Structural loads, limit states, dead and live loads (4.1.1 to 4.1.5) (Building Structural)

Last updated October 22, 2026

Values this chapter turns on

live load for assembly areas, exits and retail: 4.8 kPa; live load for assembly areas, exits and retail
live load for residential living quarters: 1.9 kPa; live load for residential living quarters
minimum partition allowance on floors: 1 kPa; minimum partition allowance on floors
concentrated load on office floors: 9.0 kN; concentrated load on office floors

Subsections 4.1.1 to 4.1.5 set up everything else in Part 4: which loads exist, how they are factored and combined, and the minimum dead and live loads. Expect plenty of calculation questions here. Most are one line of arithmetic once you have the right table row and the right factor.

General requirements and the list of loads

Buildings, including formwork and falsework, must be designed with enough structural capacity and integrity for all loads that may reasonably be expected over their service life OBC Div. B 4.1.1.3.. Members must also be protected from overload during construction. Where a structure cannot be analysed by an established theory, a specially qualified designer may instead use a load test of a full-scale structure or prototype, or studies of model analogues OBC Div. B 4.1.1.5..

Article 4.1.2.1 lists the load symbols. Learn them, because every combination uses them OBC Div. B 4.1.2.1.:

Symbol	Load	Kind
D	dead load (4.1.4)	permanent
L	live load from use and occupancy (4.1.5)	variable
S	snow and associated rain, or rain (4.1.6)	variable
W	wind (4.1.7)	variable
E	earthquake (4.1.8)	rare
H, P, T	earth pressure, prestress, imposed deformation	various

A load not on the list must still be designed for, using the most appropriate information available OBC Div. B 4.1.2.2..

Importance Category. Every building gets one of four categories for S, W and E: Low, Normal, High or Post-disaster OBC Div. B Table 4.1.2.1.. The Ontario table names community centres and elementary, middle and secondary schools as High. The category then drives the importance factors I_s, I_w and I_E in the next chapters.

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Limit states design and load combinations

Ultimate limit states (ULS) concern safety, such as exceeding capacity, overturning, sliding and fracture. Serviceability limit states (SLS) restrict use, such as deflection, vibration and cracking OBC Div. B 4.1.3.1.. The terms the exam likes to test:

Principal load: the variable or rare load that dominates a combination.
Companion load: a variable load that accompanies the principal load.
Factored load: a specified load times its principal-load or companion-load factor.
Factored resistance: the nominal resistance times the resistance factor, φ.

The design rule is simple: factored resistance must be at least the effect of factored loads OBC Div. B 4.1.3.2.. Without cranes, you use the five cases of Table 4.1.3.2.-A. In our words:

Case	Principal	Companion
1	1.4D	none
2	1.25D (or 0.9D) + 1.5L	1.0S or 0.4W
3	1.25D (or 0.9D) + 1.5S	1.0L or 0.4W
4	1.25D (or 0.9D) + 1.4W	0.5L or 0.5S
5	1.0D + 1.0E	0.5L + 0.25S

Modifiers in 4.1.3.2 that examiners like:

Use 0.9D (1.0D in case 5) when dead load resists overturning, uplift or sliding.
The 1.5 live load factor may drop to 1.25 for liquids in tanks.
The companion factor on L goes up by 0.5 for storage areas, equipment areas and service rooms.
The dead load factor for soil, plants and trees rises from 1.25 to 1.5. Where the soil is deeper than 1.2 m it may be reduced to 1 + 0.6/h_s, but not below 1.25.
H, P and T take factors of 1.5, 1.0 and 1.25.
Always also check each principal load with its companions taken as zero.

Serviceability uses its own combinations with 1.0 on the principal load and smaller companions, such as 0.35S or 0.3W OBC Div. B Table 4.1.3.4.. Drift per storey under service wind and gravity loads is limited to 1/500 of the storey height, unless a Section 4.3 standard says otherwise OBC Div. B 4.1.3.5.. Floors used for rhythmic activities with a natural frequency under 6 Hz need a dynamic analysis OBC Div. B 4.1.3.6..

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Dead loads

Dead load is the member's self-weight, plus permanent materials, partitions, permanent equipment and the vertical load of soil, plants and trees OBC Div. B 4.1.4.1.. Where partitions are not shown on the drawings, use an allowance from the expected partitions of at least 1 kPa over the floor area, and show the partition load on the drawings. Two traps: leave the partition allowance out where it would counteract other loads, and do the same for soil and plant loads, unless the soil is part of the load-resisting system.

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Live loads, concentrated loads and guards

The specified live load is the most critical of three things: the uniform load in Table 4.1.5.3, the actual loads from the intended use, or the concentrated loads in Table 4.1.5.9 OBC Div. B 4.1.5.1.. Low Importance Category buildings may apply a factor of 0.8 to live load.

