Questions:
1. Why don't you simply click on the "add" button when doing a spell check in M$ Word when it stops at a word like "soffit"? That would eliminate the problem right away, I would think.
2. Then, simply make a copy of your dictionary file and keep it somewhere in case your system crashes/requries a reboot, etc..
3. I have both the McGraw-Hill Dictionary of Engineering and Tom Philbin's Illustrated Dictionary of Building Terms at my desk at all times. Both are excellent, informative dictionaries.