Removing studs to install a range vent fan?

[Dan Friedrichs]

Our over-the-range microwave has a built-in vent fan which I'd like to make vent to the outdoors (rather than back into the kitchen, as that is perhaps the most useless feature ever conceived of in an appliance...).

My problem relates to the location of the 2x4 studs in the exterior wall I need to install the ductwork through. The red boxes in the attached picture approximately show the location of the studs, while the blue box shows where I need to install the ductwork (a 3"x10" rectangle).

Somehow, I need to cut that middle stud and reframe the wall. Is there an easy way to do this that doesn't involve ripping down much sheetrock and/or removing any cabinets?

I presume the answer is "no", so my backup plan is to duct the air up into that upper cabinet, transition to a round duct, and make a hole in the back of the upper cabinet to the right of the center stud. That involves sacrificing a lot of cabinet space, though, so I just wanted to see if anyone had any better ideas.

[Jim Koepke]

I am not an expert or of great knowledge in this area.

It seems like you have seen your alternatives clearly:

1) Remove cabinets and do some framing work.

2) Take the easy way out and lose a bit of cabinet space.

You didn't list
3) Move the stove to the right a few inches. (sounds nuts to me too.)

Is it possible to put a duct on the back of this that slopes to the right to move the rectangular ducting to the right the few inches needed to make less work with the wall and cabinetry?

jtk

[Ron Natalie]

Well, the first thing to determine is if the wall is load bearing. If the wall isn't loadbearing, you probably don't need to cut much sheetrock other than what is behind the microwave. If it is, and you can just get the cabinet over the microwave out, it should be straight forward.

[Pat Barry]

You said its exterior wall so do whatever possible to avoid cutting the stud. It is major reconstruction work to replace or move one of these in a finished space like you have. I would try to do the transistion to a round duct and route it the most efficient way possible. My microwave duct was convertible (back or top). You don't need to have the full 3x10 area covered. I bet even a 3 inch round duct (assuming you can buy one that size) would do OK.

[Dan Friedrichs]

Thanks, all - I figured there was no easy solution, but it's always nice to have some other eyes look at the problem.

I don't think there's room to shift the rectangular duct to the right, so I will just vent it out the top of the microwave, into that upper cabinet, and transition to a round duct from there. That's probably substantially less work than trying to put a header in that wall.

[Chris Rosenberger]

Unless you have a miniature microwave, I do not see that you have much of a problem. Your blue rectangle is much bigger than 10". The 3 1/4" X 10" duct will be centered side to side on the microwave. You need a little over 5" from the center of the microwave to the stud. From your drawing it looks like you have close to that amount. If you have less than 5" but more more than 3", cut the hole for the ductwork as close to center as you can. Then cut a tapered notch in the side of the stud to get the opening in the right spot behind the microwave. You will need to modify the ductwork to follow the tapered notch in the stud. You could end up with a 3 1/4" X 12" opening on the inside that tapers to a 3 1/4" X 10" opening outside. You can cap off the extra width of the inside opening to reduce it to 10".

[Myk Rian]

Can you vent through the roof? Might be a lot easier.

[Dan Hintz]

Exterior wall, load bearing... place a stud on either side of the vent, remove stud that's in the way. You've increased the load capacity of the wall and retained maximum 16" O.C.

[Eddie Watkins]

I just saw a new house with an external stove vent on an internal wall. They built a wooden canopy over the stove all the way to the ceiling with the bottom the full size of the microwave tapering to about a foot wide at the ceiling. The external vent was on the roof. It looked really nice. The ceilings were probably 10'.

[Don Alexander]

heres some good advice for DIY'ers.........................................

DO NOT cut notches in load bearing studs EVER.

will save you tons of grief down the road

[Ron Natalie]

Not all exterior walls are load bearing.

[Chris Rosenberger]

heres some good advice for DIY'ers.........................................

DO NOT cut notches in load bearing studs EVER.

will save you tons of grief down the road

OK, you are the expert.

What kind of grief will there be down the road?

Will the house fall down?

I have been in construction for over 35 years. I have yet to see a house fail inspection or fall down because a small notch was cut in one stud.

Cutting notches in floor & ceiling joists is another matter all together.

[Dan Friedrichs]

Unless you have a miniature microwave, I do not see that you have much of a problem. Your blue rectangle is much bigger than 10".

Forgive my drawing - it is not very good. I took the microwave down, and found a stud about 1/4 of the way into the 10" wide opening. The opening cannot be shifted, as the vent hole on the back of the microwave is on the very back, pressing right up against the drywall. So there is also no room to "notch and shift".


This got me thinking of something, though - last time I needed to drill a hole through an exterior wall on this house, I found that they had 3 layers of 3/4" OSB sheathing. Is that normal construction practice (apply 3 layers of OSB onto 2x4 studs)?

[Dan Hintz]

I don't build, but 3 layers sounds like massive overkill... i see no reason for more than one layer of 1/4".

As I said, though, put a new 2x4 on either side of the opening you want and remove the current 2x4.

[Art Mulder]

Forgive my drawing - it is not very good. I took the microwave down, and found a stud about 1/4 of the way into the 10" wide opening. The opening cannot be shifted, as the vent hole on the back of the microwave is on the very back, pressing right up against the drywall. So there is also no room to "notch and shift".

So you've got around 7" unobstructed? I would be seriously tempted to just live with a 7" wide duct, rather than mess with the cabinet above the microwave. (of course, in my kitchen, we are already short on cabinet space. Just leave the stud alone, and leave the left 3" of the duct opening blocked.

You said you've taken the microwave down once? Try putting duct tape over 3" of the duct on the left, and I bet you'll still get plenty of air flow. The trick might be finding a 6-7" wide exterior vent cover for the outside of the house.