The process to export a Civil 3D surface to Revit is actually quite easy to do. You simply need to extract the contours as 3D polylines from the surface. But in order to that, you’ll have to have access to Civil 3D.
Start by selecting the surface in Civil 3D and from the TIN SURFACE contextual menu select EXTRACT OBJECTS from the SURFACE TOOLS panel.
Next, select which contours to extract then click OK. Note: Selecting both major and minor contours will produce a more accurate toposurface in Revt.
To select all contours, click on one major and one minor contour, right-click and select SELECT SIMILAR.
Civil 3D will select all 3D polylines of the same layer name. Type WBLOCK to start the WRITE BLOCK command. Choose a location and name for the new drawing and click OK.
When asked to include Map information in the export click YES.
Open the contours drawing and look at it in 3D or in an elevation to verify there aren’t any contours at an unexpected elevation. Make any corrections if necessary to the surface drawing and repeat the export process again.
In the Revit model, insert the contour drawing (or link it in if you think you may need to recreate the toposurface again). When linking in the contour drawing, from the IMPORT UNITS drop down, select FEET. Click OPEN.
From the MASSING & SITE ribbon, on the MODEL SITE panel, click TOPOSURFACE to create a new toposurface.
From the EDIT SURFACE contextual ribbon select CREATE FROM IMPORT and select the contour drawing.
The ADD POINTS FROM SELECTED LAYERS dialog box will appear. Select the contour layers only and click OK.
Points will be added along the 3D polylines of the contour drawing. If the toposurface is large and/or the level of accuracy of the surface is not critical, you can reduce the number of points which helps to simplify the toposurface the selecting the SIMPLIFY SURFACE button and entering a new value in the SIMPLIFY SURFACE dialog box. The higher the number, the farther apart the points will be placed which reduces both the accuracy of the surface as well as the file size.
Click FINISH SURFACE to complete the command.
You can also create a building pad based on the building footprint to “cut” the toposurface for a more accurate representation of the grading when looking at the model in a section or 3D view. Note: You must have a toposurface to create a building pad.