This command creates a rectangular polyline around selected linework. This can be used to give a building all one elevation.
In the Draw Building Envelope dialog box, set the layer for the new polyline and the desired offset value, (the above example is offset by 5 feet). Select whether or not to be prompted for an elevation for the new polyline, and whether or not to trim existing linework that crosses the new polyline. Click OK. Select the entities that make up the building.
Select building lines:
Select objects: pick the building linework
Select
objects: press Enter
Draw another building envelope
[<Yes>/No]?
Pulldown Menu Location: 3D Data
Keyboard Command: bldg_perim
Prerequisite: Building linework
File Name: \lsp\poly3d.arx