifts in wind. Nailing too low means you puncture the waterproofing layer — potential leak. Pneumatic nailers set to correct depth (flush, not over-driven or under-driven) prevent these issues.
**Manufacturer warranties and installation specs:** Every shingle manufacturer (GAF, CertainTeed, Owens Corning, IKO) publishes installation manuals specifying: nail type and quantity, underlayment requirements, starter strip details, flashing methods, ventilation minimums. If you deviate from these specs, the warranty is void. Manufacturers look for reasons to deny claims (shingles failed prematurely due to wind or hail) — improper installation is the easiest denial. Follow the specs exactly, document the work (photos), and keep records.
When you need roofing
- check_circleYour roof is 15-25 years old and shingles are curling, cracking, or losing granules
- check_circleYou see daylight through the roof deck in the attic (gaps, holes, rot)
- check_circleYou have water stains on ceilings or walls (active leaks or past leaks)
- check_circleShingles are missing after windstorms
- check_circleIce dams form every winter and cause interior water damage
- check_circleYou're selling your home and the roof is flagged in the home inspection
- check_circleYou're doing an addition or major renovation and need to tie new roofing into existing
- check_circleMoss or algae growth is widespread (indicates moisture retention and shingle degradation)
The Process
What happens from start to finish
1. Roof Inspection and Estimate
1-2 hours for inspection, 1-3 days for estimateInspect from ground level and attic. Look for: missing or damaged shingles, curling or cupping (edges lift due to moisture absorption), granule loss (bare spots on shingles or granules in gutters), sagging roof deck (indicates rotted sheathing or structural issues), daylight visible through deck, water stains or mold in attic, inadequate ventilation (soffit vents blocked, no ridge vent). Measure roof area (square footage ÷ 100 = number of "squares" — roofing is priced per square). Identify pitch (slope) — steep roofs (8:12 or steeper) require extra safety equipment and labour. Count penetrations (chimneys, vents, skylights) — each needs flashing. Get 2-3 quotes; compare scope (tear-off vs overlay, underlayment type, shingle quality, flashing details, ventilation upgrades).
2. Material Selection and Ordering
3-5 days lead timeChoose shingles: architectural (25-50 year warranty, $100-$150 per square) vs 3-tab (15-20 year, $70-$100 per square). Choose color (darker colors absorb heat, lighter colors reflect — consider energy efficiency and curb appeal). Order underlayment: ice/water shield for eaves and valleys (required by OBC), synthetic or felt for field. Order flashing materials: aluminum or galvanized steel step flashing, valley flashing, drip edge, pipe boots, ridge vent. Order fasteners: 1-1/4" or 1-1/2" roofing nails (galvanized or stainless), cap nails for ridge. Delivery timing: materials arrive 1-3 days before start date.
3. Site Setup and Safety
0.5 daySet up roof jacks or scaffolding for steep roofs (6:12 pitch or steeper). Install fall protection (harness, rope, anchor points) per Ministry of Labour regulations. Lay tarps or plywood on ground to protect landscaping from debris. Set up debris chute or dumpster (10-20 yard bin for tear-off debris). Cover open valleys, vents, and skylights with tarps during tear-off to prevent water infiltration if it rains.
4. Tear-Off (Removing Old Shingles and Underlayment)
0.5-1 day for typical residential roofStrip old shingles, underlayment, and flashing down to roof deck. Use flat shovels or tear-off forks (wide blade with teeth). Work from ridge down to eaves — gravity helps. Toss debris into dumpster or onto tarps (hand-carry to bin). Inspect deck for damage: soft spots (rot), gaps, broken panels. Replace damaged sheathing (OSB or plywood) — cut out bad sections, nail in new panels. If more than 20% of deck is damaged, consider full re-sheath (adds $2-$5 per sq ft). Sweep deck clean (no nails or debris — punctures underlayment).
5. Underlayment Installation
0.5-1 dayInstall drip edge (metal flashing along eaves and rakes — directs water into gutters, protects fascia). Install ice/water shield at eaves (minimum 3 feet up from edge, or to a point 2 feet inside the exterior wall — whichever is greater). Install ice/water shield in valleys (minimum 36" wide, centered on valley). Roll out synthetic underlayment or felt over remaining deck, overlapping rows by 6" (felt) or per manufacturer spec (synthetic). Nail or staple underlayment to deck (cap nails or staples every 12"). Some synthetics are self-adhering (peel-and-stick). Lap underlayment over drip edge at eaves, under drip edge at rakes (water flows over underlayment, under drip edge, into gutter).
