9.23.13. Bracing to Resist Lateral Loads Due to Wind and Earthquake

9.23.13. Bracing to Resist Lateral Loads Due to Wind and Earthquake (See Note A-9.23.13.)
9.23.13.1. Requirements for Low to Moderate Wind and Seismic Forces (See Note A-9.23.13.1.)
  1. This Article applies in locations where the seismic spectral response acceleration, Sa(0.2), is not more than 0.70 and the 1-in-50 hourly wind pressure is less than 0.80 kPa.
  2. Bracing to resist lateral loads shall be designed and constructed as follows:
    1. exterior walls shall be
      1. clad with panel-type cladding in accordance with Section 9.27.,
      2. sheathed with plywood, OSB, waferboard, fibreboard, gypsum board or diagonal lumber sheathing complying with Subsection 9.23.17. and fastened in accordance with Table 9.23.3.5.-A, or
      3. finished on the interior with a panel-type material in accordance with the requirements of Section 9.29., or
    2. in accordance with
      1. Articles 9.23.13.4. to 9.23.13.7.,
      2. Part 4, or
      3. good engineering practice such as that provided in CWC 2014, "Engineering Guide for Wood Frame Construction."
9.23.13.2. Requirements for High Wind and Seismic Forces
  1. Except as provided in Article 9.23.13.1., this Article applies in locations where
    1. the seismic spectral response acceleration, Sa(0.2), is greater than 0.70 but not more than 1.8 and
      1. the lowest exterior frame wall supports not more than 1 floor in buildings of heavy construction (see Note A-9.23.13.2.(1)(a)(i)), or
      2. the lowest exterior frame wall supports not more than 2 floors in other types of construction, and
    2. the 1-in-50 hourly wind pressure is less than 1.20 kPa.
  2. Bracing to resist lateral loads shall be designed and constructed in accordance with
    1. Articles 9.23.13.4. to 9.23.13.7.,
    2. Part 4, or
    3. good engineering practice such as that provided in CWC 2014, "Engineering Guide for Wood Frame Construction."
9.23.13.3. Requirements for Extreme Wind and Seismic Forces
  1. Except as provided in Articles 9.23.13.1. and 9.23.13.2., this Article applies in locations where
    1. the seismic spectral response acceleration, Sa(0.2), is
      1. greater than 1.8,
      2. greater than 0.70 and the lowest exterior framewall supports more than 2 floors in buildings of light construction, or
      3. greater than 0.70 and the lowest exterior framewall supports more than 1 floor in buildings of heavy construction, or
    2. the 1-in-50 hourly wind pressure is equal to or greater than 1.20 kPa.
  2. Bracing to resist lateral loads shall be designed and constructed in accordance with
    1. Part 4, or
    2. good engineering practice such as that provided in CWC 2014, "Engineering Guide for Wood Frame Construction."
9.23.13.4. Braced Wall Bands
(See Note A-9.23.13.4.)
  1. Braced wall bands shall
    1. be full storey height,
    2. be not more than 1.2 m wide,
    3. lap at both ends with another braced wall band,
    4. be aligned with braced wall bands on storeys above and below, and
    5. conform to the spacing and dimensions given in Table 9.23.13.5.
  2. The perimeter of the building shall be located within braced wall bands.
  3. For split-level buildings, a braced wall band shall be located where there is a change in floor level greater than the depth of one floor joist.
9.23.13.5. Braced Wall Panels in Braced Wall Bands
  1. Except as provided in Sentences (2) to (5) and Article 9.23.13.7., braced wall panels shall
    1. be located within braced wall bands,
    2. extend, as applicable, from the top of the supporting footing, slab or subfloor to the underside of the floor, ceiling or roof framing above, and
    3. conform to the spacing and dimensions given in Table 9.23.13.5.

      Table 9.23.13.5.
      Spacing and Dimensions of Braced Wall Bands and Braced Wall Panels
      Forming Part of Sentences 9.23.13.4.(1) and 9.23.13.5.(1)

      Table 9.23.13.5. Spacing and Dimensions of Braced Wall Bands and Braced Wall Panels


      Notes to Table 9.23.13.5.:
      (1) See Note A-Table 9.23.13.5.
      (2) All constructions include support of a roof load in addition to the indicated number of floors.
      (3) See Article 9.23.13.7. for alternative methods of compliance.
      (4) See Sentence 9.23.13.3.(1) for overall limit on application to heavy construction.

