Base cabinets carry the countertop, the sink, and 90% of what people store in a kitchen. They also have to sit dead-level across the entire run — cabinet doors and drawers reveal even small misalignments, and a countertop installed on uneven cabinets cracks at the seams or rocks during use. The framing and finishing of a kitchen are forgiving; cabinet installation is not.

This guide covers a standard run of base cabinets along a wall, including the level setup, anchoring, and joining cabinets to each other. The same principles apply to islands and peninsulas, with additional considerations for free-standing assemblies.

Before you start

Five things to confirm before any cabinet comes out of the box:

1. Floor flatness. Base cabinets sit on the floor and must align to a perfectly level top. The floor must be flat and the cabinets must be shimmed level. Measure the floor with a long level — variations of more than 1/4 inch over the cabinet run length need correction. Floors slope toward drains in many older Ottawa kitchens; budget for shimming.

2. Wall straightness. Cabinets back up to the wall and any bow or wave shows up at the cabinet face. Run a long straight-edge along the wall at cabinet height (around 34 inches up from the floor). High spots in the wall need shimming behind the cabinet; low spots need either filler strips or wall correction before install.

3. Stud locations. Cabinets fasten to the wall with screws into studs. Every cabinet needs at least one stud per wall-attachment point — usually two screws per cabinet at minimum. Sweep the entire wall with a stud finder and mark stud locations with painter's tape so you can see them while positioning cabinets.

4. Plumbing and electrical rough-in. If the kitchen run includes a sink, dishwasher, or appliance circuit, the rough-in must be in place and inspected before cabinets go on. Sink supply and drain locations must align with the sink-base cabinet's plumbing access. Outlets and circuits for under-cabinet lighting, dishwasher, and disposal need to be roughed in. Cabinet install is the bottleneck for everything that follows.

5. Cabinet count and order. Lay out the kitchen on paper before starting. Determine which cabinet starts the run (usually a corner cabinet), the order along the wall, and any fillers between cabinets and walls. Most kitchens have at least one filler strip — a small piece of matching trim that bridges the gap between the last cabinet and the corner or wall. Plan filler locations during install, not after.

What you'll need

Tools

Cordless drill with various bits
Drill bits: 1/8", 3/16", 5/32" (for cabinet-to-cabinet screws)
Stud finder (electronic, deep-scan)
Tape measure
Pencil and lumber crayon
4-foot level (the most-used tool in a cabinet install)
Laser level (highly recommended — Bosch GLL2-15 or similar)
Carpenter's square
Cabinet clamps or hand clamps (for joining adjacent cabinets)
Various wood shims (cedar shims work; carpenter's plastic shims are more consistent)
Utility knife
Jigsaw or oscillating tool (for cutting cabinet backs around plumbing/electrical)
Step ladder

Materials

Base cabinets (per kitchen layout)
#8 × 2-1/2" wood screws (for attaching cabinets to studs)
#8 × 1-1/4" wood screws (for joining cabinets to each other)
Cabinet shims (cedar or plastic)
Filler strips matching cabinet finish (cut to fit)
Cabinet leveling legs (if cabinets have removable legs and the floor is significantly uneven)
Construction adhesive (for shim points to prevent shifting)

The first cabinet sets the entire run

If the first cabinet isn't perfectly level and plumb, every subsequent cabinet inherits its misalignment. A 1/16-inch tilt at the first cabinet becomes a 1/2-inch gap at the end of a 10-foot run.

Spend extra time on the first cabinet. Level it from the floor up, plumb it from the wall back, square it to the next position. Verify with the 4-foot level in three planes. The other cabinets are easier — they reference back to the first.

Step-by-step instructions

Establish the cabinet height reference line

Standard base cabinet height is 34-1/2 inches to the cabinet top (which becomes 36 inches with countertop on top).

Measure up 34-1/2 inches from the highest point on the floor along the cabinet run (find this with a level — drop a level on the floor at multiple spots; the highest reading is the high point). Mark this height with a chalk line all along the wall.

The chalk line is your reference for the top of every cabinet. All cabinets get shimmed to align with this line, regardless of what the floor below them is doing.

Pro tip: if you have a laser level, project a horizontal line at 34-1/2 inches around the entire kitchen. Working to a laser line is far more accurate than working to chalk, and you can verify level on every cabinet without dragging out the spirit level.

Find and mark the studs

Sweep the wall with a stud finder along the full cabinet run height. Mark every stud with vertical pencil lines or strips of painter's tape extending up well above the cabinet height — once cabinets are in place, you won't be able to see the wall, but you need to know where studs are to drive screws.

Standard stud spacing is 16 inches on centre, but kitchens often have non-standard framing around windows, doors, and previous renovations. Verify each stud individually.

Start with a corner cabinet (if applicable)

Most kitchen runs start at a corner. The corner cabinet sets the position of the entire run, so it goes in first.