Some uniform loads to know OBC Div. B Table 4.1.5.3.:

Use	kPa
Assembly areas, exits, retail, exterior balconies	4.8
Offices above the ground floor	2.4
Offices in the basement or a ground floor with direct exterior access	4.8
Residential sleeping and living quarters	1.9
Equipment areas and service rooms	3.6
Factories	6.0
Library stack rooms	7.2
Roofs (minimum)	1.0

Narrow corridors (1,200 mm or less), upper corridors in apartments and hotels, and interior balconies use the load of the occupancy they serve, provided they cannot become viewing areas OBC Div. B 4.1.5.4.. When one area serves several occupancies at different times, use the greatest value OBC Div. B 4.1.5.7..

Tributary area reduction OBC Div. B 4.1.5.8.. There is none for one- and two-way slabs, or for minimum-loaded roofs. For assembly areas of 4.8 kPa or more, storage, manufacturing, retail, garages and footbridges, the reduction applies above 80 m², with factor 0.5 + √(20/A). For other uses it applies above 20 m², with factor 0.3 + √(9.8/B).

Concentrated loads come from Table 4.1.5.9: 9.0 kN on 750 x 750 mm for offices, 4.5 kN for classrooms, 1.3 kN for roof surfaces and 18 kN for car garages OBC Div. B Table 4.1.5.9..

Guards and handrails OBC Div. B 4.1.5.14.:

Situation	Outward load at guard height
Grandstand, stadium, bleacher and arena egress; viewing stands	3.0 kN/m
Equipment platform access, where crowds are improbable	1.0 kN at any point
All other guards	0.75 kN/m or 1.0 kN at any point, whichever governs

The inward load is half the outward value. Pickets and panels take 0.5 kN over 100 x 100 mm. The vertical load on top is 1.5 kN/m. Handrails take 0.9 kN at any point, plus 0.7 kN/m for handrails outside dwelling units. Vehicle guardrails take 22 kN at 500 mm above the floor OBC Div. B 4.1.5.15.. A wall with more than 600 mm drop on one side acts as a guard and takes at least 0.5 kPa OBC Div. B 4.1.5.16..

Firewalls take the worse of the normal lateral loads or a factored 0.5 kPa under fire. Where the structure's fire-resistance rating is lower than the firewall's, assume lateral support on one side only, or provide another support system OBC Div. B 4.1.5.17..

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Chapter review

Chapter at a glance

One line per section: the idea to carry into the exam. Then the answers that most often catch candidates out.

Chapter at a glance: the key idea in each section
Section	Key idea
General requirements and the list of loads	Buildings, including formwork and falsework, must be designed with enough structural capacity and integrity for all loads that may reasonably be expected over their service life.
Limit states design and load combinations	Ultimate limit states (ULS) concern safety, such as exceeding capacity, overturning, sliding and fracture.
Dead loads	Dead load is the member's self-weight, plus permanent materials, partitions, permanent equipment and the vertical load of soil, plants and trees.
Live loads, concentrated loads and guards	The specified live load is the most critical of three things: the uniform load in Table 4.1.5.3, the actual loads from the intended use, or the concentrated loads in Table…

General requirements and the list of loads
Buildings, including formwork and falsework, must be designed with enough structural capacity and integrity for all loads that may reasonably be expected over their service life.
Limit states design and load combinations
Ultimate limit states (ULS) concern safety, such as exceeding capacity, overturning, sliding and fracture.
Dead loads
Dead load is the member's self-weight, plus permanent materials, partitions, permanent equipment and the vertical load of soil, plants and trees.
Live loads, concentrated loads and guards
The specified live load is the most critical of three things: the uniform load in Table 4.1.5.3, the actual loads from the intended use, or the concentrated loads in Table…

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Questions on Structural loads and procedures: general, dead and live loads (4.1.1 to 4.1.5), in the exam format, every answer explained and cited to its article. Sign in to start; a free account gets the free questions.

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Code cited in this chapter

Based on the official 2024 Building Code Compendium on ontario.ca.

