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Plan for Flexibility: Be Proactive

by the WBDG Accessible Committee

Last updated: 07-31-2013


During the early stages of developing a building, when the planning, programming, and concept design are being shaped and molded, there may be many goals. An owner may talk about the ultimate design providing a "user-friendly work environment" and "future flexibility." What exactly does this mean? Physically, these concepts are demonstrated with spaces that can be easily modified and that can serve a variety of purposes for a diverse group of users. See also WBDG Productive and WBDG Functional.

Photo of seated man talking with boy in wheelchair

Flexible design principles include spaces that:

Universal Design and Visitability

In accessible design, "flexibility" manifests in the concepts of Universal Design and Visitability described below.

Universal Design advocates addressing human needs within the mainstream of building and product design. Many of the design features that are user-friendly and flexible are simply good design practices, rather than requirements of a building code or accessibility standard or guideline. According to the Center for Universal Design at North Carolina State University, the intent of universal design is to simplify life for everyone by making products, communications, and the built environment more usable by as many people as possible at little or no extra cost. Universal Design benefits people of all ages and abilities.

As such, one should note that providing Universal Design features in a building does not necessarily mean that one has complied with the legal and regulatory accessibility criteria. These ideas must not be used interchangeably. Universal design concepts developed over the years promote environments, building components, and features designed to be "usable by all people, to the greatest extent possible, without the need for adaptation, specialized design, or significant additional cost." (Mace)

The Center for Universal Design at North Carolina State University defines Universal Design principles to include:

  • Equitable Use
  • Flexibility in Use
  • Simple and Intuitive
  • Perceptible Information
  • Tolerance for Error
  • Low Physical Effort
  • Size and Space for Approach and Use

©1997 NC State University, The Center for Universal Design

Photo of Student Union, University of Arizona-Tucson, AZCarnegie Mellon University building

Left: This grade level building entrance utilizes universal design principles. Student Union, University of Arizona—Tucson, AZ.

Right: The campus master plan at Carnegie Mellon University incorporates the principle that "All improvements to the physical environment shall adhere to the concept of universal design."

These seven principles may be applied to evaluate existing designs; guide the design process; and educate both designers and consumers about the characteristics of more usable products and environments.

The Center for Universal Design provides a comprehensive list of resources on their website.


Visitability, a movement started by Atlanta-based Concrete Change, refers to including basic barrier-free features in single-family homes so that they can be visited by relatives, friends, and others who may have disabilities. Visitors with a disability can enter the home through an accessible entrance on an accessible route; easily negotiate spaces and hallways; and enter and use the bathroom. A visitable home includes a zero-step entry, 32-inch clear width at user passage doors, and a bathroom or powder room on the entrance level. Routes through visitable homes should also be a minimum of 36 inches wide. The ICC ANSI A117.1-2009 standard includes criteria for a Type C (Visitable) Dwelling Unit.

Many states and jurisdictions have passed visitability laws that require the inclusion of visitable design features, mostly in single, two, and three family homes. Visitability laws primarily apply to publically funded projects; however, in some jurisdictions, such as the Village of Boilingbrook, Illinois (PDF 14.0 KB) and in the State of Vermont (PDF 14.5 KB), coverage is extended to privately funded homes. Other jurisdictions require builders of new production homes to provide visitable features at the request of the home buyer regardless of funding. For example, the Maryland Visibility Law (PDF 121 KB) requires builders of new single-family homes in subdivisions of 11 or more units to offer visitability features as an option for purchase. Although visitability requirements vary from among states and jurisdictions, most require at least one zero step entry, a bathroom on the entry level, wider doors and hallways, reinforced walls for grab bar installation and reachable light switches and electrical outlets. Some states and jurisdictions encourage, rather than require, visitability features through the use of tax credits, fee incentives, and voluntary compliance programs. For example, the State of Georgia offers tax credits for providing visitability features in both existing and new single-family homes.

An Additional Benefit of Flexibility: Life-Cycle Cost-Effectiveness

Studies have shown that the additional cost of providing many accessible features in new construction is minimal when compared to adding accessible features during alterations to existing construction. Features and systems that contribute to greater usability in the future should be integrated into the design at the onset of the project. For example, according to Concrete Change, on average and depending on the type of foundation, it costs approximately $150 extra for a zero-step entrance when it is included at the time of design and construction. Modifications to achieve a zero-step entry to an existing home could cost at least $1,000 or more.

Design and analysis tools can be used during the design process to evaluate the benefits of providing accessible design features and products. See also WBDG Life-Cycle Cost Analysis (LCCA) and Assessment Tools for Accessibility.

Materials and Methods

photo at Tolerances for Surface Smoothness, Flatness, and Slope Workshop

A workshop held in 2007 focused on tolerances for surface flatness, smoothness and slope.
Source: U.S. Access Board

The U.S. Access Board's guidelines for accessible buildings and facilities, including those issued under the Americans with Disabilities Act (ADA), recognize conventional industry tolerances for field conditions. The Board receives many inquiries from design, construction, and code professionals on what tolerances are considered acceptable for various materials and assemblies. This project, conducted by Architectural Research Consulting, Inc., developed a bulletin on tolerances identified by industry. As part of this project, a workshop was held that brought together representatives of design and construction industry organizations to validate the Board's approach. For more information see: Dimensional Tolerances in Construction and for Surface Accessibility.


Relevant Codes, Standards, and Guidelines

Codes and Standards



Major Resources


Design Objectives

Cost-Effective, Functional / Operational—Account for Functional Needs, Historic—Comply with Accessibility Requirements, Productive—Integrate Technological Tools, Productive—Design for the Changing Workplace, Sustainable

Organizations and Associations

  • American Association of Retired Persons (AARP)—A nonprofit membership organization dedicated to addressing the needs and interests of persons 50 and older. Through information and education, advocacy and service, AARP enhances the quality of life for all by promoting independence, dignity, and purpose. Among other things, AARP seeks to promote independent living and aging-in-place.
  • Center for Inclusive Design and Environmental Access (IDEA)—School of Architecture and Planning, University at Buffalo, Buffalo, NY—The Center is dedicated to improving the design of environments and products by making them more usable, safer, and appealing to people with a wide range of abilities, throughout their life spans.
  • Center for Universal Design—A national research, information, and technical assistance center that evaluates, develops, and promotes universal design in housing, public and commercial facilities, and related products. They have an extensive publications list including material on many aspects of accessible and universal design, as well as slide shows and video tapes to supplement print resources.
  • Concrete Change—An Atlanta-based organization that started the visit-ability movement. Concrete Change is dedicated to promoting visit-ability in all single-family homes across the U.S. As a result of its advocacy, visit-ability legislation in several cities and towns across the U.S. requires that single-family homes incorporate basic barrier-free design.
  • Institute for Human Centered Design—The Institute for Human Centered Design (IHCD), founded in Boston in 1978 as Adaptive Environments, is an international non-governmental educational organization (NGO) committed to advancing the role of design in expanding opportunity and enhancing experience for people of all ages and abilities through excellence in design. IHCD's work balances expertise in legally required accessibility with promotion of best practices in human-centered or universal design.

Federal Agencies

The major resource for guidance on accessible design is the U.S. Access Board (Access Board). The Access Board is an independent federal agency devoted to accessibility for people with disabilities. Key responsibilities of the Board include developing and maintaining accessibility requirements for the built environment, transit vehicles, telecommunications equipment, and electronic and information technology; providing technical assistance and training on these guidelines; and enforcing accessibility standards for federally funded facilities. For additional resources, see the Access Board's Links Page.