CODES

ADOPTS WITH AMENDMENTS:

International Building Code 2015 (IBC 2015)

Copyright

Preface

Acknowledgements

California Code of Regulations, Title 24

How to Distinguish Between Model Code Language and California Amendments

Effective Use of the International Building Code

Chapter 16 Structural Design

Chapter 16A Structural Design

Chapter 17 Special Inspections and Tests

Chapter 17A Special Inspections and Tests

Chapter 18 Soils and Foundations

Chapter 18A Soils and Foundations

Chapter 19 Concrete

Chapter 19A Concrete

Chapter 20 Aluminum

Chapter 21 Masonry

Chapter 21A Masonry

Chapter 22 Steel

Chapter 22A Steel

Chapter 23 Wood

Chapter 24 Glass and Glazing

Chapter 25 Gypsum Board, Gypsum Panel Products and Plaster

Chapter 26 Plastic

Chapter 27 Electrical

Chapter 28 Mechanical Systems

Chapter 29 Plumbing Systems

Chapter 30 Elevators and Conveying Systems

Chapter 31 Special Construction

Chapter 31A Systems for Window Cleaning or Exterior Building Maintenance

Chapter 31B [DPH] Public Pools

Chapter 31C [DPH] Radiation

Chapter 31D [DPH] Food Establishments

Chapter 31E Reserved

Chapter 31F [SLC] Marine Oil Terminals

Chapter 32 Encroachments Into the Public Right-Of-Way

Chapter 33 Safeguards During Construction

Chapter 34 Reserved

Chapter 34A Existing Structures

Chapter 35 Referenced Standards

Appendix A Employee Qualifications

Appendix B Board of Appeals

Appendix C Group U—agricultural Buildings

Appendix D Fire Districts

Appendix E Reserved

Appendix F Rodentproofing

Appendix G Flood-Resistant Construction

History Note Appendix

Appendix H Signs

Appendix I Patio Covers

Appendix J Grading

Appendix K Group R-3 and Group R-3.1 Occupancies Protected by the Facilities of the Central Valley Flood Protection Plan

Appendix L Earthquake Recording Instrumentation

Appendix M Tsunami-Generated Flood Hazard

Provisions of this chapter shall govern the materials, design, construction and quality of gypsum board, gypsum panel products, lath, gypsum plaster, cement plaster and reinforced gypsum concrete.

[DSA-SS, DSA-SS/CC and OSHPD 1 & 4] Details of attachment for wall and ceiling coverings which are not provided for in this code shall be detailed in the approved construction documents.

Lathing, plastering, gypsum board and gypsum panel product construction shall be done in the manner and with the materials specified in this chapter and, when required for fire protection, shall also comply with the provisions of Chapter 7.
Other approved wall or ceiling coverings shall be permitted to be installed in accordance with the recommendations of the manufacturer and the conditions of approval.

The following terms are defined in Chapter 2:

CEMENT PLASTER.

EXTERIOR SURFACES.

GYPSUM BOARD.

GYPSUM PANEL PRODUCTS.

GYPSUM PLASTER.

GYPSUM VENEER PLASTER.

INTERIOR SURFACES.

WEATHER-EXPOSED SURFACES.

WIRE BACKING.

Lath, gypsum board and gypsum panel products shall be inspected in accordance with Section 110.3.5.
[DSA-SS, DSA-SS/CC and OSHPD 1 & 4]
  1. Lath, gypsum board and gypsum panel products shall be inspected in accordance with Chapter 17A and the California Administrative Code.
  2. No lath, gypsum board and gypsum panel products or their attachments shall be covered or finished until it has been inspected and approved by the inspector of record and/or special inspector.
  3. The enforcement agency may require tests in accordance with Table 2506.2 to determine compliance with the provisions of this code.
  4. The testing of gypsum board and gypsum panel products shall conform with standards listed in Table 2506.2
The following requirements shall be met where construction involves gypsum board, gypsum panel products or lath and plaster in vertical and horizontal assemblies.

Wood supports for lath, gypsum board or gypsum panel products, as well as wood stripping or furring, shall be not less than 2 inches (51 mm) nominal thickness in the least dimension.

Exception: The minimum nominal dimension of wood furring strips installed over solid backing shall be not less than 1 inch by 2 inches (25 mm by 51 mm).

