122 Chapter 6
ing for construction and are shown on a demolition plan. Figure 6.5 is an example of a demolition plan
for interior elements of a house. It shows the elements to be demolished and to be retained. Trees and
other items that are to remain should be noted in the keynotes. Dotted lines indicate items (walls, fix-
tures, etc.) to be removed to make the space ready for the new design. A keynote legend is usually in-
cluded on a demolition drawing sheet, showing each number and corresponding note.
Topography Map.
The other important function of the site plan is to highlight the special surface conditions, or topography,
of the lot. This will indicate to the builder the slope or flatness of the site. The topography of a particular
lot may be indicated on the site plan (Figure 6.6). For some projects the topography needs to be shown
separately for clarity, and a grading plan has to be used. Topographical information includes changes in
the site’s elevation, such as slopes, hills, valleys, and other variations in the surface. These changes in
the surface conditions are shown on a site plan by means of a contour, which consists of a line connect-
ing points of equal elevation. An elevation is a distance above or below a known point of reference,
called a datum. This datum could be sea level or an arbitrary benchmark established for the particular
project.
Architects normally adjust the existing contours of a site to accommodate the building construction
and site-improvement requirements. Adjusting existing contours is one of the stages in the site-improve-
ment process, in which the architect or designer requires a topography map to study the slope condi-
tions that may impact the design. This map is usually prepared by a civil engineer and is meant to show
in drawing form the existing contour lines and their accompanying numerical elevations. Normally, ex-
isting contour lines are illustrated by a dashed line, and new or proposed contours are normally shown
as a solid line. The topography map can therefore be considered to be a plat map in which its broken
lines and numbers indicate the grades, elevations, and contours of the site. The distance between the
contour lines is at a constant vertical increment, or interval. Typically, an interval of five feet is used, but
other intervals may be substituted, and one-foot intervals are not uncommon for site plans requiring
greater detail (or where the change in elevation is more dramatic).
When reading a site plan, note that contours are continuous and often enclose large areas in com-
parison to the size of the building lot. This is why contours are often drawn from one edge to the other
edge of the site plan. Contours do not intersect or merge except in the case of a vertical wall or plane.
For example, a retaining wall shown in plan view would show two contours touching, and a cliff that over-
hangs would be the intersection of the contours. When contour lines are spaced far apart, the land is rel-
atively flat or gently sloping. When the contour lines are close together, the land is much steeper.
A benchmark is normally required, which is basically a known reference point such as an elevation
on the construction site. The benchmark is established in reference to the datum and is commonly noted
on the site print with a physical description and its elevation relative to the datum. For example, “North-
east corner of catch basin rim - elev.1085'” might be found on a site plan. When individual elevations or
grades are required for other site features, they are noted with a “+” and the grade. Grades differ from
contours in that a grade registers accuracy to two decimal places, whereas a contour is shown as a
whole number. A grading plan shows existing and proposed topography (Figure 6.7) and is used to de-
lineate elevations and drainage patterns. Grading-plan requirements will vary from one location to the
next, but a final grading plan will typically show the site boundaries, existing landform contours with a
benchmark, existing site features, and proposed site structures. In some instances the grading plan may
also show a cross section through the site at specified intervals or locations to more fully evaluate the
surface topography.