Volume Rebuild Failed - Insufficient Work Space error

I was trying to rebuild my primary HD as I have done periodically. It consistently failed with "Rebuild Error Encountered / Insufficient Work Space To Continue". I had just installed a new eDrive with updated OS and Tech Tools Pro.

TechTool Pro7 Ver 7.0.4 (998-4af11f4)

Mac Pro4.1
Quad Core
16 GB RAM
eDrive 12.13 GB Capacity, 4.82 GB available