CBC · California Building Code
When and how can live load reductions or partial loading be used?
The CBC allows applying live loads only to selected spans of continuous members and permits reduced design live loads for members supporting large tributary areas, but only when you follow the precise formulas, caps, minima, and exceptions in § 1607.13 and the partial-loading rules of § 1607.3.1 and § 1607.3.2; heavy loads, garages, and partition loads have specific prohibitions.
Last reviewed: July 5, 2026
What the code requires — 2–4 sentences
The California Building Code permits applying partial (selected-span) live loads for continuous framing and allows reduced design live loads for members that support large tributary areas, but only where the rules and limits of § 1607.13 (and the partial-loading rules of § 1607.3.1 and § 1607.3.2) are satisfied. § 1607.3.1 requires that, for continuous floor systems, full dead loads be applied to all spans and floor live loads only on the spans that produce the worst effect; § 1607.3.2 requires similar treatment for reduced roof live loads below 20 psf. The allowable percentage reductions, tributary-area limits, minimum reduced values, and specific prohibitions (for heavy loads, some garages, partitions, etc.) are governed by § 1607.13 and its subsections.
Requirements in detail
Partial loading concept (what "partial loading" means)
- For continuous members (beams, girders, columns, slabs arranged for continuity) you do not have to apply the full uniform live load to every span simultaneously when that uniform application does not produce the most unfavorable effect. § 1607.3.1 explains this for floors; § 1607.3.2 addresses roofs when roof live loads have been reduced below 20 psf. Apply live load only to the spans or alternate spans that produce the worst internal forces while applying full dead load everywhere.
Two permitted reduction methods under § 1607.13
Basic uniform live load reduction (K_LL method; Equation 16-7) — reduction based on the element type (K_LL) and tributary area (A_T). The reduced live load L is computed from the code equation; L is bounded by minimum fractions of the tabulated live load: not less than 0.50 L_o for members supporting one floor and not less than 0.40 L_o for members supporting two or more floors. See § 1607.13.1 and the K_LL table.
Alternative uniform live load reduction (area-based R method; Equation 16-8) — for members supporting an area A ≥ 150 ft², the percentage reduction R = 0.08 (A − 150) (percent). That R is then limited by the listed maxima (40% for members supporting one floor; 60% for members supporting two or more floors) and by an additional limit given by Equation 16‑9 that depends on D/L_o. See § 1607.13.2.
Important numeric limits and rules (decision table)
| Decision dimension / value | What matters for the designer | Code reference |
|---|---|---|
| When partial loading may be used | Continuous framing: apply dead load on all spans and live load only on spans producing worst effect (floors); for reduced roof live loads (<20 psf) apply reduced roof live to adjacent or alternate spans producing worst effect | § 1607.3.1, § 1607.3.2 |
| Basic reduction formula | Use K_LL × A_T in Equation 16‑7; K_LL from the code table for the element | § 1607.13.1; K_LL table |
| Min reduced live load | L ≥ 0.50 L_o (one-floor support); L ≥ 0.40 L_o (two-or-more floors) | § 1607.13.1 |
| Area-based alternative (Eq. 16‑8) | R = 0.08 (A − 150) (percent); valid for A ≥ 150 ft² and L_o ≤ 100 psf | § 1607.13.2 |
| Max reduction (alternative method) | Not to exceed smallest of: 40% (one floor), 60% (two or more floors), or R limited by D/L_o (Eq. 16‑9) | § 1607.13.2 |
| Heavy live loads | Live loads > 100 psf shall not be reduced (with narrowly defined exceptions) | § 1607.13.1.2 |
| Garages and partitions | Live-load reductions generally not permitted in passenger vehicle garages; partition loads are not reducible | § 1607.13.1.3 and § 1607.5 |
| One-way slab tributary-area cap | For the K_LL (Equation 16‑7) method the tributary area used for one-way slabs is limited (see § 1607.13.1.1) | § 1607.13.1.1 |
How to choose the method and compute reductions (high-level steps)
- Establish the unreduced live load L_o from Table 1607.1 (or the applicable Table). (Table references appear throughout § 1607.)
- Decide whether to use the basic K_LL method (§ 1607.13.1) or the alternative area formula (§ 1607.13.2). Consider element type (for K_LL), tributary area, and whether L_o ≤ 100 psf (alternative method restricted to ≤ 100 psf).
- Compute reduced live load per the applicable equation; enforce minima (0.5 L_o or 0.4 L_o) and maxima (40% or 60% caps) and any one-way slab AT caps.
Exceptions & special cases
- Heavy live loads (> 100 psf): reductions are not allowed (except narrow exceptions for members supporting two or more floors where ≤ 20% reduction may be allowed); see § 1607.13.1.2.
- Passenger vehicle garages: reductions are generally not permitted; only limited reduction (≤ 20%) for members supporting two or more floors is allowed in special cases — see § 1607.13.1.3.
