[Solved] Steam Library folder not writable Error when Install or Update on External Hard Drive

Problem: “Library folder not writable” error appear if create a new library for Steam games, especially located on external SSD or HDD drive.

Solution 1: Make Sure Folder is not Read-Only

Step 1: Close Steam client by right-clicking its icon at the system tray and choosing Exit option.

Step 2: Navigate to C drive > Program Files > Steam > SteamApps > downloading folder and delete the numbered folder corresponding to the problematic game. You can find that number at Steam Apps Page by searching for game and checking the AppID number.

Step 3: Locate Steam library folder, usually located at C drive > Program Files > Steam > SteamApps.

Step 4: Right-click on the problematic folder > Properties option > General tab > Attributes section. Clear the box next to the Read-only option and click on Apply.

Solution 2: Reinstall Problematic Game

Step 1: Login with administrator account and make sure you have backup your files using Steam Cloud.

Step 2: Go to Start > Control Panel > Select to View as: Category at the top right corner then click on Uninstall a Program under the Programs section.

Step 3: Locate the problematic game in Control Panel or Settings and click on Uninstall.

Step 4: Steam client should launch and ask you to confirm choice and delete the game files from computer.

Step 5: Reinstall the game by navigating to the Library area of Steam client and locating your game from the list at the left side of the window. Right-click on the game and choose the Install game option.

Solution 3: Perform Folder Fix from Steam Client

Step 1: Open Steam client.

Step 2: Click on Steam option at the menu at the top of the client’s window and choose Settings.

Step 3: In the Settings window, navigate to the Downloads tab and click on the Steam library folders button at the top of the window.

Step 4: Locate the folder where your problematic game is located. Choose the one you want to fix, right-click on it and choose the Repair Library Folder option.

Step 5: Confirm any UAC prompts and Steam Client Service window will open to repair the folder.

Solution 4: Use a Folder Other Than Program Files

Step 1: Create a folder and make sure you disable its read-only property.

Step 2: Right-click on Steam client either on the Desktop or in Start menu and choose Run as administrator.

Step 3: Click on the Steam option at the menu at the top of the client’s window and choose Settings. In the Settings window, navigate to Downloads tab and click on the Steam library folders button at the top of the window.

Step 4: Click on Add Library Folder and select the folder you have created

Step 5: Uninstall the game by navigating to Library tab in the Steam client, locating your game in the list at the left side of the window, right-click on it and choose Uninstall option.

Step 6: Install it again from Library and make sure you select the new folder for the installation. Right-click on the game in the Library and choose Install.

Solution 5: Restart Computer

Solution 6: Check Hard Drive for Errors

Step 1: Open Windows Explorer then right-click on the drive where your problematic game is located and choose the Properties option.

Step 2: In the Properties window, navigate to Tools tab and click on Check under the Error checking section. Follow the instructions on screen in order to progress.

Step 3: Restart computer afterwards.

Solution 7: Add Steam to Antivirus Exceptions list

Step 1: Open antivirus user interface.

Step 2: The Exceptions or Exclusions setting is located in different spots with respect to different antivirus tools.

For Kaspersky Internet Security: Home > Settings > Additional > Threats and Exclusions > Exclusions > Specify Trusted Applications > Add.

For AVG: Home > Settings > Components > Web Shield > Exceptions.

For Avast: Home > Settings > General > Exclusions.

Step 3: Add Steam’s main executable file in the box which will appear prompting you to navigate to the file.

Step 4: Restart computer.

Solution 8: Take Ownership of the Folder and Give Write Permissions

Step 1: Right-click the library folder > Properties > Security tab > Advanced button. Advanced Security Settings window will appear.

Step 2: Click the Change link next to the Owner: label, Select User or Group window will appear.

Step 3: Select the user account via the Advanced button Add your user account. Optionally, to change the owner of all subfolders and files inside the folder, select the check box Replace owner on subcontainers and objects in the Advanced Security Settings window. Click OK to change the ownership.

Step 4: In Security tab of the library folder’s Properties window, click on Edit in order to change permissions and select your personal user account you set the ownership to. Change permissions to Full Control and apply the changes.

Reference

Folder not writable : Steam – Reddit
Library folder not writable problem :: Steam Help and Tips