The minimum thickness of vertically erected studless solid plaster partitions of 3/8-inch (9.5 mm) and 3/4-inch (19.1 mm) rib metal lath, 1/2-inch-thick (12.7 mm) gypsum lath, gypsum board or gypsum panel product shall be 2 inches (51 mm).
[DSA-SS, DSA-SS/CC and OSHPD 1 & 4]

In addition to the requirements of this section, the horizontal and vertical assemblies of plaster, gypsum board or gypsum panel products shall be designed to resist the loads specified in this code.

Wood furring strips for ceilings fastened to floor or ceiling joist shall be nailed at each bearing with two common wire nails, one of which shall be a slant nail and the other a face nail, or by one nail having spirally grooved or annular grooved shanks approved by the enforcement agency for this purpose. All stripping nails shall penetrate not less than 13/4 inches (44.5 mm) into the member receiving the point. Holes in stripping at joints shall be subdrilled to prevent splitting.

Where common wire nails are used to support horizontal wood stripping for plaster ceilings, such stripping shall be wire tied to the joists 4 feet (1219 mm) on center with two strands of No. 18 W&M gage galvanized annealed wire to an 8d common wire nail driven into each side of the joist 2 inches (51 mm) above the bottom of the joist or to each end of a 16d common wire nail driven horizontally through the joist 2 inches (51 mm) above the bottom of the joist, and the ends of the wire secured together with three twists of the wire.

Wood-frame shear walls sheathed with gypsum board, gypsum panel products or lath and plaster shall be designed and constructed in accordance with Section 2306.3 and are permitted to resist wind and seismic loads. Walls resisting seismic loads shall be subject to the limitations in Section 12.2.1 of ASCE 7.
Cold-formed steel-frame shear walls sheathed with gypsum board or gypsum panel products and constructed in accordance with the materials and provisions of Section 2211.6 are permitted to resist wind and seismic loads. Walls resisting seismic loads shall be subject to the limitations in Section 12.2.1 of ASCE 7.

Section 2505.1 and 2505.2 are not permitted.

Gypsum board, gypsum panel products and accessories shall be identified by the manufacturer’s designation to indicate compliance with the appropriate standards referenced in this section and stored to protect such materials from the weather.

Gypsum board and gypsum panel products shall conform to the appropriate standards listed in Table 2506.2 and Chapter 35 and, where required for fire protection, shall conform to the provisions of Chapter 7.

TABLE 2506.2

GYPSUM BOARD MATERIALS AND ACCESSORIES

MATERIALSTANDARD
Accessories for gypsum boardASTM C1047
Adhesives for fastening gypsum boardASTM C557
Cold-formed steel studs and track, structuralAISI S200 and ASTM C955, Section 8
Cold-formed steel studs and track, nonstructuralAISI S220 and ASTM C645, Section 10
Elastomeric joint sealantsASTM C920
Fiber-reinforced gypsum panelsASTM C1278
Glass mat gypsum backing panelASTM C1178
Glass mat gypsum panelASTM C1658
Glass mat gypsum substrateASTM C1177
Joint reinforcing tape and compoundASTM C474; C475
Nails FOR gypsum boardsASTM C514, F547, F1667
Steel screwsASTM C954; C1002
Steel studs, load-bearingASTM C955
Steel studs, nonload-bearingASTM C645
Standard specification for gypsum boardASTM C1396
Testing gypsum and gypsum productsASTM C22; C472; C473
Metal suspension systems for acoustical and lay-in panel ceilings shall comply with ASTM C635 listed in Chapter 35 and Section 13.5.6 of ASCE 7 for installation in high seismic areas.
Lathing and plastering materials and accessories shall be marked by the manufacturer’s designation to indicate compliance with the appropriate standards referenced in this section and stored in such a manner to protect them from the weather.

Lathing and plastering materials shall conform to the standards listed in Table 2507.2 and Chapter 35 and, where required for fire protection, shall also conform to the provisions of Chapter 7.

