Patching drywall between two corners

Question

I have an existing floor-to-ceiling narrow deep closet (11" wide opening, straight in). I want to cover the bottom 5" with drywall, so it'll eventually look like this:

_{(source: hyarros.com)}

Where the lavender piece indicates what I want to add. The salmon portions are existing wall.

I'm not sure how I should go about this. Both of the corners have a metal corner bead, which seems difficult to cut. I was thinking of screwing an 11" 2x4 cross beam behind the patch, and then screwing the drywall to that piece. That would have a second advantage in that I was going to add a melamine shelf on top, so the 2x4 would provide the requisite support for this shelf.

Is that the best approach? If so, how should I screw the 2x4 into either side? I tried driving a 2.5" screw at a 30 degree-ish angle, but it doesn't appear that strong.

Answer 1

Since you want to have the drywall piece be 5" high I think you will want to have backer behind it for its full height. Consider making it 5.5" high and then using a piece of 2x6 lumber (that comes 5.5 inches wide) as the backer piece. Cut a couple of pieces to straddle across the bottom of this opening at the back and middle to hold up the shelf the full length. To install the front backer piece pre-drill clearance holes through the 2x6 that let your screws slide in place. Then use screws about 3" long to secure through the existing drywall at the corners. This will end up surprisingly strong! See picture below.

The trick to get the 2x6 to screw in place would be to start two screws from each end on each side (eight screws total) and tighten them down evenly and gradually. Make sure to stagger the pre-drilled holes from side to side of the 2x6 on each end so that the screws do not collide with each other as they enter the existing corner studs.

Answer 2

You will want to cut the corner bead out anyway. If you put new tape and texture on top of the existing corner bead, you will end up with two very noticeable lumps.