Ikea Varde wall cabinets are 27.5 inches wide. Most wall studs are 16 inches apart. Some, like our one wall are 24 inches apart, which is actually just right for the Varde wall cabinet hardware. We read several suggestions, including cutting out the wallboard, mounting a 2X4 onto the studs, replacing and patching the wallboard then continuing from there. That was a no go for us, since any number of things could go wrong, and end up in expensive repair. We decided on a different route, using plywood instead.
Step 1: Plywood Base
We went to Home Depot and bought regular 3/4 inch plywood. You can get birch plywood, and if I had the option again, I would spend the extra money. We had Home Depot cut the board to the height we needed, and we cut the lengths ourselves, allowing an inch or so if needed.
We marked the studs on the wall. One wall had them 16 inches apart, and the adjoining wall had them at 24 inches apart. We measured from the corner, and marked our plywood accordingly, adding in markings for the Varde hardware supports. We did this by laying the plywood down on a flat surface (garage floor) with cabinets in position, aligning the tops of the cabinets flush to the topside of the plywood. Then we traced the Varde bracket positions onto the plywood using black Sharpie.
We then mounted the plywood onto the studs, and placed the IKEA bracket screws in their place, as well.
Step 2: The Wall
We hung the cabinets to make sure we had them measured correctly and to make sure they were level, before proceeding. As you can see a bit of the plywood shows under the cabinets. This is where I might consider going with the birch if I had the choice again. It only needs to be lightly varnished, and would look much more a part of the cabinetry.
The wall was then taped for caulking, priming, and painting the plywood. Due to the way the cabinets are mounted, we decided not to use the IKEA cabinet backs, which are white.
Since we decided to abut the cabinets on the two walls, a few minor adjustments needed to be made. The doors add about an inch depth to the cabinets, preventing us from totally adjoining the corner cabinets. After mounting the cabinets, you're ready to install, adjust the doors, and shelves.
To finish it off, we bought a piece of birch plywood to fill in the hole under the cabinets, and in between, to make it appear seamless.
I had decided to eventually move photos from our hallway to the kitchen. Since the overhang from the plywood ended up being more pronounced than we had anticipated, I decided to use that overhang for my first row of photos.
And now we just fill 'em up!