I've got a site arranged the following with subdomains as subdirectories:

/ [webroot]
/subdomain1/
/subdomain2/

Let me create an htaccess file that rewrites all utilized files to maintenance.php w/ 503 message, but I am unsure why the next doesn't catch the subdirectories?

RewriteEngine On
RewriteBase /
RewriteCond %{REMOTE_ADDR} !^111\.222\.333\.444$ 
RewriteCond %{REQUEST_URI} !^/maintenance\.php$
RewriteRule ^(.*)$ /maintenance.php [L]

Must i on-site visit each subdirectory something similar to...

RewriteRule ^/subdirectory1(.*)$ /maintenance.php [L]
RewriteRule ^/subdirectory2(.*)$ /maintenance.php [L]

This will work:

RewriteEngine On
RewriteCond %{REMOTE_HOST} !^111\.222\.333\.444
RewriteCond %{REQUEST_URI} !/maintenance.php$
RewriteRule $ /maintenance.php [L]

For those who have additional htaccess files inside your subdirectories, you need to watch out for changes once you remove that file. If htacess controls rewrite, you might receive 404 errors whenever you view individuals pages.

I had been looking to begin to see the maintenance page, not recognizing I desired to possess a different ip based on the following code:

This code enables your ip to see the website and nobody else:

RewriteEngine On
RewriteBase /

#ip is not your ip. Change ip to see maintenance page
RewriteCond %{REMOTE_ADDR} !^111\.222\.333\.444$

#requests made not to maintenance.php ... 
RewriteCond %{REQUEST_URI} !^/maintenance\.php$

#rewrite to maintenance.php
RewriteRule ^(.*)$ /maintenance.php [L]