Design Guidelines

Swales, valley-like excavations into the earth, that are cut into the site to catch and direct water should be designed so they visually fit into the topography of the site. The design of sloped sites should be undertaken with care and understanding for the unique conditions that exist. Fit Uses to Slope Extra study is typically needed to mold proposed site uses to a sloped site. Retaining walls give a landscape a more architectural appearance and allow spaces to be placed closer together (Figure 13-23). An outdoor entertaining space, on the other hand, could be placed on a slope that is between 5 and 15 percent by terracing it on differ­ent levels. During site analysis, the designer should determine what locations on the site have the best views, both toward other areas of the site and to the landscape beyond. Retaining walls, sometimes located on both the uphill and downhill sides of spaces, can also be em­ployed as a means of accommodating the different elevation between spaces. Some outdoor uses may not be possible on steeply sloped sites. Swales that look like gashes because of overly steep side slopes should be avoided. Planted slopes that do not exceed a 50 percent or 2:1 grade can serve as a transition between the ele­vation of the individual spaces. This is especially so where existing trees or other forms of natural vegeta­tion cover the site. Figure 13-21
Outdoor use areas should be oriented parallel to the contours to minimize grading on a sloped site. On dramatically sloped sites, decks may be at the level of or higher than surrounding trees, thus providing a panoramic view into the distance. In extreme situations, walks or paths may need to “switch back” to avoid being too steep. This location is usually not good for many outdoor uses and may be best set aside as a planted area or place where native vegetation is allowed to grow. Outdoor use areas can also be properly tailored to a sloped site by orienting them on the site to minimize grading. Then, the designer should attempt to match the proposed uses to slope conditions where they will fit the site with minimal grading (Figure 13—20). In other words, the elevation difference between the top and bottom of the walk should be spread out over a greater distance in order to reduce the walk gradient. Again, decks should be used to take advantage of views on especially steep ground. On steeper site areas, outdoor uses may need to be molded to the site by creat­ing terraces that are cut into the slope at different elevations. Finally, all slopes that are over 50 percent also should be left untouched to minimize erosion on a sloped site. Steps are also a common necessity on sloped sites to provide access between nearby spaces. Take Advantage of Views Everything possible should be done to take advantage of the inherent views from a sloped site, assuming they are worth capturing. Outdoor use areas should be located and designed to take advantage of views downhill or off the site. To locate outdoor use areas on sloped areas in excess of 15 percent most often requires a deck. Portions of the site that lie downhill from the remainder of the site should likewise be studied and enhanced if necessary. The reader is referred to Chapter 11, where slope standards for other uses are outlined. This should start with the preparation of a slope analysis, a map depicting the different categories of slope on the site. They likewise can be designed as visual ex­tensions of the house by extending materials and edges of the house into the adjacent landscape. The design guidelines that follow will help to accom­plish this objective. Steps should fol­low the guidelines provided in Chapter 11 when they are incorporated into a design. Steps between adjoining spaces might also be wider than necessary so that the spaces feel more connected. This is frequently accomplished by placing the long dimension of outdoor spaces parallel to the contours (Figure 13—21). Some sitting or gathering spaces might even be located on the front or public side of the house if the views there are worth savoring. In addition, they should visually fit into the site context in terms of form and materials. Cut (soil that is excavated) and fill (soil that is added to existing ground) and costs are reduced by the approach. A lawn that is not for recreation can be placed on an area that is up to 25 percent slope. Outdoor areas that are large in size and/or require a gentle ground surface may need to be eliminated from a design program for a steep site. Figure 13-23
A series of terraces separated by walls can establish an architectural character on a sloped site. Even glass or Plexiglas might be used for vertical enclosure along the downhill side of a space (right side, Figure 13—26). A slope analysis will show which areas of the site are steepest and which are the most gentle (Figure 13—19). Wide steps allow adjoining spaces to visually flow together. This approach gives a soft appearance to the landscape and separates spaces by the horizontal distance across the slopes. Figure 13-22
A series of terraces can be established to fit outdoor use areas into a sloped site. Control Runoff and Erosion As indicated previously, care must be taken to drain surface runoff around the house and drain outdoor use areas from portions of the site that are located uphill. Therefore, it may also be necessary to incorporate ramps, especially in the public areas such as the approach to the front of the house. The low side of the site, on the other hand, may be wetter because of the water that drains to it. Walks that are between 5 and 8.33 percent are considered to be ramps and must adhere to ADA (American with
Disabilities Act) standards. Figure 13-26
The vertical planes should be low or transparent to allow views to extend outward from a space. Figure 13-24
A deck preserves the existing steep slope of a site while af­fording outward views. The designer might reserve the steepest areas for revegetation on disturbed or regraded lots as well.