Part 9 application, materials and structural requirements (House)

Last updated October 22, 2026

Values this chapter turns on

minimum specified snow load, Part 9 method: 1 kPa; minimum specified snow load, Part 9 method
max deflection, floor joists and beams: span/360; max deflection, floor joists and beams
min concrete strength, interior floors: 20 MPa; min concrete strength, interior floors
max lumber moisture content at installation: 19%; max lumber moisture content at installation

Sections 9.1, 9.3 and 9.4 set the ground rules for everything else in Part 9: where Part 9 sends you for site issues, what concrete, lumber and sheet metal must be, and the loads, deflections and soil pressures that the prescriptive tables are built on. Expect short lookup questions with exact numbers, plus a few calculations such as a snow load or a deflection limit.

Application of Part 9 and site issues

Part 9 applies as set out in Div. A 1.3.3. (OBC Div. B 9.1.1.1.). Several site issues are handled by single articles:

Overhead wires. Building near existing above-ground electrical conductors brings in Subsection 3.1.20. (OBC Div. B 9.1.1.5.). A building may not be located under the conductors. The horizontal clearance from maximum conductor swing is at least 1 m for 750 V or less, 3 m for over 750 V up to 46 kV, and 3.7 m for over 46 kV up to 69 kV. If the swing of a privately owned line is unknown, use at least 1.8 m (OBC Div. B 3.1.20.1.).
Radon. In three named places (City of Elliot Lake, Township of Faraday, and the geographic Township of Hyman), buildings must keep annual average radon 222 at or below 200 Bq/m³ (OBC Div. B 9.1.1.7.). Soil gas control everywhere else is in 9.13.
Flood plains. Buildings on flood plains are designed to resist hydrostatic pressures and include floodproofing that keeps exits and means of egress usable (OBC Div. B 9.1.1.8.).
Factory-built buildings. A manufactured building is deemed to comply if built to CSA Z240.2.1 (sections not wider than 4.88 m) or CSA A277. Components built away from the factory and the site installation still have to meet the code (OBC Div. B 9.1.1.9.).

Practice this topic

Concrete

Unreinforced concrete must reach these 28-day strengths (OBC Div. B 9.3.1.6.) and water to cementing material ratios (OBC Div. B 9.3.1.7.):

Use	Min. strength	Max. w/c ratio
Garage and carport floors, all exterior flatwork	32 MPa	0.45
Interior floors (not garages or carports)	20 MPa	0.65
All other uses (footings, walls)	15 MPa	0.70

Site-batched concrete for garage floors, carports and exterior flatwork needs 5 to 8% air entrainment. Aggregate in site-batched mixes may not exceed one fifth of the form width or one third of the flatwork thickness. In cold weather (air below 5°C), concrete is kept between 10°C and 25°C while mixed and placed, then at 10°C or more for 72 h, with no frozen material (OBC Div. B 9.3.1.9.).

Practice this topic

Lumber, wood products and metal

Lumber for joists, rafters, trusses and beams, and the uses in Table 9.3.2.1., carries an NLGA grade stamp (OBC Div. B 9.3.2.1.). Loadbearing stud walls need Stud, Standard or No. 2; non-loadbearing studs may be Stud, Utility or No. 3 (Table 9.3.2.1.).
Moisture content is not more than 19% at installation (OBC Div. B 9.3.2.5.).
Members up to 5% undersize may be used if the span table span is cut by 5% (OBC Div. B 9.3.2.8.).
OSB, waferboard and plywood used as sheathing or subfloor must be marked with the maker, the standard and that it is an exterior type (OBC Div. B 9.3.2.4.).

Termites and decay (OBC Div. B 9.3.2.9.):

Situation	Rule
Termite area, untreated wood	at least 450 mm clearance to finished ground, all sides visible
Wood less than 150 mm above finished ground	pressure-treated against decay
Retaining wall or cribbing over 1.2 m high, or supporting soil critical to foundations	pressure-treated wood
Termite area, window well with wood	well bottom at least 150 mm below the wood unless treated

Galvanized sheet steel exposed to weather or used as flashing needs at least a G90 (Z275) zinc coating or AZM150 aluminum-zinc coating (OBC Div. B 9.3.3.2.).

