CBC · California Building Code

When must roofs be replaced versus permitted to be recovered or left in place?

Under the California Building Code, replacing a roof means tearing off all existing roofing to the deck (§ 1512.2). Installing a new roof over an existing one (recover) is allowed only in specific cases — for example when the substrate is sound, the manufacturer permits the overlay, the existing covering is not slate/clay/cement/asbestos‑cement, and there are fewer than two existing layers (§ 1512.3). Always check for water‑soaked sheathing and follow the manufacturer’s approved instructions; otherwise a full replacement is required.

Ask a question free See coverage

Last reviewed: July 5, 2026

What the code requires

Under the CBC, reroof work is governed by SECTION 1512. In plain terms: materials/methods for recovering or replacing must meet Chapter 15 requirements (§ 1512.1), full roof replacement means tearing off all existing roofing down to the deck (§ 1512.2), and roof recover (installing a new covering over an existing covering) is allowed in specific, limited circumstances and prohibited in others (§ 1512.3).

Requirements in detail

Scope / general rule (§ 1512.1)

  • Any recovering or replacing must comply with Chapter 15 roof-covering and assembly rules (§ 1512.1). Some prescriptive requirements (for example minimum design slope and secondary drainage) have limited exceptions when re-covering or replacing low‑slope roofs that already provide positive drainage and meet other code provisions.

When full replacement is required (§ 1512.2)

  • “Roof replacement” is defined to require removal of all existing layers of roof assembly materials down to the roof deck. If the work triggers replacement, tear‑off to the deck is required.
  • Limited exceptions allow leaving specific underlayments in place only when the substrate is sound and the manufacturer permits it (see exceptions for adhered ice barrier and self‑adhered underlayment).

When recover (overlay) is permitted or prohibited (§ 1512.3)

  • Overlay (roof recover) is permitted when any of these are true:
    1. The new covering is installed per the roof‑covering manufacturer’s approved instructions.
    2. The new covering is a separate roofing system that transfers loads directly to structure (e.g., certain standing‑seam metal systems).
    3. Specific allowances for metal panels/shingles and concrete/clay tile over wood shakes when applied per the indicated sub‑section.
    4. Application of a protective roof coating over certain existing systems (built‑up, single‑ply, metal panels, foam, etc.) is allowed without tear‑off.
  • Recover is NOT permitted if any of the following are true:
    1. The existing roof or roof covering is water‑soaked or deteriorated so it is not an adequate base for additional roofing.
    2. The existing roof covering is slate, clay, cement or asbestos‑cement tile.
    3. The existing roof has two or more applications of any type of roof covering (i.e., two+ existing layers).

Decision‑relevant dimensions (table)

Decision factor What matters Typical outcome Code reference
Number of existing layers 0 or 1 layer vs. 2+ layers 2+ existing layers → recover not permitted; replacement required § 1512.3 (recover prohibitions)
Condition of substrate Water‑soaked / deteriorated vs. sound Water‑soaked or deteriorated → recover not permitted; replacement required § 1512.3 Exception 1 and § 1512.2 exceptions
Existing covering type Slate/clay/cement/asbestos‑cement tile Recover prohibited over these — tear off required § 1512.3 Exception 2
Manufacturer instructions New covering must be installed per manufacturer Recover allowed when manufacturer approves overlay § 1512.3(1)
Specific retained layers Adhered ice barrier or self‑adhered underlayment May remain if sheathing is sound and manufacturer permits § 1512.2 exceptions
Low‑slope drainage & slope Positive drainage, meeting Sections 1608.3 & 1611.2 Certain slope/secondary‑drain requirements may be excepted for reroofing § 1512.1 exceptions (refs to § 1507, § 1608.3, § 1611.2)

Exceptions & special cases

  • Ice barrier or self‑adhered underlayment: If an ice‑barrier membrane (adhered to the deck) or self‑adhered underlayment is present but the sheathing is not water‑soaked/deteriorated, those layers may be allowed to remain and be covered, subject to the roof‑covering and underlayment manufacturers’ approvals (§ 1512.2 exceptions).
  • Protective coatings: Applying a new protective roof coating over many existing membranes and coverings (built‑up, modified bitumen, single‑ply, metal panels, SPF, etc.) is explicitly permitted without tear‑off (§ 1512.3(4)).
  • Metal/standing‑seam and complete separate systems: Systems that do not rely on the existing roof for support can be installed without removing the existing covering (§ 1512.3(2)).
  • Recover over wood shakes: Metal panel/shingle and concrete/clay tile overlays over wood shakes are addressed separately and allowed only when applied per the appropriate subsection (§ 1512.3(3) and sub‑section references).
  • Low‑slope exceptions: Reroofing/recovering of existing low‑slope roofs that already provide positive drainage may be excepted from the Chapter 15 minimum design slope and secondary‑drain requirements, provided other drainage code sections are met (§ 1512.1 exceptions).