OBC Div. B 4.1.1.3. Design Requirements
(1)Buildings and their structural members and connections, including formwork and falsework, shall be designed to have sufficient structural capacity and structural integrity to safely and effectively resist all loads, effects of loads and influences that may reasonably be expected, having regard to the expected service life of buildings, and shall in any case satisfy the requirements of this Section. (See Note A-4.1.1.3.(1))
(2)Buildings and their structural members shall be designed for serviceability, in accordance with Articles 4.1.3.4., 4.1.3.5. and 4.1.3.6. (See Note A-4.1.1.3.(2))
(3)All permanent and temporary structural members, including the formwork and falsework of a building, shall be protected against loads exceeding the specified loads during the construction period except when, as verified by analysis or test, temporary overloading of a structural member would result in no impairment of that member or any other member.
(4)Reserved.
(5)Precautions shall be taken during all phases of construction to ensure that the building is not damaged or distorted due to loads applied during construction.
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OBC Div. B 4.1.1.5. Design Basis
(1)Except as provided in Sentence (2), buildings and their structural members shall be designed in conformance with the procedures and practices provided in this Part.
(2)Provided the design is carried out by a person especially qualified in the specific methods applied and provided the design demonstrates a level of safety and performance in accordance with the requirements of this Part, buildings and their structural components falling within the scope of this Part that are not amenable to analysis using a generally established theory may be designed by,
(a)evaluation of a full-scale structure or a prototype by a loading test, or
(b)studies of model analogues. (See Note A-4.1.1.5.(2))
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OBC Div. B 4.1.2.1. Loads and Effects
(1)Except as provided in Article 4.1.2.2., the following categories of loads, specified loads and effects shall be taken into consideration in the design of a building and its structural members and connections:
Loads and Effects — Forming Part of Sentence 4.1.2.1.(1)
Symbol | Description
D | dead load — a permanent load due to the weight of building components, as specified in Subsection 4.1.4.
E | earthquake load and effects — a rare load due to an earthquake, as specified in Subsection 4.1.8.
H | a permanent load due to lateral earth pressure, including groundwater
L | live load — a variable load due to intended use and occupancy (including loads due to cranes and the pressure of liquids in containers), as specified in Subsection 4.1.5.
L_XC | live load exclusive of crane loads,
C | live load due to cranes including self weight,
C_d | self weight of all cranes positioned for maximum effects,
C₇ | crane bumper impact load,
P | permanent effects caused by pre-stress,
S | variable load due to snow, including ice and associated rain, as specified in Article 4.1.6.2., or due to rain, as specified in Article 4.1.6.4.
T | effects due to contraction, expansion, or deflection caused by temperature changes, shrinkage, moisture changes, creep, ground settlement, or a combination thereof, and (See Note A-4.1.2.1.(1))
W | wind load — a variable load due to wind, as specified in Subsection 4.1.7.
where
(a)load means the imposed deformations (i.e. deflections, displacements or motions that induce deformations and forces in the structure), forces and pressures applied to the building structure,
(b)permanent load is a load that changes very little once it has been applied to the structure, except during repair,
(c)variable load is a load that frequently changes in magnitude, direction or location, and
(d)rare load is a load that occurs infrequently and for a short time only.
(2)Minimum specified values of the loads described in Sentence (1), as set forth in Subsections 4.1.4. to 4.1.8., shall be increased to account for dynamic effects where applicable.
(3)For the purpose of determining specified loads S, W or E in Subsections 4.1.6., 4.1.7. and 4.1.8., buildings shall be assigned an Importance Category based on intended use and occupancy, in accordance with Table 4.1.2.1. (See Note A-4.1.2.1.(3))
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OBC Div. B 4.1.2.2. Loads Not Listed
(1)Where a building or structural member can be expected to be subjected to loads, forces or other effects not listed in Article 4.1.2.1., such effects shall be taken into account in the design based on the most appropriate information available. (See Note A-4.1.2.2.(1))
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OBC Div. B Table 4.1.2.1. Importance Categories for Buildings[1]