Practice this topic

Structural design limits, specified loads and snow loads

Structural members follow the Part 9 prescriptive rules, or are designed to good engineering practice such as the CWC 2014 guide, or to Part 4 (OBC Div. B 9.4.1.1.). If an engineered floor sits on prescriptive walls or footings, the floor live load is capped at 2.4 kPa. Snow, wind and seismic values come from SB-1.

The Part 9 snow load method applies to light-frame construction with members not more than 600 mm o.c., clear spans not more than 12.2 m and total roof area not more than 4,550 m² (OBC Div. B 9.4.2.1.). The specified snow load is S = Cb × Ss + Sr, where Cb is 0.45 if the whole roof width is not more than 4.3 m and 0.55 otherwise. S may never be less than 1 kPa (OBC Div. B 9.4.2.2.).

Decks and balconies serving a single dwelling unit carry the roof snow load or 1.9 kPa, whichever is greater (OBC Div. B 9.4.2.3.). Ceiling joists or truss bottom chords in residential attics with limited access are designed for at least 0.35 kPa total (OBC Div. B 9.4.2.4.).

Practice this topic

Deflections and foundation conditions

Deflection limits are a fraction of the clear span; dead loads are ignored (OBC Div. B 9.4.3.1.). Key rows from Table 9.4.3.1.:

Member	Limit
Roof members, no ceiling	span/180
Roof members or ceiling joists with plaster or gypsum board ceiling	span/360
Floor joists, beams and decking	span/360
Deck or balcony serving a single dwelling unit	span/240

Allowable bearing pressures for designed footings are in Table 9.4.4.1. (OBC Div. B 9.4.4.1.): dense or compact sand or gravel 150 kPa, loose sand or gravel 50 kPa, stiff clay 150 kPa, firm clay 75 kPa, soft clay 40 kPa, till 200 kPa, sound rock 500 kPa. Section 4.2. must be used for deep foundations or footings on peat, fill or sensitive clay. If a weaker layer lies within twice the footing width below the bearing surface, the weaker soil governs, with load spread at 60° to the horizontal (OBC Div. B 9.4.4.2.). Where the water table is within one footing width below a gravel, sand or silt bearing surface, use 50% of the table value (OBC Div. B 9.4.4.3.).

Practice this topic

Common traps

Using 0.55 for Cb on a narrow roof, or forgetting the 1 kPa minimum.
Applying span/240 to all decks. It applies only to platforms serving a single dwelling unit.
Confusing 15 MPa (footings and walls) with 20 MPa (interior floors).

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
Concrete	Site-batched concrete for garage floors, carports and exterior flatwork needs 5 to 8% air entrainment.
Lumber, wood products and metal	Galvanized sheet steel exposed to weather or used as flashing needs at least a G90 (Z275) zinc coating or AZM150 aluminum-zinc coating.
Structural design limits, specified loads and snow loads	Structural members follow the Part 9 prescriptive rules, or are designed to good engineering practice such as the CWC 2014 guide, or to Part 4. If an engineered floor sits on…
Deflections and foundation conditions	Deflection limits are a fraction of the clear span; dead loads are ignored.

Concrete
Site-batched concrete for garage floors, carports and exterior flatwork needs 5 to 8% air entrainment.
Lumber, wood products and metal
Galvanized sheet steel exposed to weather or used as flashing needs at least a G90 (Z275) zinc coating or AZM150 aluminum-zinc coating.
Structural design limits, specified loads and snow loads
Structural members follow the Part 9 prescriptive rules, or are designed to good engineering practice such as the CWC 2014 guide, or to Part 4. If an engineered floor sits on…
Deflections and foundation conditions
Deflection limits are a fraction of the clear span; dead loads are ignored.