If a code excerpt needed for a nuance is not present in the retrieved files, that will be stated plainly.

Common mistakes

  • Counting layers incorrectly — assuming overlay is allowed when there are already two existing layers (recover is prohibited if there are two or more existing applications). § 1512.3 Exception 3.
  • Overlooking substrate condition — attempting recover over water‑soaked or deteriorated substrate; the code disallows recover if the existing roof is not an adequate base. § 1512.3 Exception 1.
  • Ignoring manufacturer instructions — recover is only permitted when installed per the roof‑covering manufacturer’s approved instructions. § 1512.3(1).
  • Assuming all tiles can be overlaid — slate/clay/cement/asbestos‑cement tile are specifically excluded from recover. § 1512.3 Exception 2.
  • Failing to check for concealed combustible spaces when overlaying shakes/wood shingles — special requirements apply (see related provisions).

Worked example

Scenario: A commercial low‑slope built‑up roof (BUR) has one existing layer of BUR over plywood. The owner wants to install a new modified‑bitumen cap sheet (overlay).

Step‑by‑step:

  1. Count layers: There is one existing layer → not automatically barred by the “two or more” rule. § 1512.3 Exception 3 (recover prohibition) applies only when there are two or more existing layers.
  2. Check substrate condition: Inspect sheathing for water‑soak/deterioration. If the existing roof or sheathing is water‑soaked or deteriorated, recover is prohibited — replacement (tear‑off to deck) is required. § 1512.3 Exception 1; § 1512.2.
  3. Manufacturer approval: Confirm the modified‑bitumen manufacturer permits installation over the existing BUR per their approved instructions. If the manufacturer’s instructions allow an overlay and the substrate is sound, recover is permitted (§ 1512.3(1)).
  4. Slope/drainage: For low‑slope roofs, determine if the roof provides positive drainage and otherwise meets referenced drainage sections — some Chapter 15 slope/drainage requirements may be excepted for reroofing. § 1512.1 exceptions.

Conclusion for this scenario: If the sheathing is sound and the manufacturer permits overlay, the owner may recover with the new modified‑bitumen per § 1512.3. If the sheathing is water‑soaked or there are two existing layers, full replacement per § 1512.2 is required.

Related provisions

  • § 1507 — Roof coverings (materials, slopes and installation rules referenced by § 1512.1).
  • § 1502.2 — Secondary (emergency overflow) drains / scuppers (referenced in § 1512.1 exceptions).
  • § 1608.3 — Code provision referenced for drainage performance in § 1512.1 exceptions.
  • § 1611.2 — Flood / roof drainage referenced in § 1512.1 exceptions.
  • Existing Building Code—Section on reroofing and structural considerations (relevant when additional overlay layers increase dead load). See the Existing Building Code reroofing and structural exceptions.

Code references

Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:

  • CBC § 1512.2 High relevance — show source text

    1512.2 Roof replacement. Roof replacement shall include the removal of all existing layers of roof assembly materials down to the roof deck.

    Exceptions:

    1. Where the existing roof assembly includes an ice barrier membrane that is adhered to the roof deck and the existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing, the existing ice barrier membrane shall be permitted to remain in place and covered with an additional layer of ice barrier membrane in accordance with Section 1507 where permitted by the roof covering manufacturer and new ice barrier underlayment manufacturer.
    2. Where the existing roof includes a self-adhered underlayment and the existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing, the existing self-adhered underlayment shall be permitted to remain in place and covered with an underlayment complying with Tables 1507.1.1(1), 1507.1.1(2) and 1507.1.1(3).
    3. Where the existing roof includes one layer of self-adhered underlayment and the existing layer cannot be removed without damaging the roof deck, a second layer of self-adhered underlayment is permitted to be installed over the existing self-adhered underlayment provided that the following conditions are met: 3.1. It is permitted by the roof covering manufacturer and self-adhered underlayment manufacturer. 3.2. The existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing.

    15-24 2025 CALIFORNIA BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

    3.3. The second layer of self-adhered underlayment is installed such that buildup of material at walls, valleys, roof edges, end laps and side laps does not exceed two layers.

    1512.3 Roof recover. The installation of a new roof covering over an existing roof covering shall be permitted where any of the following conditions occur:

    1. Where the new roof covering is installed in accordance with the roof covering manufacturer’s approved instructions.
    2. Complete and separate roofing systems, such as standing-seam metal roof panel systems, that are designed to transmit the roof loads directly to the building’s structural system and that do not rely on existing roofs and roof coverings for support, shall not require the removal of existing roof coverings.
    3. Metal panel, metal shingle and concrete and clay tile roof coverings shall be permitted to be installed over existing wood shake roofs when applied in accordance with Section 1512.3.1.
    4. The application of a new protective roof coating over an existing protective roof coating, metal roof panel, built-up roof, spray polyurethane foam roofing system, metal roof shingles, mineral-surfaced roll roofing, modified bitumen roofing or thermoset and thermoplastic single-ply roofing shall be permitted without tear off of existing roof coverings.

