CBC · California Building Code
What does the CBC require for roof insulation and above-deck radiant barriers?
CBC allows above‑deck insulation boards only if covered by an approved roof covering and the complete assembly passes the required fire tests; above‑deck radiant barriers must meet ASTM C1313, have their low‑emittance face toward a continuous airspace, and the barrier + roof covering must be a tested/listed system (FM 4450 or UL 1256).
Last reviewed: July 5, 2026
What the code requires — 2-4 sentences
The California Building Code permits above‑deck thermal insulation boards only when they are covered with an approved roof covering and the assembly passes the required fire tests (NFPA 276 or UL 1256) — see §1508.1 . The CBC lists accepted material standards for above‑deck insulation boards at §1508.2 and separately regulates radiant barriers installed above the roof deck: they must meet ASTM C1313/C1313M, the low‑emittance face must face the continuous airspace, and the barrier plus roof covering must comply with either FM 4450 or UL 1256 — see §1510.1–§1510.4 .
Requirements in detail
1) Above‑deck thermal insulation — what is required
- Permission and fire testing: Above‑deck insulation is allowed provided the insulation is covered with an approved roof covering and the complete assembly (insulation + roof covering) passes NFPA 276 or UL 1256 when tested as an assembly (§1508.1) .
- Exceptions in §1508.1: (a) foam plastic roof insulation is governed by Chapter 26, and (b) where a concrete or composite metal + concrete roof deck is used and the above‑deck insulation is covered with an approved roof covering the general rule still applies as stated in §1508.1 (see exceptions) .
- Material standards: The CBC requires above‑deck insulation boards to comply with the standards listed in Table 1508.2 (examples: polyisocyanurate per ASTM C1289; expanded/extruded polystyrene per ASTM C578; mineral fiber per ASTM C726; glass‑faced gypsum per ASTM C1177; etc.) — see §1508.2 and Table 1508.2 .
2) Radiant barriers installed above the deck — what is required
- General compliance: A radiant barrier above a deck must comply with §§1510.2–1510.4; it is a permitted product only when those requirements are met (§1510.1) .
- Fire testing / assembly listing: The radiant barrier (as installed above deck and covered by the roof covering) is permitted only when the system (radiant barrier + roof covering) complies with either FM 4450 or UL 1256 (§1510.2) .
- Orientation / airspace: The low‑emittance surface of the radiant barrier must face the continuous airspace between the radiant barrier and the roof covering (§1510.3) .
- Material specification: Radiant barriers installed above a deck must comply with ASTM C1313/C1313M (§1510.4) .
Quick reference table (decision‑relevant values)
| Decision factor | Required value or condition | Code reference |
|---|---|---|
| Permission to use above‑deck insulation | Allowed only if covered by approved roof covering and assembly passes NFPA 276 or UL 1256 | §1508.1 |
| Material standards for above‑deck insulation boards | Must meet the ASTM or other standards listed in Table 1508.2 (e.g., ASTM C1289 for polyiso, ASTM C578 for EPS/XPS, ASTM C1177 for glass‑faced gypsum, ASTM C726 for mineral fiber, etc.) | §1508.2 / Table 1508.2 |
| Foam plastic roof insulation | Governed by Chapter 26 (special material/installation rules) | Exception to §1508.1 |
| Radiant barrier above deck — required assembly listing | The radiant barrier + roof covering system must comply with FM 4450 or UL 1256 | §1510.2 |
| Radiant barrier orientation | Low‑emittance face must face the continuous airspace between barrier and roof covering | §1510.3 |
| Radiant barrier material standard | ASTM C1313 / C1313M | §1510.4 |
Exceptions & special cases
- Foam plastic above‑deck insulation is not covered by the §1508 general permission; foam plastic must comply with Chapter 26 (see the Exception in §1508.1) .
- The CBC’s permission for above‑deck insulation applies where the insulation is covered by an approved roof covering; the code treats concrete or composite metal + concrete decks as a specific construction type in the exceptions to §1508.1 (the insulation is still permitted when covered by approved roof covering) .
- The CBC requires the radiant barrier assembly to have a tested/listed fire performance (FM 4450 or UL 1256). If you plan a specific roof covering + barrier combination, you must confirm that whole assembly listing — the CBC text does not supply alternate test methods or numeric air gaps beyond the “continuous airspace” requirement in §1510.3; those details come from the assembly listing, manufacturer installation instructions, or other standards cited (ASTM/UL/FM) .