Usual exam traps

Using 0.55 for Cb on a narrow roof, or forgetting the 1 kPa minimum.
Applying span/240 to all decks. It applies only to platforms serving a single dwelling unit.
Confusing 15 MPa (footings and walls) with 20 MPa (interior floors).

Practice this chapter

Questions on Part 9 application, materials and structural requirements, in the exam format, every answer explained and cited to its article. Sign in to start; a free account gets the free questions.

Practice this chapter House calculations

Code cited in this chapter

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

OBC Div. B 9.1.1.1. Application
(1)The application of this Part shall be as described in Subsection 1.3.3. of Division A.
Open OBC Div. B 9.1.1.1. in the code viewer
OBC Div. B 9.1.1.5. Proximity to Existing Above Ground Electrical Conductors
(1)Where a building is constructed in close proximity to existing above ground electrical conductors, the requirements of Subsection 3.1.20. shall apply.
Open OBC Div. B 9.1.1.5. in the code viewer
OBC Div. B 3.1.20.1. Clearance to Buildings
(1)A building shall not be located beneath existing above ground electrical conductors.
(2)The horizontal clearance measured from the maximum conductor swing to the building, including balconies, fire escapes, flat roofs or other accessible projections beyond the face of the building, shall,
(a)be not less than 1 m, for electrical conductors carrying voltages 750 V or less, except where necessary to connect to the electrical wiring of the building,
(b)be not less than 3 m, for electrical conductors carrying voltages greater than 750 V but not exceeding 46 kV,
(c)be not less than 3.7 m, for electrical conductors carrying voltages greater than 46 kV but not exceeding 69 kV, or
(d)conform to the requirements of CAN/CSA-C22.3 No.1, "Overhead Systems," for electrical conductors carrying voltages greater than 69 kV.
(3)Where the swing of an above ground electrical conductor not owned or operated by an electrical supply authority is not known, a swing of not less than 1.8 m shall be used.
(4)Sentences (1) to (3) do not apply to a building containing electrical equipment and electrical installations used exclusively in the generation, transformation or transmission of electrical power or energy intended for sale or distribution to the public.
Open OBC Div. B 3.1.20.1. in the code viewer
OBC Div. B 9.1.1.7. Radon
(1)In addition to all other requirements, a building in the following designated areas shall be designed and constructed so that the annual average concentration of radon 222 does not exceed 200 Bq/m³ of air and the annual average concentration of the short lived daughters of radon 222 does not exceed 0.02 working levels inside the building for,
(a)the City of Elliot Lake in the Territorial District of Algoma,
(b)the Township of Faraday in the County of Hastings, and
(c)the geographic Township of Hyman in the Territorial District of Sudbury.
Open OBC Div. B 9.1.1.7. in the code viewer
OBC Div. B 9.1.1.8. Building in Flood Plains
(1)Buildings constructed on flood plains shall,
(a)be designed and constructed in accordance with good engineering practice to withstand anticipated vertical and horizontal hydrostatic pressures acting on the structure, and
(b)incorporate floodproofing measures that will preserve the integrity of exits and means of egress during times of flooding.
Open OBC Div. B 9.1.1.8. in the code viewer
OBC Div. B 9.1.1.9. Site Assembled and Factory-Built Buildings
(1)Except as provided in Sentence (2) and in Sentence 12.2.1.2.(2), a manufactured building is deemed to comply with this Code if it is designed and constructed in compliance with,
(a)CSA Z240.2.1, "Structural requirements for manufactured homes," if the building is constructed in sections not wider than 4.88 m, or
(b)CSA A277, "Procedure for certification of prefabricated buildings, modules, and panels."
(2)The requirements of this Code shall apply to,
(a)building components designed and constructed outside the place of manufacture, and
(b)site installation of such buildings.
Open OBC Div. B 9.1.1.9. in the code viewer
OBC Div. B 9.3.1.6. Compressive Strength (See also Article 9.12.4.1., Sentence 9.15.4.2.(1) and Article 9.18.6.1.)
(1)Except as provided elsewhere in this Part, the compressive strength of unreinforced concrete after 28 days shall be not less than,
(a)32 MPa for garage floors, carport floors and all exterior flatwork,
(b)20 MPa for interior floors other than those for garages and carports, and
(c)15 MPa for all other applications.
(2)Site-batched concrete used for garage floors, carport floors and exterior flatwork shall have air entrainment of 5 to 8%.
Open OBC Div. B 9.3.1.6. in the code viewer
OBC Div. B 9.3.1.7. Concrete Mixes
(1)For pre-mixed concrete and for the site-batched concrete mixes described in Table 9.3.1.7., the maximum ratio of water to cementing materials measured by weight shall not exceed
(a)0.45 for garage floors, carport floors and all exterior flatwork,
(b)0.65 for interior floors other than those for garages and carports, and
(c)0.70 for all other applications.
(2)The size of aggregate in unreinforced site-batched concrete mixes referred to in Sentence (1) shall not exceed,
(a)1/5 the distance between the sides of vertical forms, or
(b)1/3 the thickness of flatwork.
Open OBC Div. B 9.3.1.7. in the code viewer

