I'm trying to build a new version of a site that currently doesn't have wordpress installed on it. I'd like to be able to completely build the new website while the current website stays online and active (the site is for a business and gets substantial traffic so downtime is not an option). I guess what i'm trying to figure out is the best way to do this. I'm thinking of just installing WP into a subfolder of their domain, building the site in the subfolder, and then I guess maybe redirecting the index of the .com to the subfolder when its time to launch? I obviously can't install WP into the index directory as its already being used. Is there a more elegant way to accomplish this without redirects? I'd like to keep the old version on the server as a backup should we have to revert to the old site for any reason during development. Thanks for your help!
you should build it on a localhost(on your computer) then when it is done take down the old one and upload the new one 30min of downtime. You could build it in a subfolder with the "do not list this in search engines" clicked so no spiders index it, but that seems like a hassle.
How many pages are on the current site? Are there articles on the current site, or basically just simple static pages?
A averyz said, building a site locally is a much better option. Personally I use Wampserver to develop on http://www.wampserver.com/en/ it's quicker than making your changes live on the internet and it means you don't have to touch the existing site until you're ready. If you really must develop on a live server, you can do so in a subfolder and then follow the guide to moving a WordPress install once it's time to launch http://codex.wordpress.org/Moving_WordPress
I would do the same thing except I use another server folder altogether and point a sub-domain at the new folder. When it comes time to switch, it is easy enough to point your DNS at the new site. The old site remains in tact on the server for posterity sake, but is inaccessible via HTTP and still reachable via FTP.