If a particular parameter you need (for example: required airspace depth in inches, fastening pattern, or an R‑value requirement for above‑deck insulation) is not stated in §1508 or §1510 as retrieved, the CBC text does not set that numeric value — instead the code defers to listed standards, assembly tests, manufacturer instructions, or other code sections (e.g., Chapter 26 for foam plastics). The retrieved CBC excerpts do not specify a numeric airspace thickness for radiant barriers or an R‑value for above‑deck boards in §1508; Table 1508.2 is a materials/standard table, not an R‑value table (§1508.2) .
Common mistakes
- Installing above‑deck boards without confirming the roof covering + insulation assembly has the required assembly test/listing (NFPA 276 or UL 1256). The CBC requires the assembly to pass those tests (§1508.1) .
- Selecting a board product that does not meet one of the standards in Table 1508.2 (e.g., using an unlisted fiberboard) — the CBC requires compliance with the standards in Table 1508.2 (§1508.2) .
- Installing a radiant barrier with the wrong face toward the roof covering or without a continuous airspace. The CBC explicitly requires the low‑emittance face to face the continuous airspace between the barrier and roof covering (§1510.3) .
- Assuming a radiant barrier above deck relieves the need for an assembly listing: CBC requires the radiant barrier + roof covering system to meet FM 4450 or UL 1256 (§1510.2) .
- Applying the §1508 permission to foam plastic boards without checking Chapter 26 requirements — foam plastics are handled separately by exception (Chapter 26) (§1508.1 exceptions) .
Worked example — step‑by‑step scenario
Scenario: You plan to install 1.5" polyisocyanurate continuous insulation boards above a plywood roof deck on a low‑sloped commercial roof, then cover the boards with a single‑ply membrane roof covering.
- Confirm material standard: Select polyiso boards listed to ASTM C1289 (Type I or II) — this matches an accepted material in Table 1508.2 (§1508.2) .
- Confirm assembly fire performance: Obtain documentation that the polyiso + chosen single‑ply membrane roofing system (installed per manufacturer instructions) has been tested as an assembly and meets NFPA 276 or UL 1256, or select a roof system that has an FM 4450 or UL 1256 listing. The CBC requires the above‑deck insulation + roof covering assembly to pass those tests (§1508.1 and §1510.2 where radiant barrier systems are discussed) .
- If you also intend to put a radiant barrier above the decking (under the membrane), select a product complying with ASTM C1313 and ensure the low‑emittance face of the radiant barrier faces the continuous airspace between the barrier and the roof covering; and verify the whole system has the required FM/UL assembly compliance (§1510.3–§1510.4 and §1510.2) .
- If your insulation choice is foam plastic, stop and check Chapter 26 requirements, because foam plastics are governed there (Exception to §1508.1) .
- Record the assembly test/listing and manufacturer installation instructions on the job file for plan review and inspection; without the assembly documentation the inspector will not be able to verify compliance with §1508.1 or §1510.2 .
Note: the CBC text in §1508 and §1510 does not specify exact airgap depth in inches for a radiant barrier’s “continuous airspace” nor an R‑value requirement for above‑deck boards — those details are set by the ASTM standards, the listed assembly test, manufacturer instructions, or other code sections not quoted here (§1508.1–§1508.2; §1510.1–§1510.4) .
Related provisions (CBC sections)
- §1507 — Requirements for roof coverings (see roof covering approval and installation)
- §1509 — Roof coatings (material standards and installation)
- §1512 — Reroofing (requirements when replacing roof coverings)
- Chapter 26 — Foam plastics (material and installation requirements; referenced by exception in §1508.1)
- §1505 — Fire classification of roof coverings (relevant to assembly fire performance)
Code references
Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:
CBC § 1508.2 High relevance — show source text
[BF] 1508.2 Material standards. Above-deck thermal insulation board shall comply with the standards in Table 1508.2.
[BF] TABLE 1508.2—MATERIAL STANDARDS FOR ROOF INSULATION Col2 MATERIAL STANDARD Cellular glass board ASTM C552 or ASTM C1902 Composite boards ASTM C1289, Type III, IV, V or VII Expanded polystyrene ASTM C578 Extruded polystyrene ASTM C578 Fiber-reinforced gypsum board ASTM C1278 Glass-faced gypsum board ASTM C1177 High-density polyisocyanurate board ASTM C1289, Type II, Class 4 Mineral fiber insulation board ASTM C726 Perlite board ASTM C728 Polyisocyanurate board ASTM C1289, Type I or II Wood fiberboard ASTM C208, Type II SECTION 1509—ROOF COATINGS
1509.1 General. The installation of a roof coating on a roof covering shall comply with the requirements of Section 1505 and this section.