TABLE 2507.2

LATH, PLASTERING MATERIALS AND ACCESSORIES

MATERIALSTANDARD
Accessories for gypsum veneer base ASTM C1047
Blended cement ASTM C595
Cold-formed steel studs and track, structuralAISI S200 and ASTM C955, Section 8
Cold-formed steel studs and track, nonstructuralAISI S220 and ASTM C645, Section 10
Exterior plaster bonding compounds ASTM C932
Hydraulic cementASTM C1157; C1600
Gypsum casting and molding plasterASTM C59
Gypsum Keene's cementASTM C61
Gypsum plasterASTM C28
Gypsum veneer plasterASTM C587
Interior bonding compounds, gypsumASTM C631
Lime plastersASTM C5; C206
Masonry cementASTM C91
Metal lathASTM C847
Plaster aggregates
Sand
ASTM C35; C897
Perlite
ASTM C35
Vermiculite
ASTM C35
Plastic cementASTM C1328
Portland cementASTM C150
Steel screwsASTM C1002; C954
Steel studs and trackASTM C645; C955
Welded wire lathASTM C933
Woven wire plaster baseASTM C1032

[DSASS & DSA-SS/CC and OSHPD 1 & 4] Where interior or exterior lath is attached to horizontal wood supports, either of the following attachments shall be used in addition to the methods of attachment described in referenced standards listed in Table 2507.2.

  1. Secure lath to alternate supports with ties consisting of a double strand of No. 18 W & M gage galvanized annealed wire at one edge of each sheet of lath. Wire ties shall be installed not less than 3 inches (76 mm) back from the edge of each sheet and shall be looped around stripping, or attached to an 8d common wire nail driven into each side of the joist 2 inches (51 mm) above the bottom of the joist or to each end of a 16d common wire nail driven horizontally through the joist 2 inches (51 mm) above the bottom of the joist and the ends of the wire secured together with three twists of the wire.
  2. Secure lath to each support with 1/2-inch-wide (12.7 mm), 1 1/2-inch-long (38mm) No. 9 W & M gage, ring shank, hook staple placed around a 10d common nail laid flat under the surface of the lath not more than 3 inches (76 mm) from edge of each sheet. Such staples may be placed over ribs of 3/8-inch (9.5 mm) rib lath or over back wire of welded wire fabric or other approved lath, omitting the 10d nails.

Gypsum board, gypsum panel products and gypsum plaster construction shall be of the materials listed in Tables 2506.2 and 2507.2. These materials shall be assembled and installed in compliance with the appropriate standards listed in Tables 2508.1 and 2511.1.1 and Chapter 35.

TABLE 2508.1

INSTALLATION OF GYPSUM CONSTRUCTION

MATERIALSTANDARD
Gypsum board and gypsum panel productsGA-216; ASTM C840
Gypsum sheathing and gypsum panel productsASTM C1280
Gypsum veneer baseASTM C844
Interior lathing and furringASTM C841
Steel framing for gypsum board and gypsum panel productsASTM C754; C1007
Gypsum wallboard or gypsum plaster shall not be used in any exterior surface where such gypsum construction will be exposed directly to the weather. Gypsum wallboard shall not be used where there will be direct exposure to water or continuous high humidity conditions. Gypsum sheathing shall be installed on exterior surfaces in accordance with ASTM C1280.
Gypsum wallboard, gypsum lath or gypsum plaster shall not be installed until weather protection for the installation is provided.
Edges and ends of gypsum board and gypsum panel products shall occur on the framing members, except those edges and ends that are perpendicular to the framing members. Edges and ends of gypsum board and gypsum panel products shall be in moderate contact except in concealed spaces where fire-resistance-rated construction, shear resistance or diaphragm action is not required.

Gypsum board and gypsum panel product fire-resistance-rated assemblies shall have joints and fasteners treated.

Exception: Joint and fastener treatment need not be provided where any of the following conditions occur:

  1. Where the gypsum board or the gypsum panel product is to receive a decorative finish such as wood paneling, battens, acoustical finishes or any similar application that would be equivalent to joint treatment.
  2. On single-layer systems where joints occur over wood framing members.
  3. Square edge or tongue-and-groove edge gypsum board (V-edge), gypsum panel products, gypsum backing board or gypsum sheathing.
  4. On multilayer systems where the joints of adjacent layers are offset.
  5. Assemblies tested without joint treatment.

Gypsum board or gypsum panel products shall be permitted to be used on wood joists to create a horizontal diaphragm ceiling in accordance with Table 2508.5.

TABLE 2508.5

SHEAR CAPACITY FOR HORIZONTAL WOOD-FRAME GYPSUM BOARD DIAPHRAGM CEILING ASSEMBLIES

MATERIALTHICKNESS OF MATERIA (MINIMUM) (inches)SPACING OF FRAMING MEMBERS (inches)SHEAR VALUEa, b (PLF OF CEILING)MIMIMUM FASTENER SIZE
Gypsum board or gypsum panel product1/216 o.c.905d cooler or wallboard nail; 15/8-inch long; 0.086-inch shank; 15/64-inch headc
Gypsum board or gypsum panel product1/224 o.c.705d cooler or wallboard nail; 15/8-inch long; 0.086-inch shank; 15/64-inch headc

For SI: 1 inch = 25.4 mm, 1 pound per foot = 14.59 N/m.

