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 by architects and others for a number of purposes: to develop a design idea into a coherent proposal, to communicate ideas and concepts, to show clients the merits of a design, to assist a building contractor in construction based on design intent, to record the design and planned development, or to document a building that already exists.
Architectural drawings are made according to a set of conventions, including particular views such as floor plans and sections, sheet sizes, units of measurement, scales, annotation and cross-referencing.
Historically, drawings were made in ink on paper or similar materials, and copies had to be made by hand. The twentieth century saw a shift to drawing on tracing paper so that mechanical copies could be made more efficiently. The development of the computer had a major impact on the methods used to design and create technical drawings, making manual drawing less common and opening up new possibilities of form using organic shapes and complex geometry. Today, most architectural drawings are created using CAD software.
History
Size and scale
The size of drawings reflects the materials available and the size that is convenient to transport, whether rolled, folded, laid out on a table or pinned on a wall. The drafting process may impose limitations on the size that is realistically workable. Sizes are determined by a consistent paper size system according to local usage. Normally, the largest paper size used in modern architectural practice is ISO A0 (), or, in the United States, Arch E () or Large E size ().
Architectural drawings are drawn to scale so that relative sizes are correctly represented. The scale is chosen both to ensure that the whole building will fit on the chosen sheet size and to show the required amount of detail. On a scale of one-eighth of an inch to one foot (1:96), or the metric equivalent of 1:100, walls are typically shown as simple outlines corresponding to the overall thickness. At a larger scale, such as half an inch to one foot (1:24), or the nearest common metric equivalent of 1:20, the layers of different materials that make up the wall construction are shown. Construction details are drawn to a larger scale, in some cases full size.
Scale drawings enable dimensions to be read from the drawing. Imperial scales can be read using an ordinary ruler. On a one-eighth inch to one-foot scale drawing, the one-eighth divisions on the ruler can be read as feet. Architects normally use a scale ruler with different scales marked on each edge. A third method, used by builders in estimating, is to measure directly from the drawing and multiply by the scale factor.
Dimensions can be measured from drawings made on a stable medium such as vellum. All processes of reproduction introduce small errors, especially when the same drawing is copied repeatedly or copied using different methods. Consequently, dimensions need to be written, or "figured", on the drawing. The disclaimer "Do not scale off dimensions" is commonly inscribed on architects' drawings to guard against errors arising in the copying process.
Standard views used in architectural drawing This section deals with the conventional views used to represent a building or structure. See the types of architectural drawing section below for drawings classified according to their purpose.
Floor plan A floor plan is the most fundamental architectural diagram. It is a view from above showing the arrangement of spaces in a building in a similar way to a map, but at a particular level of a building. Technically, it is a horizontal section cut through a building, conventionally at about four feet, or 1.2 metres, above floor level, showing walls, windows, door openings and other features at that level. The plan view includes anything that could be seen below that level, such as the floor, stairs up to the plan level, fittings and sometimes furniture. Objects above the plan level, such as overhead beams, can be indicated with dashed lines.
Geometrically, plan view is defined as a vertical orthographic projection of an object onto a horizontal plane, with the horizontal plane cutting through the building.
Site plan A site plan is a specific type of plan showing the whole context of a building or group of buildings. It shows property boundaries, means of access to the site and nearby structures if they are relevant to the design. For a development on an urban site, the site plan may need to show adjoining streets to demonstrate how the design fits into the urban fabric. Within the site boundary, the site plan gives an overview of the entire scope of work. It shows existing and proposed buildings, usually as building footprints, as well as roads, parking areas, footpaths, hard landscaping, trees and planting. For a construction project, the site plan also needs to show service connections such as drainage and sewer lines, water supply, electrical and communications cables, and exterior lighting.
Site plans are commonly used to represent a building proposal before detailed design. Drawing up a site plan is a tool for deciding the site layout, size and orientation of proposed new buildings. A site plan is also used to verify that a proposal complies with local development codes, including restrictions on historical sites. In this context, the site plan may form part of a legal agreement, and there may be a requirement for it to be drawn up by a licensed professional such as an architect, engineer, landscape architect or land surveyor.
Elevation An elevation is a view of a building seen from one side, as a flat representation of one façade. This is the most common view used to describe the external appearance of a building. Each elevation is labelled in relation to the compass direction it faces. For example, looking toward the north means viewing the southern elevation of the building. Buildings are rarely simple rectangular shapes in plan, so a typical elevation may show all the parts of the building seen from a particular direction.
Geometrically, an elevation is a horizontal orthographic projection of a building onto a vertical plane, with the vertical plane normally being parallel to one side of the building. Architects also use elevation as a synonym for façade, so a north elevation is the north-facing wall of a building.
Cross section
A cross section, also called a section, represents a vertical plane cut through an object, in the same way that a floor plan is a horizontal section viewed from above. In the section view, everything cut by the section plane is shown as a bold line, often with a solid fill to show objects cut through, while anything seen beyond is generally shown with a thinner line. Sections are used to describe the relationship between different levels of a building.
In the Observatorium drawing illustrated here, the section shows the outer dome, a second dome visible only inside the building, and the way the space between the two accommodates a large astronomical telescope. These relationships would be difficult to understand from a plan or elevation alone.
A sectional elevation is a combination of a cross section and elevations of other parts of a building seen beyond the section plane. Geometrically, a cross section is a horizontal orthographic projection of a building onto a vertical plane, with the vertical plane cutting through the building.
Isometric and axonometric projections Isometric and axonometric projections are simple ways 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 understood.
There is some confusion over the distinction between the terms isometric and axonometric. Alan Piper wrote that "axonometric is a word that has been used by architects for hundreds of years" and that engineers use the word axonometric as a generic term including isometric, diametric and trimetric drawings. This article uses the terms in the architecture-specific sense.
In practical drafting, the difference between isometric and axonometric is simple. In both, the plan is drawn on a skewed or rotated grid, and the verticals are projected vertically on the page. All lines are drawn to scale so that relationships between elements are accurate. In many cases, a different scale is required for different axes, and this can be calculated or estimated by eye.
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 for explaining construction details, such as three-dimensional joints in joinery. The isometric was the standard view until the mid-twentieth century and remained popular until the 1970s, especially for textbook diagrams and illustrations. Cabinet projection is similar, but only one axis is skewed, while the others are horizontal and vertical. Originally used in cabinet making, it has the advantage that a principal side, such as 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. Cabinet projection is seen in Victorian engraved advertisements and architectural textbooks, but has largely disappeared from general use. An axonometric uses a 45-degree plan grid, which keeps the original orthogonal geometry of the plan. The advantage of this view for architecture is that the drafter 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 can introduce confusing coincidences where opposite corners align. 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.
Traditional drafting techniques used 30–60 and 45 degree set squares, and this determined the angles used in these views. Once the adjustable square became common, those limitations were lifted.
The axonometric gained 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 influential 1970s drawings by Michael Graves, James Stirling and others, using not only straightforward views but also worm's-eye views, unusual and exaggerated rotations of the plan, and exploded elements.
Detail drawings Detail drawings show a small part of the construction at a larger scale, to show how component parts fit together. They are also used to show small surface details, such as 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 junctions, window openings, eaves and roof apexes that cannot be clearly shown on a drawing that includes the full height of the building. A full set of construction details needs to show plan details as well as vertical section details. One detail is seldom produced in isolation: a set of details shows the information needed to understand the construction in three dimensions. Typical scales for details are 1:10, 1:5 and full size.