Introduction: Understanding What Your Roof is Made Of

Most homeowners think of roofing as "shingles" or "metal." But at the molecular level, roofing materials are complex engineered systems designed to withstand UV radiation, thermal cycling, water infiltration, and mechanical stress. Understanding the science helps you make better choices.

ASPHALT SHINGLES: CHEMISTRY & COMPOSITION

The Four Layers of an Asphalt Shingle

1. Fiberglass Mat (Base Layer):

• Composition: Woven glass fibers bonded with resin
• Purpose: Structural strength, dimensional stability
• Why fiberglass: Replaced organic felt (paper/rag) in 1980s
  • Stronger (tensile strength 10x higher)
  • Lighter (30% weight reduction)
  • Rot-proof (doesn't absorb water)
  • Fire-resistant (Class A rating)

2. Asphalt Coating (Waterproofing Layer):

• Composition: Petroleum-derived bitumen + fillers
• Purpose: Waterproofing, flexibility
• Chemistry: Complex hydrocarbons (C₅H₈ to C₃₅H₇₂)
  • Asphaltenes: Heavy molecules (provide durability)
  • Resins: Medium molecules (provide adhesion)
  • Oils: Light molecules (provide flexibility)

3. Ceramic Granules (Protective Layer):

• Composition: Crushed rock (basalt, granite) coated with ceramic
• Purpose: UV protection, color, fire resistance, impact protection
• Why they matter: Without granules, asphalt degrades in 2-3 years

4. Adhesive Strip (Bottom Layer):

• Composition: Thermoplastic adhesive
• Purpose: Seals shingles together (wind resistance)
• Activation: Heat from sun activates adhesive (bonds in 2-4 weeks)

How Asphalt Shingles Degrade

1. UV Degradation (Photodegradation):

UV radiation breaks chemical bonds in asphalt, causing it to harden and crack.

• Process: UV photons break C-C and C-H bonds
• Result: Asphalt loses oils (becomes brittle)
• Timeline: Starts immediately, accelerates after 15-20 years
• Protection: Ceramic granules block 95%+ of UV

2. Thermal Cycling (Expansion/Contraction):

Temperature swings cause materials to expand and contract at different rates.

• Daily cycle: Roof temp varies 50-80°F (10-45°C) daily
• Seasonal cycle: -20°C to +70°C in Fraser Valley
• Stress: Fiberglass mat and asphalt expand at different rates
• Result: Micro-cracks form, water infiltrates, freeze-thaw damage

3. Granule Loss:

Granules protect asphalt from UV. When granules are lost, degradation accelerates.

• Causes: Foot traffic, hail, wind, age
• Timeline: 10-20% loss normal over 20-30 years
• Critical threshold: 30%+ loss = rapid failure

4. Moisture Damage:

• Water absorption: Asphalt is hydrophobic, but cracks allow water in
• Freeze-thaw: Water expands 9% when frozen (cracks widen)
• Algae/moss: Biological growth holds moisture (accelerates degradation)

METAL ROOFING: METALLURGY & CORROSION

Steel Roofing Composition

Typical Steel Roof (Standing Seam):

• Base metal: Cold-rolled steel (24-26 gauge = 0.024-0.018 inches thick)
• Galvanization: Zinc coating (G-90 = 0.90 oz/ft² each side)
• Primer: Epoxy or polyester (adhesion layer)
• Paint: Kynar 500 (PVDF) or acrylic (color + UV protection)

Why Galvanization Matters

Galvanic Protection:

Zinc coating protects steel through sacrificial corrosion. Zinc corrodes instead of steel.

• Chemistry: Zinc is more reactive than iron (higher in electrochemical series)
• Process: Zinc oxidizes first (ZnO forms protective layer)
• Lifespan: G-90 coating lasts 30-50 years in Fraser Valley climate

Paint Systems: Kynar 500 vs. Acrylic

Kynar 500 (PVDF - Polyvinylidene Fluoride):

• Composition: 70% PVDF resin + 30% acrylic
• Advantages:
  • Extreme UV resistance (C-F bond is strongest in organic chemistry)
  • Chalk resistance (color retention 30+ years)
  • Chemical resistance (acid rain, salt spray)
• Cost: 30-50% more than acrylic
• Warranty: 30-40 year color warranty

