Cabinet Shims Guide: How to Level Cabinets Like a Pro

What Are Cabinet Shims?

Cabinet shims are thin, wedge-shaped pieces of material inserted between a cabinet and the wall, floor, or adjoining cabinet to correct uneven surfaces. They are the unsung heroes of professional cabinet installation — small, inexpensive, and absolutely essential for achieving a level, plumb, and square result.

Whether you are installing modern kitchen cabinets, bathroom vanity cabinets, or garage storage cabinets, shims compensate for the natural imperfections found in virtually every home. Floors slope, walls bow, and corners are rarely perfectly square. Shims bridge those gaps, ensuring your cabinets sit flush and function correctly for years to come.

Without proper shimming, cabinet doors may rub against each other, drawers can slide open on their own, and the entire installation can look crooked. For a comprehensive overview of the installation process, see our cabinet installation guide.

Why Cabinet Leveling Matters

Leveling is not just about aesthetics — it is about functionality, durability, and safety. Here is why taking the time to shim your cabinets correctly pays off:

• Door and drawer alignment: Even a slight tilt can cause doors to swing open or rub against adjacent cabinets. Proper shimming keeps everything aligned.
• Structural integrity: Cabinets that are not level place uneven stress on hinges and drawer slides, leading to premature wear. See our cabinet hinges guide and cabinet drawer slides guide for maintenance tips.
• Countertop installation: Countertops require a perfectly level base. If your cabinets are not level, your countertop may crack or fit poorly.
• Visual appeal: Crooked cabinets are immediately noticeable and can make an entire kitchen or bathroom feel unfinished.
• Safety: Unstable cabinets can tip, especially if they are not secured properly. Combine shimming with cabinet anti-tip straps for maximum safety.

Types of Cabinet Shims

Not all shims are created equal. The type you choose depends on the application, the load-bearing requirements, and the environment. Here are the most common types used in cabinet installation:

1. Wooden Shims

Traditional wooden shims are made from cedar, pine, or hardwood. They are strong, affordable, and can be trimmed or snapped to size. Wooden shims are ideal for heavy cabinets and load-bearing applications. However, they can compress over time and are susceptible to moisture damage in humid environments like bathrooms or laundry rooms.

2. Composite Shims

Composite shims are made from plastic or engineered materials. They are moisture-resistant, do not compress, and are less likely to split than wood. Composite shims are an excellent choice for bathroom vanities and laundry room cabinets where humidity is a concern.

3. Plastic Shims

Plastic shims are durable, lightweight, and impervious to water. They are often sold in pre-cut sizes and are easy to stack. Plastic shims are a great option for quick installations, but they can be slippery and may not hold as well as wood or composite under heavy loads.

4. Cardboard or Homemade Shims

While not recommended for permanent installations, cardboard or folded paper shims can be used as temporary spacers during dry fitting. For a permanent solution, always upgrade to wood, composite, or plastic shims.

5. Adjustable Legs and Leveling Feet

Some modern cabinets, particularly European-style frameless cabinets, come with adjustable legs or leveling feet. These built-in mechanisms can replace traditional shims entirely. If your cabinets have adjustable legs, you may only need shims for fine-tuning. Learn more about stock vs custom cabinets to understand which types include this feature.

Material Comparison: Which Shim Is Right for You?

Use the table below to compare the most common shim materials based on strength, moisture resistance, and best use case.

For most residential cabinet installations, composite shims offer the best balance of strength, durability, and moisture resistance. They are particularly recommended for kitchen cabinets and bathroom installations.

Where to Place Cabinet Shims

Correct shim placement is critical. Placing shims in the wrong spot can cause cabinets to twist or bow. Follow these guidelines for optimal results:

Base Cabinets

• Under the cabinet base: Place shims under the corners and along the front and back edges of the cabinet floor. This is the primary shimming location for base cabinets.
• At the toe kick: If the cabinet has a toe kick, shim behind it to maintain a consistent reveal.
• Between cabinets: When joining cabinets together, use shims to align the faces and ensure a flush fit.

