Readme:

Derelict Buildings (High Detail)

Replace the "custom" map which can be found within the teardown files, 
the file path should be something like this:

D:\SteamLibrary\steamapps\common\Teardown

You can find your within steam by right clicking teardown - properties - local files - Browse local files

Once there, Click create - custom and change the file inside the folder "Custom.vox" to the one you've 
downloaded, also called "custom.vox"

Enjoy!