Roof Restoration, Repair, and Maintenance
Chapter Introduction
This chapter covers all interventions on existing roofs, whether spot repairs, complete restoration, or preventive maintenance. For the Red Seal exam, you must master not only application techniques, but also the decision criteria between repairing and replacing, safety requirements, and applicable Canadian standards. Restoration represents a significant portion of the roofing trade's market, and exam questions often focus on practical details and common pitfalls.
Assessing the Condition of an Existing Roof
Preliminary Inspection and Documentation
Before any intervention, you must perform a systematic inspection. This inspection must be documented in writing and with photographs. The following items must be recorded:
Type of roofing system in place (bituminous, elastomeric membrane, metal, asphalt shingle, etc.)
Approximate age of the covering (verifiable through invoices, permits, or overall condition)
Roof slope (expressed as a ratio x/12 or in degrees)
Number of existing layers (limit of two layers for asphalt shingles according to most codes)
Condition of the deck (wood, concrete, steel)
Presence of moisture or mold in the insulation
Condition of flashings, penetrations, and curbs
Drainage (location and condition of drains, gutters, scuppers)
Moisture Detection Methods
Moisture in a roof is the primary cause of premature deterioration. Several methods exist:
| Method | Principle | Advantages | Limitations |
|---|
| Visual inspection | Look for blisters, delamination, stains | Simple, fast | Only detects surface moisture |
| Destructive testing | Core sampling or membrane opening | Absolute accuracy | Damages the covering |
| Pin-type moisture meter | Measures electrical resistance | Non-destructive, fast | Requires access to the deck |
| Thermal imaging | Detects temperature variations | Covers large areas | Expensive, requires specific conditions |
| Nuclear testing | Neutron backscatter | Very accurate | Regulated, requires a permit |
Decision Criteria: Repair or Replace
The decision between repair and replacement is based on several factors:
Relative cost: If the repair exceeds 40 to 50% of the replacement cost, replacement is generally recommended.
System age: A bituminous system over 15 years old with multiple repairs justifies replacement.
Extent of damage: If more than 30% of the surface is damaged, replacement is more economical.
Deck condition: If the insulation is saturated with water, its replacement is mandatory.
Warranty: Repairs on a system under warranty must be performed by the original installer or with their approval.
Repairs to Bituminous Roofs
Repairing Blisters and Bubbles
Blisters are caused by vapor pressure from moisture trapped beneath the membrane. The correct procedure is:
28.Slit the blister in a cross or "X" pattern with a membrane knife.
29.Remove the moisture and allow to dry completely (24 to 48 hours minimum).
30.Clean the area with a wire brush to remove debris.
31.Apply a bituminous primer to the exposed area.
32.Fold back the flaps and weld them with a torch or bond them with adhesive.
33.Apply a reinforcement patch (cover membrane) extending at least 150 mm (6 in) beyond each side of the blister.
34.Weld or bond the patch, ensuring there are no wrinkles.
Important: If the blister is filled with water, drain it first by making an incision at the lowest point, then follow the procedure above.
Repairing Tears and Perforations
For a tear in a bituminous membrane:
38.Clean the area around the tear to a width of at least 300 mm (12 in).
39.Remove frayed edges and cut the tear into a "V" shape at the ends to prevent propagation.
40.Apply a bituminous primer.
41.Insert a membrane plug into the tear if it is wide.
42.Apply a cover membrane patch (same type as the original membrane) extending at least 150 mm beyond the tear.
43.Torch-weld starting from the center and working toward the edges to expel air.
44.Verify the seal at the edges with a trowel.
Repairing Flashings and Counter-Flashings
Flashing areas are critical because they experience significant thermal and mechanical stress. The steps:
47.Remove the old metal flashing or damaged membrane.
48.Inspect the wall substrate (masonry, concrete) and repair any cracks.
49.Clean the surface and apply a primer.
50.Install a new membrane flashing with a horizontal return of at least 100 mm (4 in) onto the field of the roof.
51.Mechanically fasten the top of the flashing into a reglet sealed with caulking.