6. Flashing Installation (Valleys, Chimneys, Walls)
0.5-1 day depending on complexityInstall valley flashing: 24-gauge galvanized or aluminum, centered in valley, extending from eaves to ridge. Open valley (metal exposed) or woven valley (shingles interlaced) — open valley is more durable and easier to inspect. Install chimney flashing: base flashing (L-shaped metal pieces at base of chimney, overlap shingles), step flashing (each shingle course gets a flashing piece), counter-flashing (cut into chimney mortar joints, bent down over step flashing — prevents water from running behind). Install cricket/saddle (small peaked structure behind chimney to divert water around it — required for chimneys wider than 30"). Install step flashing at walls (where roof meets vertical siding). Install kick-out flashing at bottom of step flashing (diverts water into gutter — critical detail, often skipped).
7. Shingle Installation
1-2 days for typical residential roofInstall starter strip at eaves (upside-down shingles or dedicated starter shingles — provides adhesive seal for first course). Install first course of shingles along eaves, overhanging drip edge by 1/2"-3/4". Nail each shingle with 6 nails in the nailing strip (upper third, above cutouts). Work up the roof in courses, offsetting shingles by 6" (half-tab) to stagger seams and create the pattern. Snap chalk lines every 4-5 courses to keep rows straight. At valleys: cut shingles to follow valley flashing, leaving 2-3" of exposed metal (open valley). At ridges and hips: install ridge cap shingles (thicker, pre-bent shingles) with 6" exposure, nailed on both sides.
8. Ventilation (Ridge Vent, Roof Vents, Soffit Vents)
0.5 dayCut a 1-2" slot along the ridge (if installing ridge vent). Install ridge vent (mesh or baffle design) over slot, nail to deck, cover with ridge cap shingles. Verify soffit vents are open and unblocked (insulation often blocks airflow — install baffles between rafters to maintain air channel). Add roof vents or gable vents if ridge vent is not feasible. Target 1:300 ventilation ratio (1 sq ft vent per 300 sq ft attic floor), split 50/50 intake (soffit) and exhaust (ridge).
9. Cleanup and Final Inspection
0.5 dayMagnetic sweep of property to pick up nails (roofing nails are everywhere after tear-off — lawn mower hazard, tire puncture risk). Remove tarps, debris, and equipment. Inspect roof from ground: straight courses, no lifted shingles, flashing visible and properly installed, ridge vent installed, no exposed nails. Provide homeowner with warranty documents (manufacturer's shingle warranty, contractor's workmanship warranty). No building permit required for re-roofing (unless changing structure or adding skylights), so no inspection — but quality contractors self-inspect.
Investment Guide
Roofing costs depend on roof size, pitch, complexity (valleys, dormers, chimneys), shingle quality, and whether you tear off old shingles or overlay (not recommended). Expect $4-$9 per square foot installed for architectural shingles, including tear-off, underlayment, flashing, and cleanup.
Small Roof Re-Roof (1,000-1,500 sq ft, simple gable)
$4,000-$7,000
Depends on: Tear-off, ice/water shield at eaves and valleys, synthetic underlayment, architectural shingles, drip edge, ridge vent, cleanup. Low-pitch roof (4:12 to 6:12), no dormers or complex flashing.
Medium Roof Re-Roof (1,500-2,500 sq ft, multiple valleys)
$7,000-$12,000
Depends on: Tear-off, ice/water shield, synthetic underlayment, architectural shingles, valley flashing, step flashing at walls, chimney flashing, ridge vent, soffit vent upgrades. Moderate pitch (6:12 to 8:12).
Large or Complex Roof (2,500-4,000 sq ft, steep pitch, dormers)
$12,000-$20,000
Depends on: Tear-off, ice/water shield, synthetic underlayment, architectural shingles, multiple valleys, dormers, skylights, chimney crickets, extensive step flashing, ridge vent, safety equipment for steep pitch (8:12+). High labour due to complexity and pitch.
Premium Shingles (Impact-Resistant, Class 4, 50-Year Warranty)
+$1.50-$3.00 per sq ft
Depends on: GAF Timberline HDZ, CertainTeed Landmark IR, Owens Corning Duration Storm — thicker, heavier, better wind/hail resistance. May reduce insurance premiums (ask insurer). Longer warranty but requires professional installation per manufacturer specs.
Roof Deck Replacement (Sheathing)
+$2-$5 per sq ft
Depends on: If more than 20% of OSB/plywood deck is rotted or damaged, replace entire deck. Adds material cost ($30-$50 per sheet) and labour (remove old, install new, fasten to rafters).
Ice Dam Prevention Upgrades (Insulation + Ventilation)
$2,000-$6,000
Depends on: Add or upgrade attic insulation to R-50 (blown cellulose or spray foam), install soffit baffles, add ridge vent or increase vent area. Solves root cause of ice dams — cheaper than replacing water-damaged ceilings every winter.
What Affects the Price
Get a detailed roofing quote with material specs, warranty information, and a written scope — we measure your roof, inspect for hidden damage, and provide a fixed price with no surprises.
Get a ballpark estimate in under 2 minutes.
Milestone-Verified Payment Architecture
Every roofing project on RenoNext uses milestone-based escrow. Your funds are held securely and only released when work is verified at each stage.
