Section 9.12 — Excavation

(1) The topsoil and vegetable matter in all unexcavated areas under a building shall be removed. (2) In 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) The bottom of every excavation shall be free of all organic material.

(1) Excavations shall be kept free of standing water.

(1) The bottom of excavations shall be kept from freezing throughout the entire construction period.

(1) Every excavation shall be undertaken in such a manner to prevent damage to adjacent property, existing structures, utilities, roads and sidewalks at all stages of construction. (2) Material shall not be placed nor shall equipment be operated or placed in or adjacent to an excavation in a manner that may endanger the integrity of the excavation or its supports.

(1) Excavations for foundations shall extend to undisturbed soil.

(1) Except as provided in Sentences (4) to (7), the minimum depth of foundations below finished ground level shall conform to Table 9.12.2.2. Table 9.12.2.2. Minimum Depths of Foundations Forming Part of Sentence 9.12.2.2.(1) Minimum Depth of Foundation Containing Minimum Depth of Foundation Containing Type of Soil Heated Basement or Crawl Space(1) 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 Below the depth of frost Coarse grained soils No limit No limit No limit penetration Below the depth of frost Below the depth of frost Silt No limit No limit penetration(3) penetration Clay or soils not 1.2 m but not less than the 1.2 m but not less than the 1.2 m(3) 1.2 m clearly defined(4) depth of frost penetration(3) 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 Note A-Table 9.12.2.2. (2) Where a foundation is insulated in a manner that will reduce the heat flow to the soil beneath the footings, the foundation depth shall conform to that required for foundations containing no heated space. (See Note A-9.12.2.2.(2)) (3) The minimum depth of foundations for exterior concrete steps with more than 2 risers shall conform to Sentences (1), (2) and (5). (4) Concrete steps with 1 and 2 risers are permitted to be laid on ground level. (5) The 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) The foundation depths required in 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 with the requirements of the deformation resistance test in CSA 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 building 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) The 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 floor 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.

(1) Backfill shall be placed to avoid damaging the foundation wall, the drainage tile, drainage layer, externally applied thermal insulation, waterproofing and dampproofing of the wall.

(1) Backfill shall be graded to prevent drainage towards the foundation after settling.

(1) Backfill that is within 600 mm of the foundation shall be free of deleterious debris and boulders larger than 250 mm diam. (See Note A-9.12.3.3.(1)) (2) Except as permitted 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 separating dissimilar environments. (See Note A-9.4.4.4.(1)) (3) Backfill with material of any concentration that is susceptible to ice lensing is permitted where foundation walls are (a) cast-in-place concrete, (b) concrete block insulated on the exterior, or (c) concrete block protected from the backfill by a material that serves as a slip plane. (See Note A-9.4.4.4.(1))

(1) Where the height of foundation wall is such that lateral support is required, or where the required concrete strength of the wall has not been reached, the wall shall be braced or laterally supported before backfilling.

(1) The 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.