Blueprint Symbols

Blueprints are the rolls of blue paper that engineers and architects carry onto a job. They are white-on-blue copies of technical drawings, made by a contact-print process on light-sensitive paper, and sometimes on linen, Mylar, or imitation vellum. Hundreds of symbols appear on them. There is no single international standard, so a sign can shift slightly from one region to another. Reading them takes practice if you are not the person who drew the sheet.

The individual marks used for doors, switches, and plumbing traps are on the architectural symbols page. A blueprint set is the larger package those marks belong to.

Drawing types

A full set for a building is more than one sheet.

• Architectural sheets give the master view and the detail of the floor plans.
• Civil sheets give the topographic view of the site outside the building.
• Landscaping sheets give planting and irrigation. They are sometimes included with the civil drawings.
• Structural sheets give dimensions and sizes for steel, joists, concrete, footings, shafts, and beams.
• Mechanical sheets give locations, sizes, and specifications for HVAC ducts, piping, and equipment.
• Plumbing sheets give locations, sizes, and specifications for fixtures, piping, and equipment.
• Electrical sheets give locations, circuits, and specifications for equipment and fixtures.

Welds

Welding symbols on a drawing say where the weld goes. They can also give the size, the type, the number of welds, and details of the joint. A welder who works from a drawing has to read that symbol in order to prepare the joint and lay a weld of the strength the design asks for.