    Exception: A roof recover shall not be permitted where any of the following conditions occur:

    1. The existing roof or roof covering is water-soaked or has deteriorated to the point that the existing roof or roof covering is not adequate as a base for additional roofing.
    2. The existing roof covering is slate, clay, cement or asbestos-cement tile.
    3. The existing roof has two or more applications of any type of roof covering.
  • CBC § 1511.10.1 High relevance — show source text

    1511.10.1 Design. [BSC, DSA-SS, DSA-SS/CC, HCD 1 & HCD 2, OSHPD 1, 1R, 2, 4 & 5] Supports and attachments of photovoltaic panels to the roof structure, the panels, modules and components shall be designed in accordance with this code. 1. Seismic design shall be in accordance with ASCE 7 Section 13.6.12. 2. Wind design pressures shall be determined from ASCE 7 Section 29.4.3 or 29.4.4 using effective wind area in accordance with ASCE 7 Section 26.2.

    Construction documents for the supports and attachments shall be submitted to the enforcement agency for approval.

    SECTION 1512—REROOFING

    1512.1 General. Materials and methods of application used for recovering or replacing an existing roof covering shall comply with the requirements of Chapter 15.

    Exceptions:

    1. Roof replacement or roof recover of existing low-slope roof coverings shall not be required to meet the minimum design slope requirement of [1] / 4 unit vertical in 12 units horizontal (2-percent slope) in Section 1507 for roofs that provide positive roof drainage and meet the requirements of Sections 1608.3 and 1611.2.
    2. Recovering or replacing an existing roof covering shall not be required to meet the requirement for secondary (emergency overflow) drains or scuppers in Section 1502.2 for roofs that provide for positive roof drainage and meet the requirements of Sections 1608.3 and 1611.2. For the purposes of this exception, existing secondary drainage or scupper systems required in accordance with this code shall not be removed unless they are replaced by secondary drains or scuppers designed and installed in accordance with Section 1502.2.

    1512.2 Roof replacement. Roof replacement shall include the removal of all existing layers of roof assembly materials down to the roof deck.

    Exceptions:

    1. Where the existing roof assembly includes an ice barrier membrane that is adhered to the roof deck and the existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing, the existing ice barrier membrane shall be permitted to remain in place and covered with an additional layer of ice barrier membrane in accordance with Section 1507 where permitted by the roof covering manufacturer and new ice barrier underlayment manufacturer.
    2. Where the existing roof includes a self-adhered underlayment and the existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing, the existing self-adhered underlayment shall be permitted to remain in place and covered with an underlayment complying with Tables 1507.1.1(1), 1507.1.1(2) and 1507.1.1(3).
    3. Where the existing roof includes one layer of self-adhered underlayment and the existing layer cannot be removed without damaging the roof deck, a second layer of self-adhered underlayment is permitted to be installed over the existing self-adhered underlayment provided that the following conditions are met: 3.1. It is permitted by the roof covering manufacturer and self-adhered underlayment manufacturer. 3.2. The existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing.

    15-24 2025 CALIFORNIA BUILDING CODE

  • CBC § 7-4 High relevance — show source text

    7-4 2025 CALIFORNIA EXISTING BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    ALTERATIONS—LEVEL 1

    1. Where the existing roof includes a self-adhered underlayment and the existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing, the existing self-adhered underlayment shall be permitted to remain in place and covered with an underlayment complying with Tables 1507.1.1(1), 1507.1.1(2) and 1507.1.1(3) of the California Building Code .
    2. Where the existing roof includes one layer of self-adhered underlayment and the existing layer cannot be removed without damaging the roof deck, a second layer of self-adhered underlayment is permitted to be installed over the existing self-adhered underlayment provided all of the following conditions are met: 3.1. It is permitted by the roof-covering manufacturer and self-adhered underlayment manufacturer. 3.2. The existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing. 3.3. The second layer of self-adhered underlayment is installed such that buildup of material at walls, valleys, roof edges, end laps and side laps does not exceed two layers.

    [BS] 705.3 Roof recover. The installation of a new roof covering over an existing roof covering shall be permitted where any of the following conditions occur:

    1. The new roof covering is installed in accordance with the roof covering manufacturer’s approved instructions.
    2. Complete and separate roofing systems, such as standing-seam metal roof panel systems, that are designed to transmit the roof loads directly to the building’s structural system and that do not rely on existing roofs and roof coverings for support, shall not require the removal of existing roof coverings.
    3. Metal panel, metal shingle and concrete and clay tile roof coverings shall be permitted to be installed over existing wood shake roofs when applied in accordance with Section 705.3.1.
    4. The application of a new protective roof coating over an existing protective roof coating, a metal roof panel, built-up roof, spray polyurethane foam roofing system, metal roof shingles, mineral-surfaced roll roofing, modified bitumen roofing or thermoset and thermoplastic single-ply roofing shall be permitted without tear off of existing roof coverings.

