Setting out of a building

Setting out is the process of transferring the dimensions and positions of the building from the drawing to the ground, so that excavation and construction follow the plan exactly.

Procedure (for a building with walls)

1. Site clearing and base line: Clear the site. Fix a base line parallel to the road or to a reference line from the plan (a permanent line, set back as per the bye-laws). Fix a benchmark for levels.
2. Marking the first corner: Fix a peg at one corner of the building at the given distance from the base line.
3. Right angle: Set a right angle with the 3-4-5 method (a triangle with sides of 3 m, 4 m and 5 m), or with a theodolite or a box square, to mark the adjacent wall line.
4. Other corners: Measure the length and breadth with a tape, fix pegs at all corners, and check that the diagonals are equal in length (as they must be for a rectangle).
5. Marking the wall lines: Join the corner pegs with string, and mark the centre lines and the trench width with lime powder.
6. Profile boards (batter boards): Fix boards on wooden posts 1.5 to 2 m outside each corner, outside the area of excavation. Wires or nails on the boards mark the centre lines and the widths of the trench and the footing. These stay in place during excavation.
7. Levels: Mark the depth of excavation with a level and boning rods, or with a cut line at the required depth.
8. Checking: Check lengths, diagonals and levels before the excavation starts.

    P1----------------P2     P = profile boards
     |    +--------+  |      
     |    | trench |  |      Check: both diagonals equal
     |    +--------+  |
    P4----------------P3
         3-4-5 triangle for right angle

For a framed building, the column centres are fixed by a grid of centre lines laid out by tape or total station, and marked on the profile boards.