About this calculator
A foundation takeoff for a house: trench excavation, strip footing concrete, foundation brickwork up to the damp-proof course, mortar and DPC, using SANS 10400-H widths.
How it’s calculated
Footing area = external and load-bearing wall length × 0.6 m + internal non-load-bearing wall length × 0.4 m. Concrete = footing area × thickness, plus waste; excavation = footing area × trench depth.
Foundation walls run from the top of the footing to the damp-proof course, which SANS 10400-K puts at least 150 mm above the finished ground, so their height = trench depth − footing thickness + DPC height. Bricks are 104 per m² for a double-brick wall and 52 per m² for single brick, plus 5%. Mortar is Class II (150 kg of common cement and 0.6 m³ of building sand per 1,000 bricks, from the Concrete Society’s 2024 leaflet).
The SANS 10400-H rules used are from the 1990 edition, the only one publicly available: footings at least 200 mm thick and 600 mm wide under load-bearing or free-standing masonry walls (400 mm under non-load-bearing internal walls), in concrete of at least 10 MPa or mixed 1 cement : 4 sand : 5 stone.
Worked example
With these inputs:
- External and load-bearing walls (total length)
- 40 m
- Internal non-load-bearing walls (total length)
- 12 m
- Footing thickness
- 200 mm
- Trench depth (to firm ground on your site)
- 600 mm
- DPC height above finished ground
- 150 mm
- Supply as
- Mix on site (cement, sand and stone)
- Concrete mix
- Low strength (house foundations)
- Waste allowance
- 10%
the result is:
- Foundation concrete
- 6.34 m³
- Footing under external walls
- 600 mm wide
- Footing under internal walls
- 400 mm wide
- Excavation (bank volume)
- 17.28 m³
- Foundation walling height (footing to DPC)
- 550 mm
Tips from the trade
- Dig to firm natural ground. If you find clay, loose sand, fill or water, stop and get an engineer.
- Level the trench bottoms and set pegs for the top of the footing before you pour.
- Pour the footing in one go where you can, and keep it damp while it cures.
Common questions
How wide should a strip foundation be?
Under SANS 10400-H, at least 600 mm under load-bearing and free-standing masonry walls and 400 mm under non-load-bearing internal walls, and at least 200 mm thick. Problem soils need an engineer’s design.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and SANS 10400 (the National Building Regulations) and your local municipality before ordering.