    Exception: A roof recover shall not be permitted where any of the following conditions occur:

    1. Where the existing roof or roof covering is water-soaked or has deteriorated to the point that the existing roof or roof covering is not adequate as a base for additional roofing.
    2. Where the existing roof covering is slate, clay, cement or asbestos-cement tile.
    3. Where the existing roof has two or more applications of any type of roof covering.

    [BS] 705.3.1 Roof recovering over wood shingles or shakes. Where the application of a new roof covering over wood shingle or shake roofs creates a combustible concealed space, the entire existing surface shall be covered with gypsum panel products, mineral fiber, glass fiber or other approved materials securely fastened in place.

  • CBC § 140.3 High relevance — show source text

    |See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|

    150 2025 CALIFORNIA ENERGY CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES— ADDITIONS, ALTERATIONS AND REPAIRS

    B. Existing roofs of a nonresidential or hotel/motel building being replaced, recovered or recoated, as defined in Section 100.1(b) and Title 24, Part 2, Chapter 2, shall meet the requirements of Section 110.8(i). When roofs with more than 50 percent of the roof area or more than 2,000 square feet of roof, whichever is less, are being altered the requirements of i and ii apply: i. Roofing products shall comply with requirements in Section 140.3(a)1A. Exception 1 to Section 141.0(b)2Bi: An aged solar reflectance less than 0.63 is allowed for low-sloped roofs provided the maximum roof/ceiling U -factor in Table 141.0-B is not exceeded. Exception 2 to Section 141.0(b)2Bi: Roof area covered by building integrated photovoltaic panels and building integrated solar thermal panels are not required to meet the minimum requirements for solar reflectance, thermal emittance, or SRI. Exception 3 to Section 141.0(b)2Bi: Roof constructions with a weight of at least 25 lb/ft [2] are not required to meet the minimum requirements for solar reflectance, thermal emittance, or SRI.

    TABLE 141.0-B—ROOF/CEILING INSULATION TRADEOFF FOR LOW-SLOPED AGED SOLAR REFLECTANCE Col2 Col3
    NONRESIDENTIAL NONRESIDENTIAL NONRESIDENTIAL
    Aged Solar Reflectance Climate Zones 6, 7 and 8U-factor All Other Climate ZonesU-factor
    0.62–0.60 0.043 0.035
    0.59–0.55 0.041 0.034
    0.54–0.50 0.038 0.031
    0.49–0.45 0.034 0.029
    0.44–0.40 0.032 0.028
    0.39–0.35 0.029 0.026
    0.34–0.30 0.028 0.025
    0.29–0.25 0.026 0.024
  • CBC § 140.3 High relevance — show source text

    3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|See Table 140.3-B, C and D for all climate zones.|

    150 2025 CALIFORNIA ENERGY CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES— ADDITIONS, ALTERATIONS AND REPAIRS

    B. Existing roofs of a nonresidential or hotel/motel building being replaced, recovered or recoated, as defined in Section 100.1(b) and Title 24, Part 2, Chapter 2, shall meet the requirements of Section 110.8(i). When roofs with more than 50 percent of the roof area or more than 2,000 square feet of roof, whichever is less, are being altered the requirements of i and ii apply: i. Roofing products shall comply with requirements in Section 140.3(a)1A. Exception 1 to Section 141.0(b)2Bi: An aged solar reflectance less than 0.63 is allowed for low-sloped roofs provided the maximum roof/ceiling U -factor in Table 141.0-B is not exceeded. Exception 2 to Section 141.0(b)2Bi: Roof area covered by building integrated photovoltaic panels and building integrated solar thermal panels are not required to meet the minimum requirements for solar reflectance, thermal emittance, or SRI. Exception 3 to Section 141.0(b)2Bi: Roof constructions with a weight of at least 25 lb/ft [2] are not required to meet the minimum requirements for solar reflectance, thermal emittance, or SRI.

  • CBC § 141.0 High relevance — show source text
    TABLE 141.0-A—ALTERED VERTICAL FENESTRATION MAXIMUM U-FACTOR AND MAXIMUM RSHGC Col2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11 Col12 Col13 Col14 Col15 Col16 Col17
    CLIMATE
    ZONE    		 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
    U-factor 0.47 0.47 0.58 0.47 0.58 0.47 0.47 0.47 0.47 0.47 0.47 0.47 0.47 0.47 0.47 0.47
    RSHGC 0.41 0.31 0.41 0.31 0.41 0.31 0.31 0.31 0.31 0.31 0.31 0.31 0.31 0.31 0.31 0.41
    VT See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones. See Table 140.3-B, C and D for all climate zones.

