I want to add living space in my attic. I will have over 8' of head room. But my furnace is in the way. Think I can move over the garage. What is a good rule as far as spacing from walls (its gas). Also I have 2/6 joists 16" on center foundation should be fine. Should I sister 2/8 0r 2/10 and add blocking? Or is there a better way? thanks