  1. Values are not cumulative with other horizontal diaphragm values and are for short-term wind or seismic loading. Values shall be reduced 25 percent for normal loading.
  2. Values shall be reduced 50 percent in Seismic Design Categories D, E and F.
  3. 11/4-inch, No. 6 Type S or W screws are permitted to be substituted for the listed nails.
The maximum allowable diaphragm proportions shall be 11/2:1 between shear resisting elements. Rotation or cantilever conditions shall not be permitted.
Gypsum board or gypsum panel products used in a horizontal diaphragm ceiling shall be installed perpendicular to ceiling framing members. End joints of adjacent courses of gypsum board shall not occur on the same joist.
Perimeter edges shall be blocked using a wood member not less than 2-inch by 6-inch (51 mm by 152 mm) nominal dimension. Blocking material shall be installed flat over the top plate of the wall to provide a nailing surface not less than 2 inches (51 mm) in width for the attachment of the gypsum board or gypsum panel product.
Fasteners used for the attachment of gypsum board or gypsum panel products to a horizontal diaphragm ceiling shall be as defined in Table 2508.5. Fasteners shall be spaced not more than 7 inches (178 mm) on center at all supports, including perimeter blocking, and not more than 3/8 inch (9.5 mm) from the edges and ends of the gypsum board or gypsum panel product.
Gypsum board or gypsum panel products shall not be used in diaphragm ceilings to resist lateral forces imposed by masonry or concrete construction.
[DSA-SS & DSA-SS/CC and OSHPD 1 & 4]

Gypsum board shall not be used in diaphragm ceilings to resist lateral forces imposed by partitions. Connection of diaphragm ceiling to the vertical lateral force resisting elements shall be designed and detailed to transfer lateral forces.

Showers and public toilet walls shall conform to Section 1210.2.

Materials used as a base for wall tile in tub and shower areas and wall and ceiling panels in shower areas shall be of materials listed in Table 2509.2 and installed in accordance with the manufacturer’s recommendations. Water-resistant gypsum backing board shall be used as a base for tile in water closet compartment walls when installed in accordance with GA-216 or ASTM C840 and the manufacturer’s recommendations. Regular gypsum wallboard is permitted under tile or wall panels in other wall and ceiling areas when installed in accordance with GA-216 or ASTM C840.

TABLE 2509.2

BACKERBOARD MATERIALS

MATERIALSTANDARD
Glass mat gypsum backing panelASTM C1178
Nonasbestos fiber-cement backer boardASTM C1288 or ISO 8336, Category C
Nonasbestos fiber-mat reinforced cementitious backer unitASTM C1325

Water-resistant gypsum backing board shall not be used in the following locations:

  1. Over a vapor retarder in shower or bathtub compartments.
  2. Where there will be direct exposure to water or in areas subject to continuous high humidity.
Exterior and interior cement plaster and lathing shall be done with the appropriate materials listed in Table 2507.2 and Chapter 35.
Materials shall be stored in such a manner as to protect them from the weather.
Installation of these materials shall be in compliance with ASTM C926 and ASTM C1063.
Metal lath and lath attachments shall be of corrosion-resistant material.
Backing or a lath shall provide sufficient rigidity to permit plaster applications.
Where lath on vertical surfaces extends between rafters or other similar projecting members, solid backing shall be installed to provide support for lath and attachments.
Gypsum backing for cement plaster shall be in accordance with Section 2510.5.2.1 or 2510.5.2.2.

Gypsum lath or gypsum wallboard shall not be used as a backing for cement plaster.

Exception: Gypsum lath or gypsum wallboard is permitted, with a water-resistive barrier, as a backing for self-furred metal lath or self-furred wire fabric lath and cement plaster where either of the following conditions occur:

  1. On horizontal supports of ceilings or roof soffits.
  2. On interior walls.
Gypsum sheathing is permitted as a backing for metal or wire fabric lath and cement plaster on walls. A water-resistive barrier shall be provided in accordance with Section 2510.6.
Wire backing is not required under expanded metal lath or paperbacked wire fabric lath.

