Modify the structure of a building pad by assigning a function to each layer in the assembly. 
-  Open the site plan that contains the building pad. 
-  Select the building pad. 
  Note: Use 
	 Tab to cycle through the selection options. Selection options are displayed on the left side of the status bar. 
   
- Click Modify | Pads tab Properties panel Properties panel  (Type Properties). (Type Properties).
- In the Type Properties dialog, for Structure, click Edit. 
- In the Edit Assembly dialog, set the function for each layer. 
  Each layer must have a function assigned to it, so 
	 Revit can match layers accurately. Layers can be assigned for the following functions: 
   - Structure. A layer that supports the remainder of the building pad. 
	 
- Substrate. A material that acts as a foundation for another material. 
	 
- Thermal/Air Layer. A layer that provides insulation and prevents air penetration 
	 
- Finish 1. A finish layer, for example, the top surface of the building pad. 
	 
- Finish 2. A finish layer, for example, the bottom surface of the building pad. 
	 
- Membrane Layer. A membrane of zero thickness that prevents water vapor penetration. 
	 
 Note: The Wraps check box can be left unchecked. 
   
- Set the Material and Thickness for each layer. 
- Click Insert to add a new layer. Click Up or Down to change the layer order. 
- Click OK twice.