7 Best Structural Steel Shims For Leveling Roof Supports
Leveling roof supports precisely is easier with our top 7 structural steel shims. Explore our expert rankings and find the perfect fit for your project today.
Achieving a perfectly level roof support system is the difference between a structure that settles gracefully and one that develops premature leaks or structural stress. When working with steel framing or heavy mechanical units on rooftops, precision shimming prevents the uneven load distribution that ruins roofing membranes. Choosing the wrong shim under a support base isn’t just a minor oversight; it creates localized pressure points that can eventually puncture or compress roof insulation. Relying on makeshift materials like wood or plastic is a recipe for long-term failure in high-load commercial applications.
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Dayton T110 Slotted Steel Shim: Best Overall
The Dayton T110 is the industry standard for a reason. Its slotted design allows for rapid installation around existing anchor bolts without the need to completely remove heavy equipment or support feet.
These shims provide a consistent, predictable thickness that eliminates the guesswork during the leveling process. Because they are manufactured to strict tolerances, they maintain structural integrity under substantial compression.
Stick to these when the scope involves standard steel-to-steel connections where access is partially obstructed. They represent the most efficient balance of structural reliability and on-site labor savings.
G-STRUT PS 2550: Best for Heavy-Duty Loads
When dealing with massive HVAC units or heavy cable tray supports, standard thin shims will buckle under the pressure. The G-STRUT PS 2550 is engineered for high-compressive-strength applications where the dead load is extreme.
These shims are thicker and more robust than typical flat stock, ensuring that the support base remains rigid over decades. If the roof support is sitting on a steel beam or concrete curb, these shims transfer the load efficiently without deforming.
Avoid using these for fine-tuning minor slopes where a thinner shim would suffice. Save this product for the primary load-bearing points of major equipment mounts where structural stability is the absolute priority.
Precision Brand Zinc Plated Shim: Best for Corrosion
Roofing environments are inherently harsh, featuring constant exposure to moisture, temperature swings, and industrial pollutants. The zinc plating on these shims provides a critical layer of sacrificial protection against rust.
On a rooftop, a rusted-out shim is a ticking time bomb that can compromise the structural alignment of the entire system. Using zinc-plated options ensures that the shim won’t fuse to the support base or create corrosive runoff that stains roof panels.
If the project involves an exposed roof deck or a coastal environment with high salt content, these are a non-negotiable requirement. Prioritize longevity by keeping the shim material compatible with the surrounding fasteners and flashing.
Steel Supply L.P. Carbon Shim: Top Budget Pick
For large-scale projects where hundreds of leveling points are required, costs can spiral quickly if using premium-coated products. Steel Supply L.P. carbon shims provide the necessary support at a fraction of the cost.
These are essentially raw, high-strength carbon steel. While they lack the aesthetic finish of plated options, they deliver the raw mechanical performance required for non-exposed, internal support systems.
Apply a cold-galvanizing spray or rust-inhibitor paint if these are used in exterior, exposed locations. They are the most economical choice for sub-structure leveling where the shims will be covered by flashing or equipment housings.
Super-Shim Tapered Shim: Best for Sloped Beams
Not every roof beam is perfectly flat, and trying to level a flat shim on a sloped surface creates a dangerous rocking motion. Super-Shim tapered shims offer a variable thickness profile to compensate for pitch or uneven structural steel.
They are indispensable when bolting equipment to tapered flanges where a standard shim would only make contact at a single edge. By providing a full-surface bearing, they ensure that the fastener torque is applied evenly across the support plate.
This approach prevents the “bridge effect” where the support feet are bolted down but aren’t actually touching the structure underneath. Always verify the slope angle before ordering to ensure the taper matches the site conditions.
Dayton P92 Full Bearing Shim: Max Surface Contact
Many shim failures occur because the shim is too small, concentrating the weight of the roof unit into a tiny footprint. The Dayton P92 is designed to match the full surface area of the base plate.
Full bearing is critical in roofing to prevent localized stress on roof insulation or decking materials. When the load is distributed across the entire shim, the pressure remains well within the structural limits of the roof assembly.
Ignore the temptation to use small “penny” shims that only cover a fraction of the mounting base. Proper surface contact is the primary defense against long-term structural deformation and support base instability.
MAR-MAC Breakaway Shim: Most Versatile Option
The MAR-MAC breakaway shim is a clever solution for projects where the exact shim thickness needed isn’t known until the final bolt-up. These shims can be snapped or trimmed to fit precise gap requirements on the fly.
This versatility is a lifesaver when the substrate is uneven or when the equipment feet vary in height. It effectively removes the need to carry a massive inventory of different thicknesses in the toolbox.
While they are highly convenient, always check the material gauge to ensure it meets the structural load requirements of the specific support. They excel in field adjustments where unexpected gaps appear during the install process.
How to Calculate Your Required Shim Stack Height
- Take Measurements: Use a high-quality torpedo level to find the high point of your support surface.
- Determine the Gap: Measure the distance between the underside of the equipment base and the surface at each mounting bolt hole.
- Account for Load: Factor in 5-10% compression for any rubber or vibration isolation pads installed between the shim and the equipment.
- Final Selection: Choose a shim stack that gets you within 1/16th of an inch of the target height to ensure the structural bolts can be tightened correctly.
Solid vs. Slotted Shims: What’s Right for the Job
- Slotted Shims: Best for retrofits or installations where the anchor bolt is already fixed in place. They save massive amounts of time but should not be used in high-vibration environments where they could theoretically work themselves loose.
- Solid Shims: The gold standard for new construction. Because the bolt passes through the center of the shim, it is physically impossible for the shim to be displaced after the nut is torqued down.
- Recommendation: Always default to solid shims for primary structural supports, and save slotted shims for equipment adjustments or secondary mountings.
Understanding Shim Load Ratings and Limitations
Every shim is designed to handle a specific amount of compressive force, measured in pounds per square inch (PSI). If the load exceeds the rating, the shim will either yield, deform, or cause the bolt to lose tension.
Never stack more than three shims at a single location, as a tall stack creates an unstable, “springy” column. If the gap is larger than what three shims can cover, weld a steel plate to the structure or install a custom steel block to maintain structural rigidity.
Always confirm the load-bearing capacity of the roof structure itself before adding heavy equipment. Adding shims ensures the load is transferred, but it does not magically increase the structural rating of the roof deck or steel beams underneath.
Successful roofing and mechanical support installations depend on the minor details that remain invisible after the job is finished. By selecting the right shim material and ensuring full-bearing contact, you eliminate the structural stress that leads to callbacks and system failures. Take the time to measure correctly and respect the load limitations of your stack, and the installation will remain rock-solid for the life of the roof.
