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I am installing an OTR microwave between cabinets which are 15 1/4" deep. The OTR needs cabinets no more than 13" deep, so I've built out from the wall 2 1/4" using a stack of three 1x6 boards. This is along the lines of the answer presented here. The bumpout is attached to 3 studs using GRK RSS structural screws (5/16, 5 1/8" long).

For now, I have attached the OTRs metal mounting bracket/rail to the bumpout using five 1/4 2" long lag screws, as in the picture attached. These screws do not go into the studs, but are secure in the bumpout. Is this sufficient for a ~50 lbs. OTR microwave? Or should I have the rail directly attached to at least one stud, too?

an image showing the bumpout attached to 3 studs, with the metal bracket for the OTR attached using 2" lag bolts

Thank you in advance!

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  • @FreeMan microwaves typically hook on to a bracket at the bottom of the back, and then bolts come in from the cabinet/shelf above in to the top of the microwave. You can see the 4 holes in the underside of the middle cabinet in the picture above.
    – longneck
    Aug 31, 2021 at 15:46
  • Ah! Thanks, @longneck. As you may surmise, I've never installed one like this.
    – FreeMan
    Aug 31, 2021 at 15:47

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In this case, you don't need to screw the bracket all the way in to the studs. Screwing the bracket in to the wood, which is screwed in to the studs with sufficiently long screws, is more than strong enough to hold a microwave.

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  • Great, thank you! For my future reference, is there some way to know when screwing into studs would be required? For example, if I was installing something heavier than a microwave, say 200 lbs, would the same approach work, or would I need to go into studs then?
    – ramesesjd
    Aug 31, 2021 at 16:05
  • @ramesesjd The same approach will work for heavy weights. Splitting the load between two or three studs is always better that heavy load into one stud.
    – JACK
    Aug 31, 2021 at 16:10
  • @longneck- although your answer is sound in concept, my concern is the placement of the screws through the bracket into the bumpout. They are in the bottom inch of the 1x6s below the structural screws and could be prone to shearing of the 1x6s at the bottom if at least one is not in a stud. Of course, being partially supported by the four hanging bolts in the shelf above it may not be an issue. However, I would run at least one long screw through the center point of the bracket into the middle stud.
    – HoneyDo
    Sep 1, 2021 at 3:12
  • Once the bolts on the top are tightened up, the bracket on the back carries very little weight. If the wood hasn't split yet from installation, hanging it isn't going to now.
    – longneck
    Sep 1, 2021 at 14:35

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