Table 4.1.2.1. Importance Categories for Buildings[1] Forming Part of Sentence 4.1.2.1.(3) Type of Building | Importance Category A Low Importance Category building is a building that represents a low direct or indirect hazard to human life in the event of structural failure. | Low A Normal Importance Category building is a building that does not meet the criteria for a Low Importance Category building, High Importance Category building or post-disaster building. | Normal A High Importance Category building is a building that provides a greater degree of safety to human life than a Normal Importance Category building. Community centres and elementary, middle and secondary schools are High Importance Category buildings. | High A post-disaster building. | Post-disaster Notes to Table 4.1.2.1. (1) See Note A-Table 4.1.2.1.
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OBC Div. B 4.1.3.1. Definitions
(1)In this Subsection, the term,
(a)"limit states" means those conditions of a building structure that result in the building ceasing to fulfill the function for which it was designed. (Those limit states concerning safety are called ultimate limit states (ULS) and include exceeding the load-carrying capacity, overturning, sliding and fracture; those limit states that restrict the intended use and occupancy of the building are called serviceability limit states (SLS) and include deflection, vibration, permanent deformation and local structural damage such as cracking; and those limit states that represent failure under repeated loading are called fatigue limit states),
(b)"specified loads" (C, D, E, H, L, P, S, T and W) means those loads defined in Article 4.1.2.1.,
(c)"principal load" means the specified variable load or rare load that dominates in a given load combination,
(d)"companion load" means a specified variable load that accompanies the principal load in a given load combination,
(e)"service load" means a specified load used for the evaluation of a serviceability limit state,
(f)"principal-load factor" means a factor applied to the principal load in a load combination to account for the variability of the load and load pattern and the analysis of its effects,
(g)"companion-load factor" means a factor that, when applied to a companion load in the load combination, gives the probable magnitude of a companion load acting simultaneously with the factored principal load,
(h)"importance factor, I," means a factor applied in Subsections 4.1.6., 4.1.7. and 4.1.8. to obtain the specified load and take into account the consequences of failure as related to the limit state and the use and occupancy of the building,
(i)"factored load" means the product of a specified load and its principal-load factor or companion-load factor,
(j)"effects" refers to forces, moments, deformations or vibrations that occur in the structure,
(k)"nominal resistance, R," of a member, connection or structure, is based on the geometry and on the specified properties of the structural materials,
(l)"resistance factor, φ," means a factor applied to a specified material property or to the resistance of a member, connection or structure, and that, for the limit state under consideration, takes into account the variability of dimensions and material properties, workmanship, type of failure and uncertainty in the prediction of resistance, and
(m)"factored resistance, ΦR ," means the product of nominal resistance and the applicable resistance factor.
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OBC Div. B 4.1.3.2. Strength and Stability
(1)A building and its structural components shall be designed to have sufficient strength and stability so that the factored resistance, ΦR , is greater than or equal to the effect of factored loads, which shall be determined in accordance with Sentence (2).
(2)Except as provided in Sentence (3), the effect of factored loads for a building or structural component shall be determined in accordance with the requirements of this Article and the following load combination cases, the applicable combination being that which results in the most critical effect:
(a)for load cases without crane loads, the load combinations listed in Table 4.1.3.2.-A, and
(b)for load cases with crane loads, the load combinations listed in Table 4.1.3.2.-B. (See Note A-4.1.3.2.(2))
(3)Other load combinations that must also be considered are the principal loads acting with the companion loads taken as zero.
(4)Where the effects due to lateral earth pressure, H, restraint effects from pre-stress, P, and imposed deformation, T, affect the structural safety, they shall be taken into account in the calculations, with load factors of 1.5, 1.0 and 1.25 assigned to H, P and T respectively. (See Note A-4.1.3.2.(4))
(5)Except as provided in Sentence 4.1.8.16.(2), the counteracting factored dead load—0.9D in load combination cases 2, 3 and 4 and 1.0D in load combination case 5 in Table 4.1.3.2.-A, and 0.9D in load combination cases 1 to 5 and 1.0D in load combination case 6 in Table 4.1.3.2.-B—shall be used when the dead load acts to resist overturning, uplift, sliding, failure due to stress reversal, and to determine anchorage requirements and the factored resistance of members. (See Note A-4.1.3.2.(5))
(6)The principal-load factor 1.5 for live loads L in Table 4.1.3.2.-A and L_XC in Table 4.1.3.2.-B may be reduced to 1.25 for liquids in tanks.
(7)The companion-load factor for live loads L in Table 4.1.3.2.-A and L_XC in Table 4.1.3.2.-B shall be increased by 0.5 for storage areas and equipment areas and service rooms referred to in Table 4.1.5.3.