Acrylic Paint:

• Composition: Acrylic polymer resin
• Advantages: Lower cost, adequate performance
• Disadvantages: Fades faster (10-15 years), chalks
• Warranty: 10-20 year color warranty

Aluminum Roofing

Why Aluminum Doesn't Rust:

• Oxidation: Aluminum forms Al₂O₃ (aluminum oxide) instantly
• Protective layer: Al₂O₃ is hard, stable, prevents further corrosion
• Self-healing: Scratches re-oxidize immediately

Advantages:

• Rust-proof (ideal for coastal areas)
• Lightweight (1/3 weight of steel)
• Recyclable (100%)

Disadvantages:

• Softer (dents easier)
• More expensive (30-50% more than steel)
• Thermal expansion (expands 2x more than steel)

UNDERLAYMENT: POLYMER SCIENCE

Felt Paper (Organic Underlayment)

Composition:

• Base: Recycled paper or rag fibers
• Saturation: Asphalt impregnation
• Weight: #15 (15 lbs/100 ft²) or #30 (30 lbs/100 ft²)

Why Felt Fails:

• Water absorption: Organic fibers absorb water (swell, rot)
• UV degradation: Breaks down in sunlight (6-12 months exposed)
• Tears easily: Low tensile strength
• Lifespan: 5-10 years under shingles

Synthetic Underlayment

Composition:

• Base: Woven or spunbond polypropylene/polyethylene
• Coating: Polymer coating (waterproofing)
• Reinforcement: Fiberglass scrim (some products)

Why Synthetic is Superior:

• Waterproof: Polymer doesn't absorb water
• UV resistant: Lasts 6-12 months exposed (vs. felt's 6-12 weeks)
• Tear resistant: 5-10x stronger than felt
• Lifespan: 30+ years under shingles
• Lightweight: 50% lighter than felt (easier to install)

ICE & WATER SHIELD: ADHESIVE TECHNOLOGY

Composition

Layers:

• Top surface: Polyethylene film (waterproof)
• Adhesive: Rubberized asphalt (self-sealing)
• Release paper: Silicone-coated paper (removed during installation)

Self-Sealing Technology

How It Works:

• Nail penetration: Nail creates hole in membrane
• Adhesive flows: Rubberized asphalt flows around nail shank
• Seal forms: Creates waterproof seal
• Temperature-activated: Works better in warm weather

SEALANTS & ADHESIVES: POLYMER CHEMISTRY

Roofing Cement (Asphalt-Based)

Composition:

• Asphalt + mineral fillers + solvents
• Cures by solvent evaporation

Limitations:

• UV degradation (cracks, hardens)
• Temperature-sensitive (brittle when cold, soft when hot)
• Lifespan: 5-10 years

Polyurethane Sealant

Chemistry:

• Polymer formed by reaction of polyol + isocyanate
• Cures by moisture (reacts with water vapor in air)

Advantages:

• Excellent adhesion (bonds to metal, wood, masonry)
• Flexible (accommodates movement)
• UV resistant
• Lifespan: 20-30 years

DEGRADATION SCIENCE: WHY ROOFS FAIL

The Three Enemies of Roofing

1. UV Radiation:

• Energy: UV photons have 3-4 eV energy
• Bond breaking: C-C bonds require 3.6 eV to break
• Result: Polymers degrade, asphalt hardens, colors fade

2. Thermal Cycling:

• Expansion: Materials expand when heated
• Contraction: Materials contract when cooled
• Stress: Different materials expand at different rates
• Result: Cracks form, fasteners loosen, seals fail

3. Water:

• Hydrolysis: Water breaks chemical bonds
• Freeze-thaw: Water expands 9% when frozen
• Biological growth: Moss, algae, bacteria accelerate degradation

The Bottom Line

Roofing materials are complex engineered systems. Understanding the science helps you appreciate why quality materials cost more and last longer.

At Dads Roof Repair, we choose materials based on science, not marketing. We use synthetic underlayment (polymer science beats felt), extended ice shield (adhesive technology works), and Kynar 500 metal (PVDF chemistry is proven). We understand the materials at the molecular level.

Want materials that last? Call (778) 651-8021