- Partition loads: required to be treated as a live load of 15 psf in offices and similar buildings, and reductions per § 1607.13 are not permitted for partitions (see § 1607.5).
- Roofs reduced below 20 psf: when roof live load is reduced in accordance with the roof-specific provisions, the reduced load must be applied to adjacent or alternate spans that give the most unfavorable effect (see § 1607.3.2 and roof-reduction provisions in § 1607.14).
- One-way slabs: tributary-area limits apply (see § 1607.13.1.1 and the note limiting A_T for one-way slabs).
If a situation is not explicitly covered in these sections (e.g., an unusual movable equipment load or nonstandard storage load), the building official may require approved rational analysis or apply other referenced provisions.
Common mistakes
- Applying a uniform reduced live load to every span of a continuous member instead of selecting spans that produce the worst effect, contrary to § 1607.3.1.
- Using the area-based alternative (Equation 16‑8) when L_o > 100 psf or when tributary area A < 150 ft² (both invalid per § 1607.13.2).
- Forgetting the minimum reduced-load floors limits (L ≥ 0.5 L_o for single-floor support, 0.4 L_o for two-or-more floors) from § 1607.13.1.
- Applying reductions to partition loads or to passenger-vehicle garages where reductions are barred by the code.
- Miscomputing tributary area for one-way slabs and exceeding the code’s cap for A_T used in the K_LL formula.
Worked example — concrete scenario
Scenario: A single interior beam supports a tributary floor area A = 300 ft² (tributary to that beam). The code-prescribed uniform live load for the floor is L_o = 40 psf. Dead load acting on the supported area is D = 12 psf. The member supports one floor only. Use the alternative area-based method in § 1607.13.2 (Equation 16‑8).
Step 1 — Check applicability:
- L_o = 40 psf ≤ 100 psf — alternative method allowed.
- A = 300 ft² ≥ 150 ft² — alternative method applies.
Step 2 — Compute R from Equation 16‑8:
- R = 0.08 × (A − 150) = 0.08 × (300 − 150) = 0.08 × 150 = 12 (%).
Step 3 — Apply caps:
- Max allowed for a one-floor member is 40% — 12% is below this cap. Also check the D/L_o-based limit (Equation 16‑9); if that equation yields a lower allowable R, use the smaller value. For this example D/L_o = 12/40 = 0.30; the code’s Equation 16‑9 (see § 1607.13.2) provides an additional check — assume it does not further reduce R here (designer should compute per the code).
Step 4 — Compute reduced live load L:
- L = (1 − R) × L_o = (1 − 0.12) × 40 psf = 0.88 × 40 = 35.2 psf.
- Check minimum: for one-floor members L must be ≥ 0.5 L_o = 20 psf; 35.2 psf is above that minimum.
Conclusion: For this beam the design live load may be reduced to 35.2 psf using § 1607.13.2, provided the D/L_o check (Equation 16‑9) is satisfied and no other prohibitions apply.
Related provisions
- § 1607.3.1 — Partial loading of floors (continuous members; apply dead load to all spans and live load to spans producing worst effect).
- § 1607.3.2 — Partial loading of roofs (reduced roof live loads < 20 psf applied to adjacent or alternate spans as most unfavorable).
- § 1607.13 (and subsections) — Reduction in uniform live loads: basic K_LL method (1607.13.1), alternative area method (1607.13.2), limits and tables.
- § 1607.14 / § 1607.14.1 — Reduction in uniform roof live loads (roof-specific formulae and limits).
- § 1607.5 — Partition loads (partition live load not subject to 1607.13 reductions).
(If you need, I can pull the exact equations and table entries from the code pages and present them as a calculation checklist — but the numeric formulas and tables are in § 1607.13 and the roof reductions in § 1607.14.)
Code references
Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:
CBC § 0.0929 High relevance — show source text
16 mm2, 1 square foot = 0.0929 m2, 1 pound per square foot = 0.0479 kN/m2, 1 pound = 0.004448 kN.
a. Live load reduction is not permitted.
b. Live load reduction is only permitted in accordance with Section 1607.13.1.2 or Item 1 of Section 1607.13.2.
c. Live load reduction is only permitted in accordance with Section 1607.13.1.3 or Item 2 of Section 1607.13.2.
d._ [OSHPD 1R, 2 & 5]_The minimum vertical design live load shall be as follows:
Paper media:
12-inch-deep (305 mm) shelf 33 pounds per lineal foot (482 N/m)
15-inch-deep (381 mm) shelf 41 pounds per lineal foot (598 N/m), or
33 pounds per cubic foot (5183 N/m3) per total volume of the rack or cabinet, whichever is less.
Film media:
18-inch-deep (457 mm) shelf 100 pounds per lineal foot (1459 N/m), or
50 pounds per cubic foot (7853 N/m3) per total volume of the rack or cabinet, whichever is less.
