You don't want to messing with single joists that way, let alone doubles. My pipe is only 2" OD and I won't even go dead center through 2x10s in double formation EVER, unless it is a double rim joist. Your floor joists are double for a reason.
There is a code for maximum penetration based on where you live and then there is common sense as well which is not so common in some tradespeople who unfortunately don't require a special license to buy a chainsaw or sawzall.:furious:
Generally speaking if it's even a single 2x8 I won't even touch it with my 2 1/8 bits and if it's 2x10 I stay under the 1/3 maximum hole size guideline. I l drill 2 9/16 dead center and that's it. A good piping guy with some forethought will usually find a better way instead of the easy way, and furnace pipe can be manouvred into a lot of different offets.
Post more info on what you need here. It sounds like more of your ducting. If it is specific to your ducting you might also post the question about redesigning the ducting layout under HVAC but as Scuba says keep all the info together... and I don't think a rotozip would be what you're after on this one even if code allows it.
I guess I should have posted in my earlier thread then. The reason I did not was b/c the question about whether or not we can cut through the joist has been settled. The inspector came yesterday and said that it was no problem. He inspected the entire beam and said it was installed correctly and the joist we want to cut through is only there for transporting the house.
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