Chapter 15 of the California Building Code, 2025 Edition, is amended by replacing Section 1511 in its entirety with Sections 1511.1 through 1511.7 and Table A-15-A, to read as follows:
Section 1511 — REROOFING
Section 1511.1 — GENERAL
All reroofing shall conform to the applicable provisions of Chapter 15 of this Code and as otherwise required in this chapter. Roofing materials and methods of application shall comply with the approved standards or shall follow manufacturer's installation requirements when approved by the Building Official.
Section 1511.2 — INSPECTION AND WRITTEN APPROVAL
1511.2.1 Written Approval Required. New roofing shall not be applied without first obtaining written approval from the Building Official. The Building Official may allow existing roof coverings to remain when an inspection or other evidence reveals all of the following:
1. | The roof structure is sufficient to sustain the weight of the additional dead load of the new roofing. |
2. | The roof deck is structurally sound. |
3. | Roof drains and drainage are sufficient to prevent extensive accumulation of water. |
4. | The existing roofing is securely attached to the deck. |
5. | Existing insulation is not water soaked. |
6. | Fire-retardant requirements are maintained. |
1511.2.2 Required Inspections. New roof coverings shall not be applied without first conducting a pre-roofing inspection verifying that the existing roofing meets all the conditions in Section 1511.2.1. The pre-roofing inspection shall pay particular attention to evidence of accumulation of water. Where extensive ponding of water is apparent, an analysis of the roof structure for proper drainage shall be made and corrective measures, such as relocation of roof drains or scuppers, re-sloping of the roof or structural changes shall be made. Extensive ponding shall be considered areas that retain water for more than forty-eight (48) hours after the rain has stopped or as per roofing manufacturer's recommendation. An inspection report attesting to the adequacy of the roof structure, as reasonably determined from a visual inspection by a special inspector or licensed roofing contractor, prepared and signed by the same, may be required by the Building Official. Additionally, after the pre-roofing inspection and prior to applying a new roof covering, a building permit shall be obtained from the Building Official. A final inspection and approval shall be obtained from the Building Official when the reroofing is complete.
1511.2.3 - Repairs. A building permit shall not be required for roofing repairs that do not exceed ten percent (10%) of the building's roof area. This Section shall not include the roof sheathing or structural supporting elements.
Section 1511.3 — REROOFING OVERLAYS ALLOWED
1511.3.1 General. No roof shall have in any combination more than that allowed in Table A-15-A. Roofing conforming to Section 1503 overlaid on existing roofing shall comply with the provisions of this Section and manufacturer's installation requirements as an overlay when approved by the Building Official.
1511.3.2 Overlay on Existing Built-up Roofs. The Building Official may allow reroofing over existing built-up roofing when the conditions specified in Section 1515.1 have been met. When an existing built-up roof has been removed and prior to application of new roofing on a nailable deck that has residual bitumen, rosin-sized or other dry sheet shall be installed. Prior to the application of any reroofing, the existing surface shall be prepared as follows:
1. | Gravel-surfaced roofing. Not more than one overlay shall be approved over an existing built-up roof. The existing built-up roof shall be cleaned of all loose gravel and debris. All blisters, buckles, and other irregularities shall be cut and made smooth and secure. On nonnailable decks, minimum 3/8-inch (9.5 mm) insulation board shall be securely cemented to the existing roofing with hot bitumen after the existing surface has been adequately primed. On nailable decks, a rosin-sized or other dry sheet shall be installed, and a base sheet shall be mechanically fastened in place. |
2. | Smooth or cap-sheet surface. Not more than one overlay shall be applied over an existing built-up roof. All blisters, buckles, and other irregularities of existing built-up roof shall be cut and made smooth and secure. On non-nailable decks, a base sheet shall be spot cemented to the existing roof. On nailable decks, a base sheet shall be mechanically fastened in place and where residual materials on the existing surface may cause the new base sheet to adhere to the old roof, a rosin-sized or other dry sheet shall be installed under the new base sheet. |
3. | Intersecting walls. All concrete and masonry walls shall be completely cleaned and primed to receive new flashing. All other walls shall have the surface finish material removed to a minimum height of six inches (152 mm) above the new roof deck surface to receive new roofing and flashing. All rotted wood shall be replaced with new material. Surface finish material shall be replaced or reinstalled. |
4. | Parapets. Parapets of area separation walls shall have noncombustible faces, including counterflashing and coping materials. |
EXCEPTION: Combustible roofing may extend 7 inches (178 mm) above the roof surface. |
5. | Cant strips. Where space permits, cant strips shall be installed at all angles. All angles shall be flashed with at least two more layers than in the new roof with an exposed finish layer of inorganic felt or mineral surfaced cap sheet. |
6. | Asphalt and wood shingle application. Not more than one overlay of asphalt shingles shall be applied over one existing built-up roof on structures with a slope of 2 units vertical in 12 units horizontal (16.7% slope) or greater. Not more than one overlay of wood shingles shall be applied over one existing built-up roof on structures with a slope of 3 units vertical in 12 units horizontal (25% slope) or greater. The existing built-up roof shall have all surfaces cleaned of gravel and debris, all blisters and irregularities cut and made smooth and secure, and an underlayment of not less than Type 30 nonperforated felt shall be installed prior to reroofing. |