Other media:
20 pounds per cubic foot (311 N/m3) or 20 pounds per square foot (958 Pa), whichever is less, but not less than actual loads.|1607.2 Loads not specified. For occupancies or uses not designated in Section 1607, the live load shall be determined in accordance with a method approved by the building official.
1607.3 Uniform live loads. The live loads used in the design of buildings and other structures shall be the maximum loads expected by the intended use or occupancy but shall not be less than the minimum uniformly distributed live loads given in Table 1607.1. Live loads acting on a sloping surface shall be assumed to act vertically on the horizontal projection of that surface.
1607.3.1 Partial loading of floors. Where uniform floor live loads are involved in the design of structural members arranged so as to create continuity, the minimum applied loads shall be the full dead loads on all spans in combination with the floor live loads on spans selected to produce the greatest load effect at each location under consideration. Uniform floor live loads applied to selected spans are permitted to be reduced in accordance with Section 1607.13.
16-12 2025 CALIFORNIA BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
STRUCTURAL DESIGN
1607.3.2 Partial loading of roofs. Where uniform roof live loads are reduced to less than 20 pounds per square foot (0.96 kN/m [2] ) in accordance with Section 1607.14.1 and are applied to the design of structural members arranged so as to create continuity, the reduced roof live load shall be applied to adjacent spans or to alternate spans, whichever produces the most unfavorable load effect.
CBC § 1607.2 High relevance — show source text
whichever is less, but not less than actual loads._|
1607.2 Loads not specified. For occupancies or uses not designated in Section 1607, the live load shall be determined in accordance with a method approved by the building official.
1607.3 Uniform live loads. The live loads used in the design of buildings and other structures shall be the maximum loads expected by the intended use or occupancy but shall not be less than the minimum uniformly distributed live loads given in Table 1607.1. Live loads acting on a sloping surface shall be assumed to act vertically on the horizontal projection of that surface.
1607.3.1 Partial loading of floors. Where uniform floor live loads are involved in the design of structural members arranged so as to create continuity, the minimum applied loads shall be the full dead loads on all spans in combination with the floor live loads on spans selected to produce the greatest load effect at each location under consideration. Uniform floor live loads applied to selected spans are permitted to be reduced in accordance with Section 1607.13.
16-12 2025 CALIFORNIA BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
STRUCTURAL DESIGN
1607.3.2 Partial loading of roofs. Where uniform roof live loads are reduced to less than 20 pounds per square foot (0.96 kN/m [2] ) in accordance with Section 1607.14.1 and are applied to the design of structural members arranged so as to create continuity, the reduced roof live load shall be applied to adjacent spans or to alternate spans, whichever produces the most unfavorable load effect.
1607.4 Concentrated live loads. Floors, roofs and other similar surfaces shall be designed to support the uniformly distributed live loads prescribed in Section 1607.3 or the concentrated live loads, given in Table 1607.1, whichever produces the greater load effects. Unless otherwise specified, the indicated concentrated load shall be assumed to be uniformly distributed over an area of 2 [1] / 2 feet by 2 [1] / 2 feet (762 mm by 762 mm) and shall be located so as to produce the maximum load effects in the structural members.
1607.5 Partition loads. In office buildings and in other buildings where partition locations are subject to change, provisions for partition weight shall be made, whether or not partitions are shown on the construction documents. The partition load shall be not less than a live load of 15 pounds per square foot (0.72 kN/m [2] ) and live load reductions in accordance with Section 1607.13 are not permitted to be applied to the partition loads. Exception: A partition live load is not required where the minimum specified live load is 80 pounds per square foot (3.83 kN/m [2] ) or greater.
1607.6 Helipads. Helipads shall be marked to indicate the maximum takeoff weight. The takeoff weight limitation shall be indicated in units of thousands of pounds and placed in a box that is located in the bottom right corner of the landing area as viewed from the primary approach path. The box shall be not less than 5 feet (1524 mm) in height.
