What is the right concrete thickness for an overhead crane structure?

By Marc-André Martineau
Director & Partner at Premium Industrial Group

Your plan is ready: lifting zones, crane movement, column placement. Everything seems well thought out… until one detail stops the installation: your concrete slab is too thin.

Even if your floor already supports heavy machinery, a freestanding overhead crane structure imposes very different, highly concentrated loads. As a result, your project may need to be modified, delayed, or rethought.

At Groupe Industriel Premium, this is a situation we encounter often. The good news: solutions exist to better distribute loads and maintain your lifting operations.

In this article, you’ll learn why slab thickness is so important, what impact a slab that’s too thin can have on an overhead crane installation, and what options are available to fix the problem without disrupting your plans.

What concrete slab thickness is required for a freestanding overhead crane? 

A 6'' concrete slab can generally support an overhead crane with a lifting capacity of around 10 tons. However, this estimate must always be validated by an engineer based on the actual loads, the structural configuration, and the specifications of the overhead crane. 

There’s a key point to understand when it comes to installing an overhead crane and its structure in your environment: an overhead crane is not a static load. It’s a load in motion, moving up and down (lifting) and in different directions (translating). 

These movements generate continuous tensile and compressive forces during lifting, travel, and braking operations of the overhead crane. If these forces are not properly controlled, they can cause structural shifting or tipping, potentially leading to catastrophic consequences.

This is where the fastening to your concrete slab comes in, to counter the effect of these forces on the installation.

Is your slab thick enough to anchor your overhead crane? 

A freestanding overhead crane structure doesn’t simply rest on the floor it must be securely anchored to it. Each column sits on a base plate that is fixed into the concrete using anchors.

For anchors to be effective, they must be embedded at a precise depth. If the slab is too thin, the anchors may not reach the required depth, compromising the stability of the structure. See the table below for the required embedment depths based on slab thickness.

Suddenly discovering that your concrete slab is less than 6”, even if only in certain places, can be a complication in your project that will impact accessibility for important maneuvers. Which is why we will now discuss solutions for this type of situation. 

What are the solutions to compensate for a concrete slab that is too thin?

If your concrete slab is too thin, several options are available depending on its actual thickness, the crane capacity, and the available space in your building. 

 1 - Install larger base plates under the columns 

These plates help distribute the load over a larger area of the slab. This is often the simplest solution, but it can directly impact your operations: the larger the plate, the farther the column may need to be positioned from the wall, reducing hook approach and limiting certain lifting zones.

  2 - Add bracing to the structure 

Bracing reinforces the structure and redistributes the forces generated by the overhead crane. It helps reduce the load transferred directly to the slab and can be a good alternative when the slab thickness is limited but still usable. 

Example of bracing

 3 - Rebuild a foundation under the columns 

When the slab is too thin, a dedicated foundation can be built under the columns. This is a more involved solution, but sometimes necessary to ensure a stable installation.  At this stage, the company in charge of the work will have to carry it out under the construction decree, i.e. with an RBQ license and a qualified workforce (like our sister company Premium Industrial Structures, for example).

Example column with concrete foundation

In all cases, these solutions must be validated by an engineer based on your specific situation. Before anything else, the first step is to confirm the actual thickness of your slab.

How to verify the actual thickness of your concrete slab? 

The required slab thickness for your project should be specified in your lifting equipment supplier’s proposal and later confirmed in the technical drawings submitted for approval. Unless stated otherwise, it is the responsibility of the building owner or buyer to ensure that the slab meets these specifications.

The first step is to review the building plans. If the information is unavailable or needs to be confirmed, verification can be done directly on-site where the columns will be installed. For example, a hole can be drilled at each planned column location to measure the actual concrete thickness.

Companies can also perform a slab scan. This verification makes it possible to adapt the structure before it goes into production and to detect thickness variations within the same building more accurately than a single hole drilled at a specific location. For example, a slab may be 6 inches thick at the center but only 2 to 4 inches thick along the sides. The scan can also confirm the presence of reinforcing mesh.

 Concrete scanner    Detecting reinforcing mesh    Imaging showing slab thickness variation 

Check your slab before it disrupts your project  

The thickness of your concrete slab can have a major impact on the installation of an overhead crane structure. A slab that is too thin can affect the design, limit certain operations, or lead to unexpected adjustments in your facility.

That’s why this verification should be done as early as possible in the project. If an issue arises, Groupe Industriel Premium can support you with slab scanning services and help identify the right solutions.

Contact us to learn more about this service or to validate your situation before installation.