When does one need an architect, and when does one just need a designer?

“The rule of thumb is that if you’re moving a wall then you hire an architect. In offices, it’s less true, because it comes down to space planning. You want to think about efficiency of space—and architects are really good at that. I’d recommend they don’t just go for a look—”oh, someone used recycled wood, let’s do that”—but rather focus on the functionality. Make a room list, and give an accurate brief of what programmatic spaces you need and what connections each of those require, and what kind of space it is. Is it a quiet space? Is it in the center of activity? Is it a sunny space? Basically, that kind of spreadsheet will save a lot of time, and the architect doesn’t need to come in and play analyst. He or she can get right to work.”

Basically you don’t even “just need” a designer.

http://www.inc.com/articles/2010/10/marc-kushner-on-modern-office-design.html