52.Install a metal counter-flashing if required by the plans.
Restoration of Elastomeric Membrane Roofs
Repairing EPDM Membranes
EPDM (ethylene-propylene-diene monomer) is a synthetic rubber membrane. Repairs are done by bonding:
56.Clean the area with an EPDM-specific cleaner (soap and water solution or commercial product).
57.Rinse thoroughly and allow to dry.
58.Apply a contact adhesive to both the existing membrane and the repair patch.
59.Allow the adhesive to become tacky to the touch (approximately 10 to 15 minutes).
60.Apply the patch avoiding wrinkles, starting from the center and working air out toward the edges.
61.Roll the patch with a seam roller to ensure contact.
62.Seal the edges with a compatible sealant.
Common pitfall: Never use hot bitumen on an EPDM membrane — the heat degrades the rubber.
Repairing PVC and TPO Membranes
Thermoplastic membranes (PVC, TPO) are repaired by hot-air welding:
66.Clean the area with an appropriate solvent.
67.Cut the repair patch with rounded corners (to prevent peeling at the corners).
68.Preheat the area with the hot-air gun.
69.Weld the patch using an automatic or manual nozzle, maintaining a temperature of 400 to 600 °C at the outlet (per manufacturer specifications).
70.Roll the weld with a silicone roller while it is still hot.
71.Test the weld with a spatula after cooling — it must be uniform.
Welding parameters: Temperature, speed, and pressure must be adjusted according to membrane thickness and ambient temperature. The manufacturer's reference table must be consulted.
Preventive Roof Maintenance
Regular Maintenance Program
A preventive maintenance program extends a roof's service life by 25 to 50%. Inspections should take place:
Twice a year: in the spring (after snowmelt) and in the fall (before winter).
After any major weather event (storm, hail, heavy rain).
After any work on the roof (work by other trades).
Common Maintenance Tasks
| Task | Frequency | Details |
|---|
| Cleaning drains and gutters | 2 times/year minimum | Remove leaves, debris, accumulated gravel |
| Flashing inspection | 2 times/year | Check seal integrity of joints and fasteners |
| Expansion joint check | 1 time/year | Inspect condition of bellows and fasteners |
| Penetration check | 2 times/year | Verify seals around vents, chimneys, etc. |
| Surface cleaning | As needed | Remove debris, moss, lichen |
| Gravel check (ballasted roof) | 1 time/year | Distribute evenly, top up if necessary |
Winter Maintenance
Roofs in Canadian climates experience significant winter stress:
De-icing: Never use metal shovels or picks on a membrane. Use plastic or wooden shovels.
Ice dam prevention: Ensure adequate attic ventilation and sufficient insulation to keep the roof temperature close to the outdoor temperature.
Snow removal: If accumulation exceeds the roof's structural capacity (calculated by the engineer), remove snow leaving a 50 to 75 mm (2 to 3 in) layer to protect the membrane.
De-icing products: Never use de-icing salt on a roof — chloride corrodes metal flashings and degrades membranes.
Restoration of Asphalt Shingle Roofs
Repairing Damaged Shingles
Asphalt shingles can be repaired individually:
90.Carefully lift the edges of the damaged shingle.
91.Remove the nails with a nail puller.
92.Slide the new shingle into place.
93.Fasten with 4 nails (or staples) in the nailing zone (under the shingle above).
94.Apply a small amount of bituminous cement under the edges to ensure a watertight seal.
Nailing rule: Nails must be placed 25 mm (1 in) from the top edge of the shingle and 25 mm from each end, spaced 150 mm (6 in) apart for standard shingles.
Replacing Shingle Sections
For a more extensive damaged section:
98.Mark the area to be replaced.
99.Cut the damaged shingles with a hook knife.
100.Remove exposed nails.
101.Install new shingles starting from the lower course.
102.Side lap of at least 75 mm (3 in) between adjacent shingles.
103.Seal the edges with bituminous cement.
Treating Curled or Buckled Shingles
Shingle curling is caused by inadequate ventilation or improper installation. The correction:
106.Apply a strip of bituminous cement under the edge of the curled shingle.
