SANS 10400-B and SANS 10400-H are the structure and foundation Parts. Part B sets the structural design and rational design requirements and acts as the gateway: stay inside its empirical limits and you can use the simpler rules in Parts K, H and L; go outside them and you need a competent person for structures. Part H covers foundations, with empirical rules for strip foundations under single-storey masonry buildings on stable soil. SANS is the South African National Standard, published by the SABS, the South African Bureau of Standards, under the National Building Regulations and Building Standards Act 103 of 1977 (the NBR, or the Act).
A plain caveat first, because it matters most on this Part. The SABS full texts of SANS 10400-B and -H are paywalled. The foundation dimensions and soil classes below come from public secondary summaries (one of which reproduces the older SABS 0400:1990 empirical rules) and from publicly available Part H material, not the full current SABS text. The 2012 editions contain extra soil-class design tables and geotechnical requirements that are not fully reproduced in public sources. Treat everything here as an orientation, not a compliance spec. Confirm the exact current values with your local authority and the SABS SANS 10400-B and -H text before you build or submit plans.
What these Parts cover
- Part B sets out how loads (called actions) are represented, the structural design rules, and when you must move to a rational design. It is the gateway standard for the empirical rules in the trade Parts.
- Part H covers foundations: the strip-foundation empirical rules for single-storey masonry on stable soil, and the soil-class system that tells you whether those simple rules even apply to your site.
The brief notes Part B was approved in August 2012 and Part H in August 2012, both aligned to the 2008 NBR amendments. Confirm the current editions with the SABS.
Key requirements (plain English)
Keep the caveat above in mind. These are orientation values from public summaries, with the 1990-era origin flagged where it applies.
Soil classes. Part H expects a site inspection by a competent person (geotechnical) who classifies the ground. The brief sets out a simplified picture: rock is stable with very low movement; H1 and H2 soils are lightly to moderately expansive with low to moderate movement; H3 is highly expansive clay or collapsible soil where an engineer is mandatory; S soils are soft or collapsible sands that settle when wet; C soils are compressible (peat, fill, soft alluvium); and D is dolomite, where dissolution risk makes an engineer mandatory. The basic empirical foundation rules below apply only to Class H1 and H2 sites or better, where the soil is stable and there is no sign of heaving or shrinkage.
Strip foundation empirical rules (stable soil only). Drawn from the secondary summary that reproduces the 1990 empirical rules, so treat them as orientation and confirm against the current SABS text:
- Minimum concrete strength of 10 MPa at 28 days, or a 1:4:5 cement:sand:stone mix by volume.
- Minimum strip thickness of 200 mm, unless founded on solid rock.
- A width of at least 600 mm under a load-bearing or freestanding masonry wall, or a tiled or thatched timber-framed wall.
- A width of at least 400 mm under a non-load-bearing internal wall or a metal or fibre-cement-sheet timber-framed wall.
- For stepped foundations, the higher portion must lap over the lower portion by at least the foundation thickness.
- A sleeper pier or wall footing of at least 150 mm thickness, with a width of at least 450 mm for a pier and 300 mm for a wall, and a pier footing projecting at least 200 mm on all sides of the pier perimeter.
Imposed load limits for the empirical rules. The empirical masonry rules in Parts K and H apply where imposed floor loads do not exceed 3,0 kN per square metre. That covers dwelling rooms, bedrooms, offices, corridors, classrooms and light institutional uses. Heavier uses such as storage, filing rooms, banking halls and library shelving go over that limit and need engineer design.
When you need a competent person
The structural competent person, an engineer or a suitably qualified architect, owns structural compliance, and the building contractor is responsible for building correctly to the approved drawings.
You must move off the empirical rules and into rational design by a registered geotechnical or structural engineer where you are on soil classes H3, S, C or D, or on any site where subsurface investigation reveals fill, soft ground, waterlogged conditions or trees close by. A geotechnical report is also expected where the local authority has flagged the area as dolomite, highly expansive clay or collapsible sand. A double-storey building always needs structural engineer input, whatever the soil class.
Common mistakes
- Sizing foundations from the old 1990 rules on reactive (H3) soil without a geotechnical investigation.
- No geotechnical report where the council has identified the area as dolomite, highly expansive clay or collapsible sand.
- A thickened slab used as a foundation where the total thickness does not meet the 200 mm minimum.
- A stepped foundation with too little overlap, where the higher section must lap the lower by at least the foundation thickness.
- Pier footings not projecting at least 200 mm on all sides.
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