Water-resistive barriers shall be installed as required in Section 1404.2 and, where applied over wood-based sheathing, shall include a water-resistive vapor-permeable barrier with a performance at least equivalent to two layers of water-resistive barrier complying with ASTM E2556, Type I. The individual layers shall be installed independently such that each layer provides a separate continuous plane and any flashing (installed in accordance with Section 1405.4) intended to drain to the water-resistive barrier is directed between the layers.

Exception:Where the water-resistive barrier that is applied over wood-based sheathing has a water resistance equal to or greater than that of a water-resistive barrier complying with ASTM E2556, Type II and is separated from the stucco by an intervening, substantially nonwater-absorbing layer or drainage space.

Surfaces shall be clean, free from efflorescence, sufficiently damp and rough for proper bond. If the surface is insufficiently rough, approved bonding agents or a Portland cement dash bond coat mixed in proportions of not more than two parts volume of sand to one part volume of Portland cement or plastic cement shall be applied. The dash bond coat shall be left undisturbed and shall be moist cured not less than 24 hours.

Plastering gypsum plaster or cement plaster shall be not less than three coats where applied over metal lath or wire fabric lath and not less than two coats where applied over other bases permitted by this chapter.

Exception: Gypsum veneer plaster and cement plaster specifically designed and approved for one-coat applications.

Installation of lathing and plaster materials shall conform to Table 2511.1.1 and Section 2507.

TABLE 2511.1.1

INSTALLATION OF PLASTER CONSTRUCTION

MATERIALSTANDARD
Cement plasterASTM C926
Gypsum plasterASTM C842
Gypsum veneer plasterASTM C843
Interior lathing and furring (gypsum plaster)ASTM C841
Lathing and furring (cement plaster)ASTM C1063
Steel framingASTM C754; C1007
Plaster shall not be applied directly to fiber insulation board. Cement plaster shall not be applied directly to gypsum lath or gypsum plaster except as specified in Sections 2510.5.1 and 2510.5.2.
Where installed, grounds shall ensure the minimum thickness of plaster as set forth in ASTM C842 and ASTM C926. Plaster thickness shall be measured from the face of lath and other bases.
Condition of surfaces shall be as specified in Section 2510.7. Approved specially prepared gypsum plaster designed for application to concrete surfaces or approved acoustical plaster is permitted. The total thickness of base coat plaster applied to concrete ceilings shall be as set forth in ASTM C842 or ASTM C926. Should ceiling surfaces require more than the maximum thickness permitted in ASTM C842 or ASTM C926, metal lath or wire fabric lath shall be installed on such surfaces before plastering.
Showers and public toilet walls shall conform to Sections 1210.2 and 1210.3. When wood frame walls and partitions are covered on the interior with cement plaster or tile of similar material and are subject to water splash, the framing shall be protected with an approved moisture barrier.
Plastering with cement plaster shall be not less than three coats when applied over metal lath or wire fabric lath or gypsum board backing as specified in Section 2510.5 and shall be not less than two coats when applied over masonry or concrete. If the plaster surface is to be completely covered by veneer or other facing material, or is completely concealed by another wall, plaster application need only be two coats, provided the total thickness is as set forth in ASTM C926.
On wood frame or steel stud construction with an on-grade concrete floor slab system, exterior plaster shall be applied in such a manner as to cover, but not to extend below, the lath and paper. The application of lath, paper and flashing or drip screeds shall comply with ASTM C1063.
A minimum 0.019-inch (0.48 mm) (No. 26 galvanized sheet gage), corrosion-resistant weep screed with a minimum vertical attachment flange of 31/2 inches (89 mm) shall be provided at or below the foundation plate line on exterior stud walls in accordance with ASTM C926. The weep screed shall be placed a minimum of 4 inches (102 mm) above the earth or 2 inches (51 mm) above paved areas and be of a type that will allow trapped water to drain to the exterior of the building. The water-resistive barrier shall lap the attachment flange. The exterior lath shall cover and terminate on the attachment flange of the weep screed.
Only approved plasticity agents and approved amounts thereof shall be added to Portland cement or blended cements. When plastic cement or masonry cement is used, no additional lime or plasticizers shall be added. Hydrated lime or the equivalent amount of lime putty used as a plasticizer is permitted to be added to cement plaster or cement and lime plaster in an amount not to exceed that set forth in ASTM C926.
Gypsum plaster shall not be used on exterior surfaces.
Plaster coats shall be protected from freezing for a period of not less than 24 hours after set has occurred. Plaster shall be applied when the ambient temperature is higher than 40°F (4°C), unless provisions are made to keep cement plaster work above 40°F (4°C) during application and 48 hours thereafter.
The second coat shall be brought out to proper thickness, rodded and floated sufficiently rough to provide adequate bond for the finish coat. The second coat shall have no variation greater than 1/4 inch (6.4 mm) in any direction under a 5-foot (1524 mm) straight edge.

