I help companies manage projects. I'm working with one client right now who is conducting a redesign of their own so I'm a good fit to answer this question.

The term "redesign" has become ambiguous and your intention by the term will affect the answer to your question.

Are you simply redesigning the layout? Are you redesigning the navigation? The site structure? Are you writing brand new text? Are you keeping the same web pages and URLs?

When you say "ground up", I interpret it as all of the above, at the very minimum.

To answer your question:

The short answer is, if done right, no. Your search ranking will not be affected by the redesign and you will continue to enjoy business success.

The long answer is, probably. There exist so many points of failure with website redesigns "from the ground up" that the likelihood is high that somebody with limited exposure to redesigning websites will make mistakes that result in traffic loss.

Case in point:

My client is a charity. It has offices around the world, each with their own website. I'm managing the redesign of the Canadian office's website from the "ground up". I was not involved in the UK or Kenya office redesigns and their results were troubling to us in the Canadian office.

The UK office lost 60% of its traffic following its "ground up" redesign. The Kenya office, managed slightly better, lost 40% of its traffic. I'm projecting the Canadian office will lose 10% of our traffic, and that's following best practices. (I admit, I'm setting low expectations for us. I actually think we'll continue to experience traffic growth at about 20% year over year but I'm a believer in under-promising and over-delivering).

This traffic loss for the UK and Kenya websites has probably impacted the bottom line--the UK and Kenya offices both appear to have less traffic to their Donate page (although I don't have specific dollar-values to support that statement).

If your business lives and dies on the success of your business, call an expert. At the very least, get in touch with me so that I can send you some Excel spreadsheets, templates, and other documents you'll find useful if you choose to do it yourself. If your website is mission-critical, the redesign is not the time to be frugal.

Hope it helps.

Sean Power
Partner, Bansal & Power
http://bansalpower.com/