    150 2025 CALIFORNIA ENERGY CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES— ADDITIONS, ALTERATIONS AND REPAIRS

    B. Existing roofs of a nonresidential or hotel/motel building being replaced, recovered or recoated, as defined in Section 100.1(b) and Title 24, Part 2, Chapter 2, shall meet the requirements of Section 110.8(i). When roofs with more than 50 percent of the roof area or more than 2,000 square feet of roof, whichever is less, are being altered the requirements of i and ii apply: i. Roofing products shall comply with requirements in Section 140.3(a)1A.

  • CBC § 705.3.1. Medium relevance — show source text

    ** The installation of a new roof covering over an existing roof covering shall be permitted where any of the following conditions occur:

    1. The new roof covering is installed in accordance with the roof covering manufacturer’s approved instructions.
    2. Complete and separate roofing systems, such as standing-seam metal roof panel systems, that are designed to transmit the roof loads directly to the building’s structural system and that do not rely on existing roofs and roof coverings for support, shall not require the removal of existing roof coverings.
    3. Metal panel, metal shingle and concrete and clay tile roof coverings shall be permitted to be installed over existing wood shake roofs when applied in accordance with Section 705.3.1.
    4. The application of a new protective roof coating over an existing protective roof coating, a metal roof panel, built-up roof, spray polyurethane foam roofing system, metal roof shingles, mineral-surfaced roll roofing, modified bitumen roofing or thermoset and thermoplastic single-ply roofing shall be permitted without tear off of existing roof coverings.

    Exception: A roof recover shall not be permitted where any of the following conditions occur:

    1. Where the existing roof or roof covering is water-soaked or has deteriorated to the point that the existing roof or roof covering is not adequate as a base for additional roofing.
    2. Where the existing roof covering is slate, clay, cement or asbestos-cement tile.
    3. Where the existing roof has two or more applications of any type of roof covering.

    [BS] 705.3.1 Roof recovering over wood shingles or shakes. Where the application of a new roof covering over wood shingle or shake roofs creates a combustible concealed space, the entire existing surface shall be covered with gypsum panel products, mineral fiber, glass fiber or other approved materials securely fastened in place.

    [BS] 705.4 Reinstallation of materials. Existing slate, clay or cement tile shall be permitted for reinstallation, except that damaged, cracked or broken slate or tile shall not be reinstalled. Existing vent flashing, metal edgings, drain outlets, collars and metal counterflashings shall not be reinstalled where rusted, damaged or deteriorated. Existing ballast that is damaged, cracked or broken shall not be reinstalled. Existing aggregate surfacing materials from built-up roofs shall not be reinstalled.

    [BS] 705.5 Flashings. Flashings shall be reconstructed in accordance with approved manufacturer’s installation instructions. Metal flashing to which bituminous materials are to be adhered shall be primed prior to installation.

    SECTION 706—STRUCTURAL

    [BS] 706.1 General. Where alteration work includes replacement of equipment that is supported by the building or where a reroofing permit is required, the provisions of this section shall apply.

    [BS] 706.2 Addition or replacement of roofing or replacement of equipment. Any existing gravity load-carrying structural element for which an alteration causes an increase in design dead, live or snow load, including snow drift effects, of more than 5 percent shall be replaced or altered as needed to carry the gravity loads required by the California Building Code for new structures.

    Exceptions:

    1. Buildings of Group R occupancy with not more than five dwelling or sleeping units used solely for residential purposes where the altered building complies with the conventional light-frame construction methods of the California Building Code or the provisions of the California Residential Code .
    2. Buildings in which the increased dead load is due entirely to the addition of a second layer of roof covering weighing 3 pounds per square foot (0.1437 kN/m [2] ) or less over an existing single layer of roof covering.
  • CBC § 9-19 Medium relevance — show source text

    R908.2 Structural and construction loads. The structural roof components shall be capable of supporting the roof covering system and the material and equipment loads that will be encountered during installation of the roof covering system.

    R908.3 Roof replacement. Roof replacement shall include the removal of existing layers of roof coverings down to the roof deck.

