Q & A on Waldram Diagrams

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Description of the formula in the zoning code.
  Waldram Diagrams A Question and Answer Guide to Preserving Downtown Denver’s Sunlight Exposure  Q:What ’ s a Waldram diagram and why do I need one?A: A Waldram diagram is used to calculate the percentage of skyexposure that a building ’ s profile allows through to the street below.You need one because the City and County of Denver requires thatany new construction on over 15,000 square feet of site area allow atleast 15% sky exposure. Q:How does a Waldram diagram work?A: Imagine a fish eye lens placed in the center of the street, lookingup at your building. That ’ s the sort of projected view that you getwith a Waldram diagram.The diagram shows the skyline of the property divided into 100 units. Theprojected outline of the building is shaded. All the remaining unshadedarea is added together to yeild the percentage of sky exposure. Q:How do you make one?A: Just follow the step by step instructions outlined in this guide. It ’ sas easy as plotting a simple graph.First, of course, you ’ ll need all of the accurate measurements pertain-ing to your building, including its distance from the center of thestreet. Downtown right of way widths are typically 80 ’  but should beverified. This is important because all of the measurements for aWaldram diagram are calculated from the center point of the street.Thus, stepping a building back from the street or creating a narrowerprofile can let more sky show through, and this will be represented onthe diagram. See Figure 1 for the type of measurements you ’ ll need.Start with the point where the center line of the street and the centerline of the site intersect. In plan draw a straight line to each skyobstructing point of the building. Find out at what angle to the cen-ter line each straight line is ( Figure 2 ). You will also need to calculatethese angles in section ( Figure 3 ), from the center of the street tothe building ’ s sky obstructing height points. These angles will dictatethe outline of your building on a Waldram diagram. Notice that thenon-sky obstructing building edges, such as the second “ step ”  on thebuilding ’ s facade, though architecturaly prominent, are not measured. To create the diagram begin with a circle. One half of the circle willrepresent that half of the sky that is potentially visible from the streetlooking toward the project. The circle ’ s circumference represents thehorizon, and the center point is directly over head. The diagram, fromhorizon to overhead, is divided into ten segments of 9 º  each, for atotal of 90 º . The width of the horizon depends on the width of theproject site as calculated in degrees from the point where the centerline of the street and the center line of the site intersect. It will alwaysbe less than 180 º . The width of the horizon is also divided into tenequal segments. The example diagrams show horizons for typicalDenver full block dimensions: 73.26 º  for a 266 ’  block face, and78.69 º  for a 400 ’  block face ( Figures 6 & 7 ). If your site is less than afull block face, the angles will be less. 40' to centerof streetCenter lineof building site         8       4       '        6        0       '       1       4       4       '        3        6       '       4        8       '       4        8       ' 8  0  '  1 2  0  '     6  0   '  8  0   '   2  0   '   2  0   '  4  0   ' 56 º 45 º 45 º 34 º Plan34 º 56 º        1       4       4       '       4        8       ' 40'Section56 º 61 º 74 º Figure 3Figure 2Figure 1  Once you ’ ve finished calculating these angles,you ’ re ready to plot the points on yourWaldram diagram. This is a simple processthat is similar to plotting a graph.To plot each point, find both the plan andsection angles of each sky obstructing pointon your building, as determined in Figure 2 and Figure 3 . In this case, we ’ ll plot the top-most point of our example building.The plan angle ( Figure 2 ) has its points plot-ted along the horizontal axis. In this case, theangle from the center point of the street tothe corners of this part of the building is 34 º .Similarly, we plot the section (height) angle( Figure 3 ) along the vertical axis, each curvedline representing a 10 º  segment, countingdown from 90 º  at the center of the circle. Inthe case of our building, the angle of the top-most point measures 74 º .Find out the height and width angles for eachof your sky obstructing points. Then, go tothe Waldram diagram and place a point ateach set of coordinates, as in Figure 4. Then,it ’ s a simple matter of connecting the pointsand shading in the resulting building shape.Count up the remaining white units to getyour percentage of sky exposure. NOTE: DONOT count the large white areasabove 90 º  and on either side of the maximumangle marked — for instance, 73.26 º  for a 266 ’ block face, or 78.69 º  for a 400 ’  block face — incalculating your daylight exposure percentage.If your site is a full block face, you may usethe two templates on the back of this adviso-ry to produce your own base diagram asdescribed above. 90 º 0Ground14.629.343.958.673.2634 º  On Plan Diagram (Figure 2),74 º  On ElevationDiagram (Figure 3)56 º  On Plan Diagram (Figure 2),45 º  On ElevationDiagram (Figure 3)90 º 0Ground14.629.343.958.673.26 Figure 4Figure 5  90º0Ground14.629.343.958.673.26 90 º 0Ground15.731.4747.262.9578.69 Figure 6 - 266’ Block Face Divides 90 º  into 10 equaldivisions vertically Figure 7 - 400 ’  Block Face Divides angle of propertywidth (from L ) into10 equaldivisions horizontally C
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