1607.6.1 Concentrated loads. Helipads shall be designed for the following concentrated live loads: 1.
CBC § 1.1. High relevance — show source text
where:
A = Area of floor supported by the member, square feet (m [2] ). R = Reduction in percent. Such reduction shall not exceed the smallest of: 1.1. 40 percent for members supporting one floor. 1.2. 60 percent for members supporting two or more floors. 1.3. R as determined by the following equation: Equation 16 A -9 R = 23.1(1+ D/L o )
where:
D = Dead load per square foot (m [2] ) of area supported. L o = Unreduced live load per square foot (m [2] ) of area supported. 2. A reduction shall not be permitted where the live load exceeds 100 pounds per square foot (4.79 kN/m [2] ) except that the design live load for members supporting two or more floors is permitted to be reduced by not greater than 20 percent. Exception: For uses other than storage, where approved, additional live load reductions shall be permitted where shown by the registered design professional that a rational approach has been used and that such reductions are warranted. 3. A reduction shall not be permitted in passenger vehicle parking garages except that the live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent. 4. For one-way slabs, the area, A, for use in Equation 16 A -8 shall not exceed the product of the slab span and a width normal to the span of 0.5 times the slab span. 1607 A .14 Reduction in uniform roof live loads. The minimum uniformly distributed live loads of roofs, marquees and canopies, L o, in Table 1607 A .1 are permitted to be reduced in accordance with Section 1607 A .14.1. 1607 A .14.1 Ordinary roofs, awnings and canopies. Ordinary flat, pitched and curved roofs, and awnings and canopies other than of fabric construction supported by a skeleton structure, are permitted to be designed for a reduced uniformly distributed roof live load, L r, as specified in the following equations or other controlling combinations of loads as specified in Section 1605 A, whichever produces the greater load effect.
2025 CALIFORNIA BUILDING CODE 16A-17
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
�
STRUCTURAL DESIGN
In structures such as greenhouses, where special scaffolding is used as a work surface for workers and materials during maintenance and repair operations, a lower roof load than specified in the following equations shall not be used unless approved by the building official. Such structures shall be designed for a minimum roof live load of 12 psf (0.58 kN/m [2] ).
Equation 16 A -10 L r = L o R 1 R 2
where: 12 ≤ L r ≤ 20
For SI: L r = L o R 1 R 2
CBC § 1607.13.1.1 High relevance — show source text
1607.13.1.1 One-way slabs. The tributary area, A T, for use in Equation 16-7 for one-way slabs shall not exceed an area defined by the slab span times a width normal to the span of 1.5 times the slab span. 1607.13.1.2 Heavy live loads. Live loads that exceed 100 psf (4.79 kN/m [2] ) shall not be reduced.
Exceptions:
- The live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent, but the reduced live load shall be not less than L as calculated in Section 1607.13.1.
- For uses other than storage, where approved, additional live load reductions shall be permitted where shown by the registered design professional that a rational approach has been used and that such reductions are warranted.
1607.13.1.3 Passenger vehicle garages. The live loads shall not be reduced in passenger vehicle garages.
Exception: The live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent, but the reduced live load shall be not less than L as calculated in Section 1607.13.1.
1607.13.2 Alternative uniform live load reduction. As an alternative to Section 1607.13.1 and subject to the limitations of Table 1607.1, uniformly distributed live loads are permitted to be reduced in accordance with the following provisions. Such reductions shall apply to slab systems, beams, girders, columns, piers, walls and foundations.
- For live loads not exceeding 100 pounds per square foot (4.79 kN/m [2] ), the design live load for structural members supporting 150 square feet (13.94 m [2] ) or more is permitted to be reduced in accordance with Equation 16-8.
Equation 16-8 R = 0.08( A – 150)
For SI: R = 0.861( A – 13.94)
where:
A = Area of floor supported by the member, square feet (m [2] ).
R = Reduction in percent. Such reduction shall not exceed the smallest of: 1.1. 40 percent for members supporting one floor. 1.2. 60 percent for members supporting two or more floors.
2025 CALIFORNIA BUILDING CODE 16-15
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
STRUCTURAL DESIGN
1.3. R as determined by the following equation:
Equation 16-9 R = 23.1(1+ D/L o )
where:
D = Dead load per square foot (m [2] ) of area supported. L o = Unreduced live load per square foot (m [2] ) of area supported. 2. A reduction shall not be permitted where the live load exceeds 100 pounds per square foot (4.79 kN/m [2] ) except that the design live load for members supporting two or more floors is permitted to be reduced by not greater than 20 percent. Exception: For uses other than storage, where approved, additional live load reductions shall be permitted where shown by the registered design professional that a rational approach has been used and that such reductions are warranted.
CBC § 16-8 High relevance — show source text
Equation 16-8 R = 0.08( A – 150)
For SI: R = 0.861( A – 13.94)
where:
A = Area of floor supported by the member, square feet (m [2] ).
R = Reduction in percent. Such reduction shall not exceed the smallest of: 1.1. 40 percent for members supporting one floor. 1.2. 60 percent for members supporting two or more floors.
2025 CALIFORNIA BUILDING CODE 16-15
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
STRUCTURAL DESIGN
1.3. R as determined by the following equation:
Equation 16-9 R = 23.1(1+ D/L o )
where:
D = Dead load per square foot (m [2] ) of area supported. L o = Unreduced live load per square foot (m [2] ) of area supported. 2. A reduction shall not be permitted where the live load exceeds 100 pounds per square foot (4.79 kN/m [2] ) except that the design live load for members supporting two or more floors is permitted to be reduced by not greater than 20 percent. Exception: For uses other than storage, where approved, additional live load reductions shall be permitted where shown by the registered design professional that a rational approach has been used and that such reductions are warranted.
