Understanding How Buildings Get Drawn Before They Get Built
An educational resource on CAD drafting, architectural and structural drawing, BIM, Revit, and SketchUp.
Every building starts as a drawing, and today, that drawing is almost always digital. Between CAD drafting, BIM modeling, Revit, and SketchUp, the tools and processes behind architectural and structural design have changed enormously, even as the underlying goal, communicating exactly how something should be built, has stayed the same.
Blazarch is an educational resource for anyone curious about how technical drawings and digital models actually work.
This site is an independent educational publication. It does not offer professional drafting, design, or engineering services, and nothing here should be used as a substitute for work performed by a licensed architect, engineer, or professional drafter.
How a Drawing Set Comes Together
A single drawing rarely tells the whole story of a building. What actually gets used on a construction site is a coordinated set of construction documents, and understanding how that set is organized makes it much easier to follow what any individual sheet is showing.
The Cover Sheet and General Information
Most drawing sets open with a cover sheet listing the project, the design team, and an index of every sheet included, followed by general notes and symbol legends that apply across the whole set. This is usually the first place to look when trying to understand how a set is organized before diving into specific sheets.
Architectural, Structural, and MEP Sheets
Architectural sheets typically come first, covering floor plans, elevations, sections, and finish details. Structural sheets follow, documenting the framing, foundations, and load-bearing systems. MEP sheets, mechanical, electrical, and plumbing, round out the technical documentation, each discipline maintaining its own drawings while referencing the same underlying building.
Details and Schedules
Beyond the main plan sheets, a set typically includes detail sheets, zoomed-in drawings clarifying exactly how specific conditions, like a window head or a stair connection, should be built, along with schedules: organized tables listing doors, windows, finishes, or fixtures with their specifications. These details and schedules are often where the most construction-critical information actually lives.
Reading a set in this order, cover sheet, architectural, structural, MEP, then details and schedules, gives a much clearer picture of a project than jumping straight to a single sheet in isolation.
None of this replaces working directly with the actual construction documents on a real project, but it does make the overall structure of a drawing set far less intimidating to approach for the first time.
Reading Drawings: Scale, Symbols, and Line Weight
Learning to read a construction drawing is its own skill, separate from understanding the software used to create it. A few fundamentals go a long way.
Scale: Why Drawings Are Never Actual Size
Drawings are produced at a defined scale, a ratio like 1/4 inch equals 1 foot, so that a full building can be represented accurately on a manageable sheet of paper. Reading the scale noted on a drawing is essential before measuring anything directly off it, since the same drawing might appear at different scales across different sheets in the same set.
Line Weight Carries Meaning
Drafting convention uses varying line thickness, or line weight, to communicate hierarchy: heavier lines typically indicate cut elements like walls in a floor plan, while lighter lines represent elements seen beyond, like ceiling features or objects behind the cut plane. Learning to read line weight is often one of the first practical skills taught in drafting instruction.
Symbols Are a Shared Language
Doors, windows, electrical outlets, plumbing fixtures, and structural elements all have standardized symbols, which is what allows a contractor, architect, and engineer to interpret the same drawing consistently, even though each discipline focuses on a different part of it. This shared symbol language is part of what makes construction documents function as a coordinated set rather than isolated drawings.
This is also why drafting education spends real time on conventions before software: the symbols and standards stay consistent across CAD, BIM, and hand drafting alike, while the tools used to produce them have changed considerably over the decades.
What You Will Find Here
Clear explanations of the drafting and digital design fields, and the history behind them.
CAD Drafting Fundamentals
What CAD drafting is, how architectural, structural, and MEP drafting differ, and how CAD conversion works.
The History of Drafting
How the field moved from hand-drawn blueprints to CAD, and eventually to fully digital BIM modeling.
CAD, BIM, Revit, and SketchUp
What actually separates these terms, and how each one fits into a real architectural or construction workflow.
Common Questions
Is BIM just another word for CAD?
No. CAD is a broad category of computer-based drafting, while BIM is a specific methodology built around coordinated, data-rich 3D modeling. They are related, but not interchangeable.
Do architects still learn hand drafting?
Hand drafting is far less central to daily practice than it once was, but understanding drafting fundamentals, symbols, scale, and conventions, remains foundational to architectural and engineering education.
What is the difference between architectural and structural drawings?
Architectural drawings document a building’s overall design and layout, while structural drawings document the load-bearing system that keeps it standing, beams, columns, and footings.
What does "drafting standards" actually mean?
Drafting standards are the shared conventions, symbols, line weights, scale notation, sheet organization, that make a drawing produced by one person interpretable by anyone else trained in the same conventions. They exist so drawings function as a reliable shared language rather than a personal shorthand.
Why do drawing sets separate architectural, structural, and MEP sheets?
Each discipline is documenting a different system within the same building, and separating them keeps each set of drawings legible on its own while still being coordinated against the others. Overlaying all of it onto a single sheet would make each individual system much harder to read clearly.
Where should I start if I am new to this topic?
The article “What Is CAD Drafting and How Is It Used in Construction?” is a good starting point.