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ROOF ASSEMBLIES AND ROOFTOP STRUCTURES
1509.2 Material standards. Roof coating materials shall comply with the standards in Table 1509.2.
TABLE 1509.2—ROOF COATING MATERIAL STANDARDS Col2 MATERIAL STANDARD Acrylic coating ASTM D6083 Asphaltic emulsion coating ASTM D1227 Asphalt coating ASTM D2823 Asphalt roof coating ASTM D4479 Aluminum-pigmented asphalt coating ASTM D2824 Silicone coating ASTM D6694 Moisture-cured polyurethane coating ASTM D6947 SECTION 1510—RADIANT BARRIERS INSTALLED ABOVE DECK
[BF] 1510.1 General. A radiant barrier installed above a deck shall comply with Sections 1510.2 through 1510.4.
[BF] 1510.2 Fire testing. Radiant barriers shall be permitted for use above decks where the radiant barrier is covered with an approved roof covering and the system consisting of the radiant barrier and the roof covering complies with the requirements of either FM 4450 or UL 1256.
[BF] 1510.3 Installation. The low emittance surface of the radiant barrier shall face the continuous airspace between the radiant barrier and the roof covering.
[BF] 1510.4 Material standards. A radiant barrier installed above a deck shall comply with ASTM C1313/C1313M.
SECTION 1511—ROOFTOP STRUCTURES
[BG] 1511.1 General. The provisions of this section shall govern the construction of rooftop structures.
CBC § 1509.2 High relevance — show source text
1509.2 Material standards. Roof coating materials shall comply with the standards in Table 1509.2.
TABLE 1509.2—ROOF COATING MATERIAL STANDARDS Col2 MATERIAL STANDARD Acrylic coating ASTM D6083 Asphaltic emulsion coating ASTM D1227 Asphalt coating ASTM D2823 Asphalt roof coating ASTM D4479 Aluminum-pigmented asphalt coating ASTM D2824 Silicone coating ASTM D6694 Moisture-cured polyurethane coating ASTM D6947 SECTION 1510—RADIANT BARRIERS INSTALLED ABOVE DECK
[BF] 1510.1 General. A radiant barrier installed above a deck shall comply with Sections 1510.2 through 1510.4.
[BF] 1510.2 Fire testing. Radiant barriers shall be permitted for use above decks where the radiant barrier is covered with an approved roof covering and the system consisting of the radiant barrier and the roof covering complies with the requirements of either FM 4450 or UL 1256.
[BF] 1510.3 Installation. The low emittance surface of the radiant barrier shall face the continuous airspace between the radiant barrier and the roof covering.
[BF] 1510.4 Material standards. A radiant barrier installed above a deck shall comply with ASTM C1313/C1313M.
SECTION 1511—ROOFTOP STRUCTURES
[BG] 1511.1 General. The provisions of this section shall govern the construction of rooftop structures.
1511.1.1 Area limitation. The aggregate area of penthouses and other enclosed rooftop structures shall not exceed one-third the area of the supporting roof deck. Such penthouses and other enclosed rooftop structures shall not be required to be included in determining the building height, number of stories or building area as regulated by Section 503.1. The area of such penthouses shall not be included in determining the fire area specified in Section 901.7.
[BG] 1511.2 Penthouses. Penthouses in compliance with Sections 1511.2.1 through 1511.2.4 shall be considered as a portion of the story directly below the roof deck on which such penthouses are located. Other penthouses shall be considered as an additional story of the building.
[BG] 1511.2.1 Height above roof deck. Penthouses constructed on buildings of other than Type I construction shall not exceed 18 feet (5486 mm) in height above the roof deck as measured to the average height of the roof of the penthouse. Penthouses located on the roof of buildings of Type I construction shall not be limited in height.
Exception: Where used to enclose tanks or elevators that travel to the roof level, penthouses shall be permitted to have a maximum height of 28 feet (8534 mm) above the roof deck.
[BG] 1511.2.2 Use limitations. Penthouses shall not be used for purposes other than the shelter of mechanical or electrical equipment, tanks, elevators and related machinery, stairways or vertical shaft openings in the roof assembly, including ancillary spaces used to access elevators and stairways.
CBC § 0.025. High relevance — show source text
i. Roof and ceiling insulation in a ventilated attic shall meet one of the following requirements: a. In Climate Zones 1, 2, 4, and 8 through 16, achieve an overall assembly U -factor not exceeding 0.025. In wood framed assemblies, compliance with U -factors may be demonstrated by installing insulation with an R -value of R-38 or greater.
