I'm remodeling my kitchen. First major remodel. I have purchased 12" deep unfinished stock cabinets. I would like to make the face of the 30x30x12 wall cabinet that will be above the stove/oven be 15" from the wall so I can add crown molding to all the wall cabinets later on. Is this possible by attaching a couple 2x4's flat against the wall to the existing studs and attaching the cabinet to those?
You can, but...
It is unlikely but possible that the exact space you want to install the cabinet only has 1 stud available. (if studs are 16 inch on center it is possible that a stud is centered in the vicinity of the cabinet).
If that is the case, then wall anchors will be required to help support things.
Do you have plans to mount a hood or micro hood in this area? If so, this configuration could prove troublesome on installation. Further, depending on the cabinet height, you may find the cabinet intrusive for full operation of the rear of the stove, especially with a tall chef and rear-mounted controls on the stove/oven.
Either way, make plans to seal the gap created by pushing the cabinet out from the wall. That will prevent having an unclean able greasy trap for dirt which will be prone to dropping into your food.
Yes, your plan is good. Attach the first 2 additional 2x4s to studs with 3" screws. It may be better to run these horizontally so you cover at least 3 studs. When these are solid attach the next 2 also with 3" screws. Now with someone's help add the cabinet and use 1 1/4 screws to attach it to the supports.
I agree with Nomind. Two 2x4s attached one at a time will do the job. If the cabinet is at the end of a run of cabinets you will need to finish the exposed edge. Depending on the type of cabinet you will need some type of skin to run from the front rail to the back wall. If you just splice in a filler it will not look good with and exposed seam. Good luck.
1) cut 4 30" 2x4's to length to fit behind the cabinet, two at the top of the cabinet, two at the bottom. even better is to rip 3" x 3/4" strips of plywood to take the place of the 2 x 4's. its much flatter and easier to use without it twisting over time.
2) apply construction adhesive to two boards. attach with screws to whatever studs you can hit, horizontally to wall at top and bottom of cabinet location.
3) rip or plane the third and fourth 2x4 to 1.25" thickness.
4) install third and fourth board on top of first and second (respectively) using screws only.
5) install cabinet using vertical cedar shims between cabinet and outer boards. this will let you "tune" the fit to accomodate for the natural twists and variations in the 2x4's. cabientry is usually installed with 1/32" accuracy, so its important to use the shims to get the cabinet just right. otherwise your cove/crown moulding will look terrible when you are done.