If your building sits on a sloping site, the Revit Toposolid representing the terrain will likely overlap elements on the lowest levels of your building model. To remove this overlap, you can excavate the site where the building is located.
An easy approach is to excavate a flat building pad in the entire building area. This is similar to using excavation equipment to clear a site and create a level area for the new construction.
If your building has a basement or subterranean levels, an alternate approach is to use the lowest of the underground floors to excavate the site.
Excavating to Create a Flat Building Pad
Open the Floor Plan view for the lowest level of your building.
Note how the Toposolid element overlaps the lowest level.
Open the Architecture > Building > Floor tool.
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Create a new floor type for the building pad.
Choose the Generic -12” floor type from the Type Selector in the Properties palette.
Click Edit Type in the Properties palette.
Click Duplicate in the Type Properties dialog.
Enter a name for this new floor type, like “Building Pad”.
Click OK to close the Type Propertied dialog.
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Create a new floor element to represent the building pad area.
Choose a boundary line tool.
Then, draw a boundary around the area to be excavated.
It’s OK, and even desirable, to excavate an area larger than the building’s footprint.
This provides room for the construction work.
The areas immediately adjacent to the building will typically be filled in later with fine grading and landscape design elements.
Set the Height Offset from Level property to an appropriate distance below the lowest floor level:
This would typically allow room for the thickness of the lowest Floor element plus needed insulation and structural support (like sand or gravel).
Models exported from Forma Building Design have two floor layers at the lowest level:
A floor of type Forma 0’-9 27/32” (basicFloor_0.25), which is 9 27/32” thick.
Another floor of type Forma Insulation 0’-7 7/8” (basicGroundFloor_0.2), which is 7 7/8” thick.
For an early-stage model, use the combined thickness of these lowest floor elements — approximately 1’-6”. Enter this as a negative distance (-1-6”) to move the building pad below the floor level.
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Excavate the toposolid with this building pad.
Open the default 3D view.
Turn on the Section Box for the 3D view to cut a section through the project site.
Move the Section Box sides to cut through the project site.
Zoom in (ZR or scroll the middle mouse button) on the building until you can see the lowest floor level and the building pad below it.
Select the Toposolid. It will turn blue to indicate that it is selected.
Open the Modify | Toposolid > Toposolid Shaping > Excavate tool.
Select the building pad element in the 3D view.
The building pad excavates the Toposolid and creates a flat site area the building.
Reshaping the Building Pad
As you develop your design in Revit, you can reshape the building pad as needed to match your design and adjust the excavated area.