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b. In Climate Zones 3 and 5 through 7, achieve an overall assembly U- factor not exceeding 0.031. In wood framed assemblies, compliance with U- factors may be demonstrated by installing insulation with an R- value of R-30 or greater. ii. Radiant barrier. For buildings three habitable stories or less, radiant barriers shall be installed in attics with exposed attic deck undersides in Climate Zones 2–15. iii. Extensions of existing wood-framed walls may retain the dimensions of the existing walls and shall install cavity insulation of R-15 in a 2x4 framing and R-21 in a 2x6 framing; and iv. Fenestration products must meet the U- factor, RSGHC and VT requirements of Table 180.2-B. v. Quality insulation installation (QII) requirements of Section 170.2(a)6 do not apply. Exception to Section 180.1(a)1B: Insulation in an enclosed rafter ceiling shall meet the requirements of Section 160.1(a). Exception to Section 180.1(a)1: Additions that increase the area of the roof by 2,000 square feet or less are not required to comply with the solar ready requirements of Section 160.8. 2. Mechanical ventilation for indoor air quality. Additions to existing buildings shall comply with Section 160.2 subject to the requirements specified in Subsections A and B below. When field verification and diagnostic testing are required by Section 180.1(a)2, buildings with three habitable stories or fewer shall use the applicable procedures in the Residential Appendices, and buildings with four or more habitable stories shall use the applicable procedures in Nonresidential Appendices NA1 and NA2.
Exception to Section 180.1(a)2: A dwelling unit air leakage test is not required for additions. A. Whole-dwelling unit mechanical ventilation . i. Dwelling units that meet the conditions in Subsection a or b below shall not be required to comply with the whole-dwelling unit ventilation airflow specified in Section 160.2(b)2Aiv or 160.2(b)2Av. a. Additions to an existing dwelling unit that increase the conditioned floor area of the existing dwelling unit by less than or equal to 1,000 square feet. b. Junior accessory dwelling units (JADU) that are additions to an existing building. ii. Additions to an existing dwelling unit that increase conditioned floor area by more than 1,000 square feet shall have mechanical ventilation airflow in accordance with Section 160.2(b)2Aiv or 160.2(b)2Av, as applicable. The mechanical ventilation airflow rate shall be based on the conditioned floor area of the entire dwelling unit comprising the existing dwelling unit conditioned floor area plus the addition conditioned floor area.
CBC § 180.2 High relevance — show source text
TABLE 180.2-A—ROOF/CEILING INSULATION TRADEOFF FOR LOW-SLOPED AGED SOLAR REFLECTANCE Col2 Col3 MINIMUM
AGED SOLAR REFLECTANCEROOF 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. Exception to Section 180.2(b)1Aii: The following shall be considered equivalent to Subsection ii: a. Buildings with ceiling assemblies with a U- factor lower than or equal to 0.025 or that are insulated with at least R-38 ceiling insulation in an attic; or b. Buildings with a radiant barrier in the attic, where the radiant barrier is not installed directly above spaced sheathing, meeting the requirements of Section 170.2(a)1C; or c. Buildings that have no ducts in the attic in Climate Zones 2, 4, 9, 10, 12 and 14; or d. Buildings with R-2 or greater continuous insulation above or below the roof deck. Exception 1 to Sections 180.2(b)1Ai and ii: Roof area covered by building integrated photovoltaic panels and building integrated solar thermal panels is not required to meet the minimum requirements for solar reflectance, thermal emittance or SRI. Exception 2 to Sections 180.2(b)1Ai and ii: Roof constructions with a weight of at least 25 lb/ft2 are not required to meet the minimum requirements for solar reflectance, thermal emittance or SRI. iii. For low-sloped roofs, the area of the roof recover or roof replacement shall be insulated to R-14 continuous insulation or a U- factor of 0.039 in Climate Zones 1, 2, 4, and 8 through 16. Exception 1 to Section 180.2(b)1Aiii: Roof recovers with new R-10 insulation added above deck do not need to be insulated to meet R-14.
Exception 2 to Section 180.2(b)1Aiii: When existing mechanical equipment located on the roof will not be disconnected and lifted, insulation added may be limited to the greater of R-10 or the maximum installed thickness that will allow the distance between the height of the roof membrane surface to the top of the base flashing to remain in accordance with the manufacturer’s instructions. Exception 3 to Section 180.2(b)1Aiii: At the drains and other low points, tapered insulation with a thermal resistance less than R-14 may be used, provided that insulation thickness is increased at the high points of the roof so that the average thermal resistance equals or exceeds R-14. Exception 4 to Section 180.2(b)1Aiii: The area of the roof recoat is not required to be insulated. B. Roof/ceiling insulation . i. Attic roof .