(8)Except as provided in Sentence (9), the load factor 1.25 for dead load, D, for soil, superimposed earth, plants and trees given in Tables 4.1.3.2.-A and 4.1.3.2.-B shall be increased to 1.5, except that when the soil depth exceeds 1.2 m, the factor may be reduced to 1 + 0.6/h_s but not less than 1.25, where h_s is the depth of soil, in m, supported by the structure.
(9)A principal-load factor of 1.5 shall be applied to the weight of saturated soil used in load combination case 1 of Table 4.1.3.2.-A.
(10)Earthquake load, E, in load combination cases 5 of Table 4.1.3.2.-A and 6 of Table 4.1.3.2.-B includes horizontal earth pressure due to earthquake determined in accordance with Sentence 4.1.8.16.(7).
(11)Provision shall be made to ensure adequate stability of the structure as a whole and adequate lateral, torsional and local stability of all structural parts.
(12)Sway effects produced by vertical loads acting on the structure in its displaced configuration shall be taken into account in the design of buildings and their structural members.
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OBC Div. B Table 4.1.3.2-A. Load Combinations Without Crane Loads for Ultimate Limit States
Table 4.1.3.2.-A — Load Combinations Without Crane Loads for Ultimate Limit States Forming Part of Sentences 4.1.3.2.(2), (5) to (10) and 4.2.4.1.(3) Case | Load Combination[1] — Principal Loads | Load Combination[1] — Companion Loads 1 | 1.4D[2] | N/A 2 | (1.25D[3] or 0.9D[4]) + 1.5 L[5] | 1.0 S[6] or 0.4 W 3 | (1.25D[3] or 0.9D[4]) + 1.5 S | 1.0 L[6][7] or 0.4 W 4 | (1.25D[3] or 0.9D[4]) + 1.4 W | 0.5 L[7] or 0.5 S 5 | 1.0D[4] + 1.0E[8] | 0.5 L[6][7] + 0.25 S[6] Notes to Table 4.1.3.2.-A: (1) See Sentences 4.1.3.2.(2) to (4). (2) See Sentence 4.1.3.2.(9). (3) See Sentence 4.1.3.2.(8). (4) See Sentence 4.1.3.2.(5). (5) See Sentence 4.1.3.2.(6). (6) See Article 4.1.5.5. (7) See Sentence 4.1.3.2.(7). (8) See Sentence 4.1.3.2.(10).
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OBC Div. B Table 4.1.3.4. Loads and Load Combinations for Serviceability
Table 4.1.3.4. — Loads and Load Combinations for Serviceability Forming Part of Sentence 4.1.3.4.(2) Limit State | Structural Parameter | Load Case | Load Combination — Principal Loads | Load Combination — Companion Loads Deflection for materials not subject to creep | Deflection of the structure or of components of the structure[1] | 1 | 1.0D + 1.0 L | 0.3 W or 0.35 S Deflection for materials not subject to creep | Deflection of the structure or of components of the structure[1] | 2 | 1.0D + 1.0 W | 0.35 L[2] or 0.35 S Deflection for materials not subject to creep | Deflection of the structure or of components of the structure[1] | 3 | 1.0D + 1.0 S | 0.3 W or 0.35 L[2] Deflection for materials subject to creep | Total deflection of the structure or of components of the structure[3] | 1 | 1.0D + 1.0L_s[4] + 1.0L_t[5] | 0.3 W or 0.35 S Deflection for materials subject to creep | Total deflection of the structure or of components of the structure[3] | 2 | 1.0D + 1.0 W | 0.35 L[2] or 0.35 S Deflection for materials subject to creep | Total deflection of the structure or of components of the structure[3] | 3 | 1.0D + 1.0 S | 0.3 W or 0.35 L[2] Vibration serviceability | Acceleration | [6] | [6] | [6] Notes to Table 4.1.3.4.: (1) The calculated deflection due to dead load, D, is permitted to be excluded where specified in the standards listed in Section 4.3. (2) The companion load factor of 0.35 for live load, L, shall be increased to 0.5 for storage areas, equipment areas and service rooms. (3) The calculated immediate deflection due to dead load, D, is permitted to be excluded where specified in the standards listed in Section 4.3. (4) L_s = sustained portion of the live load, L. (5) L_t = transitory portion of the live load, L. (6) See Note A-Table 4.1.3.4.
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OBC Div. B 4.1.3.5. Deflection
(1)In proportioning structural members to limit serviceability problems resulting from deflections, consideration shall be given to
(a)the intended use of the building or member,
(b)limiting damage to non-structural members made of materials whose physical properties are known at the time of design,
(c)limiting damage to the structure itself, and
(d)creep, shrinkage, temperature changes and prestress.
(See Note A-4.1.3.5.(1))
(2)The lateral deflection of buildings due to service wind and gravity loads shall be checked to ensure that structural elements and non-structural elements whose nature is known at the time the structural design is carried out, will not be damaged.
(3)Except as provided in Sentence (4), the total drift per storey under service wind and gravity loads shall not exceed 1/500 of the storey height unless other drift limits are specified in the design standards referenced in Section 4.3. (See Note A-4.1.3.5.(3))
(4)The deflection limits required in Sentence (3) do not apply to industrial buildings or sheds if experience has proven that greater movement will have no significant adverse effects on the strength and function of the building.
(5)The building structure shall be designed for lateral deflection due to E, in accordance with Article 4.1.8.13.