    Exceptions:

    1. Where the existing roof assembly includes an ice barrier membrane that is adhered to the roof deck and the existing sheathing is not water soaked or deteriorated to the point that it is not adequate as a base for additional roofing, the existing ice barrier membrane shall be permitted to remain in place and covered with an additional layer of ice barrier membrane in accordance with Section R905 where permitted by the roof covering manufacturer and new ice barrier underlayment manufacturer.
    2. Where the existing roof includes a self-adhered underlayment and the existing sheathing is not water soaked or deteriorated to the point that it is not adequate as a base for additional roofing, the existing self-adhered underlayment shall be

    2025 CALIFORNIA RESIDENTIAL CODE 9-19

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    �

    ROOF ASSEMBLIES

    permitted to remain in place and covered with an underlayment complying with Table R905.1.1(1), Table R905.1.1(2) and Table R905.1.1(3). 3. Where the existing roof includes one layer of self-adhered underlayment and the existing layer cannot be removed without damaging the roof deck, a second layer of self-adhered underlayment is permitted to be installed over the existing self-adhered underlayment provided that the following conditions are met: 3.1. It is permitted by the roof covering manufacturer and new self-adhered underlayment manufacturer. 3.2. The existing sheathing is not water soaked or deteriorated to the point that it is not adequate as a base for additional roofing. 3.3. The second layer of self-adhered underlayment is installed such that buildup of material at walls, valleys, roof edges, end laps, and side laps does not exceed two layers.

    R908.4 Roof recover. The installation of a new roof covering over an existing roof covering shall be permitted where any of the following conditions occur:

    1. Where the new roof covering is installed in accordance with the roof covering manufacturer’s approved instructions.
    2. Complete and separate roofing systems, such as standing-seam metal roof systems, that are designed to transmit the roof loads directly to the building’s structural system and do not rely on existing roofs and roof coverings for support, shall not require the removal of existing roof coverings.
    3. Metal panel, metal shingle and concrete and clay tile roof coverings shall be permitted to be installed over existing wood shake roofs where applied in accordance with Section R908.4.1.
    4. The application of a new protective roof coating over an existing protective roof coating, metal roof panel, metal roof shingle, mineral surfaced roll roofing, built-up roof, modified bitumen roofing, thermoset and thermoplastic single-ply roofing and spray polyurethane foam roofing system shall be permitted without tear-off of existing roof coverings.
  • CBC § 704.3 Medium relevance — show source text

    704.3 Locking arrangements in educational occupancies. In Group E occupancies, Group B educational occupancies and Group I4 occupancies, egress doors with locking arrangements designed to keep intruders from entering the room shall comply with Section 1010.2.7 of the California Building Code .

    SECTION 705—REROOFING

    [BS] 705.1 General. Materials and methods of application used for recovering or replacing an existing roof covering shall comply with the requirements of Chapter 15 of the California Building Code .

    Exceptions:

    1. Roof replacement or roof recover of existing low-slope roof coverings shall not be required to meet the minimum design slope requirement of [1] / 4 unit vertical in 12 units horizontal (2-percent slope) in Section 1507 of the California Building Code for roofs that provide positive roof drainage and meet the requirements of Sections 1608.3 and 1611.2 of the Cali- fornia Building Code .
    2. Recovering or replacing an existing roof covering shall not be required to meet the requirement for secondary (emergency overflow) drains or scuppers in Section 1502 of the California Building Code for roofs that provide for positive roof drainage and meet the requirements of Sections 1608.3 and 1611.2 of the California Building Code . For the purposes of this exception, existing secondary drainage or scupper systems required in accordance with this code shall not be removed unless they are replaced by secondary drains or scuppers designed and installed in accordance with Section 1502 of the California Building Code .

    [BS] 705.2 Roof replacement. Roof replacement shall include the removal of all existing layers of roof coverings down to the roof deck.

    Exceptions:

    1. Where the existing roof assembly includes an ice barrier membrane that is adhered to the roof deck and the existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing, the existing ice barrier membrane shall be permitted to remain in place and covered with an additional layer of ice barrier membrane in accordance with Section 1507 of the California Building Code where permitted by the roof-covering manufacturer and new ice-barrier underlayment manufacturer.

    7-4 2025 CALIFORNIA EXISTING BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    ALTERATIONS—LEVEL 1

    1. Where the existing roof includes a self-adhered underlayment and the existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing, the existing self-adhered underlayment shall be permitted to remain in place and covered with an underlayment complying with Tables 1507.1.1(1), 1507.1.1(2) and 1507.1.1(3) of the California Building Code .
    2. Where the existing roof includes one layer of self-adhered underlayment and the existing layer cannot be removed without damaging the roof deck, a second layer of self-adhered underlayment is permitted to be installed over the existing self-adhered underlayment provided all of the following conditions are met: 3.1. It is permitted by the roof-covering manufacturer and self-adhered underlayment manufacturer. 3.2. The existing sheathing is not water-soaked or deteriorated to the point that it is not adequate as a base for additional roofing. 3.3.
  • CBC § 0.110. Medium relevance — show source text

    C. Wood framed and others. A minimum of R-11 insulation between framing members, or the area-weighted average U- factor of the wall assembly shall not exceed U-0.110. D. Spandrel panels and curtain walls. A minimum of R-4, or the area-weighted average U- factor of the wall assembly shall not exceed U-0.280.