  2. In basements or crawl spaces where the perimeter foundation walls extend from the footings to the underside of the supported floor, braced wall bands constructed with braced wall panels shall be spaced not more than
    1. 15 m from the perimeter foundation walls,
    2. 15 m from interior foundation walls, and
    3. 15 m from adjacent braced wall bands constructed with braced wall panels. (See Note A-9.23.13.5.(2).)
  3. Portions of the perimeter of a single open or enclosed space need not comply with Sentence (1), where
    1. the roof of the space projects not more than
      1. 3.5 m from the face of the framing of the nearest parallel braced wall band, and
      2. half the perpendicular plan dimension,
    2. that portion of the perimeter structure does not support a floor, and
    3. the roof of the space is
      1. integral with the roof of the rest of the building with framing members not more than 400 mm o.c., or
      2. constructed with roof framing not more than 400 mm o.c. fastened to the wall framing (see Table 9.23.3.4. and Article 9.23.9.1. for balloon framing). (See Note A-9.23.13.5.(3).)
  4. Walls in detached garages and in accessory buildings serving a single dwelling unit, and the front wall of attached garages serving a single dwelling unit need not comply with Sentence (1) where these walls do not support a floor.
  5. Braced wall panels in the braced wall band at the front of an attached garage serving a single dwelling unit need not comply with Sentence (1), provided
    1. the maximum spacing between the front of the garage and the back wall of the garage does not exceed 7.6 m,
    2. there is not more than one floor above the garage,
    3. not less than 50% of the length of the back wall of the garage is constructed of braced wall panels, and
    4. not less than 25% of the length of the side walls is constructed of braced wall panels.
9.23.13.6. Materials in Braced Wall Panels
  1. Required braced wall panels shall be
    1. clad with panel-type cladding complying with Section 9.27. and Table 9.23.3.4.,
    2. sheathed with plywood, OSB, waferboard or diagonal lumber sheathing complying with Subsection 9.23.16. and Table 9.23.13.6., and fastened in accordance with Article 9.23.3.5., or
    3. finished on the interior with a panel-type material in accordance with the requirements of Section 9.29. and Table 9.23.13.6.

      Table 9.23.13.6.
      Minimum Thicknesses of Cladding, Sheathing or Interior Finish for Braced Wall Panels
      Forming Part of Sentence 9.23.13.6.(1)


      Notes to Table 9.23.13.6.:
      (1) See Sentences (5) and (6).

  2. Except as provided in Sentence (3), required interior braced wall panels shall be
    1. sheathed or finished on both sides with a wood-based material, or
    2. finished on both sides with gypsum board.
  3. Required interior braced wall panels of wood-based material may be sheathed on one side only, provided
    1. the sheathing material is plywood, OSB or waferboard, and
    2. the maximum spacing of fasteners along the edge is half of the maximum spacing shown in Table 9.23.3.5.-B.
  4. For stacked braced wall bands, where the construction of any one braced wall panel is required to be of a wood-based material, a wood-based material shall be installed in all the required braced wall panels in that braced wall band.
  5. Gypsum board interior finish shall not be considered as an acceptable sheathing material to provide the required bracing in exterior walls. (See Note A-9.23.13.6.(5) and (6).)
  6. At braced wall band spacing intervals of not more than 15 m, braced wall panels shall be constructed with OSB, plywood or diagonal lumber. (See Note A-9.23.13.6.(5) and (6).)
9.23.13.7. Additional System Considerations
  1. Except as provided in Sentences (2) and (3), one exterior wall of the uppermost storey in each orthogonal direction may be set back from the exterior wall of the storey below, provided the adjacent interior braced wall band of the storey below the setback
    1. is spaced not more than 10.6 m from the exterior wall of the storey below the setback wall,
    2. consists of braced wall panels that are constructed of a wood-based material in conformance with Sentence 9.23.13.6.(2),
    3. extends to the foundation, and
    4. is not taken into consideration when providing braced wall panels constructed of a wood-based material at spacing intervals of not more than 15 m as per Sentence 9.23.13.6.(6).
  2. Where the exterior wall of the uppermost storey is set back from the exterior wall of the storey below, the roof and floor space supporting the setback wall shall be sheathed with a wood-based material between the exterior wall of the storey below the setback and the adjacent interior braced wall bands of the storey below the setback.
  3. Where the exterior wall of the uppermost storey is set back from the exterior wall of the storey below, the exterior walls perpendicular to the setback wall shall
    1. have their top plate connected with nails that are spaced at no greater than half the spacing required in Table 9.23.3.4., and
    2. have their top plate splices fastened with twice the number of nails specified in Sentences 9.23.11.4.(4) and (5).
  4. The maximum distance between adjacent required braced wall panels in a braced wall band, measured from the edge of the panels, may be increased to 7.3 m provided that, throughout the height of the building, the length of any braced wall panel within the braced wall band is not less than 1.2 m.
  5. The maximum spacing between the centre lines of required braced wall bands given in Table 9.23.13.5. may be increased from 7.6 m to no more than 10.6 m, provided that the interior braced wall band whose spacing is being increased is replaced with an interior braced wall band that
    1. consists of braced wall panels that are constructed of a wood-based material in conformance with Sentence 9.23.13.6.(2),
    2. extends to the foundation, and
    3. is not taken into consideration when providing braced wall panels constructed of a wood-based material at spacing intervals no greater than 15 m as per Sentence 9.23.13.6.(6).
  6. For each orthogonal direction of the building, the length of required braced wall panels of one exterior wall given in Table 9.23.13.5. may be reduced from 40% to no less than 25% of the length of the braced wall band, provided an additional parallel and adjacent interior braced wall band is constructed that
    1. is spaced not more than 10.6 m from the exterior wall,
    2. consists of braced wall panels that are constructed of a wood-based material in conformance with Sentence 9.23.13.6.(2) and whose lengths sum to no less than 25% of the length of the braced wall band,
    3. extends to the foundation, and
    4. is not taken into consideration when providing braced wall panels constructed of a wood-based material at spacing intervals no greater than 15 m as per Sentence 9.23.13.6.(6).
  7. Where the length of required braced wall panels of an exterior wall is reduced as described in Sentence (6), the ratio of the length of braced wall panels in the respective upper braced wall bands to the length of braced wall panels in the reduced exterior braced wall band shall not exceed 2.

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