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OBC Div. B 4.1.3.6. Vibration
(1)Floor systems susceptible to vibration shall be designed so that vibrations will have no significant adverse effects on the intended occupancy of the building. (See Note A-4.1.3.6.(1))
(2)Where floor vibrations caused by resonance with operating machinery or equipment are anticipated, dynamic analysis of the floor system shall be carried out. (See Note A-4.1.3.6.(2))
(3)Where the fundamental vibration frequency of a structural system supporting an assembly occupancy used for rhythmic activities, such as dancing, concerts, jumping exercises or gymnastics, is less than 6 Hz, the effects of resonance shall be investigated by means of a dynamic analysis. (See Note A-4.1.3.6.(3))
(4)A building susceptible to lateral vibration under wind load shall be designed in accordance with Article 4.1.7.1. so that the vibrations will have no significant adverse effects on the intended use and occupancy of the building. (See Note A-4.1.3.6.(4))
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OBC Div. B 4.1.4.1. Dead Loads
(1)The specified dead load for a structural member consists of,
(a)the weight of the member itself,
(b)the weight of all materials of construction incorporated into the building to be supported permanently by the member,
(c)the weight of partitions,
(d)the weight of permanent equipment, and
(e)the vertical load due to soil, superimposed earth, plants and trees.
(2)In areas of a building for which partitions are shown on the drawings, the weight of partitions referred to in Clause (1)(c) shall be taken as the actual weight of such partitions. (See Note A-4.1.4.1.(2))
(3)In areas of a building for which partitions are not shown on the drawings, the weight of partitions referred to in Clause (1)(c) shall be a partition weight allowance determined from the anticipated weight and position of the partitions, but shall not be less than 1 kPa over the area of floor being considered. (See Note A-4.1.4.1.(3))
(4)Partition loads used in design shall be shown on the drawings.
(5)Where the partition weight allowance referred to in Sentence (3) is counteractive to other loads, it shall not be included in the design calculations.
(6)Except for structures where the dead load of soil is part of the load-resisting system, where the dead load due to soil, superimposed earth, plants and trees is counteractive to other loads, it shall not be included in the design calculations. (See Note A-4.1.4.1.(6))
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OBC Div. B 4.1.5.1. Loads Due to Use of Floors and Roofs
(1)Except as provided in Sentence (2), the specified live load on an area of floor or roof depends on the intended use and occupancy, and shall not be less than either the uniformly distributed load patterns listed in Article 4.1.5.3., the loads due to the intended use and occupancy, or the concentrated loads listed in Article 4.1.5.9., whichever produces the most critical effect. (See Note A-4.1.5.1.(1))
(2)For buildings in the Low Importance Category as described in Table 4.1.2.1., a factor of 0.8 may be applied to the live load.
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OBC Div. B Table 4.1.5.3. Specified Uniformly Distributed Live Loads on an Area of Floor or Roof
Table 4.1.5.3. — Specified Uniformly Distributed Live Loads on an Area of Floor or Roof Forming Part of Sentence 4.1.5.3.(1) Use of Area of Floor or Roof | Minimum Specified Load, kPa (a) Assembly Areas Arenas[1] (areas without fixed seats that have backs) | 4.8 (a) Assembly Areas Auditoria | 4.8 (a) Assembly Areas Churches (areas without fixed seats that have backs) | 4.8 (a) Assembly Areas Dance floors | 4.8 (a) Assembly Areas Dining areas[2] | 4.8 (a) Assembly Areas Foyers and entrance halls | 4.8 (a) Assembly Areas Grandstands[1] (areas without fixed seats that have backs), reviewing stands and bleachers | 4.8 (a) Assembly Areas Gymnasia | 4.8 (a) Assembly Areas Lecture halls[1] (areas without fixed seats that have backs) | 4.8 (a) Assembly Areas Museums | 4.8 (a) Assembly Areas Promenades | 4.8 (a) Assembly Areas Rinks | 4.8 (a) Assembly Areas Stadia[1] (areas without fixed seats that have backs) | 4.8 (a) Assembly Areas Stages | 4.8 (a) Assembly Areas Theatres (areas without fixed seats that have backs) | 4.8 (a) Assembly Areas Other areas with similar uses | 4.8 (b) Classrooms and courtrooms with or without fixed seats[1] | 2.4 (c) Portions of assembly areas with fixed seats that have backs for the following uses: Arenas[1] | 2.9 (c) Portions of assembly areas with fixed seats that have backs for the following uses: Grandstands[1] | 2.9 (c) Portions of assembly areas with fixed seats that have backs for the following uses: Stadia[1] | 2.9 (d) Portions of assembly areas with fixed seats that have backs for the following uses: Churches | 2.4 (d) Portions of assembly areas with fixed seats that have backs for the following uses: Lecture halls[1] | 2.4 (d) Portions of assembly areas with fixed seats that have backs for the following uses: Theatres | 2.4 (e) Vomitories, exits, lobbies and corridors[1] | 4.8 Attics[1] Accessible by a stairway in residential occupancies only | 