MSU Extension Planning

Contemporary zoning often overlooks enclosure ratios and other aspects important to creating outdoor rooms out of a community’s public spaces. Planning and zoning tools can be one way for communities to create more productive public spaces that feel like an outdoor room.

Enclosure refers to the extent to which buildings, walls, trees, and other vertical items frame a street and public space. Public spaces that are framed by vertical elements in relative proportion to the width of the space between the elements have a room-like quality that is comfortable for people. Creating these outdoor rooms is important to creating places that pedestrians feel comfortable occupying. Gordon Cullen, in his book “The Concise Townscape,” states that “…enclosure, or the outdoor room, is perhaps the most powerful, the most obvious, of all the devices to instill a sense of position, of identity with surroundings…. it embodies the idea of here-ness.”

The importance of enclosure in public spaces is represented in the Michigan Association of Planning (MAP) Community Planning Principles. These principles serve as a definition of quality planning in Michigan and many communities around the state have adopted them. Community Principles #6 and #7 state that “The scale and configuration of streets and open spaces (parks, greens, squares) should be attractive and comfortable to pedestrians” and “The design of streets and buildings should result in the physical definition of streets and other public spaces.”

The reason behind creating enclosure for pedestrian areas is the need in humans for prospect and refuge. Prospect is based on the pleasure received from views out onto a space and refuge is based on perception of safety and observation of a defined space. There are other urban design concepts that contribute to these two factors such as complexity of design, but enclosure is the main design element behind prospect and refuge.

In a suburban or urban setting, ideal traditional commercial or mixed-use districts are host to enclosures formed by unbroken lines of building fronts. Traditionally, this built landscape framed the thoroughfare in a ratio where the building height and the distance from building to building in any direction were equal. In locations where the ratio is not what is desired, for example, the distance between buildings is more than twice the height, pedestrians can feel exposed and uncomfortable due to the large gaps between buildings. To correct a problem like this, other vertical elements can be used to frame the space. If the road surface is too wide for example, a median or boulevard with street trees can frame the space. Street trees can also be used to frame enclosed space between buildings and the edge of the sidewalk. If trees are not a viable option, street furniture such as banners and building awnings can recreate the feeling of a physical enclosure of an outdoor room.

To help communities understand and implement pedestrian scale design that can create a sense of enclosure, the Michigan Economic Development Corporation (MEDC) and MAP developed the “Pedestrian Scale Design and the Public Realm” resource. This resource provides detail on enclosure ratios stating that the “best proportion [between street and building walls] is a 1:1 ratio (1 street unit: 1 wall unit, meaning that if your right-of-way (sidewalks and streets) is 66 feet wide, then your building wall height should be close to 66 feet (about 4 to 5 stories).” Varying beyond the 1:1 ratio through taller buildings or wider streets can still result in defined public spaces but may require more consideration of other features that can create framing, like trees. Beyond just thinking about enclosure ratios, MAP and the MEDC highlight several other key elements of designing for the pedestrian scale like the type of materials used on building fronts.

Communities can use planning and zoning to help create comfortable outdoor rooms. The planning process can help take stock of the status of enclosure in public spaces and set the shared vision for those spaces into the future. After that vision has been identified, communities can begin implementing changes to achieve the vision. For some communities, that may mean adopting a form-based code that expressly regulates the form of the built environment to create enclosure. The exact implementation of enclosure will vary by community, but it should all be supported by the planning process.

Michigan State University (MSU) Extension offers training and outreach on planning and zoning topics. For more information on placemaking visit www. Miplace.org or contact a MSU Extension land use educator for more information on these training programs.