CBC § 1507.17.4.2 High relevance — show source text
Exception: As an alternative, adhered underlayment complying with ASTM D1970 shall be permitted.
1507.17.4.2 Ice barrier. In areas where there has been a history of ice forming along the eaves causing a back-up of water, an ice barrier consisting of not fewer than two layers of underlayment cemented together or of a self-adhering polymer modified bitumen sheet shall be used instead of normal underlayment and extend from the lowest edges of all roof surfaces to a point not less than 24 inches (610 mm) inside the exterior wall line of the building.
Exception: Detached accessory structures that do not contain conditioned floor area.
1507.17.5 Material standards. BIPV roof panels shall be listed and labeled in accordance with UL 7103.
1507.17.6 Attachment. BIPV roof panels shall be attached in accordance with the manufacturer’s installation instructions.
1507.17.7 Flashing. Flashing for BIPV roof panels shall be installed in accordance with the roof covering manufacturer’s installation instructions to prevent water from entering the wall and roof through joints in copings, through moisture-permeable materials and at intersections with parapet walls and other penetrations through the roof plane.
SECTION 1508—ROOF INSULATION
[BF] 1508.1 General. The use of above-deck thermal insulation shall be permitted provided that such insulation is covered with an approved roof covering and passes the tests of NFPA 276 or UL 1256 when tested as an assembly.
Exceptions:
- Foam plastic roof insulation shall conform to the material and installation requirements of Chapter 26.
- Where a concrete or composite metal and concrete roof deck is used and the above-deck thermal insulation is covered with an approved roof covering.
[BF] 1508.2 Material standards. Above-deck thermal insulation board shall comply with the standards in Table 1508.2.
[BF] TABLE 1508.2—MATERIAL STANDARDS FOR ROOF INSULATION Col2 MATERIAL STANDARD Cellular glass board ASTM C552 or ASTM C1902 Composite boards ASTM C1289, Type III, IV, V or VII Expanded polystyrene ASTM C578 Extruded polystyrene ASTM C578 Fiber-reinforced gypsum board ASTM C1278 Glass-faced gypsum board ASTM C1177 High-density polyisocyanurate board ASTM C1289, Type II, Class 4 Mineral fiber insulation board ASTM C726 Perlite board ASTM C728 Polyisocyanurate board ASTM C1289, Type I or II Wood fiberboard ASTM C208, Type II SECTION 1509—ROOF COATINGS
1509.1 General. The installation of a roof coating on a roof covering shall comply with the requirements of Section 1505 and this section.
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ROOF ASSEMBLIES AND ROOFTOP STRUCTURES
1509.2 Material standards. Roof coating materials shall comply with the standards in Table 1509.2.
CBC § 17.5 High relevance — show source text
OF**
CEILING (inches)|MINIMUM THICKNESS OF
CEILING (inches)| |FLOOR OR ROOF
CONSTRUCTION|ITEM
NUMBER|CEILING CONSTRUCTION|**4 **
hours|**3 **
hours|**2 **
hours|**1 **
hour|**4 **
hours|**3 **
hours|**2 **
hours|**1 **
hour| |11. 11/2"-deep steel roof
deck on steel-framing wood
fiber insulation board, 17.5
pcf density on top applied
over a 15-lb asphalt-satu-
rated felt. Class A or B roof
covering.|11-1.1|Ceiling of gypsum plaster on metal
lath. Lath attached to3/4" furring
channels with 0.049" (No. 18 B.W.
gage) wire ties spaced 6" on center.
3/4" channels saddle tied to 2" chan-
nels with doubled 0.065" (No. 16
B.W. gage) wire ties. 2" channels
spaced 36" on center suspended 2"
below steel framing and saddle tied
with 0.165" (No. 8 B.W. gage) wire.
Plaster mixed 1:2 for scratch coat
and 1:3 for brown coat, by weight,
gypsum-to-sand aggregate for 1-
hour system. For 2-hour system,
plaster mix is 1:2 by weight, gypsum-
to-sand aggregate.|—|—|11/2|1|—|—|7/8
g|3/4
1| |12. 11/2" deep steel roof deck
on steel-framing insulation
of rigid board consisting of
expanded perlite and fibers
impregnated with integral
asphalt waterproofing;
density 9 to 12 pcf secured to
metal roof deck by1/2"-wide
ribbons of waterproof, cold-
process liquid adhesive
spaced 6" apart. Steel joist or
light steel construction with
metal roof deck, insulation,
and Class A or B built-up roof
covering.e|12-1.1|Gypsum-vermiculite plaster on
metal lath wire tied at 6" intervals to
3/4" furring channels spaced 12" on
center and wire tied to 2" runner
channels spaced 32" on center.