Show all 25 articles

OBC Div. B 9.3.1.9. Cold Weather Requirements
(1)When the air temperature is below 5°C, concrete shall be
(a)kept at a temperature of not less than 10°C or more than 25°C while being mixed and placed, and
(b)maintained at a temperature of not less than 10°C for 72 h after placing.
(2)No frozen material or ice shall be used in concrete described in Sentence (1).
Open OBC Div. B 9.3.1.9. in the code viewer
OBC Div. B 9.3.2.1. Grade Marking
(1)Lumber for joists, rafters, trusses and beams and for the uses listed in Table 9.3.2.1. shall be identified by a grade stamp to indicate its grade as determined by the NLGA, "Standard Grading Rules for Canadian Lumber." (See Note A-9.3.2.1.(1))
Open OBC Div. B 9.3.2.1. in the code viewer
OBC Div. B Table 9.3.2.1. Minimum Lumber Grades for Specific End Uses Forming Part of Sentences 9.3.2.1.(1) and 9.3.2.2.(1)
Table 9.3.2.1. — Minimum Lumber Grades for Specific End Uses Forming Part of Sentences 9.3.2.1.(1) and 9.3.2.2.(1) Forming Part of Sentences 9.3.2.1.(1) and 9.3.2.2.(1) Use | Boards, All Species: Paragraph 113 in the NLGA Grading Rules Under Which Boards are Graded[1] | Boards, All Species: Paragraph 114 in the NLGA Grading Rules Under Which Boards are Graded[1] | Boards, Eastern White Pine & Red Pine: Paragraph 118 in the NLGA Grading Rules Under Which Boards are Graded[1] | Framing: All Species Stud wall framing (loadbearing members) | N/A | N/A | N/A | Stud, Standard, No. 2 Stud wall framing (non-loadbearing members) | N/A | N/A | N/A | Stud, Utility, No. 3 Plank frame construction (loadbearing members) | No. 3 Common | N/A | No. 3 Common | No. 2 Plank frame construction (non-loadbearing members) | No. 5 Common | N/A | No. 5 Common | Economy, No. 3 Posts and beams less than 114 mm in thickness | N/A | N/A | N/A | Standard, No. 2 Posts and beams not less than 114 mm in thickness | N/A | N/A | N/A | Standard Roof sheathing | No. 3 Common | Standard | No. 4 Common | N/A Subflooring | No. 3 Common | Standard | No. 3 Common | N/A Wall sheathing when required as a nailing base | No. 4 Common | Utility | No. 4 Common | N/A Wall sheathing not required as a nailing base | No. 5 Common | Economy | No. 5 Common | N/A Notes to Table 9.3.2.1.: (1) See Note A-Table 9.3.2.1.
Open OBC Div. B Table 9.3.2.1. in the code viewer
OBC Div. B 9.3.2.5. Moisture Content
(1)Moisture content of lumber shall be not more than 19% at the time of installation.
Open OBC Div. B 9.3.2.5. in the code viewer
OBC Div. B 9.3.2.8. Undersized Lumber
(1)Joist, rafter, lintel and beam members up to 5% less than the actual Canadian standard sizes are permitted to be used provided the allowable spans for the grade and species of lumber under consideration are reduced 5% from those shown in the Span Tables for full size members. (See Note A-9.3.2.8.(1))
Open OBC Div. B 9.3.2.8. in the code viewer
OBC Div. B 9.3.2.4. OSB, Waferboard and Plywood Marking
(1)OSB, waferboard and plywood used for roof sheathing, wall sheathing and subflooring shall be legibly identified on the face of the material indicating,
(a)the manufacturer of the material,
(b)the standard to which it is produced, and
(c)that the material is of an exterior type.
Open OBC Div. B 9.3.2.4. in the code viewer
OBC Div. B 9.3.2.9. Termite and Decay Protection
(1)In localities where termites are known to occur,
(a)clearance between structural wood elements and the finished ground level directly below them shall be not less than 450 mm and, except as provided in Sentence (2), all sides of the supporting elements shall be visible to permit inspection, or
(b)structural wood elements, supported by elements in contact with the ground or exposed over bare soil, shall be pressure-treated with a chemical that is toxic to termites. (See Note A-9.3.2.9.(1))
