In previous lectures, we have talked about how to add grid lines and levels. These elements help us to position other BIM model elements on horizontal planes. In this video, I am going to show you how to draw the boundary of a building lot, which indicates the allowable construction area. First, we need to import the site plan from a CAD file as an underlay. In the Project Browser, open “site” plan view in the branch of “architecture plan view.” Under the “Insert” tab, select “Import CAD” and find the CAD file named “A-2-1-1”. Check “Current view only” checkbox and select “centimeter” in the “Import unit” drop-down menu. Make sure to select the same unit with the one used by the imported CAD file. Then, set “Positioning” as “Auto - Center to Center”. Click on “Open” to start importing the CAD file. Let’s take a look at the underlay. We can see that the boundary of the building lot of our project is composed of two line types. One is property line, and the other one is building line. The property line is used to indicate the legal boundary of real estate, and the building line is used to indicates the setbacks from roads or streets. Let us create property lines now. To ensure property lines can be seen in the view, we should first check their visibility setting by selecting “Visibility/Graphics” under the “View” tab. Check both “Site” and “Topography” checkboxes and click on “OK.” Now we are ready to create property lines. Select “Property Line” under the “Massing and Site” tab. On the “Modify” panel, choose “Pick Lines” tool in the “Draw” toolbox. Pick on the CAD lines to create the upper side, left side, right side, and lower side property lines. Note that there is an building line overlapping right on the top of the lower side property line. So, we need to use another type of line to add an building line here. Because Revit doesn’t provide building line, here I am going to use annotation line as a substitution. On the underlay we can see the style of the building line is different from that of default annotation line, so we need to select a proper line style before drawing a building line. Let me demonstrate the process. Under “Annotate” tab, click on the “Detail Line” tool on the “Detail” panel. On the right-hand side, find the “Line Style” drop-down menu and select “<Centerline>”. After that, use “Pick Lines” tool to draw the lower side building line and drag the endpoints to appropriate locations. Notice that we use the annotation lines to represent the building lines. Unlike property lines, annotation lines can only be seen in the views they are drawn. So if we want to see them in other floor plan views, we have to copy them to the other floor plan views. To copy them, select the annotation line first, and then click on the “Copy to Clipboard” tool and the “Paste” tools in sequence. In the drop-down menu, choose “Aligned to Selected Views” and select all the floor plan views by holding down the Shift key. Click on “OK,” and now we can see the building line in all the floor plan views. After drawing the property lines and building lines, we can start to create a toposurface by using the “Toposurface” tool. First, in the “Project Browser”, open the “GL” plan view under “Floor Plans”. To ensure we can see site and toposurface in the “GL” plan view, we should first check the visibility setting of their categories. Let us click on the “Visibility/Graphics” icon under the “View” tab, and find the “Site” and “Topography” checkboxes. Let us make sure these checkboxes are checked, and then click on “OK”. Next, under the “Massing and Site” tab, select the “Toposurface” tool to start creating a toposurface. On the “Tool” panel, click on the “Place Point” icon and select the four corners formed by the property lines and building lines. Then, click on the green check icon on the “Surface” panel to finish edit mode. If you want to make this BIM model more realistic, you can change the material of the toposurface. On the left-hand side, in the “Properties Palette,” let us select the “Material” field. We can choose any material from this drop-down menu. Here, we use “Grass” material. After that, we can see the color of the toposurface changed. Now, let us use the section box to see the surface of the topography and the cross-section of the soil under the surface. In this way, we can let everyone know about the geometry of the site. Besides, it provides a way to visualize the soil excavation process. After creating the toposurface, we can start to create the boundary of the excavation area. First, we need four reference lines to specify the area we are going to excavate. By experience, they can be placed fifty to eighty centimeters inside the toposurface from the property or building lines. However, in a Revit project, Revit does not provide line type reference objects, so we need to use reference plane instead. In the “Architecture” tab, select the “Reference Plane” tool and create the upper edge of our excavation rectangle first. After that, change the distance between this reference plane and the grid line “D” to 50 cm. Let us create the other three edges using the same steps and adjust their locations. Here, the distance between the left side reference plane and the grid line “1” is 70 cm, and that between the right side plane and the grid line “4” is also 70 cm; for the lower side plane and the grid line “A”, the distance is 80 cm. After placing all the reference planes, we can use the “Building Pad” tool to create a building pad for excavating the volume under the toposurface. Under the “Massing and Site” tab, we click on “Building Pad” icon and choose “10 cm Concrete Pad” in the “Properties” palette. Then, set the “Level” field to “GL” and the offset to be “-500”. This means we position the pad five meters below the ground level because the unit in this project is in centimeters. Under the “Modify” tab, use the “Rectangle” sketching tool to sketch a closing loop along the reference planes we’ve created before. This step defines the area we are going to place the building pad, and by doing this, we excavate soil between the pad and the toposurface. Finally, click on the green check icon. We’ll see a ten-centimeter thick pad with a rectangular shape, 5 meters below the “GL” plane. Now, we can explore the 3D view and see the excavated space in our model.