6 Best Galvanized Steel Shim Plates For Leveling Floor Grating

A rattling floor grating is more than an annoyance; it is a structural safety hazard that creates trip points and accelerates wear on support beams. Achieving a perfectly level surface requires more than just eyeballing the gap—it demands high-quality, galvanized steel shims that can withstand the crushing weight of foot traffic or machinery. Selecting the right shim ensures load distribution remains uniform, preventing localized stress that could lead to structural failure over time. Proper installation turns a wobbly platform into a rock-solid foundation that lasts for decades.

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Precision Brand Slotted Shims: Top Versatility

Precision Brand slotted shims stand out because of their tight manufacturing tolerances, which are critical when fine-tuning a floor grating installation. These shims slide easily around anchor bolts without requiring the removal of heavy hardware, saving significant labor time on a crowded job site.

The range of thicknesses available makes them the go-to choice for leveling uneven concrete substrates where the gap varies across the floor area. By stacking these shims, installers can achieve precise elevations with minimal movement once the grating is bolted down.

Bottom line: Choose these when the installation demands high-precision leveling in a tight, existing footprint.

G-L Stamping Galvanized Shims: For Heavy Loads

G-L Stamping produces shims specifically designed to resist deformation under intense mechanical pressure. When dealing with heavy-duty industrial floor grating that supports rolling loads or machinery, thinner shims often compress and fail, causing the grating to shift.

These shims maintain their structural integrity even under high clamping forces. They provide a stable, non-compressible interface between the support steel and the grating, which is essential for maintaining a level deck in high-vibration environments.

Bottom line: If the floor grating supports heavy equipment or frequent forklift traffic, prioritize these for their superior yield strength.

Steel Supply Co. A36 Shims: Best Value Pick

Steel Supply Co. offers A36 steel shims that hit the sweet spot between structural reliability and cost-effectiveness. These are industry-standard pieces that provide exactly what is expected: consistent thickness and effective corrosion resistance through a standard galvanizing process.

While they may not offer the extreme precision of niche machine-shop brands, they are perfectly sufficient for standard commercial walkway grating. They handle typical environmental exposure well, resisting rust even in damp or humid utility rooms.

Bottom line: For large-scale projects where bulk purchasing is necessary to manage the budget, these provide the best performance-to-price ratio.

McMaster-Carr Pre-Cut Shims: Widest Selection

McMaster-Carr is unmatched for contractors who need specific, non-standard dimensions on short notice. Their catalog includes an exhaustive variety of slot widths and plate sizes, ensuring that any bolt pattern can be accommodated without field modification.

Having the right physical footprint for the shim is as important as the thickness; a shim that is too small for the grating bearing bar area creates a point-loading problem. McMaster-Carr allows for ordering the exact surface area needed to support the load correctly.

Bottom line: Use this source when dealing with custom grating profiles or odd bolt spacing that prevents the use of standard, off-the-shelf sizes.

All-Slotted Shim Co. Plates: For Large Gaps

All-Slotted Shim Co. excels in providing thicker plates that are necessary when the gap between the grating and the substrate exceeds the standard 1/8-inch tolerance. Using ten thin shims to fill a half-inch gap is a recipe for a spongy, unstable floor.

These thicker, singular plates provide the rigidity required for major leveling adjustments. By using one or two thick plates instead of a stack of many, the assembly remains stiffer and less prone to shifting under lateral loads.

Bottom line: Invest in these for major leveling projects where the underlying steel structure is significantly out of plane.

Fastenal House Brand Shims: Easiest to Source

Fastenal is the practical choice for contractors who find themselves short of materials in the middle of a project. Their house-brand galvanized shims are readily available at physical branches, allowing for immediate pickup when a job-site discovery demands an unexpected adjustment.

Availability is a critical factor in construction efficiency. Being able to secure these parts without waiting for shipping keeps the workflow moving and ensures that the grating is fastened securely before the crew moves on to the next task.

Bottom line: Rely on these for site-based agility and when local availability trumps the need for specialized dimensions.

Shim Sizing: How to Pick the Right Thickness

Accurate measurement is the foundation of a successful shim job. Use a feeler gauge or a wedge-style level tool to determine the exact void under each grating support point. Never estimate, as a gap of even an 1/8-inch can cause significant grating flex.

Always aim for the fewest number of shims possible. A stack of four thin shims is significantly less stable than one shim of an equivalent thickness. When high levels of vibration are present, keeping the shim stack height low is non-negotiable for long-term safety.

Slotted vs. Solid Shims: When to Use Each Type

Slotted shims are the industry favorite because they allow for installation around an existing bolt. This eliminates the need to remove or reposition heavy structural fasteners, which is a major time-saver during maintenance or leveling work.

Solid shims—those without an open slot—are reserved for initial installations where bolts are being dropped into place after the grating is positioned. Use solid shims if the application is high-vibration or if the shim must remain locked in a specific position where a slot could potentially slip out of alignment over time.

Load Ratings: Don’t Overlook This Key Spec

Not all galvanized shims are created equal when it comes to load-bearing capacity. Standard hardware store shims are often made from softer steel that can deform or “squish” under the heavy bolt tension required for structural grating installations.

Check the spec sheet for the yield strength of the steel used. If the grating is supporting personnel, the load requirements are moderate, but if it supports machinery, ensure the shims are rated for the anticipated weight. A shim that deforms under load will result in loose bolts and a dangerous grating system.

How to Safely Install Shims Under Floor Grating

Start by cleaning the substrate surface thoroughly to remove any debris, concrete burs, or scale that would prevent the shim from laying flat. Place the shim directly beneath the bearing bar of the grating to ensure the load transfers directly to the support structure.

Tighten the anchor bolts using a calibrated torque wrench to the manufacturer’s specification. Always check the grating for “rock” after tightening; if the grating still moves, it indicates that the shim stack is not flush or that another support point needs adjustment.

Properly shimming floor grating is a detail-oriented task that defines the quality of an installation. By choosing the right material for the load and taking the time to ensure the shims are properly seated, you guarantee a safe, stable surface that holds up to the demands of daily use. Always prioritize structural integrity over installation speed, and your floor systems will remain secure for years to come.