About pantries...several years ago, there was a lot of discussion about pantries, with an emphasis on shelf depth. The consensus was that 12" is the "sweet spot" for shelf depth.
12" is deep enough to hold all food (cereal boxes, 2 or 3 deep cans, etc.), pantry storage containers (e.g., Tupperware), and the vast majority of small appliances (KA stand mixers, blenders, breadmakers, etc.).
12" is not so deep that things get lost in the "depths". Even 18" is too deep -- I had that in my old Kitchen and things got lost all the time! Plus you end up putting things in the front that are unrelated to those behind them.
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The most efficient pantry storage is one that
Allows you to see everything in it with one look
Doesn't "let" you stack unrelated things deep (e.g., cans of peaches in front of cans of green beans or pantry storage containers holding different things, ...)
Utilizes the entire space floor-to-ceiling, or as close to that as possible
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Pantry Types:
24" deep pantry cabinets don't meet any of the three above, made even worse when over 18" wide. Even if they have doodads that swing/pull out (and are generally expensive), storage is limited b/c of the need to accommodate the hardware and other parts to the swing out.
18" wide x 24" deep pullout pantry cabinets meet #1 & 2. BUT, they have to be pullout pantries, not shelves unattached to the door or roll out tray shelves (ROTS) (which don't work above waist level or so anyway). They work only because you can see everything when you pull the door open fully by looking at both sides. If you had to move things around, they wouldn't work.
15" deep pantry cabinets meet #1 and 2 and have the added advantage that you can look without moving things around. The 15" depth includes the back wall, so the shelves are really only 14" or so deep. (In non-IKEA framed cabinets, both the back wall and the face frame are included in the 15" depth, so shelves are 13" deep or so.)
Built-in pantries, whether reach-in, step-in, or walk-in, are the most efficient and meet all three above.
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The pantries I put in your layout, combined, will provide you with much more and much more usable pantry (and other) storage than one 24" x 24" pantry cabinet.
Q