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There are certain regulations, contained in SANS 10400:1990 part H, regarding foundations. Let us consider these.

• General requirement (SANS 10400:1990 Regulation H1)
• The foundation of any building shall be designed to safely transmit all the loads from such building to the ground.
  The requirement of sub-regulation (1) shall be deemed to be satisfied where the design and construction of such foundation complies with Part H of section 3 of SANS 10400:1990.

Deemed-to-satisfy rules (SANS 10400:1990 Sub-regulation HH1 – General)

The regulation contained in Part H of the National Building Regulations shall be deemed to be satisfied where:

• any foundation is the subject of a rational design in accordance with the requirements contained in Part B; or
• the construction of any foundation complies with deemed-to-satisfy rules contained in the following provisions of this Part.

Building design requirements (SANS 10400:1990 Regulation H1)

Any building and any structural element or component shall be so designed, having regard to accepted principles of structural design, that it will safely sustain, without exceeding the safety and other limitations applicable to the design used, the loads to which it is likely to be subjected without impairing the strength, stability or serviceability of such building or any other building or property or causing a danger to life.

Empirical rules for foundations (SANS 10400:1990 Sub-regulation HH2.1)

Any foundation constructed in accordance with sub-rules HH2.2 to HH2.8 inclusive shall not be used to support any wall forming part of the structural system of any building except where:

• such wall is placed centrally on such foundation;
• such wall is the wall of any building contemplated in rule KK2 of this code;
• the soil supporting such foundation is not a heaving soil or shrinkable clay and/or a soil with a collapsible fabric.

Foundation concrete (SANS 10400:1990 Sub-regulation HH2.2)

Any such foundation shall be constructed in concrete having compressive strength of not less than 10 MPa at 28 days, or be mixed in proportions by volume of 1 part of cement, 4 parts of sand and 5 parts of coarse aggregate.

Thickness of foundation (SANS 10400:1990 Sub-regulation HH2.3)

Any continuous strip foundation shall have a thickness of not less than 200 mm: provided that where the foundation is laid on solid rock such a thickness shall not apply.

Width of foundation (SANS 10400: 1990 Sub-regulation HH2.4)

The width of any continuous strip foundation shall not be less than:

• 600 mm in the case of a foundation to a load-bearing or free-standing masonry wall or to a timber-framed wall supporting a roof with Class B covering contemplated in sub-rule LL3.4 of this code; or
• 400 mm in the case of a foundation to a non load-bearing internal masonry wall or to a timber-framed wall supporting a roof with Class A or C covering contemplated in sub-rule LL3.4 of this code.

Steps in foundation concrete (SANS 10400:1990 Sub-regulation HH2.5)

Concrete floor slab (SANS 10400:1990 Sub-regulation HH2.6)

Where any concrete floor slab is thickened to form a foundation:

• the thickness, including that of such floor slab, shall be not less than that required for continuous strip foundation; and
• the width of the thickened portion below such floor slab shall be not less than that required for a continuous strip foundation: provided that such thickening shall not be required under non load-bearing timber-framed wall.

Wall thickness (SANS 10400:1990 Sub-regulation HH2.7)

• Where any pier is built into or forms part of any wall, the thickness of the foundation to such pier shall be the same as that required for such wall.
• The length and width of the foundation to such pier shall be such as to project by 200 mm at any point on the perimeter of such pier, as shown in Figure 2.13.

Figure 2.13

Plan layout of a pier foundation

Thickness of foundation to any sleeper pier (SANS 10400:1990 Sub-regulation HH2.8)

• The thickness of the foundation to any sleeper pier or sleeper wall shall be not less than 150 mm.
• The length or width of the foundation to such sleeper pier shall be not less than 450 mm.
• The width of the foundation to such sleeper wall shall be not less than 300 mm.

Non load-bearing foundations (SANS 10400:1990 Regulation H)

Non load-bearing foundations according to SANS 10400 are for internal and partition walls. They do not carry the weight of the roof structure.

Figure 2.14, below, shows the typical non load-bearing foundations recommended by the National Building Regulations. These foundations are for internal and partition walls.

Figure 2.14

Non load-bearing foundations

Load-bearing foundations (SANS 10400:1990 Regulation H)

Load-bearing foundations are for external, internal and freestanding loadbearing walls. Figure 2.15 below and on the next page shows the typical loadbearing foundations recommended by the National Building Regulations.

Figure 2.15

Load-bearing foundations

Figure 2.15

Load-bearing foundations

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