Division B
Acceptable Solutions

Part 9 — Housing and Small Buildings

Section 9.12. Excavation

9.12.1. General

9.12.1.1. Removal of Topsoil and Organic Matter
1) Intent StatementThe topsoil and vegetable matter in all unexcavated areas under a building shall be removed.
2) Intent StatementIn localities where termite infestation is known to be a problem, all stumps, roots and other wood debris shall be removed from the soil to a depth of not less than 300 mm in unexcavated areas under a building.
3) Intent StatementThe bottom of every excavation shall be free of all organic material.
9.12.1.2. Standing Water
1) Intent StatementExcavations shall be kept free of standing water.
9.12.1.3. Protection from Freezing
1) Intent StatementThe bottom of excavations shall be kept from freezing throughout the entire construction period.

9.12.2. Depth

9.12.2.1. Excavation to Undisturbed Soil
1) Intent StatementExcavations for foundations shall extend to undisturbed soil.
9.12.2.2. Minimum Depth of Foundations
1) Except as provided in change beginSentences (4) to (7)change end, the minimum depth of foundations below finished ground level shall conform to Table 9.12.2.2.

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Table 9.12.2.2.
Minimum Depths of Foundations
Forming part of Sentence 9.12.2.2.(1)

Type of Soil

Minimum Depth of Foundation Containing Heated Basement or Crawl Space(1)

Minimum Depth of Foundation Containing No Heated Space(2)

Good Soil Drainage

Poor Soil Drainage

Good Soil Drainage

Poor Soil Drainage

Rock

 No limit No limit No limit No limit

Coarse grained soils

 No limit No limit No limit Below the depth of frost penetration
Silt No limit No limit

Below the depth of frost penetration(3)

 Below the depth of frost penetration

Clay or soils not clearly defined(4)

1.2 m (3 ft. 11 in.)(3)

1.2 m (3 ft. 11 in.)

1.2 m (3 ft. 11 in.) but not less than the depth of frost penetration(3)

1.2 m (3 ft. 11 in.) but not less than the depth of frost penetration

Notes to Table 9.12.2.2.:
(1) Foundation not insulated to reduce heat loss through the footings.
(2) Including foundations insulated to reduce heat loss through the footings.
(3) Good soil drainage to not less than the depth of frost penetration.
(4) See Appendix A.
2) Intent StatementWhere a foundation is insulated in a manner that will reduce heat flow to the soil beneath the footings, the foundation depth shall conform to that required for foundations containing no heated space. (See Appendix A.)
3) Intent StatementThe minimum depth of foundations for exterior concrete steps with more than 2 risers shall conform to Sentences (1), (2) and (5).
4) Intent StatementConcrete steps with 1 and 2 risers are permitted to be laid on ground level.
5) Intent StatementThe foundation depths required in Sentence (1) are permitted to be decreased where experience with local soil conditions shows that lesser depths are satisfactory, or where the foundation is designed for lesser depths.
6) Intent StatementThe foundation depths required by Sentence (1) do not apply to foundations for
a) buildings
i) that are not of masonry or masonry veneer construction, and
ii) whose superstructure conforms to the requirements of the deformation resistance test in Z240.2.1, “Structural Requirements for Manufactured Homes,” or
b) accessory buildings
i) that are not of masonry or masonry veneer construction,
ii) not more than 1 storey in height,
iii) not more than 55 m2 in building area, and
iv) where the distance from finished ground to the underside of the floor joists is not more than 600 mm.
7) Intent StatementThe foundation depths required by Sentence (1) do not apply to foundations for decks and other accessible exterior platforms
a) of not more than 1 storey,
b) not more than 55 m2 in area,
c) where the distance from finished ground to the underside of the joists is not more than 600 mm,
d) not supporting a roof, and
e) not attached to another structure, unless it can be demonstrated that differential movement will not adversely affect the performance of that structure.
8) Intent StatementWhere decks or other accessible exterior platforms are supported on surface foundations supported on other than coarse-grained soil with good drainage or rock, access to the foundation positions to permit re-levelling of the platform shall be provided
a) by passageways with a clear height under the platform of not less than 600 mm and a width of not less than 600 mm, or
b) by installing the decking in a manner that allows easy removal.

9.12.3. Backfill

9.12.3.1. Placement of Backfill
1) Intent StatementBackfill shall be placed to avoid damaging the foundation wall, the drainage tile, externally applied thermal insulation and waterproofing or dampproofing of the wall.
9.12.3.2. Grading of Backfill
1) Intent StatementBackfill shall be graded to prevent drainage towards the foundation after settling.
9.12.3.3. Deleterious Debris and Boulders
1) Intent StatementBackfill that is within 600 mm of the foundation shall be free of deleterious debris and boulders larger that 250 mm diam. (See Appendix A.)
2) Intent StatementExcept as provided in Sentence (3), backfill shall not contain pyritic material or material that is susceptible to ice lensing in concentrations that will damage the building to a degree that would adversely affect its stability or the performance of assemblies. (See A-9.4.4.4.(1) in Appendix A.)
3) Intent StatementBackfill with material of any concentration that is susceptible to ice lensing is permitted where foundation walls are cast-in-place concrete, concrete block insulated on the exterior or concrete block protected from the backfill by a material that serves as a slip plane. (See A-9.4.4.4.(1) in Appendix A.)

9.12.4. Trenches beneath Footings

9.12.4.1. Support of Footings
1) Intent StatementThe soil in trenches beneath footings for sewers and watermains shall be compacted by tamping up to the level of the footing base, or shall be filled with concrete having a strength not less than 10 MPa to support the footing.