Understanding Roof Recover Changes in the 2024 IRC

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The 2024 International Residential Code (IRC) introduces some important updates to roof recover requirements compared to the 2021 IRC. Roof recovery refers to the process of installing a new roof covering over an existing one without removing the original materials. Understanding these updates helps ensure compliance, safety, and durability in residential roofing projects.

2021 IRC: Roof Recover Requirements (R908.3.1)​

The 2021 IRC provided clear guidance on when roof recover projects were permitted:

1. Manufacturer Instructions:
   • The new roof covering must be installed following the manufacturer's approved instructions.
2. Independent Roofing Systems:
   • Complete and separate roofing systems, like standing-seam metal roofs, designed to transmit loads directly to the structure without relying on existing coverings, do not require removal of old materials.
3. Wood Shake Roofs:
   • Metal panel, metal shingle, and concrete/clay tile roofs could be installed over wood shake roofs when installed in accordance with R908.4.
4. Protective Roof Coatings:
   • New protective coatings could be applied over existing coatings or various roofing materials (e.g., metal, mineral-surfaced roll roofing, built-up roofs, modified bitumen, thermoset, thermoplastic, and spray polyurethane foam) without removal of the old coating.

Exceptions: Roof recover was prohibited if:

• The existing roof was water-soaked or deteriorated.
• The existing roof was slate, clay, cement, or asbestos-cement tile.
• The roof already had two or more layers of any type of covering.

2024 IRC: Roof Recover Requirements (R908.4)​

The 2024 IRC retains the core principles of the 2021 code but includes some noteworthy updates for clarity and consistency.

Key Similarities:​

• The four primary conditions for allowing roof recover projects remain unchanged:
  • Installation must follow manufacturer instructions.
  • Independent roofing systems that transmit loads directly to the structure are exempt from tear-off.
  • Installation of metal, clay, or concrete tile roofs over wood shakes remains permitted.
  • Applying new protective coatings over compatible existing coatings is allowed without removal.

Key Changes:​

• Section Numbering:
  • The section number changed from R908.3.1 in the 2021 IRC to R908.4 in the 2024 IRC. This reflects a restructuring within the roofing provisions for better organization.
• Terminology Adjustments:
  • Language updates for better clarity and consistency, particularly around protective coatings and structural load requirements.
• Emphasis on Structural Integrity:
  • The updated language underscores the importance of the structural system's ability to carry loads independently when using complete roofing systems like standing-seam metal roofs.

Exceptions Remain Unchanged:​

• Recover is still prohibited if:
  • The existing roof is water-soaked or deteriorated.
  • The existing roof covering is slate, clay, cement, or asbestos-cement tile.
  • There are already two or more layers of roofing.

New Section: R908.3 Roof Replacement​

The 2024 IRC adds new provisions under R908.3 for roof replacement, requiring the removal of existing layers down to the roof deck with specific exceptions:

1. Ice Barrier Membrane:
   • If an adhered ice barrier membrane is present and the sheathing is in good condition, it can remain and be covered with a new ice barrier membrane, following manufacturer instructions.
2. Self-Adhered Underlayment:
   • If a self-adhered underlayment exists and the sheathing is sound, it may remain and be covered with compliant underlayment materials.
3. Second Layer of Self-Adhered Underlayment:
   • A second layer is permitted if the first cannot be removed without damaging the roof deck, provided that:
     • It is approved by the manufacturer.
     • The sheathing is not deteriorated.
     • Material buildup at walls, valleys, edges, and laps does not exceed two layers.

Insights from Code Change Proposal RB281-22​

This new section was introduced through proposal RB281-22, supported by the Insurance Institute for Business and Home Safety (IBHS), the Asphalt Roofing Manufacturers Association (ARMA), and the National Roofing Contractors Association (NRCA). Key insights include:

• Reason for the Change:
  • Existing self-adhered membranes are difficult to remove, often damaging the roof deck and increasing costs. The proposal provides clear guidance on when these membranes can remain in place.
• Collaboration and Research:
  • The change is based on over 20 years of industry observation, showing that self-adhered membranes perform effectively against water intrusion, especially after roof covering damage in high-wind events.
• Technical Guidance:
  • The ARMA Technical Bulletin recommends removing membranes when possible. If removal would damage the deck, a second layer can be installed, ensuring laps are offset and feathered to avoid drainage issues.
• Cost Impact:
  • This change is expected to reduce costs by avoiding unnecessary deck damage and replacement when only one layer of membrane exists.
• Public Hearing Outcome:
  • The committee unanimously approved the proposal (10-0) with minor clarifications to manufacturer terminology.

Practical Implications​

For contractors and homeowners, the updated 2024 IRC provisions mean:

• No significant technical changes to how roof recover projects are carried out.
• Improved clarity in code language helps reduce misinterpretations.
• New considerations for roof replacements involving ice barriers and self-adhered underlayments.
• Clearer guidance for scenarios involving difficult-to-remove underlayment layers.
• Consistency with manufacturer requirements remains crucial to avoid code violations.

Pro Tip: Always verify the condition of the existing roof covering before proceeding with a recover project to avoid potential code violations and ensure long-term performance.