(2)In localities where termites are known to occur and foundations are insulated or otherwise finished in a manner that could conceal a termite infestation,
(a)a metal or plastic barrier shall be installed through the insulation and any other separation or finish materials above finished ground level to control the passage of termites behind or through the insulation, separation or finish materials, and
(b)all sides of the finished supporting assembly shall be visible to permit inspection.
(3)Structural wood elements shall be pressure-treated with a preservative to resist decay where the vertical clearance between structural wood elements and the finished ground level is less than 150 mm. (See Note A-9.3.2.9.(3))
(3.1)In localities where termites are known to occur and where windows or other openings at or below grade contain wood elements, the bottom of window wells or adjacent ground shall be at least 150 mm below the nearest wood unless the wood is pressure-treated with a chemical toxic to termites.
(4)Structural wood elements used in retaining walls and cribbing shall be pressure-treated with a preservative to resist decay, where
(a)the retaining wall or cribbing supports ground that is critical to the stability of building foundations, or
(b)the retaining wall or cribbing is greater than 1.2 m in height. (See Note A-9.3.2.9.(4))
(5)Where wood is required by this Article to be treated to resist termites or decay, such treatment shall be in accordance with Table 2, "Use Categories for Specific Products, Uses, and Exposures," of CAN/CSA-O80.1, "Specification of treated wood," as follows:
(a)Use Category 1 (UC1), where the wood member is used in
(i)interior construction,
(ii)above-ground applications, and
(iii)applications where the wood member remains dry,
(b)Use Category 2 (UC2), where the wood member is used in
(i)interior construction,
(ii)above-ground applications, and
(iii)applications where the wood member may be subjected to occasional sources of moisture,
(c)Use Category 3.2 (UC3.2), where the wood member is used in
(i)exterior construction,
(ii)above-ground applications, and
(iii)applications where the wood member is uncoated or is used in a configuration conducive to moisture accumulation,
(d)Use Category 4.1 (UC4.1), where
(i)the wood member is used in contact with the ground,
(ii)the wood member is used in contact with fresh water, or
(iii)the vertical clearance between the wood element and the finished ground level is less than 150 mm and the wood elements are not separated from permeable supporting materials by a moisture barrier, or
(e)Use Category 4.2 (UC4.2), where the wood member is used in critical structural components, including permanent wood foundations.
(6)Where wood is protected in accordance with UC1 or UC2 using an inorganic boron preservative, the wood shall be
(a)protected from direct exposure to water during and after the completion of construction, and
(b)separated from permeable supporting materials by a moisture barrier that is resistant to all expected mechanisms of deterioration in the service environment if the vertical clearance to the ground is less than 150 mm.
(7)Wood that is required by this Article to be treated to resist termites or decay shall be identified by a mark to indicate the type of preservative used and conformance to the relevant required Use Category.
Open OBC Div. B 9.3.2.9. in the code viewer
OBC Div. B 9.3.3.2. Galvanized Sheet Steel
(1)Where sheet steel is required to be galvanized, it shall be metallic-coated with zinc or an alloy of 55% aluminum-zinc meeting the requirements of
