6 Best Structural Shims For Steel Column Leveling

Leveling a steel column is not just a suggestion; it is the fundamental step that ensures the structural integrity of the entire framing system. When a base plate sits unevenly on a concrete pier, every beam and joist connected above it inherits that inaccuracy. Proper shimming distributes the building load evenly across the foundation, preventing localized stress concentrations that lead to cracks or worse. Selecting the right material for this gap-filling process is as critical as selecting the right structural steel itself.

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Le-High Solid Steel Shims: The Industry Standard

Solid steel shims are the heavyweights of the structural world, favored for their immense compressive strength and predictable performance. When the design calls for significant load transfer through a column base, these steel plates provide the peace of mind that nothing will compress or settle over time. They are essentially an extension of the column itself, maintaining the same modulus of elasticity.

These shims shine in high-load commercial applications where weight is measured in tons rather than pounds. Because they do not deform under extreme pressure, they ensure the base plate remains perfectly flush against the column flange. Professionals rely on them when the engineering plans strictly mandate metallic-to-metallic contact for load paths.

The trade-off is the lack of flexibility; steel shims offer no room for field adjustments like trimming or bending. They require precise planning during the foundation pour to minimize the height variation. Stick with solid steel if the structural engineer has specified rigid, non-compressible materials for the connection.

Steel Supply Co. Slotted Shims: For Easy Installs

Slotted shims are designed for speed, allowing a installer to slide them into place around anchor bolts without removing the column or loosening the entire assembly. This U-shaped design is a massive time-saver when minor adjustments are needed to bring a column into plumb after it has been lowered onto the anchor bolts.

The primary advantage is efficiency during the steel erection phase. In a fast-paced environment where cranes are billed by the hour, the ability to slide a shim into a gap in seconds is invaluable. These shims come in various thicknesses and galvanized finishes, making them highly versatile for different site conditions.

However, avoid using slotted shims if the load requirements are extremely high or if the column base is subject to heavy vibration. The open-ended design means there is slightly less surface area contact compared to a full-perimeter shim. Use them primarily for leveling and plumbing, but ensure the area is properly grouted afterward to restore full load distribution.

Groveko Black Bear Plastic Shims: Corrosion-Proof

Plastic shims serve a specific purpose in environments where steel-on-steel contact creates a potential for galvanic corrosion or moisture trapping. These high-density plastic units are immune to rust, making them ideal for exterior columns or areas exposed to high humidity and salt air. They essentially eliminate the risk of the shim deteriorating and causing a loss of grout bond over time.

They are incredibly easy to work with because they can be cut, filed, or stacked with high precision. Many versions are color-coded by thickness, which removes the guesswork when the crew is trying to achieve a specific level across a grid of columns. This makes them a favorite for projects that require rapid, repeatable leveling across a wide footprint.

The limiting factor is the compressive strength. While modern high-density plastics are impressively durable, they are not a replacement for steel in heavy-load-bearing columns. Always verify the manufacturer’s load-bearing specifications against the building’s structural loads before opting for plastic in a primary structural assembly.

Dayton Superior Tapered Shims: For Fine Tuning

Tapered shims are the precision instruments of the trade, specifically used when the concrete surface or the base plate itself is slightly out of level. Instead of stacking multiple flat shims to compensate for a sloped surface, a tapered shim provides a continuous, sloping plane of contact. This ensures full surface engagement, which is far superior to “point loading” on a stack of uneven flat shims.

These are particularly useful in retrofit projects where the existing concrete slab is uneven or has settled over time. By using a tapered edge, the installer achieves a tighter fit and a more secure base. It effectively bridges the gap between a tilted foundation and a perfectly vertical column.

Using these shims requires a more methodical approach to measurement. The installer must identify the exact degree of slope to select the correct taper angle. If the math is slightly off, it creates a wedge effect that can actually put more stress on one side of the anchor bolt.

Deslauriers Horseshoe Shims: Around Anchor Bolts

The horseshoe design is a variation of the slotted shim, specifically engineered to provide maximum stability around a singular anchor bolt point. They are durable, stackable, and provide a secure “seat” that prevents the shim from shifting once the column is set in place. This makes them exceptionally reliable for residential steel supports or lighter commercial applications.

These shims are often made from high-impact plastic or light-gauge steel, offering a balance between cost and performance. Because they are designed to be “locked” around the bolt, they stay put during the final tightening of the nuts. This eliminates the frustration of shims sliding out of alignment during the critical final adjustment phase.

They are not meant for the massive, wide-flange columns found in high-rise construction, where full-plate contact is required. Use them for garage supports, patio posts, or steel beam columns where smaller footprint contact is sufficient. Always ensure the stack remains stable and does not exceed height limits defined by local building codes.

