If you are tearing down your web site and rebuilding it completely from the ground up, you should expect a lot of search ranking fluctuations. If you want to control and track as much as you can on the SEO side, it is recommended you do it in stages and split the process up.

John Mueller of Google was asked about this on Reddit and John said “I’d try to split it time-wise so that you can recognize any negative effects in each part, and take action to improve them.”

The thing is, if you don’t split up the move then it can be really hard to understand what site changes impacted the Google ranking changes. John said “If you do everything at once, you’ll never know what to fix, and even if things end up “same as before”, you won’t know if one part went down, and was compensated by an improvement on the other part.”

“Keep things controllable & trackable,” John Mueller said.

Here is John’s full answer:

Whenever I do site migrations, even to new CMS platforms, I try to keep the URLs, content, meta data, etc all the same. But sometimes you can’t and if you cannot, you do want to isolate whatever you can.

Forum discussion at Reddit.