    Exception to Section 180.2(a)2: Light and heavy mass walls. 3. Floor insulation. For the altered portion of raised floors that separate conditioned spaces from unconditioned spaces or ambient air shall meet the applicable requirements of Items A and B below: A. Raised framed floors. A minimum of R-11 insulation between framing members, or the area-weighted average U- factor of the floor assembly shall not exceed U-0.071. B. Raised mass floors. A minimum of R-6 insulation, or the area-weighted average U- factor of the floor assembly shall not exceed U-0.111.

    (b) Prescriptive approach. The altered component and any newly installed equipment serving the alteration shall meet the applicable requirements of Sections 110.0 through 110.9 and all applicable requirements of Sections 160.0, 160.1, 160.2(c) and (d), 160.3(a) through 160.3(b)5J, 160.3(b)6, 160.3(c) and 160.5; and

    2025 CALIFORNIA ENERGY CODE 273

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    MULTIFAMILY BUILDINGS—ADDITIONS, ALTERATIONS AND REPAIRS TO EXISTING MULTIFAMILY BUILDINGS

    1. Envelope. A. Roof alterations . Existing roofs being replaced, recovered or recoated of a multifamily building shall meet the requirements of Section 110.8(i). For roofs with more than 50 percent of the roof area or more than 2,000 square feet of roof, whichever is less, being altered, the requirements of i through iii below apply: i. Low-sloped roofs in Climate Zones 2, 4, and 6 through 15 shall have a minimum aged solar reflectance of 0.63 and a minimum thermal emittance of 0.75, or a minimum SRI of 75. Exception to Section 180.2(b)1Ai: The aged solar reflectance requirement can be met by using insulation at the roof deck specified in Table 180.2-A.
    TABLE 180.2-A—ROOF/CEILING INSULATION TRADEOFF FOR LOW-SLOPED AGED SOLAR REFLECTANCE Col2 Col3
    MINIMUM
    AGED SOLAR REFLECTANCE    		 ROOF DECK CONTINUOUS INSULATIONR-
    VALUE (Climate Zones 6–7)    		 ROOF DECK CONTINUOUS INSULATION_R-_VALUE
    (Climate Zones 2, 4, 8–15)
    0.60 2 16
    0.55 4 18
    0.50 6 20
    0.45 8 22
    No requirement 10 24

    ii. Steep-sloped roofs in Climate Zones 4 and 8 through 15 shall have a minimum aged solar reflectance of 0.20 and a minimum thermal emittance of 0.75, or a minimum SRI of 16.

  • CBC § 3111.1.2 Medium relevance — show source text

    3111.1.2

    Materials Chapter 6 Penetration of fire-resistant assemblies

    714 Protection from adjacent construction 3307.1

    Rain loads 1611

    Roof deck 1609.6.1 Signs, roof mounted H110 Slope, minimum Chapter 15

    Snow load 1608 Solar systems, rooftop-mounted 3111.1, 3111.3.2 Trusses 2206.1.3, 2303.4, 2308.11.12 Ventilation 1202.2

    Wood (see Roof Construction, Wood) Roof Construction, Wood 602.4, 602.5 Anchorage to walls 1604.8.2 Attic access 1209.2 Ceiling joists 2308.11.1 Diaphragms 2305.1, 2306.2 Fastening requirements 2304.10 Fire-retardant-treated Table 601,

    603.1

    Framing 2304.11.4, 2308.11 Rafters 2306.1.1, 2308.11.2 Sheathing 2304.8.2, 2308.11.9 Trusses 2303.4, 2308.11.12 Ventilation, attic 1202.2 Wind uplift 2308.11.4 Roof Coverings 1507 Asphalt shingles 1507.2, 1609.2.1 Built up 1507.10 Clay tile 1507.3, 1513 Concrete tile 1507.3, 1513 Fire district D102.2.4

    Fire resistance 603.1, 1505 Flashing 1503.2, 1503.5, 1507.2.8, 1507.3.9, 1507.5.7, 1507.7.7, 1507.8.8, 1507.9.9 Impact resistance 1504.7 Insulation 1508 Liquid-applied coating 1507.14 Membrane 3102 Metal roof panels 1507.4 Metal roof shingles 1507.5 Modified bitumen 1507.11 Photovoltaic roof panels, buildingintegrated 1507.17 Photovoltaic shingles 1507.16 Plastics, light-transmitting panels 2609 Reroofing 1512 Roll 1507.6