- A reduction shall not be permitted in passenger vehicle parking garages except that the live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent.
- For one-way slabs, the area, A, for use in Equation 16-8 shall not exceed the product of the slab span and a width normal to the span of 0.5 times the slab span.
1607.14 Reduction in uniform roof live loads. The minimum uniformly distributed live loads of roofs, marquees and canopies, L o, in Table 1607.1 are permitted to be reduced in accordance with Section 1607.14.1.
1607.14.1 Ordinary roofs, awnings and canopies. Ordinary flat, pitched and curved roofs, and awnings and canopies other than of fabric construction supported by a skeleton structure, are permitted to be designed for a reduced uniformly distributed roof live load, L r, as specified in the following equations or other controlling combinations of loads as specified in Section 1605, whichever produces the greater load effect.
In structures such as greenhouses, where special scaffolding is used as a work surface for workers and materials during maintenance and repair operations, a lower roof load than specified in the following equations shall not be used unless approved by the building official. Such structures shall be designed for a minimum roof live load of 12 psf (0.58 kN/m [2] ).
Equation 16-10 L r = L o R 1 R 2
where: 12 ≤ L r ≤ 20
For SI: L r = L o R 1 R 2
CBC § 0.25 High relevance — show source text
For SI:
L = Lo 0.25 + ---------------------4.57 KLLAT
where:
L = Reduced design live load per square foot (m [2] ) of area supported by the member. L o = Unreduced design live load per square foot (m [2] ) of area supported by the member (see Table 1607.1). K LL = Live load element factor (see Table 1607.13.1). A T = Tributary area, in square feet (m [2] ).
L shall be not less than 0.50 L o for members supporting one floor and L shall be not less than 0.40 L o for members supporting two or more floors.
TABLE 1607.13.1—LIVE LOAD ELEMENT FACTOR, K
LLCol2 ELEMENT _K_LL Interior columns 4 Exterior columns without cantilever slabs 4 Edge columns with cantilever slabs 3 Corner columns with cantilever slabs 2 Edge beams without cantilever slabs 2 Interior beams 2 Members not previously identified including: 1 Edge beams with cantilever slabs Edge beams with cantilever slabs Cantilever beams Cantilever beams One-way slabs One-way slabs Two-way slabs Two-way slabs Members without provisions for continuous shear transfer normal to their span Members without provisions for continuous shear transfer normal to their span 1607.13.1.1 One-way slabs. The tributary area, A T, for use in Equation 16-7 for one-way slabs shall not exceed an area defined by the slab span times a width normal to the span of 1.5 times the slab span. 1607.13.1.2 Heavy live loads. Live loads that exceed 100 psf (4.79 kN/m [2] ) shall not be reduced.
Exceptions:
- The live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent, but the reduced live load shall be not less than L as calculated in Section 1607.13.1.
- For uses other than storage, where approved, additional live load reductions shall be permitted where shown by the registered design professional that a rational approach has been used and that such reductions are warranted.
1607.13.1.3 Passenger vehicle garages. The live loads shall not be reduced in passenger vehicle garages.
Exception: The live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent, but the reduced live load shall be not less than L as calculated in Section 1607.13.1.
CBC § 3.1 High relevance — show source text
For members supporting a tributary area of 200 square feet or more, this_
additional load may be reduced to 15 pounds per square foot.
f._ [DSA-SS]__ Live load reduction is not permitted for classrooms classified as Group A occupancies.
g.** [DSA-SS]** The minimum uniform live load for a press box floor or accessible roof with railing is 100 psf.
h.** [DSA-SS]** Item 38 applies to pedestrian bridges and walkways that are not subjected to uncontrolled vehicle access._|�
1607 A .2 Loads not specified. For occupancies or uses not designated in Section 1607 A, the live load shall be determined in accordance with a method approved by the building official. 1607 A .3 Uniform live loads. The live loads used in the design of buildings and other structures shall be the maximum loads expected by the intended use or occupancy but shall not be less than the minimum uniformly distributed live loads given in Table 1607 A .1. Live loads acting on a sloping surface shall be assumed to act vertically on the horizontal projection of that surface. 1607 A .3.1 Partial loading of floors. Where uniform floor live loads are involved in the design of structural members arranged so as to create continuity, the minimum applied loads shall be the full dead loads on all spans in combination with the floor live loads on spans selected to produce the greatest load effect at each location under consideration. Uniform floor live loads applied to selected spans are permitted to be reduced in accordance with Section 1607 A .13. 1607 A .3.2 Partial loading of roofs. Where uniform roof live loads are reduced to less than 20 pounds per square foot (0.96 kN/m [2] ) in accordance with Section 1607 A .14.1 and are applied to the design of structural members arranged so as to create continuity, the reduced roof live load shall be applied to adjacent spans or to alternate spans, whichever produces the most unfavorable load effect. 1607 A .4 Concentrated live loads. Floors, roofs and other similar surfaces shall be designed to support the uniformly distributed live loads prescribed in Section 1607 A .3 or the concentrated live loads, given in Table 1607 A .1, whichever produces the greater load effects. Unless otherwise specified, the indicated concentrated load shall be assumed to be uniformly distributed over an area of 2 [1] / 2 feet by 2 [1] / 2 feet (762 mm by 762 mm) and shall be located so as to produce the maximum load effects in the structural members. 1607 A .5 Partition loads. In office buildings and in other buildings where partition locations are subject to change, provisions for partition weight shall be made, whether or not partitions are shown on the construction documents. The partition load shall be not less than a live load of 15 pounds per square foot (0.72 kN/m [2] ) and live load reductions in accordance with Section 1607 A .13 are not permitted to be applied to the partition loads. Exception: A partition live load is not required where the minimum specified live load is 80 pounds per square foot (3.83 kN/m [2] ) or greater.
