Building Drawing
This domain tests whether you can read and produce a plan, elevation and section at a stated scale, and extract dimensions, levels and symbols accurately.
The three views
A plan is a horizontal cut about 1.2 m above floor level, viewed from above. An elevation shows an outside face. A section is a vertical cut showing construction detail such as foundation, floor and roof. A working drawing carries dimensions, notes, grid lines and a north arrow; a line without a dimension is not buildable.
Scale and linework
1:100 means 1 mm on paper represents 100 mm on site. Common scales are 1:50 for details, 1:100 for plans and 1:1000 for site plans. Continuous thick lines show cut or visible edges, dashed lines show hidden work, chain-dotted lines mark centre lines and boundaries, and thin lines carry dimensions and extension lines.
Worked example
A room 4.2 m by 3.6 m with 230 mm walls, drawn at 1:100. The internal size becomes 42 mm by 36 mm on paper and each wall 2.3 mm. External size = (4.2 + 0.23 + 0.23) by (3.6 + 0.23 + 0.23) = 4.66 m by 4.06 m, that is 46.6 mm by 40.6 mm on the sheet. Outside dimensions are larger than inside ones, so always add wall thickness.
Symbols and reading order
Read the title block, scale, north point and grid first; then walls, openings, fixtures and levels; finally the notes. Standard symbols include the door swing arc, window with sill line, WC, wash basin, floor drain, electrical point and water supply line.
Traps
Dividing instead of multiplying when converting to scale, adding wall thickness twice at a shared wall, confusing elevation with section, and ignoring the north arrow when checking light and ventilation.