Last Saturday I HWE'd 1,600 sq ft of offices by myself with a TM - it took me 6 hrs. There was no furniture to move, to speak of, and almost no spot treatment. With a well-set up porty, with APO and a hose on a hot tap it would probably have taken about an hour longer, apart from set-up time, so at 225 sq ft per hour, 12,000 sq ft would be 53 hrs work.