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.
[edit]Floor plan
A floor plan is the most fundamental architectural diagram, a view from above showing the arrangement of spaces in building 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 (conventionally at three feet / one metre above floor level), 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.
Geometrically, plan view is defined as a vertical orthographic projection of an object on to a horizontal plane, with the horizontal plane cutting through the building.
[edit]Site plan
A site plan is a specific type of plan, showing the whole context of a building or group of buildings. A site plan shows property boundaries and 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 in to the urban fabric. Within the site boundary, the site plan gives an overview of the entire scope of work. It shows the buildings (if any) already existing and those that are proposed, usually as a building footprint; roads, parking lots, footpaths, hard landscaping, trees and planting. For a construction project, the site plan also needs to show all the services connections: drainage and sewer lines, water supply, electrical and communications cables, exterior lighting etc.
Site plans are commonly used to represent a building proposal prior to detailed design: drawing up a site plan is a tool for deciding both the site layout and the size and orientation of proposed new buildings. A site plan is used to verify that a proposal complies with local development codes, including restrictions on historical sites. In this context the site plan forms part of a legal agreement, and there may be a requirement for it to be drawn up by a licenced professional: architect, engineer, landscape architect or land surveyor.
[edit]Elevation
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 labelled in relation to the compass direction it faces, e.g. the north elevation of a building is the side that most closely faces north.Buildings are rarely a simple rectangular shape in plan, so a typical elevation may show all the parts of the building that are seen from a particular direction.
Geometrically, an elevation is a horizontal orthographic projection of a building on to a vertical plane, the vertical plane normally being parallel to one side of the building.
Architects also use the word elevation as a synonym for façade, so the north elevation is literally the north wall of the building.
[edit]Cross section
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. In the section view, everything cut by the section plane is shown as a bold line, often with a solid fill to show objects that are cut through, and anything seen beyond generally shown in 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 dome seen from the outside, a second dome that can only be seen inside the building, and the way the space between the two accommodates a large astronomical telescope: relationships that would be difficult to understand from plans alone.
A sectional elevation is a combination of a cross section, with elevations of other parts of the building seen beyond the section plane.
Geometrically, a cross section is a horizontal orthographic projection of a building on to a vertical plane, with the vertical plane cutting through the building.
[edit]Isometric and axonometric projections
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.” This article uses the terms in the architecture-specific sense.
Despite fairly complex geometrical explanations, for the purposes of practical draughting the difference between isometric and axonometric is simple (see diagram above). 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 again this can be calculated but in practice was often simply 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 to explain construction details (e.g. three dimensional joints in joinery). The isometric was the standard view until the mid twentieth century, remaining popular until the 1970s, especially for textbook diagrams and illustrations.
- 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. The cabinet projection is seen in Victorian engraved advertisements and architectural textbooks, but has virtually disappeared from general use.
- 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 draughtsman 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. 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 draughting techniques used 30-60 and 45 degree set squares, and that determined the angles used in these views. Once the adjustable square became common those limitations were lifted.
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.
The axonometric view is not readily generated by CAD programmes, which work best by generating a view from a three dimensional model. Consequently it is now little used except to illustrate relatively simple construction details.
[edit]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. 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.
In traditional construction, many details were so fully standardised, that few detail drawings were required to construct a building. For example, the construction of a sash window would be left to the carpenter, who would fully understand what was required, but unique decorative details of the facade would be drawn up in detail. In contrast, modern buildings need to be fully detailed because of the proliferation of different products, methods and possible solutions.
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