1.4 Attics[1] Having limited accessibility so that there is no storage of equipment or material | 0.5 Balconies Exterior | 4.8 Balconies Interior and mezzanines that could be used by an assembly of people as a viewing area[1] | 4.8 Balconies Interior and mezzanines other than above | [3] Corridors, lobbies and aisles[1] Other than those listed below | 4.8 Corridors, lobbies and aisles[1] Not more than 1 200 mm in width and all upper floor corridors of residential areas only of apartments, hotels and motels (that cannot be used by an assembly of people as a viewing area) | [3] Corridors, lobbies and aisles[1] In a Group B, Division 3 occupancy that contains sleeping accommodation for not more than 10 persons and not more than 6 occupants require assistance in evacuation in case of an emergency | 2.4 Equipment areas and service rooms including Generator rooms | 3.6[4] Equipment areas and service rooms including Mechanical equipment exclusive of elevators | 3.6[4] Equipment areas and service rooms including Machine rooms | 3.6[4] Equipment areas and service rooms including Pump rooms | 3.6[4] Equipment areas and service rooms including Transformer vaults | 3.6[4] Equipment areas and service rooms including Ventilating or air-conditioning equipment | 3.6[4] Exits and fire escapes | 4.8 Factories | 6.0[4] Footbridges | 4.8 Garages for Vehicles not exceeding 4 000 kg gross weight | 2.4 Garages for Vehicles exceeding 4 000 kg but not exceeding 9 000 kg gross weight | 6.0 Garages for Vehicles exceeding 9 000 kg gross weight[1] | 12.0 Kitchens (other than residential) | 4.8 Libraries Stack rooms | 7.2 Libraries Reading and study rooms | 2.9 Office areas[1] (not including record storage and computer rooms) located in Basement, and floors, including mezzanines, with direct access to the exterior at ground level | 4.8 Office areas[1] (not including record storage and computer rooms) located in Other floors | 2.4 Operating rooms and laboratories | 3.6 Patients’ bedrooms | 1.9 Recreation areas that cannot be used for assembly purposes including Billiard rooms | 3.6 Recreation areas that cannot be used for assembly purposes including Bowling alleys | 3.6 Recreation areas that cannot be used for assembly purposes including Pool rooms | 3.6 Residential areas (within the scope of Article 1.3.3.2. of Division A) Sleeping and living quarters in apartments, hotels, motels, boarding schools and colleges | 1.9 Residential areas (within the scope of Article 1.3.3.2. of Division A) Work areas within live/work units | 2.4 Residential areas (within the scope of Article 1.3.3.2. of Division A) Bedrooms and other areas | 1.9 Residential areas (within the scope of Article 1.3.3.2. of Division A) Other areas | 1.9 Residential areas (within the scope of Article 1.3.3.2. of Division A) Stairs within dwelling units | 1.9 Retail and wholesale areas | 4.8 Roofs[1] | 1.0[5] Sidewalks and driveways over areaways and basements[1] | 12.0[5] Storage areas, including locker rooms in apartment buildings | 4.8[4] Toilet areas | 2.4 Underground slabs with earth cover | [5] Warehouses | 4.8[4] Notes to Table 4.1.5.3.: (1) See Note A-Table 4.1.5.3. (2) See Article 4.1.5.6. (3) See Article 4.1.5.4. (4) See Sentence 4.1.5.1.(1). (5) See Article 4.1.5.5.
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OBC Div. B 4.1.5.4. Loads for Occupancy Served
(1)The following shall be designed to carry not less than the specified load required for the occupancy they serve, provided they cannot be used by an assembly of people as a viewing area:
(a)corridors, lobbies and aisles not more than 1,200 mm wide,
(b)all corridors above the first storey of residential areas of apartments, hotels and motels, and
(c)interior balconies and mezzanines.
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OBC Div. B 4.1.5.7. More Than One Occupancy
(1)Where an area of floor or roof is intended for 2 or more occupancies at different times, the value to be used from Table 4.1.5.3. shall be the greatest value for any of the occupancies concerned.
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OBC Div. B 4.1.5.8. Variation With Tributary Area
(1)One- and two-way floor slabs shall have no reduction for tributary area applied to live load.
(2)An area used for assembly occupancies designed for a live load of less than 4.8 kPa and roofs designed for the minimum loading specified in Table 4.1.5.3. shall have no reduction for tributary area.
(3)Where a structural member supports a tributary area of a floor or a roof, or a combination thereof, that is greater than 80 m² and either used for assembly occupancies designed for a live load of 4.8 kPa or more, or used for storage, manufacturing, retail stores, garages or as a footbridge, the specified live load due to use and occupancy is the load specified in Article 4.1.5.3. multiplied by
0.5 + sqrt(20/A)
where A is the tributary area in square metres for this type of use and occupancy.
(4)Where a structural member supports a tributary area of a floor or a roof, or a combination thereof, that is greater than 20 m² and used for any use or occupancy other than those indicated in Sentences (2) and (3), the specified live load due to use and occupancy is the load specified in Article 4.1.5.3. multiplied by