Slide the corner cabinet into position. Check the back of the cabinet against the corner walls. If the walls aren't perfectly square (most aren't), you may need to scribe (cut to fit) the cabinet's back side to follow the wall contour.

Level the first cabinet from the floor up

Place a 4-foot level on top of the cabinet. The level should sit flat and the bubble should be centred.

If the cabinet tilts, slide shims under the low corners. Drive shims gently — too much force and you'll lift the cabinet up off the floor entirely. Re-check level after each shim adjustment.

Once the cabinet is level front-to-back, check side-to-side. Then check that the cabinet top aligns with your 34-1/2 inch reference line. Adjust shims as needed.

Plumb the cabinet against the wall

Now check that the cabinet is also plumb (vertical). The cabinet face should be perpendicular to the floor — a level held against the cabinet's front face should read plumb.

If the cabinet tilts forward or backward, shim between the cabinet back and the wall. Cabinet bottoms typically have small adjustable feet or a recessed kick plate; the upper back of the cabinet bears against the wall.

Both leveling and plumbing must be correct simultaneously. Take time on the first cabinet — every other cabinet referencing this one gets exposed if this one is off.

Anchor the first cabinet to the wall

Once leveled and plumbed, drive #8 × 2-1/2" wood screws through the cabinet's mounting rail (the heavy strip across the top back of the cabinet) into the wall studs.

Two screws per cabinet minimum, into different studs if possible. Drive screws snug but not over-tight — over-driving distorts the cabinet box and pulls the cabinet out of plumb.

Check level and plumb one more time after the cabinet is anchored. If anything shifted during fastening, back off the screws, re-shim, and re-anchor.

Position the next cabinet against the first

Slide the next cabinet against the first along the wall. The two cabinets should share a face frame edge — a vertical seam where their fronts meet.

Check that the second cabinet sits at the same height as the first (top edges flush against the chalk line / laser line). Shim the second cabinet's floor as needed.

Apply a clamp across the front face frames where the two cabinets meet. The clamp pulls the cabinets tightly together — this is what eliminates the visible gap between them.

Join adjacent cabinets to each other

With the cabinets clamped together, predrill through the face frame of one cabinet into the face frame of the other. Use a 5/32" bit (smaller than the screw) to prevent splitting.

Drive #8 × 1-1/4" cabinet screws through the predrilled holes. Two screws per cabinet pair — one near the top of the face frame, one near the bottom.

The screws pull the face frames flush together. After driving, the joint should be invisible — no gap between cabinet fronts.

Then anchor the second cabinet to the wall studs through its mounting rail, same as the first.

Continue along the run, leveling each cabinet

Repeat for each subsequent cabinet: position, level, plumb, clamp to neighbour, predrill and screw to neighbour, anchor to wall.

Verify the cabinet top is at the reference line at every cabinet. As the run gets longer, small errors accumulate — if cabinet 5 is 1/16-inch low and you don't catch it, cabinet 6 will be 1/16-inch low, and so on.

Use the 4-foot level across multiple cabinets at once to verify the entire run is flat. If the level reads off, find the low spot and re-shim.

Cut and install filler strips

When the cabinet run reaches a corner or wall, there's typically a gap between the last cabinet and the wall. This gap gets filled with a matching filler strip — a piece of trim that matches the cabinet finish.

Measure the gap at top and bottom (walls aren't always plumb). If the gap is wider at one end, scribe the filler to match the wall contour. Cut with a fine-tooth saw or a jigsaw.

Attach the filler with brad nails or finish screws. The filler should sit flush with the adjacent cabinet's face.

Cut openings for plumbing and electrical

The sink-base cabinet needs holes cut through its back for the supply lines and drain. The dishwasher cabinet needs an opening for the supply line and drain hose access from the sink-base cabinet.

Mark the locations carefully against the rough-in plumbing on the wall. Cut openings with a jigsaw, hole saw (for round holes around supply lines), or oscillating tool. Cut slightly larger than necessary to leave room for plumbing flex; the cabinet's back panel can be patched with cardboard or thin plywood backing later if needed.

Final verification before countertop install

Before any countertop goes on, verify:

Top-of-cabinet flat across the entire run: a 4-foot level placed across all cabinets should read flat.
Cabinet fronts plumb: each cabinet should read plumb on a level held against the face.
Cabinet face frames flush at every joint: no visible gaps or steps between cabinet fronts.
All anchoring screws driven: each cabinet is anchored to studs and to its neighbours.
Doors and drawers operate: open every door and drawer to verify nothing binds. Misaligned cabinets reveal themselves through binding doors.

