Every mistake made at setting out is built into the house — a column a few inches off, a room out of square, a wall in the setback. It takes a day to do properly and a lifetime to live with if not.
The Steps
- Confirm the plot boundary with the survey sketch and boundary stones.
- Fix a base line — usually parallel to the front boundary at the front setback distance.
- Mark centre lines of columns and walls from the centre-line drawing, measuring from the base line.
- Check right angles at every corner (3-4-5).
- Check diagonals of each rectangle — they must be equal.
- Fix batter boards outside the excavation, marking each centre line.
- Mark footing outlines from the centre lines with lime.
- Recheck setbacks from all boundaries before excavation.
The 3-4-5 Check
From a corner, measure 3 m along one line and 4 m along the other. The diagonal between the two points must be 5 m. Use 6-8-10 m for larger layouts — the bigger the triangle, the more accurate.
Common Mistakes
| Mistake | Result |
|---|---|
| Measuring from a wrong or assumed boundary | Building in the neighbour's plot or a setback |
| Not checking diagonals | Out-of-square rooms |
| Marking footing edges instead of centre lines | Accumulated errors across columns |
| Lime marks only, no batter boards | Lines lost once digging starts |
The Short Version
Work from centre lines, check squareness with 3-4-5 and equal diagonals, fix batter boards, and confirm setbacks before the first trench.
