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View Full Version : Removing studs to install a range vent fan?



Dan Friedrichs
01-02-2011, 5:56 PM
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
01-02-2011, 6:27 PM
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
01-02-2011, 7:07 PM
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
01-02-2011, 7:23 PM
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
01-02-2011, 8:21 PM
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
01-02-2011, 8:25 PM
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
01-02-2011, 8:54 PM
Can you vent through the roof? Might be a lot easier.

Dan Hintz
01-02-2011, 9:12 PM
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
01-02-2011, 11:46 PM
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
01-03-2011, 12:32 AM
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
01-03-2011, 6:08 AM
Not all exterior walls are load bearing.

Chris Rosenberger
01-03-2011, 8:04 AM
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
01-03-2011, 10:15 AM
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
01-03-2011, 11:19 AM
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
01-03-2011, 12:57 PM
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.

Don Alexander
01-03-2011, 6:16 PM
everybodies definition of small is different
i've seen plumbers and electricians who ought to know better "notch" over halfway through load bearing studs sometimes 5-6 in row or more same for floor joists

1 stud in a basic wall probably wouldn't be too big of a deal , just better for those who don't know for sure to not assume its fine is all
and people tend to pay a bit more attention to "DO NOT" than they do to "you might want to think that through a bit better"

cracked sheetrock joints is "tons of grief" to most folks ; doesn't take much sagging to cause those either

hope that explains where i'm coming from no angst here hopefully none there either :)

Ben Franz
01-03-2011, 7:57 PM
I would suggest that you need a solution that does not reduce the size of the duct. Microwave/vent units are already a comprimise - the sump area that collects smoke and fumes is not very effective and the fans are underpowered compared to "real" vent hoods. That said, it is much better than no vent or a recirculating fan that does nothing useful. The addition of 2 new studs to replace the one in the way isn't hard to do but might run into wiring that will be in the way - you can notch the new studs at the edge and protect the wire with a nail plate. The biggest hassle is having to remove a section of drywall floor to ceiling to get the studs in place.

Jim Becker
01-03-2011, 8:04 PM
I would either install two new studs with the required separation, or install a header above the location that the vent needs to pass, just as would be done with any opening in a wall. This would also allow for putting in a more capable range hood/vent fan in the future in a way that will not present questions. And yes, the size of the duct should not be compromised as it will lower the air flow significantly from the fan...and the fans in this type of microwave/hood combinations are already challenged in that department.

That said, it's unlikely that removing one stud would seriously compromise the structure unless that specific stud was lined up to support something else...and if that was the case, it would usually be more than a single stud if the wall was constructed properly.

brian watson
01-04-2011, 11:06 AM
You're problem is identical to the same problem my wife and i have -- your microwave may be the same model as well -- we are looking to solve this problem this year but haven't engaged any contractors, etc. -- what make/model # microwave do you have?

Matt Meiser
01-04-2011, 11:27 AM
It really shouldn't be that hard to cut out drywall. If you pull the stove, the microwave and the cabinet you could cut the drywall, remove the part of the old stud that's in the way and install new studs. Leave a couple inches of drywall at the top so you don't get into the ceiling. Hire a good drywall guy and he can blend everything in. Then get paint mixed to match a piece of the cut out drywall and paint the wall corner to corner. Only you will know what's been done. The biggest obstacle I see is that there's probably some wiring in there but Ben had a suggestion for dealing with that.