107.Press firmly and hold with a weight for 24 hours.
108.If the problem is widespread, check attic ventilation (net free ventilation area: 1/300 of the attic floor area per the National Building Code).
Restoration of Metal Roofs
Repairing Metal Panels
Metal roofs (steel, aluminum, copper) require specific techniques:
Perforations: Clean, apply a rust-inhibitive primer, then a caulking sealant compatible with the metal. For large holes, install a metal patch fastened with rivets and sealed.
Corrosion: Sand the corroded area, apply a rust converter, then a metal finishing paint.
Joint separation: Clean, apply an elastomeric sealing compound, then re-compress the joint.
Panel Replacement
Replacing a damaged metal panel:
117.Remove the fasteners from the damaged panel.
118.Release the panel by sliding it out of the interlock.
119.Install the new panel, engaging the interlock correctly.
120.Fasten with appropriate attachments (self-drilling screws with EPDM washers).
121.Seal the screw heads with a compatible sealant.
Important: Screws must be installed perpendicular to the surface. An angled screw creates a potential leak point.
Applicable Standards and Codes
National Building Code of Canada (NBC)
The NBC, in Part 5 (Environmental Separation) and Part 9 (Housing), contains requirements related to roofs:
Article 5.6.1.1: Roofs must be designed to shed rainwater.
Article 9.26.2.1: Asphalt shingles must be installed in accordance with the manufacturer's instructions.
Article 9.26.4.1: Flashings must be installed at junctions between the roofing and vertical elements.
CSA Standards
| Standard | Subject |
|---|
| CSA A123.1 | Asphalt shingles |
| CSA A123.2 | Bituminous roofing felt |
| CSA A123.21 | Polymer-modified bituminous membranes |
| CSA A123.22 | Elastomeric membranes (EPDM) |
| CAN/CGSB-37.51 | Polyurethane-based sealant |
Canadian Electrical Code, Part I
For work involving electrical equipment on the roof (de-icing cables, lighting, etc.):
Rule 8-200: Branch circuits must be protected in accordance with capacity requirements.
Rule 12-012: Cables must be protected against mechanical damage.
Note: The roofer does not perform electrical work, but must know the location of cables to avoid damaging them.
Hazardous Products Act and WHMIS
Products used in roof restoration (primers, adhesives, sealants) are subject to the Workplace Hazardous Materials Information System (WHMIS) . You must:
Consult the Safety Data Sheets (SDS) before use.
Wear the required personal protective equipment (PPE).
Know the emergency procedures in case of a spill.
Safety During Restoration Work
Fall Protection
Restoration work presents a high risk of falls. Safety requirements include:
Guardrails: Mandatory if the roof edge is more than 3 m (10 ft) above the ground.
Lifeline: Must be anchored to a certified anchor point (minimum capacity of 22 kN).
Safety harness: Must be worn and attached at all times when guardrails are not installed.
Ladders: Must extend at least 1 m (3 ft) above the roof edge and be secured.
Fire Safety
Torch work presents a fire risk:
Have a Class ABC fire extinguisher within reach (minimum 10 lb).
Protect combustible surfaces with thermal barriers.
Verify there are no combustible materials within 3 m (10 ft) of the work area.
Wait 30 minutes after completing torch work before leaving the site.
Ventilation and Respiratory Protection
Solvent vapors and hot bitumen fumes are harmful:
Use adequate ventilation in confined spaces.
Wear a NIOSH-approved respirator with organic vapor cartridges.
Take regular breaks in fresh air.
Complete Restoration Procedures
Re-covering (Overlay)
Re-covering involves installing a new membrane over the old one. Conditions:
The old membrane must be in generally good condition (less than 15% damage).
The slope must be adequate for the new system.
The insulation must be dry.
Structural capacity must be verified (additional weight of the new system).
Advantages: Lower cost, less waste, insulation preserved.
Disadvantages: Reduced service life (80% of a new system), masks underlying problems.
Full Tear-Off and Replacement
Full tear-off is necessary when:
The insulation is saturated with water.
The deck is damaged.
