What Makes a Built In Different From a Cabinet Run
One is cut to an opening, the other is chosen from a size chart
Modular casework arrives in fixed widths, usually 3 inch increments from 9 up to 48. Say the alcove beside a chimney breast measures 61 and a half inches. The stock answer is two 30 inch boxes and a filler, or a 36 and a 24 with the leftover split between two strips of matching material at the walls. The result is a 60 inch product plus 1.5 inches of apology.
Fitted work starts from the other direction. The carcass gets cut at whatever the opening allows, 60 and a quarter in that example, and the missing width is deliberately carried by stiles that overhang the box by an inch or so on each side and are then cut to the actual shape of the plaster. The face is dimensioned to the room. The box behind it is dimensioned to the face.
Integrated with the structure, or standing in front of it
A cabinet run sits on its own base, typically a 4 and a half inch toe kick, in front of the baseboard, which frequently stays where it is, hidden behind the boxes forever. The assembly is reversible and it stops at the wall surface.
A built in cuts into that surface. The baseboard is removed across the opening and the new plinth is butted or scarfed into the cut ends so the horizontal line continues around the room without a break. Blocking gets screwed to the studs at the top rail and at hanging rail height, and the case is fastened back to it rather than to drywall anchors. If there is a top treatment it dies into the ceiling or into the existing picture rail. The finished piece has no independent perimeter: there is no line at which the cabinet stops and the room starts.
End panels, fillers and the gap that gives it away
Look at the two vertical edges. A modular installation shows a finished end panel, three quarters of an inch thick, with a visible seam where it meets the wall, or a flat filler strip caulked into the corner. In an older Yakima house that seam is rarely parallel, so the caulk bead runs from a hairline at the top to a quarter inch at the floor and reads as a taper.
Fitted work has no such joint because the stile itself is the closing piece. It is run wide, held against the plaster, and scribed. Set a compass to the widest gap, run the point down the wall while the pencil rides the stile, then cut to that pencil line and back bevel the edge about five degrees so only the front eighth of an inch touches. A wall out of plumb by three eighths over 84 inches closes to nothing. There is no filler because there is nothing left to fill.
How it is actually held
Fastening reflects the same logic. Cabinet screws through a hanging rail into framing at every stud, adhesive on the blocking, a leveled and shimmed base fixed to the floor, then the face frame or applied trim pinned with 18 gauge brads, filled and sanded flush. The nail holes disappear under paint. On a factory run the screws are usually visible inside the case, deliberately, because the assembly is designed to come apart again.
The part nobody puts in the brochure
All of that has one consequence: a real built in cannot be removed and reused. The plinth is joined to the room's baseboard, the stiles are cut to that particular wall, the fasteners are set into blocking and the trim is filled and painted over. Taking it out means a pry bar, damaged plaster and a pile of parts that fit no other opening, since the wall it was scribed to does not exist twice.
That is worth understanding before commissioning one. It stays with the building, and in the Yakima Valley, where a lot of the housing stock changes hands with the original 1920s casing still on the walls, that is often the intent. It also means the work has to be right the first time. A wrong door on a modular run is a reorder. A wrong carcass in a fitted alcove is demolition.