Plans, Specifications and Setting Out
Domain 2 checks whether you can turn drawings and specifications into accurate lines on the ground: reading scales and details, working from datum and grid lines, and setting out square, level and within the consented setbacks.
Reading the documents
- Plans give layout, elevations give heights, sections give construction, details give junctions at 1:5 or 1:10, and schedules list windows, doors and lintels.
- Build to the latest revision. Superseded drawings should be removed from site; where documents conflict, raise an RFI rather than guessing.
- The datum is the height reference; RLs are levels above it. Grid lines locate structural elements, and figured dimensions always beat scaled ones.
Setting out
Place profiles clear of the excavation and stretch lines offset from the building line. Check a right angle with the 3-4-5 method, and check the whole rectangle by comparing both diagonals. Confirm levels with a dumpy, rotary laser or by transferring from a known benchmark - never by eye.
Worked example
A 4.8 m × 6.4 m slab. Required diagonal = √(4.8² + 6.4²) = √(23.04 + 40.96) = √64 = 8.000 m. If one diagonal reads 8.010 m and the other 7.995 m, the corners are not square. Shift the corner on the short diagonal outward by half the difference, then re-measure both diagonals and both side lengths until all agree.
Traps that cost marks
- Measuring from a fence or the neighbour's boundary instead of survey pegs and consent setbacks.
- Scaling off a drawing instead of using the figured dimension.
- Ignoring cladding and cavity thickness, so the finished wall crosses the boundary.
- Working from a revision that has been superseded by an RFI response.