(a)ASTM A653 / A653 M, "Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process," or
(b)ASTM A792 / A792 M, "Standard Specification for Sheet Steel, 55% Aluminum-Zinc Alloy-Coated by the Hot-Dip Process."
(2)Where galvanized sheet steel is intended for use in locations exposed to the weather or as a flashing material, it shall have a zinc coating not less than the G90 (Z275) coating designation or an aluminum-zinc alloy coating not less than the AZM150 coating designation, as referred to in Sentence (1).
Open OBC Div. B 9.3.3.2. in the code viewer
OBC Div. B 9.4.1.1. General
(1)Subject to the application limitations defined elsewhere in this Part, structural members and their connections shall
(a)conform to requirements provided elsewhere in this Part,
(b)be designed according to good engineering practice such as provided in the CWC 2014, "Engineering Guide for Wood Frame Construction," or
(c)be designed according to Part 4 using the loads and deflection and vibration limits specified in,
(i)this Part, or
(ii)Part 4.
(2)Where floor framing is designed in accordance with Clause (1)(b) or (c) and where supporting wall framing and fastenings, or footings, are designed according to Clause (1)(a), the maximum specified live load on the floor according to Table 4.1.5.3. shall not exceed 2.4 kPa.
(3)Location-specific information for structural design, including snow and wind loads and seismic spectral response accelerations, shall be determined according to MMAH Supplementary Standard SB-1, "Climatic and Seismic Data." (See Note A-9.4.1.1.(3))
Open OBC Div. B 9.4.1.1. in the code viewer
OBC Div. B 9.4.2.1. Application
(1)This Subsection applies to light-frame construction whose wall, floor and roof planes are generally comprised of frames of small repetitive structural members, and where
(a)the roof and wall planes are clad, sheathed or braced on at least one side,
(b)the small repetitive structural members are spaced not more than 600 mm o.c.,
(c)the clear span of any structural member does not exceed 12.2 m,
(d)the maximum deflection of the structural roof members conforms to Article 9.4.3.1.,
(e)the maximum total roof area, notwithstanding any separation of adjoining buildings by firewalls, is 4,550 m², and
(f)for flat roofs, there are no significant obstructions on the roof, such as parapet walls, spaced closer than the distance calculated by
D_0 = 10(H_0 - 0.8S_s/γ)
where
D_o = minimum distance between obstructions, m,
H_0 = height of the obstruction above the roof, m,
S_s = ground snow load, kPa, and
γ = specific weight of snow taken as 4.0kN/m^3or 0.43S_s + 2.2kN/m^3,whichever is lesser.
Open OBC Div. B 9.4.2.1. in the code viewer
OBC Div. B 9.4.2.2. Specified Snow Loads
(1)Except as provided in Sentences (2) and (4), specified snow loads shall be not less than those calculated using the following formula:
S = C_bS_s + S_r
where
S = specified snow load,
C_b = basic snow load roof factor, which is 0.45 where the entire width of a roof does not exceed 4.3 m and 0.55 for all other roofs,
S_s = 1 -in-50 year ground snow load in kPa, determined according to MMAH Supplementary Standard SB-1, "Climatic and Seismic Data," and
S_r = associated 1-in-50 year rain load in kPa, determined according to MMAH Supplementary Standard SB-1, "Climatic and Seismic Data."
(2)In no case shall the specified snow load be less than 1 kPa.
(3)Bow string, arch or semi-circular roof trusses having an unsupported span greater than 6 m shall be designed in conformance with the snow load requirements in Subsection 4.1.6.
(4)Where the height of a roof step at the intersection of an upper level roof and a lower level roof is greater than 2 m, and the upper level roof has a slope less than 1 in 6 and an area greater than 600 m², the specified snow load on the lower level roof shall be