First and second coats of cement plaster shall be applied and moist cured as set forth in ASTM C926 and Table 2512.6.

TABLE 2512.6

CEMENT PLASTERS

COATMINIMUM PERIOD

MOIST CURING
MINIMUM INTERVAL

BETWEEN COATS
First48 hoursa48 hoursb
Second48 hours7 daysc
FinishNote c
  1. The first two coats shall be as required for the first coats of exterior plaster, except that the moist-curing time period between the first and second coats shall be not less than 24 hours. Moist curing shall not be required where job and weather conditions are favorable to the retention of moisture in the cement plaster for the required time period.
  2. Twenty-four-hour minimum interval between coats of interior cement plaster. For alternative method of application, see Section 2512.8.
  3. Finish coat plaster is permitted to be applied to interior cement plaster base coats after a 48-hour period.
Where applied over gypsum backing as specified in Section 2510.5 or directly to unit masonry surfaces, the second coat is permitted to be applied as soon as the first coat has attained sufficient hardness.
The second coat is permitted to be applied as soon as the first coat has attained sufficient rigidity to receive the second coat.
When using this method of application, calcium aluminate cement up to 15 percent of the weight of the Portland cement is permitted to be added to the mix.
Curing of the first coat is permitted to be omitted and the second coat shall be cured as set forth in ASTM C926 and Table 2512.6.
Cement plaster finish coats shall be applied over base coats that have been in place for the time periods set forth in ASTM C926. The third or finish coat shall be applied with sufficient material and pressure to bond and to cover the brown coat and shall be of sufficient thickness to conceal the brown coat.
Exposed natural or integrally colored aggregate is permitted to be partially embedded in a natural or colored bedding coat of cement plaster or gypsum plaster, subject to the provisions of this section.
The aggregate shall be applied manually or mechanically and shall consist of marble chips, pebbles or similar durable, moderately hard (three or more on the Mohs hardness scale), nonreactive materials.
The bedding coat for interior or exterior surfaces shall be composed of one part Portland cement and one part Type S lime; or one part blended cement and one part Type S lime; or masonry cement; or plastic cement and a maximum of three parts of graded white or natural sand by volume. The bedding coat for interior surfaces shall be composed of 100 pounds (45.4 kg) of neat gypsum plaster and a maximum of 200 pounds (90.8 kg) of graded white sand. A factory-prepared bedding coat for interior or exterior use is permitted. The bedding coat for exterior surfaces shall have a minimum compressive strength of 1,000 pounds per square inch (psi) (6895 kPa).
The bedding coat is permitted to be applied directly over the first (scratch) coat of plaster, provided the ultimate overall thickness is a minimum of 7/8 inch (22 mm), including lath. Over concrete or masonry surfaces, the overall thickness shall be a minimum of 1/2 inch (12.7 mm).
Exposed aggregate plaster is permitted to be applied over concrete, masonry, cement plaster base coats or gypsum plaster base coats installed in accordance with Section 2511 or 2512.
Masonry and concrete surfaces shall be prepared in accordance with the provisions of Section 2510.7.
Cement plaster base coats shall be cured in accordance with ASTM C926. Cement plaster bedding coats shall retain sufficient moisture for hydration (hardening) for 24 hours minimum or, where necessary, shall be kept damp for 24 hours by light water spraying.

Reinforced gypsum concrete shall comply with the requirements of ASTM C317 and ASTM C956.

Exception: [DSA-SS and OSHPD 1 & 4] Reinforced gypsum concrete shall be considered as an alternative system.

The minimum thickness of reinforced gypsum concrete shall be 2 inches (51 mm) except the minimum required thickness shall be reduced to 11/2 inches (38 mm), provided the following conditions are satisfied:

  1. The overall thickness, including the formboard, is not less than 2 inches (51 mm).
  2. The clear span of the gypsum concrete between supports does not exceed 33 inches (838 mm).
  3. Diaphragm action is not required.
  4. The design live load does not exceed 40 pounds per square foot (psf) (1915 Pa).
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