Replacing roof shingles is one of the most physically demanding renovation tasks. The work involves stripping old shingles, replacing damaged sheathing, installing underlayment, and laying new shingles in proper overlap pattern. Done well, the new roof lasts 25-30 years. Done poorly, leaks develop and warranty is voided.
This guide is an overview of full re-roof work — sufficient for understanding scope. Most homeowners hire roofing contractors; this is not first-time DIY work.
Before you start
Three things to settle:
1. Strip down to sheathing. Layer-over (new shingles on top of old) is allowed in some jurisdictions but reduces lifespan and shows wear faster. Best practice: full strip-and-replace. Two layers is typical maximum (Code in many areas).
2. Replace damaged sheathing. Stripping reveals sheathing condition. Soft, rotted, or damaged sheathing must be replaced before re-roofing. Common around chimneys, valleys, and edges.
3. Time and weather windows. Roofing requires multiple consecutive dry days. Weather forecasting drives schedule. Don't strip if rain is forecast within 48 hours unless tarped properly.
What you'll need
Tools
- Roofing nail gun (or hammer)
- Pry bar (for stripping old shingles)
- Utility knife
- Tape measure
- Chalk line
- Reciprocating saw (for damaged sheathing)
- Roofing safety harness with rope and anchor
Materials
- Asphalt shingles (matching ratings to climate — Ottawa: cold-rated)
- Underlayment (synthetic or 30-lb felt)
- Ice and water shield (eaves and valleys)
- Drip edge (metal at perimeter)
- Roofing nails (1.5-2 inch galvanized)
- Plywood sheathing (for damaged areas)
- Flashing (for chimneys, walls, vents)
- Roofing cement (Henry 208)
- Hip and ridge cap shingles
Ice and water shield mandatory at eaves
Ottawa Code requires ice and water shield (self-adhering) at the eaves: 6 ft up from edge or 3 ft past the inside of exterior wall, whichever is more.
Prevents ice damming damage in winter.
Apply BEFORE underlayment and shingles.
Step-by-step instructions
Plan and pull permit
Re-roofing typically requires building permit in Ontario.
Application includes scope, materials, contractor info.
A building permit fee applies, set by the City of Ottawa and based on project scope.
Prepare the site
Tarp around perimeter of house to catch debris.
Move vehicles, outdoor furniture away from house.
Set up garbage disposal (dumpster or roll-off bin) for old shingles.
Coordinate with weather forecast.
Strip old shingles
Roofing shovel or pry bar to lift and remove shingles.
Work top-down, one course at a time.
Pull nails as you go.
Sweep debris off as you progress.
Inspect and replace damaged sheathing
Walk on freshly stripped roof — feel for soft spots.
Replace any damaged sheathing with same-thickness plywood.
Around chimneys, valleys, and edges: most prone to damage.
Sheathing goes back per OBC Section 9.23.
Install drip edge at perimeter
Drip edge metal: at eaves and rakes (gable edges).
Aluminum or galvanized.
Nail to sheathing per manufacturer.
Eaves drip edge installed FIRST, then ice/water shield over.
Apply ice and water shield at eaves and valleys
Self-adhering membrane.
At eaves: 6 ft up (or 3 ft past inside wall).
In valleys: continuous strip up the valley.
Around penetrations: full coverage.
Apply underlayment over rest of roof
Synthetic underlayment OR 30-lb felt.
Roll across roof from low to high, overlapping seams.
Stapled or nailed per manufacturer.
Covers everything not covered by ice/water shield.
Install flashing
Step flashing at walls.
Chimney flashing.
Valley flashing (if open valley).
Vent pipe flashing.
Per separate flashing guide.
Install starter shingles at eaves
Starter shingles along bottom edge of roof.
Pre-cut or cut from regular shingles.
Provides solid first course.
Install shingles in overlap pattern
Snap chalk lines to keep courses straight.
Each shingle course offset from the one below (typical 6 inch offset).
Nails at proper location per manufacturer (typically 4 nails per shingle).
Don't expose nails.
Install hip and ridge caps
Cap shingles at hip lines and ridge.
Match colour to field shingles.
Bend over hip; nail per cap shingle pattern.
Install ridge vent (if used)
Cut sheathing slot.
Install ridge vent product.
Cap shingles over ridge vent.
Per ridge vent guide.
Final inspection and clean-up
Building inspector verifies install per Code.
Clean up debris from yard, magnet sweep for nails.
Document with photos for warranty.
Common mistakes that cost you
- Skipping ice and water shield. Ice damming damages eaves. Code-required minimum.
- Wrong shingle nailing pattern. Wind warranty void; shingles blow off. Follow manufacturer.
- Layer-over without permission. Reduces life. Strip and replace is best practice.
- Damaged sheathing not replaced. Spongy roof, shingles fail early. Replace damaged sheathing.
- Working in poor weather. Slippery, dangerous; partial install can leak. Plan dry weather.
Frequently asked questions
Should I do my own roof?
Physically demanding, weather-dependent, high consequences for mistakes.
Most homeowners hire professional roofers — material grade, roof pitch, square footage, tear-off layers, and access all drive the price.
DIY means buying materials yourself plus 3-7 days of labour, fall risk, and a learning curve.
First-time DIY roofing not recommended.
What shingle warranty applies?
Standard asphalt shingles: 25-year limited.
Architectural shingles: 30-50 year limited.
Premium (designer or impact-rated): 30-50 year warranty + wind/hail.
Improper installation voids warranty.
Do I need a permit?
Most jurisdictions require permit for re-roofing.
Like-for-like: simpler permit process.
Major changes (different shingle weight, structural): more involved permit.
Verify with your municipality.
When to call us instead
Roofing is licensed-contractor work. Our team coordinates roofing as part of full-scope renovations or stand-alone projects.
Book a free 60-minute site visit →Related Ottawa services
If your renovation includes roofing, our team coordinates with roofing contractors. Book a free 60-minute consultation.