A boundary or garden wall stands on its own, with nothing to brace it but its own thickness and its piers. Wind, a leaning child or a car bumping it all push sideways, and a wall that is too tall or too thin for its piers will crack or fall. SANS 10400-K gives deemed-to-satisfy limits for these free-standing walls, so you can build an ordinary wall without an engineer’s design as long as you stay within them.
The rules for free-standing walls
SANS 10400-K 4.2.4.2 says a free-standing boundary or garden wall must:
- be no higher than tables 17 (solid units) and 18 (hollow units) allow;
- retain no earth;
- have piers that run to the top of the wall without getting smaller;
- end in a pier or a return;
- have the cores of all piers solidly filled where the units are hollow.
Where the ground on one side is higher than on the other by more than 0.3 m, the allowed height is reduced by the difference over 0.3 m. And 4.2.4.3 says free-standing walls get no horizontal damp-proof course, which would create a weak plane in the wall.
How high? Table 17, solid units
| Wall | Piers | Maximum height | Pier size (depth × width) | Pier spacing (max) |
|---|---|---|---|---|
| 110 mm (single brick) | None | 1.0 m | – | – |
| 110 mm | One side | 1.5 m | 330 × 330 mm | 1.8 m |
| 110 mm | One side | 1.9 m | 550 × 330 mm | 2.0 m |
| 110 mm | Both sides | 1.6 m | 550 × 330 mm | 1.8 m |
| 220 mm (double brick) | None | 1.8 m | – | – |
| 220 mm | One side | 2.3 m | 660 × 440 mm | 3.2 m |
| 220 mm | Both sides | 2.1 m | 660 × 440 mm | 3.2 m |
The table also covers other thicknesses, Z-shaped walls and diaphragm walls, and table 18 covers hollow blocks, which are allowed less height. Walls higher than the tables allow, and any wall that holds back soil, need a design by an engineer.
The foundation
SANS 10400-H asks for a strip footing at least 600 mm wide and 200 mm thick under free-standing masonry walls, with the foundations under piers projecting 200 mm all round. As with a house, the footing must sit on firm natural ground. See strip foundations under SANS 10400-H.
Taking off the materials
Worked example: a 20 m double-brick wall, 1.8 m high, with piers on one side. Table 17 allows up to 2.3 m with 660 × 440 mm piers at no more than 3.2 m centres.
- Piers = 20 ÷ 3.2 = 6.25, rounded up to 7 bays, so 8 piers including the one at each end.
- Wall bricks = 20 × 1.8 × 104 = 3,744.
- Each pier adds (0.66 − 0.22) × 0.44 = 0.19 m² of brickwork in plan. With standard bricks taking 0.232 × 0.116 m per course and 22 courses in 1.8 m, that is about 158 bricks per pier, 1,266 for 8 piers.
- With 5% for breakage: about 5,261 bricks.
- Foundation = 20 × 0.6 × 0.2 = 2.4 m³ of concrete, plus waste and the pier foundations.
- Mortar: Class II at 150 kg of cement and 0.6 m³ of building sand per 1,000 bricks.
The boundary wall calculator picks the row from table 17 for your height and layout and does this whole takeoff.
Control joints
Long walls crack as the bricks expand and shrink, so SANS 10400-K 4.2.6 asks for vertical control joints. Table 19 sets the longest unbroken run of an unreinforced free-standing wall: 16 m, 10 m or 6 m for clay bricks, depending on their moisture expansion (under 0.05%, 0.05 to 0.10%, or 0.11 to 0.20%; the brick maker can tell you), and 5 to 7 m for concrete blocks. The joints run right down to the top of the foundation (4.2.6.3) and are butt joints across the full wall, 10 to 12 mm wide in clay brick and no more than 12 mm in concrete units (4.2.6.5).
Before you build
- Confirm where the boundary is. Building on the wrong line is an expensive mistake.
- Check what your municipality, estate or title deed allows for boundary walls, and whether the wall needs approved plans.
- Look for services: water, sewer and electrical cables often run along boundaries.
- Leave openings or weep holes where water must drain through.
- Don’t backfill soil against a free-standing wall. Once it holds back earth, it is a retaining wall and needs a different design. See retaining walls with Terraforce and Löffelstein.
This guide is general information for estimating. It is not engineering, legal or tax advice. Check SANS 10400 (the National Building Regulations) and your local municipality’s building control officer for your project.