CAD and BIM Architecture and Design Software

Computer Applications for Architects and Builders

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What's Next in Computer Design?. Sean Gallup/Getty Images (cropped)

The letters CAD stand for computer-aided design. BIM is an acronym for Building Information Modeling. These applications are the software tools of architects, drafters, engineers, and builders. Various types of software can create plans, construction drawings, precise lists of building materials, and even instructions on how and when to put together the parts. The first two letters of each acronym define the software and their derivatives — CA- is Computer-Aided software for many design projects, including computer-aided engineering (CAE), computer-aided design and manufacturing (CADAM), and computer-aided three-dimensional interactive application (CATIA); BI- is all about Building Information. CAD and BIM are usually pronounced like words.

Before the art of papermaking made its way from China to Europe, structures were built with no written plans or documentation — a process that no doubt introduced the "change order." Hundreds of years ago, before the age of computers, drawings and blueprints were drafted by hand. Today, every architecture studio is filled with computers, as well as paper. Lines are still drawn to represent the length and width of walls and openings, but the information about the lines is also kept by computer programs. For constructing and designing things, CAD and BIM are more efficient than paper and pencil because the application records lines as vectors based on mathematical equations. Using algorithms or sets of directions, software programs allow designers to twist, stretch, and move portions of a drawing, testing a design under a variety of conditions and circumstances. The digital lines automatically adjust in 2D (height and width), 3D (height, width, and depth), and 4D (3D time). What is called 4D BIM brings efficiency to the construction process by adding the element of time — sequencing events in the architecture process.

About CAD

The idea of designing with the help of computers began in the 1960s with the growth of automobile and aerospace companies. The CAD industry became firmly established in the 1970s with software and hardware sold together in very expensive, dedicated machines. It wasn't until the 1980s that personal computing (PC) was possible and affordable, with the goal of having a PC on every desk in the office.

CAD is also known as CADD, which stands for Computer-Aided Design & Drafting. Patrick Hanratty is the name you hear most as the developer of a usable drafting software system. CAD software let the designer become more efficient, and in business time is money. With CAD a designer could switch between two-dimensional (2D) and three-dimensional (3D) views; zoom in and out for close-up and distant views; rotate images to view them from different perspectives; manipulate the shape of images; and change the scale of images — when one value changed, related values automatically adjust.

About BIM

Many building and design professionals have moved from CAD to BIM or Building Information Modeling applications for many reasons, including its advanced capabilities for parametric modeling.

All components of built structures have "information." For example, imagine a "2-by-4." You visualize the component because of its information. A computer can do this for thousands of components, so an architect can easily change a design model by changing the information that makes up the design. This flexibility without redrawing can produce interesting and daring designs that can be tested without risk and at little cost. 

The construction process is integrated with the design process. After a design is complete, the BIM application lists the component parts for the builder to put together. BIM software not only digitally represents the physical, but also the functional aspects of a building. Combined with file-sharing and collaboration software ("cloud computing"), BIM files can be tweaked and updated across all parties in the project — sectors of the Architecture, Engineering and Construction (AEC) Industry.  BIM keeps track of the nuts and bolts of design, literally.

Some call this aspect of the process 4D BIM. In addition to the length, width, and depth dimensions, the fourth dimension (4D) is time. BIM software can track a project through time as well as the three spacial dimensions. Its "clash detection" abilities red-flag system conflicts before construction begins.

BIM software doesn't do anything that architects and designers haven't been doing all along — the integrated databases of information simply improve a project's productivity and safety. Another dimension that can be manipulated is pricing of labor and cost of materials — sometimes called 5D BIM. What if the windows and doors are different? or the bay window is prefabricated? or the tile comes from Italy? Integrated budgeting can lessen cost overruns — theoretically.

Some call BIM "CAD on steroids," because it can do what 3D CAD can do and more. Its most common use is in commercial construction. If a project is very complicated, more complicated software is often used in order to save money in the form of time and effort. So, why doesn't BIM always save money for the consumer? Dollars saved on design can be moved into more expensive construction materials (why not use marble?) or overtime pay to hurry the pace of construction. It can also line the pockets and coffers of other projects, but that's another story.

BIM Has Changed the Way We Work

As architectural firms have made the change in software, BIM use has also demonstrates a philosophical change in doing business — from paper-based, proprietary ways (the CAD approach) to collaborative, information-based operations (the BIM approach). Construction law attorneys have addressed many of the legal concerns surrounding an inclusive, shared process of design and construction. Issues of risk and liability should be clearly defined in any contract where information is shared and design drawings can be freely manipulated. Who owns all of this information when the project is complete? Sometimes called 6D BIM, the operations and maintenance manual collated from a project's information can be an invaluable byproduct for any owner of a new building.

CAD and BIM Standards in the United States

The National Institute of Building Sciences buildingSMART alliance™ develops and publishes consensus-based standards for both CAD and BIM. Standards help the many groups involved in building projects to more easily share information. They are (NCS) and (NBIMS-US).

Help Deciding

Change is difficult. It was laborious for the ancient Greeks to write down their temple plans. It was frightening for human drafting machines to sit next to the first personal computer. It was awkward for the CAD specialists to learn BIM from the intern right out of architecture school. Many companies make changes during construction slowdowns, when "billable hours" are few and far between. But everyone knows this: many commercial projects begin with a competition put out to bid, and a competitive edge becomes more difficult without change. 

Computer software is complicated even for the technically savvy architect. Private companies have grown up around these complications, with the aim of helping small businesses and corporations buy the appropriate software for their needs. Companies like the online will help you "find the right software for your business" —  for free by using a business model similar to travel agents helping you for free. "Capterra is free for users because vendors pay us when they receive web traffic and sales opportunities. Capterra directories list all vendors—not just those that pay us—so that you can make the best-informed purchase decision possible." A good deal, if you trust and respect your consultant and know what you're getting into. is a good start.

FAST FACTS: Most Popular Products

CAD: Popular CAD programs used by architects, engineers, builders and home designers include:

  • by autoDesk
  • by Bentley
  • Architectural Home Design Software by
  • by Trimble.

Simplified versions of CAD tools can be found in home design software tailored for nonprofessionals. Home Designer® by Chief Architect is one such product line.

BIM: Popular BIM programs used by architects, engineers, and builders include:

  • ® by Autodesk
  • from Bentley Systems
  • by Graphisoft
  • from Nemetschek Vectorworks