16A-14 2025 CALIFORNIA BUILDING CODE
CBC § 1607.1 High relevance — show source text
Anchorages of horizontal lifelines and the structural elements that support these anchorages shall be designed for the maximum tension that develops in the horizontal lifeline from these live loads.
1607 A .13 Reduction in uniform live loads. Except for uniform roof live loads, all other minimum uniformly distributed live loads, L o, in Table 1607.1 are permitted to be reduced in accordance with Section 1607 A .13.1 or 1607 A .13.2. Uniform roof live loads are permitted to be reduced in accordance with Section 1607 A .14.
1607 A .13.1 Basic uniform live load reduction. Subject to the limitations of Sections 1607 A .13.1.1 through 1607 A .13.1.3 and Table 1607 A .1, members for which a value of K LL A T is 400 square feet (37.16 m [2] ) or more are permitted to be designed for a reduced uniformly distributed live load, L, in accordance with the following equation:
Equation 16 A -7
L = Lo 0.25 + ---------------------15 KLLAT
For SI:
L = Lo 0.25 + ---------------------4.57 KLLAT
where:
L = Reduced design live load per square foot (m [2] ) of area supported by the member. L o = Unreduced design live load per square foot (m [2] ) of area supported by the member (see Table 1607 A .1). K LL = Live load element factor (see Table 1607 A .13.1). A T = Tributary area, in square feet (m [2] ).
L shall be not less than 0.50 L o for members supporting one floor and L shall be not less than 0.40 L o for members supporting two or more floors.
16A-16 2025 CALIFORNIA BUILDING CODE
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STRUCTURAL DESIGN
TABLE 1607A.13.1—LIVE LOAD ELEMENT FACTOR, K
LLCol2 ELEMENT _K_LL Interior columns 4 Exterior columns without cantilever slabs 4 Edge columns with cantilever slabs 3 Corner columns with cantilever slabs 2 Edge beams without cantilever slabs 2 Interior beams 2 Members not previously identified including: 1 Edge beams with cantilever slabs Edge beams with cantilever slabs Cantilever beams Cantilever beams One-way slabs One-way slabs Two-way slabs Two-way slabs Members without provisions for continuous shear transfer normal to their span Members without provisions for continuous shear transfer normal to their span 1607 A **.13.1.1 One-way slabs.
CBC § 14.1. High relevance — show source text
1607 A .14 Reduction in uniform roof live loads. The minimum uniformly distributed live loads of roofs, marquees and canopies, L o, in Table 1607 A .1 are permitted to be reduced in accordance with Section 1607 A .14.1. 1607 A .14.1 Ordinary roofs, awnings and canopies. Ordinary flat, pitched and curved roofs, and awnings and canopies other than of fabric construction supported by a skeleton structure, are permitted to be designed for a reduced uniformly distributed roof live load, L r, as specified in the following equations or other controlling combinations of loads as specified in Section 1605 A, whichever produces the greater load effect.
2025 CALIFORNIA BUILDING CODE 16A-17
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
�
STRUCTURAL DESIGN
In structures such as greenhouses, where special scaffolding is used as a work surface for workers and materials during maintenance and repair operations, a lower roof load than specified in the following equations shall not be used unless approved by the building official. Such structures shall be designed for a minimum roof live load of 12 psf (0.58 kN/m [2] ).
Equation 16 A -10 L r = L o R 1 R 2
where: 12 ≤ L r ≤ 20
For SI: L r = L o R 1 R 2
where: 0.58 ≤ L r ≤ 0.96 L o = Unreduced roof live load per square foot (m [2] ) of horizontal projection supported by the member (see Table 1607 A .1). L r = Reduced roof live load per square foot (m [2] ) of horizontal projection supported by the member.