    Roof recover 1512.3 Roof replacement 1512.2 Single-ply membrane 1507.12 Slate shingles 1504.4.4, 1507.7, 1513 Sprayed polyurethane foam 1507.13 Thermoplastic single-ply 1507.13 Wind loads 1504.1, 1609.6 Wood shakes 1507.9 Wood shingles 1507.8 Roof Deck 1609.6.1 Roof Drainage 1502 Scuppers 1502.2 Room Dimensions 1209 Rooming House (see Boarding House) 310 Safeguards During Construction Chapter 33 Accessibility Chapters 11A and 11B Adjoining property protection 3307 Construction 3302

    Demolition 3303

    Excavations 1804.1 Fire extinguishers 3309 Fire watch 3314

  • CBC § 702.7 Medium relevance — show source text

    702.7 Materials and methods. New work shall comply with the materials and methods requirements in the California Building Code, California Energy Code, California Mechanical Code and California Plumbing Code, as applicable, that specify material standards, detail of installation and connection, joints, penetrations and continuity of any element, component or system in the building.

    SECTION 703—FIRE PROTECTION

    703.1 General. Alterations shall be done in a manner that maintains the level of fire protection provided.

    703.2 Fire alarm and detection.

    703.2.1 Replacement devices, combinations of devices, appliances, and equipment shall be listed and approved.

    703.2.2 Systems out of service. Existing fire alarm and detection systems shall be maintained in accordance with Section 901.7 of the California Fire Code, C.C.R. Title 24, Part 9.

    703.3 Construction in existing buildings. On-site fire protection during construction shall be in accordance with Chapter 33 of the Cali- fornia Building Code, C.C.R. Title 24, Part 2, and California Fire Code, C.C.R. Title 24, Part 9.

    SECTION 704—MEANS OF EGRESS

    704.1 General. Alterations shall be done in a manner that maintains the level of protection provided for the means of egress.

    704.2 Casework. Addition, alteration or reconfiguration of nonfixed and movable cases, counters and partitions not over 5 feet 9 inches (1753 mm) in height shall maintain the required means of egress path.

    704.3 Locking arrangements in educational occupancies. In Group E occupancies, Group B educational occupancies and Group I4 occupancies, egress doors with locking arrangements designed to keep intruders from entering the room shall comply with Section 1010.2.7 of the California Building Code .

    SECTION 705—REROOFING

    [BS] 705.1 General. Materials and methods of application used for recovering or replacing an existing roof covering shall comply with the requirements of Chapter 15 of the California Building Code .

    Exceptions:

    1. Roof replacement or roof recover of existing low-slope roof coverings shall not be required to meet the minimum design slope requirement of [1] / 4 unit vertical in 12 units horizontal (2-percent slope) in Section 1507 of the California Building Code for roofs that provide positive roof drainage and meet the requirements of Sections 1608.3 and 1611.2 of the Cali- fornia Building Code .
    2. Recovering or replacing an existing roof covering shall not be required to meet the requirement for secondary (emergency overflow) drains or scuppers in Section 1502 of the California Building Code for roofs that provide for positive roof drainage and meet the requirements of Sections 1608.3 and 1611.2 of the California Building Code . For the purposes of this exception, existing secondary drainage or scupper systems required in accordance with this code shall not be removed unless they are replaced by secondary drains or scuppers designed and installed in accordance with Section 1502 of the California Building Code .

    [BS] 705.2 Roof replacement. Roof replacement shall include the removal of all existing layers of roof coverings down to the roof deck.

Frequently asked questions

Do I always need a permit to replace or recover a roof?

Most jurisdictions require a reroofing permit for either replacement or recover; check with your local enforcement agency. The CBC sections governing the work (§ 1512.x) set the technical limits, but permitting is governed locally.

Can I install a new metal roof over old clay tile?

No — the CBC explicitly prohibits recover over slate, clay, cement or asbestos‑cement tile; tear‑off is required in those cases (§ 1512.3 Exception 2).

The existing roof has two layers already — can I overlay again?

No. If the roof already has two or more existing applications, a roof recover is not permitted; the roof must be replaced (tear‑off) per § 1512.3 Exception 3.

My roof has an adhered ice barrier—do I have to remove it when replacing the roof?

Not necessarily. If the ice barrier is adhered to the deck and the sheathing is not water‑soaked or deteriorated, the existing ice barrier may remain and be covered, subject to manufacturer approvals (§ 1512.2 exceptions).

What if the sheathing is water‑soaked?

If the existing roof or roof covering is water‑soaked or deteriorated so it is not an adequate base, recover is prohibited and full replacement (tear‑off to deck) is required (§ 1512.3 Exception 1 and § 1512.2).

More in California Building Code

Ask about the CBC

Get cited, plain-English answers on the California Building Code for your project — any code section, any scenario.

Start Free Trial

Related in the CBC

What does the CBC require for roof insulation and above-deck radiant barriers?

What rooftop structures are regulated and when is a penthouse treated as a story?

Roof insulation, reroofing rules, and rooftop structures

California Building Code