7. | Spray-applied polyurethane foam application. Spray-applied polyurethane foam may be applied directly to existing built-up roofing systems when the completed assembly is a Class A, B, or C fire-retardant roofing assembly and complies with Section 2603.6. When applied on a fire-resistive roof-ceiling assembly, the completed assembly shall also comply with Section 711. Base sheets or dry sheets are not required over existing surfaces when applying spray polyurethane foam roofing systems. Miscellaneous materials such as adhesives, elastomeric caulking compounds, metal, vents, and drains shall be a composite part of the roof system. |
1511.3.3 Overlay on Existing Wood Roofs or Asphalt Shingle Roofs. The Building Official may allow reroofing over existing wood shingle roofing or asphalt shingle roofing. Only fire-retardant roofing assemblies or noncombustible roof covering may be applied over existing wood shake roofs in accordance with the listing or manufacturer's installation requirements when approved by the Building Official. When the application of new roofing over existing wood shingle or wood shake roofs creates a combustible concealed space, the entire existing surface shall be covered with gypsum board, mineral fiber, glass fiber or other approved materials securely fastened in place. Hip and ridge cover on an existing shake or shingle roofing shall be removed prior to reroofing application. Roofing overlays may be installed in accordance with the following:
1. | Asphalt shingles. Not more than two overlays of asphalt shingles shall be applied over an existing asphalt or wood shingle roof. Asphalt shingles applied over wood shingles shall not have less than Type 30 nonperforated felt underlayment installed prior to reroofing. |
2. | Wood shakes. Not more than one overlay of wood shakes shall be applied over an existing asphalt shingle or wood shingle roofing on structures with a slope of 4 units vertical in 12 units horizontal (33% slope) or greater. One layer of 18-inch (457 mm), Type 30 nonperforated felt shall be shingled between each course in such a manner that no felt is exposed to the weather below the shake butts. |
3. | Wood shingles. Not more than one overlay of wood shingles shall be applied over existing wood or asphalt shingles. Wood shingles applied over asphalt shingles shall not have less than Type 30 nonperforated felt underlayment installed prior to reroofing. |
Section 1511.4 – TILE
Tile may be applied to roofs with a slope of 4 units vertical in 12 units horizontal (33% slope) or greater over existing roof coverings in accordance with Table A-15-A. Such installations shall be substantiated by a report prepared by an engineer or architect licensed by the state to practice as such, indicating that the existing or modified framing system is adequate to support the covering. Tile shall be applied in accordance with the original manufacturer's specifications or when the original manufacturer's specifications are no longer available, in accordance with Section 1507.3. Tile may be repaired to match the prior installation except for clay and terra-cotta hips and ridge tile shall be reinstalled with Portland cement mortar.
Section 1511.5 – METAL ROOF COVERING
Metal roof covering may be applied over existing roofing in accordance with Table A-15-A. Reroofing with metal roof covering shall be in accordance with the original manufacturer's specifications or when the original manufacturer's specifications are no longer available as required by Section 1507.4.
Section 1511.6 – OTHER ROOFING
Reroofing with systems not covered elsewhere in this Code, such as, but not limited to, those that are fluid applied or applied as non asphaltic sheets shall be done with materials and procedures approved by the Building Official.
Section 1511.7 – FLASHING AND EDGING
Missing, rusted or damaged flashing and counterflashing, vent caps, and metal edging shall be installed or replaced with new materials. When existing built-up roofs remain, vent flashing, metal edging, drain outlets, metal counterflashing and collars shall be removed and cleaned. All metal allowed to be reinstalled shall be primed prior to reroofing installation. Collars and flanges shall be flashed per the roofing manufacturer's instructions.
TABLE A-15-A—ALLOWABLE REROOFS OVER EXISTING ROOFING (Inspection and Written Approval Required Prior to Application) |
|---|
EXISTING ROOFING | NEW OVERLAY ROOFING |
|---|
Built Up | Wood Shake | Wood Shingle | Asphalt Shingle | Tile Roof | Metal Roof | Modified Bitumen | Spray Poly-urethane Foam |
|---|
Built Up | Yes | NP | Yes (3:12) | Yes (2:12) | Yes (2.5:12) | Yes | Yes | Yes |
Wood Shakel | NP | NP | NP | NP | Yes2 | Yes2 | NP | NP |
Wood Shingle1 | NP | Yes3 (4:12) | Yes4 | Yes4 | Yes2 | Yes2 | NP | NP |
Asphalt Shingle1 | NP | Yes3 (4:12) | Yes4 (3:12) | Yes | Yes (2.5:12) | Yes | Yes | NP |
Asphalt over Wood | NP | NP | NP | Yes | Yes2 | Yes2 | Yes | NP |
Asphalt over Asphalt | NP | NP | NP | Yes | Yes | Yes | Yes | NP |
Tile Roof | NP | NP | NP | NP | NP | NP | NP | NP |
Metal Roof | NP | NP | NP | NP | NP | Yes | NP | NP |
Modified Bitumen | Yes | NP | Yes (3:12) | Yes | Yes (2.5:12) | Yes | Yes | NP |
NP = Not Permitted. |
Note: (Minimum Roof Slope) |
1 | See Section 1507.8 for specific requirements. |
2 | Board and batten leveling system must be fire stopped in accordance with Section 718.2.6. |
3 | One layer 18-inch (457 mm) Type 30 nonperforated felt interlaced between shake courses required. |
4 | Type 30 nonperforated felt underlayment required for reroofing. |
(Ord. 2019-10, eff. 1/1/20; Ord. 2022-06, eff. 1/1/23; Ord. 2025-05, eff. 1/1/2026)