0.3 + sqrt(9.8/B)
where B is the tributary area in square metres for this type of use and occupancy.
(4) Where the specified live load for a floor is reduced in accordance with Sentence (3) or (4), the structural drawings shall indicate that a live load reduction factor for tributary area has been applied and which structural elements are impacted by this factor.
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OBC Div. B Table 4.1.5.9. Specified Concentrated Live Loads on an Area of Floor or Roof
Table 4.1.5.9. — Specified Concentrated Live Loads on an Area of Floor or Roof Forming Part of Sentence 4.1.5.9.(1) Area of Floor or Roof | Minimum Specified Concentrated Load, kN | Loaded Area, mm × mm Roof surfaces | 1.3 | 200 × 200 Floors of classrooms | 4.5 | 750 × 750 Floors of offices, manufacturing buildings, hospital wards and stages | 9.0 | 750 × 750 Floors and areas used by vehicles not exceeding 4,000 kg gross weight | 18 | 120 × 120 Floors and areas used by vehicles exceeding 4,000 kg but not exceeding 9,000 kg gross weight | 36 | 120 × 120 Floors and areas used by vehicles exceeding 9,000 kg gross weight | 54[1] | 250 × 600[1] Driveways and sidewalks over areaways and basements | 54[1] | 250 × 600[1] Notes to Table 4.1.5.9.: (1) See Note A-Table 4.1.5.9.
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OBC Div. B 4.1.5.14. Loads on Guards and Handrails)
(1)The minimum horizontal specified live load applied outward at the minimum required height of every required guard shall be
(a)3.0 kN/m for open viewing stands without fixed seats and for means of egress in grandstands, stadia, bleachers and arenas,
(b)1.0 kN applied at any point, so as to produce the most critical effect, for access ways to equipment platforms, contiguous stairs and similar areas where the gathering of many people is improbable, and
(c)0.75 kN/m or 1.0 kN applied at any point so as to produce the most critical effect, whichever governs for locations other than those described in Clauses (a) and (b).
(2)The minimum horizontal specified live load applied inward at the minimum required height of every required guard shall be half that specified in Sentence (1).
(3)Individual elements within the guard, including solid panels and pickets, shall be designed for a horizontal specified live load of 0.5 kN applied outward over an area of 100 mm by 100 mm located at any point on the element or elements so as to produce the most critical effect.
(4)The size of the opening between any two adjacent vertical elements within a guard shall not exceed the limits required by Part 3 when each of these elements is subjected to a horizontal specified live load of 0.1 kN applied in opposite directions in the in-plane direction of the guard so as to produce the most critical effect.
(5)The specified live loads required in Sentence (3) need not be considered to act simultaneously with the loads provided for in Sentences (1), (2), (6) and (7).
(6)The minimum specified live load applied vertically at the top of every required guard shall be 1.5 kN/m and need not be considered to act simultaneously with the horizontal specified live load provided for in Sentences (1), (3) and (7).
(7)Handrails and their supports shall be designed and constructed to withstand the following minimum specified live loads, which need not be considered to act simultaneously:
(a)0.9 kN applied at any point and in any direction for all handrails, and
(b)0.7 kN/m applied in any direction for handrails not located within dwelling units.
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OBC Div. B 4.1.5.15. Loads on Vehicle Guardrails
(1)Vehicle guardrails shall be designed for a concentrated load of 22 kN applied horizontally outward at any point 500 mm above the floor surface so as to produce the most critical effect. (See Note A-4.1.5.14. and A-4.1.5.15.(1))
(2)The loads required in Sentence (1) need not be considered to act simultaneously with the loads provided for in Article 4.1.5.14.
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OBC Div. B 4.1.5.16. Loads on Walls Acting As Guards
(1)Where the floor elevation on one side of a wall, including a wall around a shaft, is more than 600 mm higher than the elevation of the floor or ground on the other side, the wall shall be designed to resist the appropriate outward lateral design loads prescribed elsewhere in Subsection 4.1.5. or 0.5 kPa acting outward, whichever produces the more critical effect.
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OBC Div. B 4.1.5.17. Firewalls
(1)Firewalls shall be designed to resist the maximum effect due to,
(a)the appropriate lateral design loads prescribed elsewhere in this Section, or
(b)a factored lateral load of 0.5 kPa under fire conditions, as described in Sentence (2).
(2)Under fire conditions, where the fire-resistance rating of the structure is less than that of the firewall,
(a)lateral support shall be assumed to be provided by the structure on one side only, or
(b)another structural support system capable of resisting the loads imposed by a fire on either side of the firewall shall be provided.
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