Pallet Rack Shims: When You Need Them, Uses & Safety Guidelines
If you’re installing pallet racking on an uneven warehouse floor, steel shims may be used to create a safe and level base. While shims are rarely needed, they become important in certain situations, especially in older buildings where concrete has settled, cracked, or worn over time.
Pallet racking needs to sit on a flat, stable surface to perform properly. Even small gaps under a base plate can create stress points that affect load capacity and long-term stability. That’s why proper pallet racking installation matters from the start.
When Are Pallet Rack Shims Needed?
Shims come into play when the floor prevents full contact between the upright base plate and the concrete.
This usually shows up in older or worn slabs where you’ll see dips, cracks, or slight elevation changes. Instead of forcing the rack to sit unevenly, shims fill those gaps and create a level bearing surface so the load transfers properly into the floor.
Are Pallet Rack Shims Always Required?
No… pallet rack steel shims are not a standard part of most installations and in reality, are rarely needed.
In over 31 years of selling and installing pallet racking, we’ve only used shims in a small percentage of projects. Most warehouse floors are poured well enough to support racking without any additional adjustment.
Where steel shims do become necessary is in older buildings. Concrete that has settled, chipped, or deteriorated can prevent the base plate from sitting flush. In those cases, shims provide a simple way to correct the issue without tearing up the floor.
What Are Pallet Rack Shims Made Of?
Pallet rack shims are typically steel plates designed to handle the same load as the racking system. They come in different thicknesses so installers can make small adjustments at each base plate. If needed, they can be combined to eliminate gaps and bring the upright into proper alignment.
Generally speaking, they are 4.5″ x 3.5″ x .25″ (10 gauge) material. Of course, shims used in seismic areas, for use with larger seismic footplates are much larger.
Because they’re steel, they won’t compress or break down over time, which is key for maintaining a stable system.
Where Do Shims Get Installed?
Steel shims are installed directly under the upright base plate, between the footplate and the concrete.
Their job is to eliminate any gap so the entire base sits firmly on the floor. If part of the base plate is unsupported, it can create uneven pressure that affects anchors and overall rack alignment.
How Installers Determine Shim Thickness
During installation, each upright location is checked to make sure it sits flat and plumb. If a gap is present, shims are added until full contact is achieved. This is usually done by checking level across the row and making small adjustments as needed.
Shims are also quick and easy to install, which makes them a practical solution when minor floor inconsistencies are found.
How Do You Know if a Warehouse Floor Is Level?
Before installation begins, the floor is evaluated to identify uneven areas. Installers typically use laser levels or long levels to check consistency across the slab. As the layout is marked, each base plate location is checked. If the upright doesn’t sit flush, that’s a clear sign that shimming may be needed.
It’s also important to separate a floor that is slightly out of level from one that is uneven or damaged. A consistent slope can often be worked with, but dips, cracks, or surface damage usually require correction.
How Many Shims Can You Stack?
Sometimes more than one shim is needed, but there are limits.
The total steel shim stack should not exceed six times the diameter of the anchor bolt. Smaller stacks don’t require additional securing, but once you get into larger stacks, they need to be stabilized to prevent movement.
How to Secure Shim Stacks
When required, shim stacks are secured by welding them together or by adding a second anchor bolt.
If they aren’t properly secured, they can shift over time, which can affect the stability of the rack.
Anchor Bolt Considerations
As shim height increases, anchor bolt length becomes more important.
Longer anchors may be needed to maintain proper embedment in the concrete. It’s a small detail, but it plays a big role in keeping the system secure.
Can You Use Washers Instead of Pallet Rack Shims?
No, washers are not a substitute for pallet rack shims.
They don’t provide full support under the base plate and can create point pressure, which may lead to instability or damage over time. Proper shim plates are designed to distribute the load correctly and should always be used.
Why Proper Shimming Matters
Shimming might seem minor, but it directly affects how pallet racking performs.
When it’s done right, it helps keep uprights aligned, reduces stress on anchors, and ensures loads are distributed properly. It becomes part of the overall stability of the system.
Common Questions About Pallet Rack Shims
Do pallet rack shims require inspection approval?
In some cases, yes. Requirements can vary depending on local codes or the authority having jurisdiction, especially if permits are involved.
Can pallet racking be installed on cracked concrete?
It depends on the severity. Minor surface issues can often be corrected with shimming, but structural damage may need to be addressed first.
How do you know if racking isn’t level after installation?
You might notice gaps under base plates, uneven beam levels, or slight leaning in the uprights. These are all signs the base may not be fully supported.
Are shims a long-term solution?
Yes, when installed correctly, steel shims are a permanent part of a safe and stable pallet racking system.
Get Help with Pallet Racking Installation
If you’re installing pallet racking and aren’t sure whether your floor needs to be corrected, it’s worth having it looked at before the project starts.
Most installations won’t require shims, but when they do, it’s important to get it right. A properly installed system starts with a solid base.
If you need help with pallet racking or installation, Midwest Material Handling can walk the site, evaluate your floor, and make sure everything is installed safely and correctly.