Runners wire tied to bottom chord of
steel joists.|—|—|1|—|—|—|7/8|—| |13. Double wood floor over
wood joists spaced 16" on
center.m, n|13-1.1|Gypsum plaster over3/8" Type X
gypsum lath. Lath initially applied
with not less than four 11/8" by No. 13
gage by19/64" head plasterboard
blued nails per bearing.CBC § 1507.1.1 High relevance — show source text
Fasteners shall be applied along the overlap at not more than 36 inches (914 mm) on center. Underlayment installed where V asd is not less than 120 mph (54 m/s) shall comply with ASTM D226, Type III, ASTM D4869, Type IV or ASTM D6757. The underlayment shall be attached in a grid pattern of 12 inches (305 mm) between side laps with a 6-inch (152 mm) spacing at the side laps. The underlayment shall be applied in accordance with Section 1507.1.1 except all laps shall be not less than 4 inches (102 mm). Underlayment shall be attached using cap nails or cap staples. Caps shall be metal or plastic with a nominal head diameter of not less than 1 inch (25.4 mm). Metal caps shall have a thickness of not less than 0.010 inch (0.25 mm). Power-driven metal caps shall have a thickness of not less than 0.010 inch (0.25 mm). Thickness of the outside edge of plastic caps shall be not less than 0.035 inch (0.89 mm). The cap nail shank shall be not less than 0.083 inch (2.11 mm) for ring shank cap nails and 0.091 inch (2.31 mm) for smooth shank cap nails. Staple gage shall be not less than 21 gage [0.0.2 inch (0.81 mm)]. Cap nail shank and cap staple legs shall have a length sufficient to penetrate through-the-roof sheathing or not less than [3] / 4 inch (19.1 mm) into the roof sheathing.
Exception: As an alternative, adhered underlayment complying with ASTM D1970 shall be permitted.
1507.17.4.2 Ice barrier. In areas where there has been a history of ice forming along the eaves causing a back-up of water, an ice barrier consisting of not fewer than two layers of underlayment cemented together or of a self-adhering polymer modified bitumen sheet shall be used instead of normal underlayment and extend from the lowest edges of all roof surfaces to a point not less than 24 inches (610 mm) inside the exterior wall line of the building.
Exception: Detached accessory structures that do not contain conditioned floor area.
1507.17.5 Material standards. BIPV roof panels shall be listed and labeled in accordance with UL 7103.
1507.17.6 Attachment. BIPV roof panels shall be attached in accordance with the manufacturer’s installation instructions.
1507.17.7 Flashing. Flashing for BIPV roof panels shall be installed in accordance with the roof covering manufacturer’s installation instructions to prevent water from entering the wall and roof through joints in copings, through moisture-permeable materials and at intersections with parapet walls and other penetrations through the roof plane.
SECTION 1508—ROOF INSULATION
[BF] 1508.1 General. The use of above-deck thermal insulation shall be permitted provided that such insulation is covered with an approved roof covering and passes the tests of NFPA 276 or UL 1256 when tested as an assembly.
Exceptions:
- Foam plastic roof insulation shall conform to the material and installation requirements of Chapter 26.
- Where a concrete or composite metal and concrete roof deck is used and the above-deck thermal insulation is covered with an approved roof covering.
CBC § 180.1 High relevance — show source text
Exception 7 to Section 180.1 : Dwelling unit space heating system. New or replacement space heating systems serving an addition may be a heat pump or gas heating system.
(a) Prescriptive approach. The envelope and lighting of the addition; any newly installed space-conditioning or ventilation system, electrical power distribution system, or water-heating system; any addition to an outdoor lighting system; and any new sign installed in conjunction with an indoor or outdoor addition shall meet the applicable requirements of Sections 110.0 through 110.12; 160.0, 160.1, and 160.2(c) and (d); and 160.3 through 170.2.
- Envelope. A. Additions that are greater than 700 square feet shall meet the requirements of Section 170.2(a), with the following modifications:
i. Framed walls extension. Extensions of existing wood-framed walls may retain the dimensions of the existing walls and shall install cavity insulation of R-15 in a 2x4 framing and R-21 in a 2x6 framing. ii. The maximum allowed fenestration area shall be the greater of 175 square feet or 20 percent of the addition floor area.
iii. When existing siding of a wood-framed wall is not being removed or replaced, cavity insulation of R-15 in a 2x4 framing and R-21 in a 2x6 framing shall be installed and continuous insulation is not required. iv. Additions that consist of the conversion of existing spaces from unconditioned to conditioned space shall not be required to perform the air sealing part of QII when the existing air barrier is not being removed or replaced. B. Additions that are 700 square feet or less shall meet the requirements of Section 170.2(a), with the following modifications.
i. Roof and ceiling insulation in a ventilated attic shall meet one of the following requirements: a. In Climate Zones 1, 2, 4, and 8 through 16, achieve an overall assembly U -factor not exceeding 0.025. In wood framed assemblies, compliance with U -factors may be demonstrated by installing insulation with an R -value of R-38 or greater.
