Building Drawing: Plans, Elevations and Sections
The drawing set
A building drawing contains the plan (view from above, cut about 1.2 m above floor level, showing walls, openings, fixtures and the line of section), the elevation (front view showing plinth, doors, windows, sunshades and parapet) and the section (vertical cut showing foundation, flooring, DPC, lintel and roof levels). Scales: 1:100 for plan and elevation, 1:50 or 1:25 for details, 1:200 for site plans.
Conventions to quote
Brick walls 230 mm thick; door 900 × 2100 mm; window 1200 × 1200 mm with sill at 900 mm; DPC 25 mm at plinth level; plinth height 600 mm; sunshade projecting 600 mm; parapet 900 mm. Standard abbreviations GL, FL, SL, DPC, FF and LH. Plans and elevations must be vertically aligned, the section line A–A must be marked on the plan with arrows pointing toward the view drawn, and levels are given in metres while dimensions are in millimetres.
Worked example
A room 4000 × 3000 mm internally with 230 mm walls. At 1:100 the internal rectangle is 40 × 30 mm; the overall size is (4000 + 230 + 230) = 4460 mm by 3460 mm, drawn 44.6 × 34.6 mm. Each wall is therefore 2.3 mm on paper - enough to show two separate lines, never one.
Traps
Dimensioning an internal dimension as the overall size; forgetting wall thickness outside the room; plan and elevation out of alignment; a section line that misses every door and window, so the section shows no openings; doors and windows placed at the wrong level relative to plinth and floor.