Base cabinets are the structural skeleton of any kitchen. Set them out of level by even an eighth of an inch and your countertops will rock, your dishwasher will not seat properly, and your drawers will drift open on their own. Learning how to install base cabinets correctly takes about 6 to 10 hours for a typical 12-foot run if you have never done it, and the difference between a good install and a bad one is almost entirely in the prep work. The screwing-to-the-wall part is the easy part.
Tools and Materials You Need
Skip even one of these and you will pay for it later:
- 4-foot or 6-foot level (Stabila Type 196-2 is the contractor standard at $115)
- Stud finder (Franklin Sensors ProSensor 710 at $50 — multiple sensors prevent missed studs)
- Cordless drill plus impact driver
- 2.5-inch and 3-inch GRK or Spax cabinet screws (not drywall screws)
- Cabinet shims — composite or hardwood, never the brittle pine stuff
- Pencil, chalk line, painter’s tape, measuring tape
- Pony or Jorgensen face-frame clamps
- Oscillating multi-tool for trimming filler strips and toe kicks
Total tool investment if you own none of this: roughly $400 to $550. Renting saves about half that but kills weekend flexibility.
Find the High Spot on the Floor
Every kitchen floor has a high point. Find it by laying a 6-foot level along the cabinet run and measuring the gap at each end and the middle. Move the level in 2-foot increments until you identify the spot where the floor is highest relative to a true horizontal line. Mark it with painter’s tape.
This high spot becomes your reference point. All cabinets get shimmed up to match the height of the cabinet sitting on the high spot — never down to the low spot. A typical kitchen floor varies 3/8 to 3/4 inch over a 12-foot run. If yours varies more than 1 inch, address the floor before installing cabinets, especially if it slopes toward the room rather than away from the wall.
Layout and Reference Lines
Measure up 34.5 inches from the high spot of the floor — this is the standard top-of-base-cabinet height before countertop. Snap a level chalk line all the way around the room at this height. This single line is the reference for every cabinet you install.
Next, find every stud in the wall behind the cabinet run and mark them above your chalk line where they will not get covered by cabinets. Mark the centerline of each stud, not just the edge. Drywall screws into stud edges strip out within months under the weight of a loaded cabinet.
Set the Corner Cabinet First
The corner cabinet sets every other cabinet in the run. If you have a blind corner or a lazy susan corner, install it first and shim it perfectly level in both directions. Use a torpedo level on the front face frame and the side panel simultaneously.
Drive 3-inch cabinet screws through the back hanging rail into wall studs. Two screws per stud, never just one. If your cabinet does not have a thick hanging rail (cheaper RTA cabinets often skip this), add a 1×4 cleat across the back inside the cabinet at the screw line to spread the load.
Working Out from the Corner
Set each adjacent cabinet against the previous one and clamp the face frames together with face-frame clamps. The face frames must align flush across the front — if they do not, shim the back of the lower cabinet until they do.
Drive 2.5-inch cabinet screws through the side of one face frame into the next. Two screws per joint, one near the top and one near the bottom. Predrill with a 1/8-inch bit to prevent splitting hardwood face frames. Skip this and you will hear a crack and watch a $400 cabinet split right in front of you.
Shimming the Right Way
Shims go under the cabinet at the front and the back, never just one or the other. Drive shims in from both sides until the cabinet sits dead level front-to-back and side-to-side. Check with a level after each cabinet, not just at the end of the run.
Once level, drive a screw through the cabinet bottom into the shim to lock it. Trim shims flush with an oscillating multi-tool or a sharp utility knife. Do not snap them off — the snapped end leaves a void that will compress under load and throw the cabinet out of level a year later.
Filler Strips and Scribe Cuts
Walls are never straight. Where a cabinet meets a wall, you will have a gap at the top, the bottom, or both. Filler strips solve this. Order a 3-inch filler in the matching cabinet finish and rip it to width on a table saw or with a circular saw and a straight edge.
To scribe-fit a filler to an irregular wall, set the filler in place against the wall and run a compass along the wall with the pencil leg on the filler. The compass transfers the wall’s shape to the filler. Cut to the line with a jigsaw or a belt sander. A clean scribe takes 20 minutes and looks 10x better than caulk filling a gap.
Common Mistakes That Ruin the Job
Watch for these errors:
- Using drywall screws instead of cabinet screws — drywall screws are brittle and snap under shear load
- Skipping the chalk line and leveling each cabinet individually — guarantees an uneven run
- Not predrilling face frame joints — splits the wood and ruins the joint
- Installing cabinets over thin vinyl that is not yet sealed at the toe kick — water gets behind the floor
- Forgetting to plumb the cabinets front-to-back — countertops will sit at an angle
After the Install
Reinstall doors and drawer fronts only after the cabinets are screwed to the wall and to each other. Adjust hinges so doors align with a consistent 1/8-inch reveal between them — Blum and Salice hinges adjust in three planes with the small Phillips screws on the cabinet-side mounting plate. Caulk the gap between the cabinet sides and the wall with a paintable acrylic latex caulk like DAP Alex Plus, then run painter’s tape and prep for the countertop template within 48 hours of install. Done right, base cabinets installed today will still be plumb, level, and tight in 25 years.
