ARE Programming and Analysis: Site-Specific Constraints

Architectural design is largely a practice of working within the parameters of project-specific constraints. There are many types of project constraints that an architect must contend with. These often include, among others, project budget, code requirements and limitations, zoning restrictions, and site-specific constraints. It is the last of these aspects which are covered in the Programming & Analysis division of the ARE. With regard to this specific topic, the exam-taker is expected to have the ability to analyze and evaluate the site-specific environmental conditions which may be encountered at particular project sites and understand how these might limit or impact potential building design solutions for the given site. If a site has adverse or constraining conditions, it is necessary to understand how to mitigate or work within these conditions. Alternatively, one might be given possible sites (or areas within a site) for building development and be tasked with selecting the site (or area within the site) which is most feasible or appropriate for a given project. For projects which are programmatically bound to a particular location within a selected site, which may be the case for additions to existing buildings, adverse site-specific constraints may even make a project unfeasible or add expenses as to be financially unrealizable. In such cases, an architect may be enlisted to perform a feasibility study for the project.

Constraining environmental and site conditions with which a design team may have to contend with, include those related to soil conditions, topography, the potential for flooding, and contaminated or hazardous materials, among other such conditions. In addition to these challenges, there may be the need to avoid impacting nearby protected wildlife areas such as wetlands or an imperative to avoid the destruction of trees or other flora near the building area. In some cases, these considerations can have a major impact on the design of a project.

On a macro scale and often incorporated into the building codes of the particular jurisdiction where the project is located are considerations given to the conditions which the buildings of a particular geographic region are prone to contend with. For example, the southeastern coasts of the United States are subject to seasonal hurricanes, while states such as California are prone to strong earthquakes. These conditions, for example, may constrain the architectural possibilities of the design on the basis of satisfying necessary structural conditions. Understanding these requirements from the outset allows the architect to develop appropriate design solutions at an early stage of project development.

Regarding thermal conditions, it is necessary for designers to follow, at a minimum, the code requirements for appropriate R-values of the wall, floor, and roof assemblies for the particular region where the project is located. The designer should be familiar too with the more localized microclimatic conditions of the particular building site and how those conditions may impact or place limitations on design possibilities. These may include solar orientations, sunlight access, and prevailing wind directions, among other factors. A well-designed building can use such conditions to its advantage, for example utilizing solar gain for passive heating, winds for passive cooling, or deciduous trees for shade during the summer months. Climatic conditions, including relative humidity and average temperatures, can influence strategies for dealing with moisture at the building envelope, such as determining where within a wall assembly an insulation layer or air-vapor barrier may be located. The potential use of solar panels for on-site renewable energy generation should be considered by the designer, and the particular building location, form, and orientation should be evaluated to optimize their use where employed.

The grading of the project site may make certain design possibilities more feasible than others. For example, a site with a significant difference in grade elevation from one side of the building to the other may necessitate that a building user may enter (or egress) the building at a certain floor on one side, while another user might access (or egress) the building at different floors on that opposite side of the building. Thus, the topography of a site can impact circulation patterns within a building and consequently cause possible programmatic challenges for the designer as well. Significant existing grade changes may also make challenges for establishing appropriate accessible routes to and from a building, particularly if the project site constraints make long ramps difficult to fit in where needed. Whether or not the terrain can accommodate the programmatic necessities for the site or whether retaining walls or earth stabilization may be required are also a function of the topographic conditions of the particular building site.

Even for project sites where topographic conditions allow for a relatively flat site, the designer needs to be familiar with basic concepts related to providing for surface drainage of stormwater on a site. Typically, minimal slopes of at least 2% should be provided at paved surfaces in order to direct surface runoff towards catch basins or other drainage elements, which can capture the water and channel it into municipal stormwater lines. Other possibilities include the direction of runoff into swales or rain gardens. Consideration should also be given to the possibility of using permeable paving systems to reduce the amount of runoff from the project site. In any case, a clear plan for providing drainage at the site should be developed, particularly for sites prone to flooding.

Geotechnical analyses may reveal soil conditions that present additional challenges for a building site or at least dictate the logical structural foundation systems which may be selected. For example, inadequate soil strength may disallow the use of strip footings and may require more costly foundation solutions such as piles or caissons. It is, therefore, necessary to determine the properties of the soil at the project outset, and the architect will likely need to provide to the geotechnical engineer, at an early stage, possible preliminary exterior wall and column locations so that soil testing can occur at the appropriate locations on the project site. Designers should be familiar with the various structural foundation types and the particular conditions in which they may be best employed.

Where a site is assessed and found to contain hazardous materials, designers may be faced with decisions as to how to best deal with the situation. Depending on the type and the extent of contamination, particular mitigation measures may be pursued. In some cases, the encapsulation of a material may be possible. While such contaminated project sites pose challenges, there are also potential advantages in utilizing such sites for building projects. There may be municipal funding available for site redevelopment or other financial incentives that outweigh the difficulties of building at the site. If certification through a green building rating system is sought, such rehabilitation of contaminated sites can provide a significant number of points toward meeting the certification.

In summary, there are several potential site constraints that building projects may have to contend with. Those related to environmental, topographic, and climatic conditions are only part of the site characteristics with which designers must contend, but we have focused here on some of these aspects as they are covered within the Site-Specific Constraints topic of the Programming & Analysis section of the ARE. While such site-specific constraints can present significant challenges to a building project, designers who can properly analyze and evaluate site conditions and understand possible design solutions are in a better position to successfully complete a project while meeting budget and project schedule goals.

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