2.2 Tear-Off Procedures, Overlay Limitations, and Hazardous Materials

2.2 Tear-Off Procedures, Overlay Limitations, and Hazardous Materials

Quick Answer: Under California Building Code (CBC Chapter 15 / CRC Section R908), a building may never support more than two roof coverings. A complete tear-off down to the structural deck is legally required if the existing roof has two or more coverings, if the existing material is wood shake/shingle, slate, or tile, or if the assembly is water-soaked or structurally decayed. When stripping roofs built prior to 1980, contractors must test for asbestos-containing materials (transite, felts, mastics). Handling ACM constitutes Cal/OSHA Title 8 CCR §1529 Class II work requiring wet methods, HEPA dust containment, and a 10-working-day advance notification to the regional Air Quality Management District (e.g., SCAQMD Rule 1403).

Reroofing represents a major share of roofing contract volume in California. C-39 contractors must accurately differentiate between situations where a recover (overlay) is permitted and those where a full tear-off is legally mandated, while strictly enforcing occupational health standards for toxic substances.

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1. Systematic Tear-Off Operations and Specialized Equipment

A full tear-off requires a systematic methodology that balances worker ergonomics, fall safety, and building protection.

Tear-Off Tooling

• Shingle Shovels / Rippers: Heavy-duty steel pry tools equipped with notched or serrated blades and a fulcrum skid heel. The teeth slide under fastener heads, levering shingles and roofing nails out of the decking in a single stroke.
• Spud Bars & Rotary Scarifiers: Manual spud bars feature a chisel blade offset from a heavy steel shaft, designed to scrape embedded gravel, aggregate, and coal tar pitch from underlying felts. Powered mechanical spudders and rotary scarifiers automate aggregate removal on large commercial built-up roofs (BUR).
• Walk-Behind Powered Strippers: Self-propelled motorized machines equipped with reciprocating hardened steel blades. They slice through multi-ply asphalt membranes, wood fiberboard, and bonded isocyanurate insulation, lifting adhered systems from wood, concrete, or steel decks.

Sequential Removal Protocol

1. Strip from Ridge to Eave: On steep-slope roofs, crews generally work from the ridge downward toward the eaves or from upper gables toward collection chutes. This maintains clean footing on exposed rafters or deck sheathing above the working edge.
2. Pull All Fasteners Flush: Nails that fail to pull out with the shingle shovel must be hammered flush or pulled with a cat's paw. Protruding fastener heads will puncture new underlayment membranes and cause immediate leaks.
3. Strip Flashing Interfaces Down to Bare Deck: All perimeter drip edges, rake metals, valley liners, step flashings along sidewalls, and chimney crickets must be stripped completely unless explicitly certified by the local building official as sound and reusable.

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2. California Building Code Reroofing and Overlay Rules

Contractors cannot simply add an overlay layer because a customer requests a lower bid. The California Building Code (CBC Chapter 15) and California Residential Code (CRC Section R908) strictly govern reroofing limits.

Aggregate Removal Mandates for Low-Slope Systems

Under CBC §1511 and Cal/OSHA standards, loose aggregate surfacing must be completely cleared prior to reroofing:

• Torch-Applied Systems: Open-flame application of modified bitumen over loose gravel or dusty residue is strictly prohibited. Trapped organic debris or exposed asphalt slag ignites instantly under a propane torch.
• Spray Polyurethane Foam (SPF): SPF requires a completely clean, aggregate-free, dry substrate. Residual gravel prevents chemical bonding, leading to immediate wind peel-off and core delamination.

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3. Asbestos-Containing Materials (ACM) in Roofing

Until federal regulations curtailed asbestos in construction products during the late 1970s and 1980s, asbestos was widely blended into roofing products for fire resistance, tensile strength, and weathering durability.

Typical Historical Roofing ACM

• Transite Shakes and Shingles: Asbestos-cement exterior siding and roofing tiles containing 15% to 50% chrysotile or amphibole asbestos fibers. They are hard, brittle, and release microscopic respirable fibers when cut, broken, or dropped.
• Asphalt Asbestos Felts: Base sheets, ply sheets, and saturated organic felts in commercial BUR assemblies.
• Flashing Cements, Mastics, and Coatings: Plastic roof cements, troweled flashing adhesives, and silver aluminum asphalt coatings formulated before 1980 frequently contained 5% to 25% asbestos fiber binders.

Cal/OSHA Title 8 CCR §1529 Mandates

Cal/OSHA categorizes the removal of intact asbestos-containing roofing materials as Class II asbestos work:

1. Permissible Exposure Limit (PEL): The 8-hour Time-Weighted Average (TWA) is 0.1 fiber per cubic centimeter of air (0.1 f/cc). The 30-minute Excursion Limit is 1.0 f/cc.
2. Competent Person On-Site: A designated Competent Person who has completed Cal/OSHA-approved asbestos supervisor training must supervise all Class II operations.
3. Wet Methods Mandatory: Workers must mist materials with amended water (surfactant mix) continuously during removal to suppress airborne dust. Dry sweeping, compressed air cleaning, or high-speed dry abrasive cutting is illegal.
4. HEPA Dust Collection: Any mechanical rotary cutters or power spudders must be fully enclosed in local exhaust ventilation hoods connected to HEPA vacuums.
5. Intact Removal: Transite shingles must be removed whole by pulling fasteners without cracking or shattering the tiles. Dropping transite shingles from roofs is prohibited; they must be lowered manually or via an enclosed hoist.
6. Disposal Packaging: Waste must be sealed in leak-tight, double 6-mil polyethylene bags or labeled rigid drums bearing OSHA danger warnings, and transported by a California-certified hazardous waste hauler to a Class I or permitted disposal site.

Air District Notification Rules (e.g., SCAQMD Rule 1403)

In California, local Air Quality Management Districts (such as South Coast AQMD, Bay Area AQMD, or San Joaquin Valley APCD) enforce strict notification rules. Contractors must submit written notification at least 10 working days prior to initiating any demolition or renovation involving specified threshold quantities (typically 100 square feet or 100 linear feet of ACM).

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4. Lead-Based Paint and Metal Exposure (Title 8 CCR §1532.1)

Structures constructed before 1978 frequently contain lead-based paint on exterior wooden fascia boards, eaves, barge rafters, and soffits. Additionally, older structures utilize solid sheet lead plumbing vent pipe jacks and soldered lead/copper valley flashings.

• Cal/OSHA PEL for Lead: 50 micrograms per cubic meter of air (50 µg/m³) as an 8-hour TWA; the Action Level is 30 µg/m³.
• Safe Removal Work Practices: Crew members scraping or replacing lead-painted fascia boards must utilize HEPA-shrouded power scrapers or chemical strippers, wear half-mask elastomeric respirators equipped with P100 filters, and lay disposable drop cloths beneath work zones to catch paint flakes. Open-flame burning or torching of lead-coated surfaces is strictly prohibited.