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How do I safely attach an over range microwave support bracket to granite backsplash? The top of granite backsplash ends an inch above bottom of microwave so I am installing 1inch plywood to make wall behind microwave flush with the granite. Should I drill all the way thru the granite and attach screw to wall behind granite to prevent the weight from cracking the granite ?

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    Your title is a bit misleading. There's no reason you need to mount anything to the granite. Commented Apr 10 at 17:57

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The proper mounting method is dependent on the design of the support bracket and the exact location it needs to be mounted to.

With 1 inch of plywood on the wall it is very strong. The plywood should be mounted to the wall studs with construction screws. If that is done, place the support where it needs to be anchored to the wall.

Many support brackets are 2 or more inches high and have many mounting holes. This should put mounting holes at the plywood allowing you to attach the bracket to the plywood. Ideally you should know where the studs are and predrill and use 3 inch screws through the plywood and into the studs. If this can be achieved only 2 mounting points are needed.

Should you not be able to locate the studs, the plywood can hold the bracket and the microwave. Install 3 to 5, 1-1/4" construction screws through the bracket into the plywood.

If there are no mounting spots where you can screw into the plywood, your could drill holes for your own mounting spots, and/or drill through the stone with a masonry bit and screw through the stone into studs. While it is not preferred, you can use a toggle bolt. This is least preferred as it could result in cracking of the stone. Don't overtighten the toggle bolts.

The micro should also be held by screws down from the cabinet above, or from additional brackets holding the top to the wall. ( You didn't indicate the total details of the install.) The bottom bracket does not hold all of the units weight.

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  • Yep. Even the skeletal back plates these days tend to have full height strips up the sides. As long as you get a few screws into your plywood, there's no way the microwave is coming down. Commented Apr 10 at 17:57
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Yes, I agree the safest it to drill through and use toggle bolts (or bolt directly to studs) behind the backsplash. Do not over-tighten the bolts.

That "granite" is actually an engineered material, a composite of stone and plastic. Unless the manufacturer provides actual data on its tensile strength, assume that it cannot support too much weight, and expansion bolts might even cause it to crack or split.

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    Togglers don't seem necessary here at all. With only one inch of overlap for the mounting plate there's no need to drill through the backsplash either. Commented Apr 10 at 17:56
  • Thank you very much and for the screw sizes and details. Commented Apr 11 at 6:46
  • How many and what size and type of screw should I use to hold plywood to wall behind microwave that microwave will attach to? Commented Apr 11 at 6:48
  • @KarynGephart that depends what you're going screw into—presumably wood studs behind drywall. Pretty much any kind of screw intended for wood would work—I'd probably use screws with self-countersinking heads. Drill holes in the plywood just big enough for the shank of the screw, and drive the screw so the head is flush with the ply. Number of screws probably depends how many studs you're able to hit. Commented Apr 12 at 17:15

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