2025 CALIFORNIA ENERGY CODE 271
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b. In Climate Zones 3 and 5 through 7, achieve an overall assembly U- factor not exceeding 0.031. In wood framed assemblies, compliance with U- factors may be demonstrated by installing insulation with an R- value of R-30 or greater. ii. Radiant barrier. For buildings three habitable stories or less, radiant barriers shall be installed in attics with exposed attic deck undersides in Climate Zones 2–15. iii. Extensions of existing wood-framed walls may retain the dimensions of the existing walls and shall install cavity insulation of R-15 in a 2x4 framing and R-21 in a 2x6 framing; and iv. Fenestration products must meet the U- factor, RSGHC and VT requirements of Table 180.2-B. v. Quality insulation installation (QII) requirements of Section 170.2(a)6 do not apply. Exception to Section 180.1(a)1B: Insulation in an enclosed rafter ceiling shall meet the requirements of Section 160.1(a).
CBC § 2.9 High relevance — show source text
Fire district D102.2.9 Height modifications 503.1.4, 504.3 Impact resistance 1504.7 Insulation 1508 Lightning protection systems 1511.7.6 Materials 1506 Mechanical equipment screen 1511.6 Parapet walls 1503.2, 1503.3 Penthouses 713.12.1, 1511.2 Photovoltaic panels and modules 1511.10, 1511.10.1 Radiant barrier 1510
Tanks 1511.3 Towers, spires, domes and cupolas 1511.5, 3108 Weather protection 1503 Wind resistance 1504.1, 1504.3, 1504.4, 1609.6 Roof Construction Construction walkways 3306.7 Coverings (see Roof Coverings) 1609.6.2 Draftstopping 718.4 Fire resistance Table 601 Fireblocking 718.2 Live loads 1607.14, Table 1607.1,
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
CBC § 15-20 High relevance — show source text
1508 Roof Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-20
1509 Roof Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-20
1510 Radiant Barriers Installed Above Deck . . . . . . . . . .15-21
1511 Rooftop Structures . . . . . . . . . . . . . . . . . . . . . . . . . . .15-21
1512 Reroofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-24
1513 [DSA-SS & DSA-SS/CC, OSHPD 1, 1R, 2, 4 & 5] Seismic Anchorage of Slate Shingle, Clay and Concrete Tile Roof Coverings. . . . . . . 15-25
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INDEX-1
HISTORY NOTE TO VOLUME 1 . . . . . . . . . . . . . . . . . . . . . .HIST-1
VOLUME 2
CHAPTER 16 STRUCTURAL DESIGN . . . . . . . . . . . . . . . . . .16-1
1601 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-3
1602 Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-3
1603 Construction Documents . . . . . . . . . . . . . . . . . . . . . . . 16-4
1604 General Design Requirements. . . . . . . . . . . . . . . . . . . 16-5
1605 Load Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-8
1606 Dead Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-9
1607 Live Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16-10
1608 Snow Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16-18
1609 Wind Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16-24
1610 Soil Loads and Hydrostatic Pressure. . . . . . . . . . . .16-31
CBC § 14-23 High relevance — show source text
1413 [DSA-SS & DSA-SS/CC, OSHPD 1, 1R, 2, 4 & 5] Additional Requirements for Anchored and Adhered Veneer. . . . . . . . . . . . . . 14-23
CHAPTER 15 ROOF ASSEMBLIES AND ROOFTOP
STRUCTURES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1
1501 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-3
1502 Roof Drainage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-3
1503 Weather Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-3
1504 Performance Requirements . . . . . . . . . . . . . . . . . . . . 15-3
1505 Fire Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-5
1506 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-6
1507 Requirements for Roof Coverings . . . . . . . . . . . . . . . 15-7
1508 Roof Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-20
1509 Roof Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-20
1510 Radiant Barriers Installed Above Deck . . . . . . . . . .15-21
1511 Rooftop Structures . . . . . . . . . . . . . . . . . . . . . . . . . . .15-21
1512 Reroofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15-24
1513 [DSA-SS & DSA-SS/CC, OSHPD 1, 1R, 2, 4 & 5] Seismic Anchorage of Slate Shingle, Clay and Concrete Tile Roof Coverings. . . . . . . 15-25
INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . INDEX-1
HISTORY NOTE TO VOLUME 1 . . . . . . . . . . . . . . . . . . . . . .HIST-1
VOLUME 2
CHAPTER 16 STRUCTURAL DESIGN . . . . . . . . . . . . . . . . . .16-1
CBC § 1.5 Medium relevance — show source text
; clips C, E; reinforcement: none;1/2″ plas-
ter, 1.5:2.5 mill mix.|N/A|55 min|||3|5, 8|3/4|RESOURCE A-96 2025 CALIFORNIA EXISTING BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
RESOURCE A—GUIDELINES ON FIRE RATINGS OF ARCHAIC MATERIALS AND ASSEMBLIES
TABLE 3.2—continued
FLOOR/CEILING ASSEMBLIES—STEEL STRUCTURAL ELEMENTSCol2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 ITEM
CODEMEMBRANE
THICKNESSCONSTRUCTION DETAILS PERFORMANCE PERFORMANCE REFERENCE NUMBER REFERENCE NUMBER REFERENCE NUMBER NOTES REC.
