7 Best Deck Leveling Shims for Uneven Surfaces

Walking onto a deck that rocks or slopes with every step transforms a relaxing evening into a source of constant frustration. Correcting these surface irregularities is a fundamental maintenance task that protects both the structural integrity of the home and the safety of family members. Selecting the right shims ensures that repairs are durable, cost-effective, and suited to the specific environment of the outdoor space.

Wobble Wedge Shims: Best All-Purpose Leveling Solution

Wobble Wedges serve as the go-to choice for homeowners who need a versatile fix for minor surface inconsistencies. These tapered, flexible plastic shims are designed to grip surfaces firmly, preventing the sliding often associated with wood or harder plastics.

Because they are stackable and feature a textured surface, they work exceptionally well for stabilizing deck furniture or filling small gaps between joists and beams. They are particularly useful for quick fixes that do not require specialized tools or permanent fasteners.

The primary benefit lies in the material’s slight pliability, which allows it to conform to irregular gaps without splitting under pressure. While not intended for massive structural loads, they provide the most reliable solution for everyday stabilizing needs around the house.

Nelson Wood Shims: The Traditional Carpenter’s Go-To

For those performing traditional deck framing repairs, cedar or pine wood shims remain the industry standard. These shims are inexpensive, widely available, and easily trimmed with a utility knife to fit exact dimensions during installation.

Wood shims excel in scenarios where a slight amount of moisture absorption is acceptable or when matching the aesthetic of a wood-framed deck is a priority. Because they are porous, they can be easily glued into place using standard construction adhesives for a semi-permanent hold.

Keep in mind that untreated wood shims will eventually succumb to rot if exposed to standing water over many seasons. Using these products is a smart, budget-friendly choice for covered porches or decks where moisture exposure remains minimal.

Pylex Deck Support Shims: For Heavy-Duty Joist Gaps

When dealing with significant structural settling, standard shims often lack the necessary footprint to support heavy joists. Pylex support shims are engineered specifically for exterior framing, providing a wider base that distributes weight more evenly across the post or beam.

These shims are usually manufactured from heavy-duty steel or high-density polymers, ensuring they do not compress over time under the weight of the deck structure. They are the ideal choice for homeowners addressing deep gaps that have developed over several years of soil movement.

Because they are intended for structural load-bearing, they often include pre-drilled holes for secure fastening with lag screws or structural bolts. Using these is a practical investment for any deck that feels “bouncy” or shows visible separation between the joists and supports.

Enviro-Shim Composite Shims: Best for Damp Conditions

Composite shims are the ultimate solution for decks located in humid climates or areas prone to heavy rain. Since they are composed of a blend of recycled plastic and wood fibers, they provide the ease of cutting found in wood with the rot-resistance of plastic.

These shims do not expand, contract, or decay when exposed to persistent moisture, making them superior to traditional wood options in damp environments. They provide a reliable, “set-it-and-forget-it” solution for leveling joists that are in constant contact with masonry or damp ground.

While the upfront cost is higher than simple pine wedges, the longevity provided by composite materials justifies the expense for most homeowners. Choosing these prevents the need for follow-up repairs after a single wet season.

EZ-Shim Interlocking Shims: Easiest to Snap and Adjust

Homeowners who are tackling a DIY project for the first time often appreciate the intuitive design of interlocking shims. These systems allow multiple shims to snap together, creating a perfectly level surface without the frustration of pieces sliding out of alignment during installation.

The interlocking mechanism ensures that once the desired height is reached, the stack remains stable while fasteners are driven through the assembly. This feature eliminates the need for a second pair of hands during the leveling process, making it a favorite for solo weekend projects.

These are best used for moderate adjustments where precise height control is required across a long span of ledger board. They offer a clean, professional finish with significantly less effort than traditional friction-fit wedges.

Quik-Shim Plastic Spacers: Ideal for Minor Adjustments

Quik-Shim plastic spacers function similarly to washers but are designed with a unique horseshoe shape. This design allows them to be slipped over an existing bolt or anchor without the need to completely remove the hardware.

They are indispensable for fine-tuning the level of a post-to-beam connection where the gap is less than a quarter-inch. Because they are made from durable high-density plastic, they resist rust and chemical degradation from pressure-treated lumber.

For small, precise adjustments, these spacers save hours of labor compared to lifting a heavy joist. Their small size makes them easy to store in any toolbox, providing a convenient solution for unexpected, minor wobbles.

Timber Tuff Steel Shims: For Ultimate Load-Bearing Power

When the structural integrity of a deck is compromised by significant settling, only steel shims offer the necessary safety margin. Timber Tuff and similar steel products are designed to handle the extreme compression forces exerted by deck support posts.

These shims are typically finished with a weather-resistant coating to prevent oxidation, though occasional maintenance is recommended. They are not meant for minor surface leveling but rather for heavy-duty structural correction where failure is not an option.

Use these shims when a post has clearly separated from its concrete pier or when the frame requires rigid, non-compressible support. They represent the most robust, long-term fix for high-stress areas of a backyard deck.

Wood vs. Plastic Shims: Which Is Right for Your Deck?

Deciding between wood and plastic requires a clear look at the deck’s specific environment and the intended lifespan of the repair. Wood shims offer excellent compression resistance and are easily trimmed, but they are vulnerable to rot in areas with poor ventilation.

Plastic or composite shims provide superior moisture resistance and are ideal for ground-contact applications or regions with heavy rainfall. However, some cheaper plastic shims can be slippery, potentially causing the joist to shift if not properly secured with fasteners.

• Choose Wood: For indoor-facing decks, covered porches, or projects requiring an immediate, inexpensive fix.
• Choose Plastic/Composite: For decks exposed to direct rain, snow, or humid soil conditions where durability is the priority.
• Choose Steel: For primary structural support points, such as post-to-pier connections, where weight-bearing capacity is non-negotiable.

How to Properly Install and Secure Your Deck Shims

Installation begins with a quality level to identify exactly where the surface deflection occurs. Once identified, place the shim under the joist, ensuring that the shim extends fully across the width of the framing member to prevent point-loading.

Never leave a shim loose; all shims must be secured with construction adhesive or, preferably, mechanical fasteners. If using wood, ensure the shim is slightly wider than the joist so it can be trimmed flush for a clean appearance after the structure is secured.

When installing, always verify the level again after tightening the bolts, as the force of the fastener can sometimes compress the shim or pull the joist in an unexpected direction. Proper installation is as much about careful checking as it is about the materials chosen.

Stacking Shims Safely: A Guide to Getting It Right

Stacking shims is common when the gap to fill is larger than a single wedge, but this practice requires caution. To ensure stability, interlock the wedges in opposite directions—one pointing left and one pointing right—to create a flat, parallel surface.

Avoid creating a “house of cards” by using too many thin shims; instead, use a single thicker shim or a solid block if the gap exceeds half an inch. Excessive stacking creates potential weak points that can slide or shear under the weight of the deck over time.

For any stack exceeding two shims, apply a generous amount of outdoor-rated construction adhesive between each layer. This transforms multiple pieces into a single, unified support block that will not shift when the deck experiences normal thermal expansion.

Maintaining a level deck is a manageable task that enhances the comfort and safety of any home. By selecting the appropriate material for the specific environmental conditions and taking the time to secure each shim properly, homeowners can ensure their outdoor living spaces remain solid for years to come.