(a)for distances from the roof step that are less than or equal to the drift length, x_d , calculated in accordance with Sentence (5), not less than 1.5 times the specified snow load, S, calculated using the formula in Sentence (1) with C_b equal to 0.55, and
(b)for distances from the roof step that are greater than the drift length, x_d , calculated in accordance with Sentence (5), as specified in Sentence (1).
(5)For the purposes of Sentence (4), the drift length, x_d , in m, shall be calculated as follows:
x_rmd = 5(h - (0.55S_rms)/(γ))
where
h = height of the roof step, in m, and
γ = specific weight of snow as specified in Clause 9.4.2.1.(1)(f).
Open OBC Div. B 9.4.2.2. in the code viewer
OBC Div. B 9.4.2.3. Platforms Subject to Snow and Occupancy Loads
(1)Balconies, decks and other accessible exterior platforms intended for an occupancy and subject to snow loads shall be designed to carry the specified roof snow load or 1.9 kPa, whichever is greater, where the platform, or each segregated area of the platform, serves a single dwelling unit. (See Note A-9.4.2.3.(1))
Open OBC Div. B 9.4.2.3. in the code viewer
OBC Div. B 9.4.2.4. Attics and Roof Spaces
(1)Ceiling joists or truss bottom chords in residential attic or roof spaces having limited accessibility that precludes the storage of equipment or material shall be designed for a total specified load of not less than 0.35 kPa, where the total specified load is the sum of the specified dead load plus the specified live load of the ceiling. (See Note A-9.4.2.4.(1))
Open OBC Div. B 9.4.2.4. in the code viewer
OBC Div. B 9.4.3.1. Deflections
(1)The maximum deflection of structural members shall conform to Table 9.4.3.1.
(2)Dead loads need not be considered in computing deflections referred to in Sentence (1).
Open OBC Div. B 9.4.3.1. in the code viewer
OBC Div. B 9.4.4.1. Allowable Bearing Pressures
(1)Footing sizes for shallow foundations shall be
(a)determined in accordance with Section 9.15., or
(b)designed in accordance with Section 4.2. using,
(i)the maximum allowable bearing pressures in Table 9.4.4.1., or
(ii)allowable bearing pressures determined from subsurface investigation.
(2)The design procedures described in Section 4.2. are permitted to be used in lieu of the design procedures in this Subsection.
(3)The design procedures described in Section 4.2. shall be used where,
(a)deep foundations are used,
(b)the footing size falls outside the scope of this Section, or
(c)the foundation is constructed on peat, filled ground or on sensitive clays as described in Article 9.15.1.1.
Open OBC Div. B 9.4.4.1. in the code viewer
OBC Div. B 9.4.4.2. Foundation Capacity in Weaker Soil and Rock
(1)Where a soil or rock within a distance equal to twice the footing width below the bearing surface has a lower allowable bearing pressure than that at the bearing surface as shown in Article 9.4.4.1., the design capacity of the foundation shall not be greater than would cause the weakest soil or rock to be stressed beyond its allowable bearing pressure.
(2)In calculating subsurface pressures referred to in Sentence (1), the loads from the footings shall be assumed to be distributed uniformly over a horizontal plane within a frustum extending downward from the footing at an angle of 60° to the horizontal.
Open OBC Div. B 9.4.4.2. in the code viewer
OBC Div. B 9.4.4.3. High Water Table
(1)Where a foundation bears on gravel, sand or silt, and the water table is within a distance below the bearing surface equal to the width of the foundation, the allowable bearing pressure shall be 50% of that determined in Article 9.4.4.1.
Open OBC Div. B 9.4.4.3. in the code viewer