HOURSITEM
CODEMEMBRANE
THICKNESSCONSTRUCTION DETAILS LOAD TIME PRE-BMS-92 BMS-92 POST-BMS-92 POST-BMS-92 POST-BMS-92 F/C-S-8 1/2″ Spec. 9′ × 4′4″; S.J. 103 bar joists, 18″ o.c.;
deck: 4 lbs rib lath base; 6″ × 6″ 10 × 10 gage
reinforcement; 2″ deck 1:2:4 gravel concrete;
membrane: furring,3/4″ C.R.S., 16″ o.c.; clips C,
E; reinforcement: none;1/2″ plaster, 1.5:2.5
mill mix.300 psf 1 hr
10 min3 2, 3, 8 1 F/C-S-9 5/8″ 10′ × 13′6″; S.J. 103, 24″ o.c.; deck: 2″
concrete, 1:2:4; membrane: furring 12″ o.c.;
clips A, B, G; Extra “A” clips reinforcement;5/8″
plaster, 1.5:2, 1.5:3.145 psf 3 hrs 3 6, 8 3 F/C-S-10 5/8″ 18′ × 13′6″; joists, S.J. 103, 24″ o.c.; deck: 4 lbs
rib lath; 6″ × 6″ 10 × 10 gage reinforcement; 2″
deck, 1:2:3.5 gravel concrete; membrane:
furring, spacing 16″ o.c.
Frequently asked questions
Can I install any rigid board above the deck if I cover it with membrane roofing?
No — above‑deck boards must meet the material standards in Table 1508.2 and the full assembly (insulation + roof covering) must pass NFPA 276 or UL 1256 when tested as an assembly (§1508.1, §1508.2) .
Does the CBC require a specific air gap thickness for an above‑deck radiant barrier?
The CBC requires the low‑emittance surface to face a continuous airspace but does not specify a numeric airgap thickness in §1510.3; follow the product listing, ASTM C1313, the listed assembly (FM/UL) and manufacturer instructions for the required gap and installation details (§1510.3–§1510.4) .
Are radiant barriers above the deck allowed without assembly testing?
No — a radiant barrier installed above deck is permitted only where the radiant barrier + roof covering system complies with FM 4450 or UL 1256 (§1510.2) .
If I use polyiso above the deck, do I still need to show a fire test?
Yes. Even if the board is an acceptable material per Table 1508.2, the complete assembly (polyiso + roof covering) must pass NFPA 276 or UL 1256 as required by §1508.1 .
Does §1508 set R‑value minimums for above‑deck insulation?
No. §1508 and Table 1508.2 identify permitted materials and standards; the CBC excerpt retrieved does not set R‑value minima for above‑deck boards — R‑values are handled elsewhere (Energy Code / Part 6) or by design tradeoffs, not in §1508.2 as quoted here (§1508.2) .
More in California Building Code
- Administration & Permits
- Energy Efficiency
- Existing Buildings
- Occupancy Classification & Use
- Hazardous Materials & Occupancies
- Types of Construction
- Fire-Resistance & Fire Safety
- Interior Finishes
- Means of Egress
- Accessibility
- Exterior Walls
- Roofing & Roof Assemblies
- Structural Design
- Special Inspections & Tests
- Foundations & Soils
- Concrete
- Masonry
- Steel
- Wood
- Elevators & Conveying Systems
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