7 Cabinet Installation Shims for Level Mounting Tips

Leveling cabinets is the secret bridge between a kitchen that feels “DIY” and one that looks professionally finished. Even the most expensive cabinetry will fail to function correctly if the underlying frame sits unevenly on an imperfect floor. Selecting the right shim ensures that doors hang straight, drawers glide smoothly, and countertops remain crack-free for years to come.

Nelson Wood Shims: The Pro’s Go-To for Reliability

Traditional cedar or pine wood shims remain the industry standard for a reason. Because they are tapered along their entire length, they offer a long, gradual slope that allows for highly precise height adjustments.

These shims are ideal for homeowners tackling full kitchen renovations where walls may be slightly bowed or floors noticeably sloped. When stacked, wood-on-wood creates a stable, friction-heavy bond that stays firmly in place once the cabinet is screwed into the wall studs.

While they require a bit more effort to trim with a utility knife, their reliability is unmatched for heavy-duty applications. For large cabinetry projects, sticking with these wooden classics ensures long-term stability without the risk of plastic deformation.

EZ-Shim Composite: Best for Kitchens and Bathrooms

Moisture is the primary enemy of any kitchen or bathroom cabinetry installation. Wood shims can swell or rot if they absorb standing water from a plumbing leak or a spilled bucket, which can compromise the level of the entire unit over time.

EZ-Shim composites are engineered from high-density, moisture-resistant polymers. They provide the same load-bearing support as wood but won’t warp when exposed to damp environments like a basement laundry room or an upstairs bathroom.

These are an excellent choice for households that prioritize “set it and forget it” solutions. While slightly more expensive than basic cedar packs, the peace of mind they offer in high-moisture zones is well worth the incremental cost.

Wobble Wedges: Top Pick for Tiny, Precise Gaps

Sometimes, a cabinet frame is almost perfectly level, but a tiny 1/16th-inch gap causes the unit to rock slightly. In these instances, standard wood shims are often too thick or bulky to fit the space properly.

Wobble Wedges are designed for these granular, fine-tuning tasks. They feature ridges that grip the underside of the cabinet, preventing them from sliding out once placed under the frame.

These wedges work exceptionally well for small apartment kitchens where floor space is tight and precision is mandatory for a clean aesthetic. Keep a small assortment on hand to handle those last-minute adjustments that prevent drawer faces from rubbing against each other.

Builder’s Best Shims: The Best Value for Big Jobs

Large-scale remodeling projects can quickly inflate a budget if every component is chosen based on convenience alone. Builder’s Best shims provide a cost-effective bulk solution that doesn’t sacrifice the necessary strength for hanging upper or base cabinets.

These are often sold in large packs, making them the most economical choice for contractors and ambitious homeowners renovating entire kitchens. They are sturdy enough to support the weight of heavy oak cabinets but remain easy to trim once the install is complete.

When the goal is to balance quality with a tight budget, these shims perform exactly as intended. They allow you to allocate funds to higher-quality drawer pulls or cabinet hardware while still ensuring the structural foundation is rock-solid.

Go-Ez Handi-Shims: Easy to Snap and Place by Hand

Precision cutting isn’t always possible when working in tight corners or behind a deep base cabinet. Go-Ez Handi-Shims are designed to be broken off at specific intervals without the need for a saw or a heavy-duty knife.

This feature is a major advantage for homeowners who may not have a complete workshop of power tools on hand. Simply slide the shim into the gap, find the score line, and snap the excess plastic away with a flick of the wrist.

Their ease of use makes them a favorite for quick repairs and minor adjustments in existing homes. If you value efficiency and want to avoid the mess of wood shavings, these pre-scored plastic shims are the most convenient option available.

Horseshoe Shims: Ideal for Aligning Cabinet Frames

Horseshoe shims, also known as U-shims, are unique because they slide directly over mounting bolts or screws. Instead of wedging them under the bottom of the cabinet, you place them behind the frame where it meets the wall.

These are indispensable when the wall studs are not perfectly plumb. By using horseshoe shims, the cabinet frame can be pulled flush against the wall without bowing the cabinet material itself.

They come in various color-coded thicknesses, making it easy to identify which size is needed for a specific gap. They are the most precise way to ensure that large runs of upper cabinets look like one seamless, continuous unit.

Swedge Plastic Shims: Best for Heavy Cabinet Loads

When installing heavy custom cabinetry—especially tall pantry units or cabinets housing stone countertops—the weight distribution is critical. Plastic shims that are too soft can compress under extreme pressure, leading to sagging cabinets later on.

Swedge plastic shims are constructed from a stiffer, more rigid material that resists compression. They maintain their shape under the heavy load of dense hardwoods, preventing the “shifting” that sometimes occurs with cheaper alternatives.

They are the most reliable option for long-term installations where you cannot afford any movement or settling. For larger household projects, invest in these for the base cabinets that bear the most significant structural weight.

Wood vs. Plastic Shims: Making the Right Choice

Choosing between wood and plastic comes down to the environment and the method of installation. Wood shims offer superior grip due to their porous surface, making them excellent for shimming against painted drywall or wood studs.

Plastic shims, however, win on durability and resistance to environmental factors. They are the logical choice for any area prone to humidity, such as near a sink, a dishwasher, or on a concrete floor in a basement or garage.

Do not feel pressured to use only one type throughout the entire home. It is perfectly acceptable to use wood shims where the structure is dry and secure, while switching to plastic in areas that face moisture or extreme temperature shifts.

How to Score and Snap Shims for a Clean Break

The secret to a professional installation is a clean finish that hides the shim entirely. For wooden shims, use a sharp utility knife to score the wood on both sides before snapping it; this prevents the wood from splintering and potentially scratching your floor.

If using plastic shims, ensure they are properly scored at the desired depth before applying pressure. A quick, decisive snap usually creates a cleaner edge than trying to saw through the material slowly.

Always leave a small amount of the shim protruding until the cabinet is permanently anchored. Once the screws are tightened and the cabinet is level, trim the shim flush with the wall or floor to provide a seamless appearance.

Common Shimming Mistakes That Ruin a Good Install

The most common error is failing to use enough support points. Installing a cabinet with only one shim at the center often leads to sagging ends over time, which puts unnecessary stress on the cabinet joints.

Another mistake is “stacking too high.” If the floor is so uneven that it requires a stack of shims taller than three-quarters of an inch, the stack becomes inherently unstable. In these cases, it is better to use a solid piece of plywood or a thicker filler strip to bridge the gap.

Finally, never forget to finish the edges. Leaving visible plastic or wooden shims sticking out from under the toe kick is an amateur look that is easily avoided with a little patience during the final trimming process.

Investing the time to shim your cabinets properly pays dividends in the form of quiet, smooth-closing doors and square drawers that don’t stick. By selecting the shim material that best matches your floor type and environmental conditions, you ensure that your hard work stands the test of time. Keep these techniques in mind, stay patient, and your kitchen will function with professional precision for years to come.