I'm working on my kitchen to add a range hood that goes outside the house. I'm putting the 6" exhaust pipe in my ceiling, between my 1st and 2nd floor, going in the direction of the ceiling joists, as represented by the red arrow in the next picture:
While going this direction however I found 2 boards put together of at least 12 inch height, probably more, in perpendicular direction of the other joists, which marks the end of the inside of the house (Siding would be attached to the other side of the board).
As you can see in the following picture, there are 2 sides in the ceiling:
Side A is inside the house, the blue lines are the studs in the ceiling holding the second floor. Side B is a part that extends a bit out of the house (backyard), there is nothing on top of it, just a small roof on the backyard.
I want to put the exit of my exhaust on this small roof. My question is: Is this, is this a loading bearing joist? Is it safe to put a 6" hole in it (you can see I started it before realizing what I was doing)? What can I do to safely put the exhaust through it?
Best Answer
That joist is carrying something, even if it the weight of the material that make up that part of the house. I would say it is more than that since the new 2X with the framing anchor is attached to it, is telling me it is passing the load from the new 2X onto the one you wish to drill.
Now onto drilling dimensional lumber. Code only allows you to drill a hole that is no larger than 1/3 the total height of the material you plan to drill. 12" material, 4" hole maximum. There are metal brackets available online that will allow larger holes to be drilled.
10-23 edit
If I might add, and it should have been obvious earlier...That doubled joist is actually a beam, not a joist. Those follow a more stringent rule for drilling. I do not know what the largest allowable hole is, short of a 3/4" hole for electrical wiring, but that is all I do know. The mention by the OP about the outside roof and inside the house, that beam is carrying the outside wall above it with possibly the roof portion as well