Restore Steam games from non-Steam backup [duplicate]

The following instructions are a simple way to move your Steam installation along with your games:

1. Exit the Steam client application.

2. Browse to the Steam installation folder for the Steam installation you would like to move (C:\Program Files\Steam by default).

3. Delete all of the files and folders except the SteamApps folder and Steam.exe

4. Cut and paste the whole Steam folder to the new location, for example: D:\Games\Steam\

5. Launch Steam and log into your account.

This is from the official Steam support post and I suggest you to take a look you'll find more informations and related topics.

In order for Steam to recognize a non-Steam backup, you not only require the game files themselves, but the manifest appmanifest_[appid].acf files found in the base SteamApps folder.

For example, if I wanted to move Audiosurf, I would move the Audiosurf folder and appmanifest_12900.acf.

Otherwise, Steam will automatically perform a verification and most likely update all the files; re-download the whole game.

Note: If an update has come up between your install date and the date the backup was created, Steam will mark the game for updating and will update it as if you had it installed previously, as opposed to redownloading the whole game.

create a bunch of *.csd and *.csm files so Steam can identify it as restoreable?

With your game folder and manifest .acf file, just stick them in a directory and from there, you can do whatever you want to them. 7-zip them, regular zip them, ISO them, etc.

Here is what you need to do

1. Copy paste the Game backup files in \Steam\steamapps\common\GAME-NAME(Folder name should be correct or it won't recognize the files)

2. Install that game. Here it should detect the files if folder name was correct but will start download from start anyway.

3. Let it download 1 MB or 2.
4. Pause the download and then resume it. It will detect the files and only download required updates.