The Ontario Building Code | Minimum Depth of Foundations

9.12.2.2. Minimum Depth of foundations

(1) Except as provided in Sentences (4) to (7), the minimum depth of foundationsbelow 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)

Item	Column 1	Column 2	Column 3	Column 4	Column 5
	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
1.	Rock	No limit	No limit	No limit	No limit
2.	Coarse grained soils	No limit	No limit	No limit	Below the depth of frost penetration
3.	Silt	No limit	No limit	Below the depth of frost penetration(3)	Below the depth of frost penetration
4.	Clay or soils not clearly defined	1.2 m(3)	1.2 m	1.2 m but not less than the depth of frost penetration(3)	1.2 m 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 foundationscontaining heated space insulated to reduce heat loss through the footings.

⁽³⁾ Good soildrainage to not less than the depth of frost penetration.

(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.

(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) Thefoundation depths required in Sentence (1) are permitted to be decreased where experience with local soilconditions shows that lesser depths are satisfactory, or where the foundation is designed for lesser depths.

(6) Thefoundation 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 the finished ground to the underside of the floor joists is not more than 600 mm.

(7) Thefoundation depths required in Sentence (1) do not apply to foundations for decks and other accessible exterior platforms,

(a) that are of not more than 1 storey,

(b) that are not more than 55 m² in area,

(c) where the distance from the finished ground to the underside of the floor joists is not more than 600 mm,

(d) that are not supporting a roof, and

(e) that are not attached to another structure, unless it can be demonstrated that differential movement will not adversely affect the performance of that structure.

9.12.3. Backfill