More than two layers already exist.
The slope must be modified.
Procedure:
175.Remove the entire existing system down to the structural deck.
176.Inspect the deck and repair damaged sections.
177.Install a vapor barrier if required.
178.Install insulation (verify the required thickness for the R-value).
179.Install the new membrane according to the manufacturer's specifications.
Calculating R-Value and Insulation Thickness
The total R-value of a roof is the sum of the thermal resistances of each layer:
R_total = R_insulation + R_membrane + R_deck
For insulation: R = thickness (m) ÷ thermal conductivity (W/m·K)
Example: Polyisocyanurate insulation with a conductivity of 0.024 W/m·K, thickness of 100 mm:
R = 0.100 ÷ 0.024 = 4.17 m²·K/W
To convert to imperial units (ft²·°F·h/BTU): multiply by 5.678.
R = 4.17 × 5.678 = 23.7 ft²·°F·h/BTU
Pitfalls to Avoid
189.Not identifying the membrane type before repairing: A hot bitumen repair on an EPDM or PVC membrane causes irreversible damage. Always identify the material before choosing the method.
190.Forgetting to check insulation moisture: A surface repair on saturated insulation will fail quickly. Always probe the insulation during inspection.
191.Ignoring manufacturer's instructions: Warranties are voided if repairs do not meet the manufacturer's specifications. Always consult the technical documentation.
192.Torch welding in wet or cold weather: Torch welding in rain or below 5 °C produces defective seams. Check weather conditions before starting.
193.Neglecting surface preparation: A surface that is not cleaned, primed, or dry compromises the adhesion of any repair.
194.Using nails that are too long: Nails that penetrate through the wood deck create leak points. Use nails of appropriate length (25 to 30 mm for shingles).
195.Confusing provincial and national standards: The Red Seal exam covers national standards (NBC, CSA). Provincial requirements vary and are not assessed.
196.Forgetting the minimum slope: A multi-ply bituminous membrane requires a minimum slope of 1:50 (2%). Insufficient slope causes water ponding and premature deterioration.
197.Not ventilating properly: Inadequate ventilation causes shingle curling and ice formation. Check ventilation requirements (1/300 of the attic area).
198.Working without fall protection: Falls are the leading cause of death in the trade. Never compromise safety to save time.
Summary
The repair/replace decision is based on relative cost (40-50%), system age, extent of damage (30%), deck condition, and warranties.
Bituminous repairs require rigorous preparation: cleaning, priming, drying, then applying patches with a minimum overlap of 150 mm.
EPDM membranes are repaired by bonding with contact adhesive; PVC/TPO membranes by hot-air welding at 400-600 °C.
Preventive maintenance (2 inspections/year) extends service life by 25 to 50%.
Key standards are the NBC (Parts 5 and 9), CSA A123.x standards, and the Canadian Electrical Code, Part I.
Safety is paramount: fall protection mandatory above 3 m, fire extinguisher within reach during torch work, appropriate PPE.
Re-covering is possible if the old membrane is in good condition, the insulation is dry, and the structure is adequate; otherwise, full tear-off.
R-value calculations use the formula R = thickness ÷ conductivity, with conversion to imperial units (× 5.678).
Review Questions
209.What are the three main criteria for deciding between repairing and replacing a roof?
210.What is the correct procedure for repairing a blister in a bituminous membrane?
211.Why should you never use hot bitumen on an EPDM membrane?
212.What are the ventilation requirements for an attic according to the NBC?
213.What is the minimum slope for a multi-ply bituminous membrane?
214.What are the welding parameters for a PVC membrane?
215.What is the minimum capacity of an anchor point for a lifeline?
216.How do you calculate the R-value of 150 mm of insulation with a conductivity of 0.022 W/m·K?
217.What are the conditions for a re-cover to be acceptable?
218.What are the three types of fall protection mentioned in this chapter?
This chapter covers the essential knowledge required to pass the "Roof Restoration, Repair, and Maintenance" section of the Red Seal exam. Review the procedures in detail, memorize the key values, and practice applying the decision criteria in practical scenarios.
