How To Install Rack Shims Safely In Warehouse Racking

Rack Shim A leveling plate placed under rack uprights to compensate for uneven floors. Proper installation ensures the shim transfers load safely, preserves rated capacity, and prevents misalignment across rack rows.

Pre-Installation Survey

Start by mapping the slab with a straightedge and feeler gauges or a laser level. Record each upright with a gap and measure the maximum offset. Take pictures and note adjacent dock or slab features that may affect bearing, such as saw cuts, joints, or repairs. Confirm the racking supplier’s allowable shim thickness and material recommendations before proceeding.

Selecting The Right Shim

• Material Match: Choose stainless or galvanized steel when the baseplate is steel and exposure could cause corrosion; use polymer where chemical exposure or electrical isolation is needed.
• Thickness Strategy: Use a single shim of correct thickness where possible; avoid multiple thin layers that can slide or compact.
• Profile: Ensure the shim is slightly smaller than the baseplate footprint but large enough to avoid edge concentration.

Installation Steps

Follow this step sequence for consistent results:

• Clean: Sweep and remove debris under the baseplate so the shim achieves full contact.
• Place The Shim: Center the shim beneath the baseplate so it fully supports the plate without extending beyond the plate edge.
• Insert Anchor: With the shim in place, install anchor bolts through the baseplate and shim into the slab per anchor instructions.
• Tighten To Spec: Torque bolts to the racking supplier’s specified value to compress the shim and ensure bearing—do not under-torque.
• Re-check Alignment: After torqueing, re-check level along the row and adjust other uprights as necessary to maintain beam seating and aisle straightness.

Torque, Anchors, And Bearing

Anchor bolt torque matters because proper clamping compresses the shim and produces full bearing. Use the anchor type and torque specified by the supplier—mechanical anchors, adhesive anchors, and cast-in sleeves each have different installation requirements. Never use shims to make up for an improperly selected anchor system.

Seismic, Impact, And Uplift Considerations

In seismic regions or where impact from forklifts is possible, consult the manufacturer and local code for restrictions on shim use. Some designs may require welded or bolted baseplates, continuous grouting, or specific anchor patterns to meet uplift and lateral load requirements. Where uplift is a concern, shims alone may not provide the necessary resistance.

Post-Installation Documentation And Inspection

Record shim material, thickness, and location in the racking installation log. Include before-and-after photos and torque values. Add shim checks to routine inspection forms and look for signs of movement, corrosion, or settling. If temporary shims are used, schedule a permanent fix—typically grouting—during planned maintenance.

Common Field Issues And Fixes

• Shim Migration: Use adhesive-backed or keyed shims if slippage is observed during installation; otherwise replace with single-thickness plate.
• Over-Shimming: Remove extra layers and replace with a single engineered shim or plan grout if offset is too large.
• Corrosion: Swap to galvanized or stainless shims and paint or seal exposed edges.

Practical Example: Step-By-Step Installation

A beverage distributor discovered three uprights with 1/8" depressions after rolling new concrete near the dock. The installer used 1/8" stainless shims specified by the racking vendor. They cleaned beneath each baseplate, placed the shim centered under the plate, installed mechanical anchors, and tightened to spec. They documented locations and scheduled a grout repair during the next facility shutdown to restore permanent bearing.

Installer Tips For Durable Results

• Calibrate Tools: Use a calibrated torque wrench for anchor tightening.
• Use Manufacturer Guidance: When in doubt, follow the rack supplier’s installation manual over house rules.
• Plan Permanence: Treat shims as either a long-term approved fix per supplier or a documented temporary measure pending grout.

In short, the Rack Shim must be selected, placed, and torqued correctly to safely correct small floor irregularities. With proper survey, selection, installation, and documentation, shims keep operations running while protecting rack geometry and load performance.