The reduction factors R 1 and R 2 shall be determined as follows: Equation 16 A -11 R 1 = 1 for A t ≤ 200 square feet (18.58 m [2] )
Equation 16 A -12 R 1 = 1.2 - 0.001 A t for 200 square feet < A t < 600 square feet Equation 16 A -13 R 1 = 0.6 for A t ≥ 600 square feet (55.74 m [2] )
where:
A t = Tributary area (span length multiplied by effective width) in square feet (m [2] ) supported by the member, and
Equation 16 A -14 R 2 = 1 for F ≤ 4
Equation 16 A -15 R 2 = 1.2 - 0.05 F for 4 < F < 12
Equation 16 A -16 R 2 = 0.6 for F ≥ 12
where:
CBC § 13.1.2 High relevance — show source text
1607 A .13.1.2 Heavy live loads. Live loads that exceed 100 psf (4.79 kN/m [2] ) shall not be reduced. Exceptions:
- The live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent, but the reduced live load shall be not less than L as calculated in Section 1607 A .13.1.
- For uses other than storage, where approved, additional live load reductions shall be permitted where shown by the registered design professional that a rational approach has been used and that such reductions are warranted. 1607 A .13.1.3 Passenger vehicle garages. The live loads shall not be reduced in passenger vehicle garages. Exception: The live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent, but the reduced live load shall be not less than L as calculated in Section 1607 A .13.1. 1607 A .13.2 Alternative uniform live load reduction. As an alternative to Section 1607 A .13.1 and subject to the limitations of Table 1607.1, uniformly distributed live loads are permitted to be reduced in accordance with the following provisions. Such reductions shall apply to slab systems, beams, girders, columns, piers, walls and foundations.
- For live loads not exceeding 100 pounds per square foot (4.79 kN/m [2] ), the design live load for structural members supporting 150 square feet (13.94 m [2] ) or more is permitted to be reduced in accordance with Equation 16 A -8. Equation 16 A -8 R = 0.08( A – 150) For SI: R = 0.861( A – 13.94)
where:
A = Area of floor supported by the member, square feet (m [2] ). R = Reduction in percent. Such reduction shall not exceed the smallest of: 1.1. 40 percent for members supporting one floor. 1.2. 60 percent for members supporting two or more floors. 1.3. R as determined by the following equation: Equation 16 A -9 R = 23.1(1+ D/L o )
where:
D = Dead load per square foot (m [2] ) of area supported. L o = Unreduced live load per square foot (m [2] ) of area supported. 2. A reduction shall not be permitted where the live load exceeds 100 pounds per square foot (4.79 kN/m [2] ) except that the design live load for members supporting two or more floors is permitted to be reduced by not greater than 20 percent. Exception: For uses other than storage, where approved, additional live load reductions shall be permitted where shown by the registered design professional that a rational approach has been used and that such reductions are warranted. 3. A reduction shall not be permitted in passenger vehicle parking garages except that the live loads for members supporting two or more floors are permitted to be reduced by not greater than 20 percent. 4. For one-way slabs, the area, A, for use in Equation 16 A -8 shall not exceed the product of the slab span and a width normal to the span of 0.5 times the slab span.
CBC § 3.1 High relevance — show source text
The minimum vertical design live load shall be as follows:
Paper media:
12-inch-deep (305 mm) shelf 33 pounds per lineal foot (482 N/m)
15-inch-deep (381 mm) shelf 41 pounds per lineal foot (598 N/m), or
33 pounds per cubic foot (5183 N/m3) per total volume of the rack or cabinet, whichever is less.
Film media:
18-inch-deep (457 mm) shelf 100 pounds per lineal foot (1459 N/m), or
50 pounds per cubic foot (7853 N/m3) per total volume of the rack or cabinet, whichever is less.
Other media:
20 pounds per cubic foot (311 N/m3) or 20 pounds per square foot (958 Pa), whichever is less, but not less than actual loads.
e.** [DSA-SS]** The following minimum loads for stage accessories apply:
1. Gridirons and fly galleries: 75 pounds per square foot uniform live load.
2. Loft block wells: 250 pounds per lineal foot vertical load and lateral load.
3. Head block wells and sheave beams: 250 pounds per lineal foot vertical load and lateral load. Head block wells and sheave beams shall be designed for all tributary loft block
well loads. Sheave blocks shall be designed with a safety factor of five.
