In Unreal Editor for Fortnite (UEFN), both “building prop” and “building static mesh” refer to different types of objects you can place within your game world, each with unique characteristics and uses.
A building prop is a mesh Actor whose parameters aren’t exposed to the user in Creative. This means you can’t alter its behavior, but you can modify its size (scale), location (coordinates), or rotation (axis). Props are primarily used to make the environment more visually interesting. An example of a Prop would be a PreFab Building.
On the other hand, a building static mesh, or Static Mesh, is a 3D object without animations, drawn within a level. It can have a transform modification that applies to the whole object. Static Meshes are 3D models created in external applications (such as 3dsMax, Maya, or Blender) and imported into Unreal Editor through the Content Browser. They form the basic unit for creating world geometry for levels in Unreal Engine and can be more complex than other types of geometry due to being cached in video memory.
The key difference lies in their flexibility and functionality: props are easier to manipulate but offer limited customization options, whereas static meshes can be more intricate and versatile but may require more resources.
It’s also worth noting that you have the option of converting your asset into a prop. This lets you dictate how your asset interacts with player characters, devices, other props, and the phone tool in Fortnite Creative, including handling gameplay elements like damage and destruction, and choosing the resource type dropped when the asset is destroyed.
Here is a great guide that shows you how to create your asset into props:
https://dev.epicgames.com/documentation/en-us/uefn/converting-assets-into-props-in-unreal-editor-for-fortnite
Hope that helps 