Wall Cabinets

• Behind the cabinet: Place shims between the cabinet back and the wall to correct for bowed or uneven walls.
• At the mounting rail: Shim behind the mounting rail where the cabinet attaches to the wall studs.
• Between adjacent cabinets: Use shims to align the faces of side-by-side wall cabinets.

Bathroom Vanities

• Under the vanity base: Similar to base cabinets, shim under the corners and edges.
• Around plumbing: Use shims to level the vanity while accommodating plumbing rough-ins.

For more detailed placement guidance, see our cabinet placement guide and cabinet leveling guide.

Step-by-Step: How to Level Cabinets with Shims

Follow these steps for a professional-level cabinet installation. This process applies to base cabinets, wall cabinets, and bathroom vanities.

Common Cabinet Shimming Mistakes to Avoid

Even experienced DIYers make these mistakes. Avoid them for a flawless installation:

• Over-shimming: Stacking too many shims creates an unstable base. Use fewer, thicker shims instead.
• Shimming only one side: Always check both sides and the front and back of the cabinet. A cabinet can be level left-to-right but tilted forward.
• Using the wrong material: Wood shims in a bathroom will swell and rot. Use composite or plastic in moisture-prone areas.
• Not securing shims: Loose shims can shift over time. Glue or staple shims in place before securing the cabinet.
• Ignoring the floor: If the floor is severely uneven, consider using a self-leveling compound before installing cabinets.
• Forgetting about appliance clearance: Ensure shimming does not interfere with cabinet appliance clearance.
• Skipping the level check after fastening: Fastening can shift the cabinet. Always re-check level after securing.

For more pitfalls to avoid, read our cabinet buying mistakes guide.

Tools You'll Need for Cabinet Shimming

Gather these tools before you begin. Having everything on hand makes the job faster and easier:

• 4-foot level: Essential for checking level across the entire cabinet run.
• Torpedo level: Useful for tight spaces and checking plumb.
• Tape measure: For accurate placement and alignment.
• Utility knife or oscillating tool: For trimming excess shim material.
• Wood glue or construction adhesive: To secure shims in place.
• Staple gun: For fastening shims to the cabinet base.
• Drill and driver bits: For securing cabinets to studs.
• Stud finder: To locate wall studs accurately.
• Pencil: For marking low spots and reference lines.
• Safety glasses and gloves: Always prioritize safety.

For a complete list of installation tools, see our installation and accessories hub.

Frequently Asked Questions About Cabinet Shims

How many shims do I need per cabinet?

The number depends on how uneven your floor or wall is. As a rule of thumb, use at least one shim at each corner of a base cabinet. For wall cabinets, shim at each mounting point. It is better to have extra shims on hand than to run out mid-installation.

Can I use coins or cardboard as shims?

While coins or cardboard can work as temporary spacers during dry fitting, they are not recommended for permanent installations. They can compress, shift, or deteriorate over time. Always use purpose-made shims for a lasting result.

What is the best shim material for kitchen cabinets?

Composite shims are generally the best choice for kitchen cabinets. They are strong, moisture-resistant, and do not compress. For heavy base cabinets, hardwood shims are also an excellent option.

Do I need to shim wall cabinets?

Yes, if the wall is uneven. Wall cabinets should be shimmed behind the cabinet back where it meets the wall. This ensures the cabinet face is plumb and aligns with adjacent cabinets.

How do I shim a cabinet on an uneven floor?

Place shims under the low corners of the cabinet base. Stack shims from opposite directions for stability. Check level frequently and adjust as needed. For severely uneven floors, consider using a self-leveling compound first.

Can I shim a cabinet after it is installed?

It is much easier to shim before securing the cabinet. However, if you need to adjust after installation, you can loosen the mounting screws, insert shims, and re-secure. Always re-check level after adjustments.

What if my cabinet has adjustable legs?

If your cabinet has adjustable legs, use them for primary leveling. Use shims only for fine-tuning or if the adjustable range is insufficient. Many European-style cabinets come with adjustable legs, which can simplify the process.