Sharepoint 2010 Farm Administrator Gets Access Denied

Its a common misconception that SharePoint Farm Administrator will get access to all SharePoint sites in the farm automatically! Farm administrator get access denied error in SharePoint 2010 site collection when trying to browse.
Farm Administrators gets control over SharePoint Central Administration, but not all sites. So, we have to explicitly grant access to required web applications to the Farm Administrator through web application user policies by navigating to:

• Central Administration  >>
• Security >>
• Specify web application user policy >>

Add web application user policy in SharePoint 2010 with PowerShell 
Above step can be automated for all web applications using PowerShell.  

Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue

#User to Add
$UserID="Global\SPAdmin"

#Add user to Web App user Policy

#Get All Web Applications and Iterate through
   Get-SPWebApplication | foreach-object {
                $WebAppPolicy = $_.Policies.Add($UserID, $UserID)
                #Set Full Access 
                $PolicyRole = $_.PolicyRoles.GetSpecialRole([Microsoft.SharePoint.Administration.SPPolicyRoleType]::FullControl)
                $WebAppPolicy.PolicyRoleBindings.Add($PolicyRole)
                $_.Update()
  Write-Host "Added user to $($_.URL)"
                }