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Escrow-Held Funds
Your money sits in a regulated escrow account, not the contractor's pocket.
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Each phase is documented and verified before payment is released.
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10% Holdback Compliance
Automatic CPA-compliant holdback ensures warranty protection.
Project Center
Roofing
Escrow Balance
$4,000-$7,000
Roofing Failures: Why Roofs Leak (Hint: It's Not the Shingles)
- error**Kick-out flashing: the detail that saves your walls:** Where a roof slope meets a vertical wall (common in L-shaped houses, dormers, additions), water running down the roof hits the wall. Without kick-out flashing (a bent metal piece at the bottom of the step flashing), water runs behind the siding and into the wall cavity. Over 2-5 years, this rots the sheathing, studs, and siding. Repair cost: $5K-$15K (strip siding, replace rotted framing and sheathing, re-side). Kick-out flashing costs $30 and takes 10 minutes to install. Roofers skip it because it's not visible from the ground — but it's the #1 cause of wall leaks in homes with complex rooflines. Demand it in your contract.
- error**Ice dams are an insulation and ventilation problem, not a roofing problem:** Ice dams form when heat escapes through the ceiling into the attic, melts snow on the roof, and the melt refreezes at the cold eave — creating an ice barrier that backs water under shingles. The water leaks into the house, causing ceiling stains, mold, and drywall damage. The bandaid solution: ice/water shield at eaves (required by code, prevents leaks but doesn't stop ice dams). The real solution: insulate the attic to R-50 (reduces heat loss), ventilate properly (1:300 ratio, soffit intake + ridge exhaust), and install soffit baffles (maintain airflow channel under roof deck). Cost: $2K-$6K for insulation and vent upgrades. Do this when you re-roof — it's cheaper than repairing water damage every winter.
- error**Nailing too high or too low causes shingle blow-offs:** Shingles must be nailed in the nailing strip (upper third of shingle, above the cutouts). Nailing too high means the shingle below doesn't trap the nail head — wind lifts the shingle and it tears off. Nailing too low means you puncture the waterproofing tar strip on the shingle below — potential leak. Pneumatic nailers set to correct depth (flush, not over-driven or under-driven) prevent these issues. Hand-nailing is more reliable but slower. If your roofer uses a nail gun, verify they calibrate air pressure and check nail depth throughout the job.
- error**Manufacturer warranties are not what you think:** A "50-year shingle warranty" sounds great, but read the fine print. It's usually a limited warranty that covers material defects (rare) but not installation errors (common), wind damage (excluded), or wear-and-tear (excluded). The warranty is prorated — after 10 years, you get 60% reimbursement, after 20 years, 30%, etc. And it's void if you deviate from the manufacturer's installation manual: wrong underlayment, wrong number of nails, overlay instead of tear-off, improper ventilation. Document your installation (photos of underlayment, flashing, ventilation) and keep records — you'll need them if you file a claim.
- error**Overlay (layering new shingles over old) is a bad idea:** Saves $1-$2 per sq ft by skipping tear-off, but: (1) hides deck damage (rot, gaps, sagging), (2) adds weight to the roof (old shingles + new shingles = 6-8 lbs per sq ft extra — may exceed rafter capacity), (3) shortens new shingle life (old shingles create an uneven substrate, new shingles conform to bumps and wear faster), (4) voids most manufacturer warranties. OBC allows one layer of overlay (two layers of shingles total), but best practice is full tear-off. Pay the extra $1,500-$3,000 and do it right.
- error**Valley flashing failures cause interior water damage:** Valleys handle high water flow — water from two roof planes converges and flows fast down the valley. If valley flashing is undersized (less than 24-gauge metal, less than 36" wide), improperly lapped (seams face upslope — water gets under the flashing), or missing ice/water shield underlayment, water backs up under shingles and leaks into the attic. Symptoms: water stains on ceiling near valleys, mold in attic along valley line. The fix: strip shingles in valley, install ice/water shield (36" wide minimum), install metal valley flashing (open valley, not closed), re-shingle with proper overlap. Cost: $1,500-$4,000 depending on valley length. Prevent it by specifying open metal valleys and ice/water shield in your contract.
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Poor attic insulation causes ice dams and shortens roof life. Upgrade insulation when you re-roof.
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Learn morearrow_forwardCommon Questions
How long does a roof last in Ontario?expand_more
Do I need to replace the roof deck (sheathing) when re-roofing?expand_more
What's the difference between architectural shingles and 3-tab shingles?expand_more
Can I install new shingles over old shingles (overlay)?expand_more
How do I prevent ice dams?expand_more
What is a roof cricket (saddle), and do I need one?expand_more
Do I need a building permit to replace my roof?expand_more
How do I choose a roofing contractor?expand_more
Do asphalt shingles off-gas harmful chemicals?expand_more
Should I insist on open metal valley flashing instead of woven shingles?expand_more
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