Architectural Drawings:  An architectural drawing or architect’s drawing is a technical drawing of a building (or building project) that falls within the definition of architecture. Architectural drawings are used for a number of purposes: to develop a design idea, a coherent proposal, to communicate ideas and concepts, to convince clients of the merits of a design, to enable a building contractor to construct it, as a record of the completed work, and to make a record of a building that already exists.

Architectural drawings are drawn according to a set of conventions, which include particular views (floor plan, section etc.), sheet sizes, units of measurement and scales, annotation and cross referencing.

Plan:  Plans are drawings that show a horizontal cut through a structure, exposing a building’s organization of rooms and spaces.

  • Floor plan: A floor plan is the most fundamental architectural diagram, a view from above showing the arrangement of spaces in the same way as a map, but showing the arrangement at a particular level of a building. Technically it is a horizontal section cut through a building, showing walls, windows and door openings and other features at that level. The plan view includes anything that could be seen below that level: the floor, stairs (but only up to the plan level), fittings and sometimes furniture. Objects above the plan level (e.g. beams overhead) can be indicated as dotted lines.
  • Site plan: A plan showing the whole context of a building or group of buildings. It shows property boundaries and access to the site, and nearby relevant structures.  A site plan may show adjoining streets to demonstrate how the design fits. The site plan gives an overview of the entire scope of work. It shows buildings (if any) already existing and proposed; roads, parking lots, footpaths, hard landscaping, trees and planting. For a construction project, the site plan needs to show all the services connections: drainage and sewer lines, water supply, electrical and communications cables, exterior lighting etc.

Section:   Sections are drawings showing vertical cuts through a structure. They are used to depict floor and building heights as well as vertical connectivity.

A cross section, also simply called a section, represents a vertical plane cut through the object, in the same way as a floor plan is a horizontal section viewed from the top. Sections are used to describe the relationship between different levels of a building.

A sectional elevation is a combination of a cross section, with elevations of other parts of the building seen beyond the section plane.

Elevation:  Elevations show a wall’s face, expressing where every element is placed vertically on a facade or interior.

An elevation is a view of a building seen from one side, a flat representation of one façade. This is the most common view used to describe the external appearance of a building. Each elevation is labeled in relation to the compass direction it faces. Architects use the word “elevation” as a synonym for façade, so the north elevation is literally the north wall of the building.

Isometric and Axonometric:  Isometric drawings represent the three-dimensionality of a structure or space. Every line’s length in an isometric drawing is represented accurately to scale, but the angles of material connection in an isometric drawing are not correct.

Isometric and axonometric projections are a simple way of representing a three dimensional object, keeping the elements to scale and showing the relationship between several sides of the same object, so that the complexities of a shape can be clearly understood.

There is some confusion about the terms isometric and axonometric. “Axonometric is a word that has been used by architects for hundreds of years. Engineers use the word axonometric as a generic term to include isometric, diametric and trimetric drawings.”

  • An isometric uses a plan grid at 30 degrees from the horizontal in both directions, which distorts the plan shape. Isometric graph paper can be used to construct this kind of drawing. This view is useful to explain construction details (e.g. three dimensional joints in joinery).
  • Cabinet projection is similar, but only one axis is skewed, the others being horizontal and vertical. Originally used in cabinet making, the advantage is that a principal side (e.g. a cabinet front) is displayed without distortion, so only the less important sides are skewed. The lines leading away from the eye are drawn at a reduced scale to lessen the degree of distortion.
  • An axonometric uses a 45 degree plan grid, which keeps the original orthogonal geometry of the plan. The great advantage of this view for architecture is that the draftsman can work directly from a plan, without having to reconstruct it on a skewed grid. In theory the plan should be set at 45 degrees, but this introduces confusing coincidences where opposite corners align.
  • In Planometric or Plan Oblique View unwanted effects can be avoided by rotating the plan while still projecting vertically. This is sometimes called a planometric or plan oblique view, and allows freedom to choose any suitable angle to present the most useful view of an object.

The axonometric gained in popularity in the twentieth century, not just as a convenient diagram but as a formal presentation technique, adopted in particular by the Modern Movement. Axonometric drawings feature prominently in the influential 1970’s drawings of Michael Graves, James Stirling and others, using not only straightforward views but worms-eye view, unusually and exaggerated rotations of the plan, and exploded elements.

Perspective:  Perspectives are drawings that depict what the eye or a camera sees. The drawings are not to scale, but they accurately represent how a structure or space is perceived. Perspective is the view from a particular fixed viewpoint.

Diagrams:  Drawings that express structural data visually. A structural diagram, showing the amount of load or weight a beam must carry, is an example of an architectural diagram.

Reflected Ceiling Plan:  A reflected ceiling plan (RCP) is a drawing, which shows the items that are located on the ceiling of a room or space. It is referred to as a reflected ceiling plan since it is drawn to display a view of the ceiling as if it was reflected onto a mirror on the floor. This way the reflected ceiling plan has the same orientation as the floor plan associated with it. It is as if the ceiling was see-through and you could see right through it to the floor below.

Detail Drawings:  Detail drawings show a small part of the construction at a larger scale, to show how the component parts fit together. They are also used to show small surface details, for example decorative elements. Section drawings at large scale are a standard way of showing building construction details, typically showing complex junctions (such as floor to wall junction, window openings, eaves and roof apex) that cannot be clearly shown on a drawing that includes the full height of the building.