Common mistakes that cost you

Skipping the floor flatness check. Cabinets installed on a floor that slopes 1/2 inch over 8 feet end up with a sloped countertop and out-of-level cabinet doors. Always identify the high point and shim everything to match.
Anchoring before leveling. Once the first cabinet is screwed to the wall, it's nearly impossible to re-shim without removing the cabinet. Level and plumb completely before driving any anchor screws.
Not joining adjacent cabinet face frames. Without screws between adjacent cabinets, the face frame seam opens up over years as the cabinets shift slightly. The visible gap is unfixable without disassembly.
Using the wrong screw size. Anchor screws (cabinet-to-wall) need #8 × 2-1/2" minimum to bite into studs through the cabinet's mounting rail. Too short and they fail. Too long and they protrude into the wall behind, possibly hitting plumbing or wiring.
Forgetting fillers. Most kitchens have small gaps between cabinets and walls or appliances. Plan for filler strips during install — adding them later is much harder.
Not predrilling cabinet-to-cabinet screws. Driving a 1-1/4" screw through dry hardwood face frames without predrilling splits the wood. Predrill with a 5/32" bit through the leading face frame before driving the screw.
Over-tightening anchor screws. Too much torque distorts the cabinet box and pulls the cabinet out of plumb. Snug is enough; the cabinet's weight plus the screws is the holding force, not raw clamping pressure.
Skipping verification before countertop. Countertops installed on misaligned cabinets crack at seams or rock during use. The 30-minute final check catches problems before they become permanent and expensive.

Frequently asked questions

Do I need to remove the floor before installing cabinets?

No, but the flooring is typically installed before cabinets in modern kitchens — this is the 'flooring first' approach. The cabinets sit on top of the finished floor, with the kick plate covering the visible floor edge. Future flooring updates can replace floors without removing cabinets.

Alternative: install cabinets first, then floor up to (but not under) the cabinets. This approach is older and makes future flooring changes harder. Either approach works structurally.

What if my walls are wavy?

Most walls are slightly wavy. Cabinets rest on the high points and need shimming behind the low points. Run a straight edge along the wall at cabinet height to map the high and low spots before installing.

If the wall is significantly out of plumb (more than 1/2 inch over 8 feet), consider correcting the wall before installing cabinets. Adding furring strips or even rebuilding the wall straight is sometimes faster than fighting the cabinet install.

How do I install cabinets in a corner?

Most kitchen corners use a specialized corner cabinet (lazy susan, blind corner, or diagonal cabinet) designed to fit the 90-degree corner geometry. Install the corner cabinet first; subsequent cabinets along both walls reference back to it.

If you don't use a corner cabinet, the alternative is two cabinets that meet at the corner with one filler strip between them. The lazy-susan corner is more usable but more expensive; the dual-cabinet-with-filler is cheaper but loses corner storage.

Do I need to remove cabinet doors during install?

Yes — remove all doors and drawers before installing. The cabinet boxes are heavy enough; doors add weight and create snag hazards during positioning.

Re-install doors and drawers after all cabinets are anchored and the run is verified flat. Adjust the hinge screws to align the doors evenly.

How tall should base cabinets be?

Standard base cabinet height is 34-1/2 inches to the cabinet top (which becomes 36 inches finished with the countertop). This is comfortable for most adults.

For taller users, consider 36-inch tall cabinets (38 inches finished) — these are sometimes called 'comfort height' cabinets and help with back and shoulder comfort during food prep. Custom height adjustments are possible during install with thicker kick plates.

How do I install a sink-base cabinet?

Same process as any other cabinet, with two additions. First, cut openings in the cabinet back for plumbing supply lines and drain access. Second, the sink itself drops into the countertop after cabinets are installed and the countertop is in place — not into the cabinet directly.

Disconnect any existing plumbing before removing the old sink-base cabinet. Cap the supply lines and drain temporarily so dust doesn't enter.

What's the order of trades for a kitchen renovation?

Demolition → framing changes (if any) → plumbing rough-in → electrical rough-in → drywall → painting (cabinet area) → flooring → base cabinets → upper cabinets → countertops → backsplash → final plumbing connections → appliances → final electrical → trim and finishing.

Cabinet install is in the middle of this sequence. Get it wrong and every subsequent trade fights your mistakes.

When to call us instead

If your kitchen has structural changes, requires electrical or plumbing rough-in modifications, or uses high-end cabinets where a cosmetic flaw is a four-figure problem, this becomes professional cabinet-installer territory. Cabinet installers do dozens of installs per year and have the eye for the small alignment details that make a kitchen feel custom.

We do kitchen renovations as a fixed-price scope including cabinet install, countertop, plumbing, electrical, and finishing. For homeowners doing a full kitchen update, the cost of professional install is small relative to the rest of the project and removes a significant DIY risk.

Book a free 60-minute site visit →

Related Ottawa services

Kitchen renovations are one of our core services. Our kitchen renovation team handles cabinets, countertops, flooring, plumbing, and electrical as a fixed-price project. Book a free 60-minute consultation.