4. Scenery beams where there is no gridiron: 300 pounds per lineal foot vertical load and lateral load.
5. Ceiling framing over stages shall be designed for a uniform live load of 20 pounds per square foot. For members supporting a tributary area of 200 square feet or more, this
additional load may be reduced to 15 pounds per square foot.
f.** [DSA-SS]** Live load reduction is not permitted for classrooms classified as Group A occupancies.
g.** [DSA-SS]** The minimum uniform live load for a press box floor or accessible roof with railing is 100 psf.
h.** [DSA-SS]** Item 38 applies to pedestrian bridges and walkways that are not subjected to uncontrolled vehicle access._|�
1607 A .2 Loads not specified. For occupancies or uses not designated in Section 1607 A, the live load shall be determined in accordance with a method approved by the building official. 1607 A .3 Uniform live loads. The live loads used in the design of buildings and other structures shall be the maximum loads expected by the intended use or occupancy but shall not be less than the minimum uniformly distributed live loads given in Table 1607 A .1. Live loads acting on a sloping surface shall be assumed to act vertically on the horizontal projection of that surface. 1607 A .3.1 Partial loading of floors. Where uniform floor live loads are involved in the design of structural members arranged so as to create continuity, the minimum applied loads shall be the full dead loads on all spans in combination with the floor live loads on spans selected to produce the greatest load effect at each location under consideration. Uniform floor live loads applied to selected spans are permitted to be reduced in accordance with Section 1607 A .13. 1607 A **.3.2 Partial loading of roofs.
CBC § 0.96 High relevance — show source text
** Where uniform roof live loads are reduced to less than 20 pounds per square foot (0.96 kN/m [2] ) in accordance with Section 1607 A .14.1 and are applied to the design of structural members arranged so as to create continuity, the reduced roof live load shall be applied to adjacent spans or to alternate spans, whichever produces the most unfavorable load effect. 1607 A .4 Concentrated live loads. Floors, roofs and other similar surfaces shall be designed to support the uniformly distributed live loads prescribed in Section 1607 A .3 or the concentrated live loads, given in Table 1607 A .1, whichever produces the greater load effects. Unless otherwise specified, the indicated concentrated load shall be assumed to be uniformly distributed over an area of 2 [1] / 2 feet by 2 [1] / 2 feet (762 mm by 762 mm) and shall be located so as to produce the maximum load effects in the structural members. 1607 A .5 Partition loads. In office buildings and in other buildings where partition locations are subject to change, provisions for partition weight shall be made, whether or not partitions are shown on the construction documents. The partition load shall be not less than a live load of 15 pounds per square foot (0.72 kN/m [2] ) and live load reductions in accordance with Section 1607 A .13 are not permitted to be applied to the partition loads. Exception: A partition live load is not required where the minimum specified live load is 80 pounds per square foot (3.83 kN/m [2] ) or greater.
16A-14 2025 CALIFORNIA BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
STRUCTURAL DESIGN
1607 A .6 Helipads. Helipads shall be marked to indicate the maximum takeoff weight. The takeoff weight limitation shall be indicated in units of thousands of pounds and placed in a box that is located in the bottom right corner of the landing area as viewed from the primary approach path. The box shall be not less than 5 feet (1524 mm) in height.
1607 A .6.1 Concentrated loads. Helipads shall be designed for the following concentrated live loads:
- A single concentrated live load, L, of 3,000 pounds (13.35 kN) applied over an area of 4.5 inches by 4.5 inches (114 mm by 114 mm) and located so as to produce the maximum load effects on the structural elements under consideration. The concentrated load is not required to act concurrently with other uniform or concentrated live loads.
- Two single concentrated live loads, L, 8 feet (2438 mm) apart applied on the landing pad (representing the helicopter’s two main landing gear, whether skid type or wheeled type), each having a magnitude of 0.75 times the maximum takeoff weight of the helicopter, and located so as to produce the maximum load effects on the structural elements under consideration. The concentrated loads shall be applied over an area of 8 inches by 8 inches (203 mm by 203 mm) and are not required to act concurrently with other uniform or concentrated live loads.
Frequently asked questions
When can I use partial loading rather than full uniform live load on every span?
When framing is continuous, apply full dead load to all spans and apply live load only to the spans that produce the worst internal forces per § 1607.3.1 (floors) and apply similar rules for reduced roof live loads per § 1607.3.2.
Which method should I use to reduce live load — K_LL (Eq. 16‑7) or area-based (Eq. 16‑8)?
Use the K_LL method when element type and tributary area suit it (see the K_LL table and Equation 16‑7 in § 1607.13.1). Use the area-based Equation 16‑8 alternative when L_o ≤ 100 psf and the member supports ≥ 150 ft². Choose the method that yields allowable, code-compliant reductions and satisfies the minima and caps.
Can I reduce live loads for storage or heavy equipment areas?
Live loads exceeding 100 psf shall not be reduced ( § 1607.13.1.2). For storage or other heavy-load uses, reductions are restricted; a registered design professional may justify additional reduction for some non-storage uses, but this requires approval.
Are partition loads reducible under these rules?
No. Partition live loads (15 psf in many cases) are not permitted to be reduced under § 1607.13; treat them separately as required by § 1607.5.
Do one-way slabs have special tributary-area rules?
Yes. The tributary area used in the K_LL (Equation 16‑7) method for one-way slabs is capped by a width limit (see § 1607.13.1.1).
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