The main purpose of construction drawings (also called plans, blueprints, or working drawings) is to show what is to be built, while the specifications focus on the materials, installation techniques, and quality standards. However, the distinction is not clear cut. Most designers put basic construction information in the drawings and use the specs to elaborate on materials, techniques, and standards to be met. Others pack their drawings with written notes that cover many of the issues commonly contained in the specs. In some cases, you’ll find the same information in both places. If there is a conflict between the specs and drawing, the specs generally override the plans, at least legally.
Scale Drawings. Nearly all construction drawings are drawn to scale. The large blueprints or “working drawings” used on the job site are typically drawn at a scale of ¼” per foot. Drawings of the whole house, or small details, may be at a different scale. At a scale of ¼” per foot, a line 1 in. long equals 4 ft., a line 4 in. long equals 16 ft., and so on. A special architectural scale ruler (photo below) makes it very easy to read dimensions on construction drawings – or to create your own scale drawings.
Architectural symbols. Over many years, a set of standard architectural symbols has developed for construction drawings so that anyone familiar with the building trades can understand their meaning. Different designers and draftsperson have small variations in their style of drawing, but usually their meaning is clear to anyone familiar with construction drawings. When an designer or tradesman looks at a set of drawings, every little line, arrow, squiggle, and symbol has significance. Together they provide a detailed guide to how the building goes together and what it will look like.
TYPES OF DRAWINGS
A complete set of house plans usually contains floor plans, elevations, sections and “details” that together form a detailed picture of the entire house. There is often a separate page for each major trade, including a site plan, floor plans, foundation plan, electrical plan, plumbing plan, and framing plan. In general, each drawing is either an elevation, plan, or section view, as described below:
Exterior elevations:These are the sides of the building viewed looking straight at them (see below). These can be a little deceptive, since everything appears as a single, flat plane, with no clues as to depth. So, for example, a sloped roof viewed from the side looks like a flat vertical rectangle – not what you would actually see in a 3D world. Two walls or objects, offset by 10 ft. appear in the same plane. Exterior elevations give you a pretty good idea of what the house will look like on each side, but 3D perspective drawings provide a much more realistic view.
Floor plans:These are views looking straight down at the floor, showing precisely dimensioned rooms, closets, kitchens and baths, and the locations of doors, windows, stairs, and other interior elements (at left).
Sections: These drawings show what you would see if you cut a slice through the building, revealing the inside of walls, floors, foundations, and other elements. Most common are elevation sections, cut vertically through the walls and floors. Sections are especially useful for carpenters trying to see how the framing and other elements fit together (at left).
Details: These are drawings of specific elements where the designer wants to provide more detailed information than can be seen in the larger drawings of the entire house. A larger scale may be used. Details are often section drawings of the foundation, exterior walls, windows, stairs, framing, or other construction elements. Where section drawings are cut through is usually indicated on the floor plans with an arrow and letter label matching the elevation drawing (at left).