6 Best Steel Shims For Structural Alignment Pros Use

Structural alignment represents the silent backbone of a successful construction project. When beams don’t sit flush or columns lack perfect verticality, the entire load path of the structure can shift, leading to cracked masonry or compromised roof trusses. Selecting the right steel shim is not merely a task of filling a gap; it is an act of engineering precision. Professionals rely on these small steel components to ensure that every ounce of load is distributed exactly as the architect intended.

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Precision Brand Slotted Steel Shims: Best Overall

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Precision Brand slotted shims serve as the industry workhorse for a reason. Their consistent thickness and standardized dimensions allow for rapid adjustment when leveling base plates or machinery.

The U-shaped slot design is critical for speed. It allows the shim to slide around anchor bolts without requiring the full removal of a nut, drastically cutting down installation time on large-scale steel erection jobs.

Stick to these for general structural steel or heavy equipment leveling where high-carbon steel properties provide the necessary rigidity. They are not intended for environments with extreme chemical exposure, but for standard frame alignment, they are the gold standard.

Dayton Superior T11: For Heavy Bearing Loads

Dayton Superior T11 shims are specifically engineered for heavy-duty structural applications where load-bearing capacity cannot be sacrificed. These units are built to withstand immense compressive forces without deforming or failing under the weight of steel columns or bridge beams.

When dealing with high-capacity connections, conventional thin-gauge shims often buckle or “creep” over time. The T11 series provides a robust profile that maintains its integrity even when the load is applied off-center or during the shifting cycles of thermal expansion.

Use these when the structural engineer specifies high-strength grout or heavy loading at the base plate. Never substitute these with generic washers or low-grade sheet metal, as the risk of structural settling is simply too high.

Steel Supply L.P. U-Shims: For Bolt Alignment

Steel Supply L.P. U-shims are designed specifically for those moments when an anchor bolt is slightly off-center or the bolt pattern doesn’t perfectly match the base plate hole. Their wider U-profile accommodates alignment discrepancies that would stop a standard square shim in its tracks.

These are invaluable during the rough-in stage of steel erection. Because they are designed with extra clearance around the bolt shank, they provide enough wiggle room to pivot the steel member into place before tightening the connections.

For site conditions where concrete foundations have shifted slightly or anchor bolts were set manually, these shims provide the necessary tolerance to keep the job moving. They turn a potential field-modification nightmare into a simple adjustment.

G-S Products Tapered Wedges: For Precise Slopes

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When the substrate is uneven or requires a specific incline to achieve a level surface, tapered wedges are the only tool for the job. G-S Products offers a consistent taper that ensures even contact across the entire width of the shim.

Using a non-tapered shim on a sloped surface creates a point-load, which can cause the steel to twist or the shim to pop out under tension. A tapered wedge maximizes surface contact, ensuring that the load path remains continuous rather than concentrated on a single edge.

These are essential for leveling machinery or installing structural members on sloped concrete pads. Always check the slope ratio before ordering to ensure the wedge angle matches the required degree of correction.

Martin 316 Stainless Shims: For Corrosive Jobs

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In coastal regions or areas with high humidity and salt spray, traditional carbon steel shims will oxidize and lose structural integrity within a few years. Martin 316 Stainless Shims are the go-to solution for these high-moisture, corrosive environments.

Stainless steel provides a superior resistance to the galvanic corrosion that often occurs when different metals meet in the presence of moisture. While more expensive than carbon steel, the longevity they provide prevents future structural failure and the exorbitant costs associated with jacking up a structure to replace rusted shims.

If you are working on an exterior structure or a project near a saltwater environment, the extra cost for 316 stainless is an insurance policy. Never settle for galvanized steel in these zones, as the coating can be scratched during installation, exposing the core to rust.

Custom Laser-Cut Shim Packs: For Complex Jobs

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Sometimes a project requires a specific shape or size that isn’t available in standard catalog offerings. Custom laser-cut shim packs allow for exact reproduction of complex footprint geometries, ensuring that the shim surface perfectly mirrors the base plate or connection member.

Laser cutting ensures that there are no sharp burrs or irregularities on the edges, which is critical for ensuring a tight, flush fit. These are typically used in specialized aviation or high-end architectural steel projects where standard rectangular shapes do not provide enough support area.

If the blueprint calls for a non-standard connection, do not attempt to cut these from scrap steel on a bandsaw. Precision in the cut is just as important as the material thickness itself.

Carbon vs. Stainless Shims: Choosing Your Material

The choice between carbon steel and stainless steel ultimately comes down to the environment. Carbon steel is harder and typically more affordable, making it ideal for interior, climate-controlled structural steel connections.

Stainless steel is softer but offers exceptional corrosion resistance. In the world of structural alignment, you must account for the lifetime exposure of the joint; once the base plate is grouted in, you will never see the shims again.

If the environment is prone to water intrusion, condensation, or chemical exposure, always spec stainless. For dry, internal environments, carbon steel is perfectly adequate and usually performs better under extreme compressive loads due to its higher material hardness.

How to Safely Install and Secure Shim Stacks

The key to a successful shim stack is stability. Never stack more than three or four individual shims, as multiple layers increase the risk of the stack sliding or twisting under load.

If you find yourself using a high number of thin shims, it is a sign that the foundation or the steel fabrication is significantly out of tolerance. In such cases, pull back and use a thicker plate or a specialized leveling grout to close the gap before finalizing the connection.

When installing, ensure the shims are placed as close to the anchor bolts as possible to minimize the cantilever effect on the base plate. Once the alignment is locked in, ensure the shims are either welded in place or fully encapsulated in high-strength non-shrink grout to prevent movement.

Understanding Full Contact Bearing Requirements

Full contact bearing means that the entire underside of the structural member is supported, not just the points where the shims are located. Relying solely on shims to hold a load over a large area will result in the base plate bending or bowing over time.

Think of shims as the “temporary positioners” that hold the steel at the correct height while the grout handles the actual weight distribution. The shim provides the grade; the grout provides the bearing strength.

Always verify the grout manufacturer’s specifications regarding the maximum gap they are rated to fill. If the gap between the concrete and the steel exceeds the grout’s capability, you must increase the shim height rather than trying to bridge the gap with under-specified material.

Reading Blueprints for Shim and Grout Specs

Blueprints often contain specific instructions regarding shim location, quantity, and the type of material to be used. Ignoring these specs because a certain shim “looks like it will work” is a primary cause of structural inspection failures.

Look for the “Grout Plan” or the “Foundation Detail” section in the structural drawings. These will indicate if the engineer requires a specific type of steel for the shims to match the base plate or if they need to be removed after the grout has achieved initial set.

If the drawings are ambiguous, reach out to the project engineer for clarification. Never guess on structural load paths; the cost of a mistake in a structural assembly is measured in thousands of dollars and potential safety hazards.

Getting structural alignment right the first time is the hallmark of a professional. By choosing the correct material for the environment and respecting the limitations of shim stacks, the integrity of the entire structure is secured for the long haul.