Custom-Fab Steel Plates: For Max Load Bearing

When the span between the base plate and the foundation is unusually large—often due to a botched concrete pour—off-the-shelf shims may not be enough. In these instances, having custom steel plates fabricated to the exact dimensions of the column base is the only professional solution. A custom plate mimics the full footprint of the column, ensuring the load is transferred to the foundation as if the gap never existed.

This approach is expensive and requires lead time, but it is the correct way to handle significant structural voids. It eliminates the “pancake stack” risk, where too many individual shims lead to instability or shearing. A single, thick, custom-machined plate is infinitely more stable than a pile of six thinner ones.

Never attempt to fill massive gaps with a tall stack of loose shims. If the required height exceeds a standard stack limit, stop the job and spec a custom plate. It is a one-time investment that prevents long-term structural failure, cracked concrete, and massive repair costs later down the road.

Steel vs. Plastic Shims: What’s Right for the Job

The decision between steel and plastic ultimately comes down to load requirements and environmental exposure. Steel shims are the gold standard for compression strength and fire resistance, which are non-negotiable in primary structural steel columns. If the engineer has specified a “rigid connection,” steel is usually the only material that satisfies the requirement.

Plastic shims, conversely, are the hero of the moist, high-corrosion environment. If a column is sitting on an exterior patio or in a damp crawlspace, steel shims risk oxidizing and expanding, which can eventually crack the grout or concrete. Plastic provides a permanent, inert solution that does not degrade over the life of the building.

If the choice remains unclear, consult the structural drawings or the site engineer. A general rule of thumb is to use steel for the main vertical load-bearing columns and reserve high-density plastic for lighter, non-critical supports or shims meant to be encased in non-shrink grout.

How to Calculate Your Required Shim Stack Height

Calculating the shim height begins with an accurate survey of the concrete pier elevation relative to the target finish floor height. Use a laser level to determine the highest point on the foundation; this is the benchmark. Every other column position will likely require a shim stack to reach the same elevation.

Subtract the actual pier elevation from the required base plate elevation to determine the precise gap size. Always aim for the minimum number of shims possible to reach that height. A single 1/2-inch plate is almost always preferable to two 1/4-inch plates or four 1/8-inch plates, as fewer layers reduce the chance of shifting or “walking” under load.

Never stack more than three or four shims in a single location. If the gap requires more than that, it is time to re-evaluate the site prep or look into custom fabricated plates. Excessive stacking introduces a failure point that can compromise the verticality of the column over time.

Preventing Corrosion in Your Steel Shim Stacks

Corrosion is the silent killer of steel connections. Once a shim stack is installed and grouted, it becomes very difficult to inspect or replace. For this reason, always specify galvanized or stainless steel shims for exterior or high-moisture applications to prevent rust from expanding and compromising the bond between the grout and the base plate.

If using standard carbon steel, ensure the shims are fully encapsulated by the structural grout. High-quality, non-shrink grout creates a sealed, alkaline environment that protects the steel from moisture and oxygen. Any exposed edges should be painted with a cold-galvanizing compound to add a secondary layer of protection.

Periodically inspect the base plates after installation to ensure no moisture is wicking into the gap. If rust stains appear at the edge of the grout line, it is a sign that the grout seal has been breached. Immediate attention to these signs can prevent the structural integrity of the base from becoming a major issue.

Key Grouting Techniques for Shimmed Base Plates

Grouting is the final step that “locks” the shimmed column into the foundation, turning a temporary leveling setup into a permanent, monolithic structure. The key is to use a high-strength, non-shrink, flowable grout. This material is designed to expand slightly as it cures, ensuring that it fills every void under the base plate and around the shims.

Before applying the grout, clean the concrete surface thoroughly to ensure a strong bond. Build a simple wooden or metal form around the base plate that is a few inches higher than the plate itself. This allows for a “head” of grout, creating the necessary pressure to force the material under the plate and through the gaps in the shim stack.

Work from one side to the other, allowing the air to escape as the grout flows in. Once the grout is set, remove the forms and inspect the perimeter for any gaps. If the grout does not reach the edges or if it appears honeycombed, it must be addressed immediately to ensure uniform load transfer.

Properly shimmed and grouted columns are the backbone of any structure, literally and figuratively. By selecting the correct material—whether it is the rugged strength of solid steel or the corrosion resistance of high-density plastic—and following through with precise, professional grouting, these connections provide the reliability that a building demands. Take the time to get the shim stack right during the initial install, and the structure will remain plumb and stable for the long haul.