How to Prevent and Repair Frost Heave Under Your Freezer Floor

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How to Prevent and Repair Frost Heave Under Your Freezer Floor

Are you failing to tend to what’s right underneath your feet? Though concrete freezer floors can last up to more than half a century, the underfloor heating system beneath still requires regular preventive maintenance. If you don’t take the proper precautions, frost can form in the sub-grade soils resulting in raised, cracked floors and a host of potential problems, including: safety concerns, operational issues and significant structural damage.

How does frost heave occur?

Soil underneath your freezer floor must be heated, ensuring it remains above freezing temperature. This is achieved through heating systems, such as:

  • Static vent tubes
  • Forced air vent tubes
  • Heated forced air vent tubes
  • Electric heat
  • Heated glycol

However, if your heating system malfunctions and the soil isn’t heated to above 32 degrees Fahrenheit, the extreme cold can penetrate through the concrete floor, past the insulation and  through to the soil. This causes the moisture within the soil to freeze, forming an ice lens that pushes upward, heaving the concrete floor above. Given time, the lens will grow and, in nearly every case, will begin pushing the building foundations up.



What damage can frost heave cause?

Frost heave can cause damage structurally and logistically, including:

  • Compromised operations
  • Loss of pallet positions in racks
  • Threats to worker safety
  • Freezer floor cracks
  • Heaved foundations
  • Significant repair costs
  • Columns and roof members bending to points of failure
  • Loss of facility

The longer frost heave is unattended to, the more damage it can cause. Stellar has seen facilities where foundations severely heaved, bending columns and roof members to the point of failure. In one particular case, the facility was in a catastrophic condition and had to be demolished and replaced with a new building.

How can you repair frost heave?

First, understand the warning signs before frost heave occurs.  Typical signs include:

  • Freezer-floor cracks
  • Uneven freezer-floor grade
  • Tilted, unaligned racking or pallet positions
  • Forklifts experiencing difficulty maneuvering over the freezer floor

Depending on the severity of the floor damage, repairs can range from just mending the underfloor heating system to removing and replacing the wear slab. In all cases, however, the underfloor heating system MUST be fixed and operating correctly. In instances of major repairs, it is essential frozen soils are remediated and re-compacted prior to re-pouring new concrete floors. Stellar’s trademark soil remediation method involves thawing and re-compacting the soils to prevent settlement of the new flooring system.

How can you prevent frost heave in the first place?

As I mentioned previously, properly maintaining your underfloor heating system is imperative to preventing frost heave. Check your system monthly and understand that time is of the essence.

If your facility has underfloor temperature sensors, make sure they are working properly and program your sensors to alarm if the sub soils fall below 40 degrees Fahrenheit. Frost heave can form quickly depending on the moisture in the soil beneath your freezer floor, in addition to surrounding weather conditions. Ensure you keep an eye out for the warning signs above, and take action immediately.

If your plant personnel needs assistance with this, there are a variety of vendors (Stellar included) that can perform an inspection of your underfloor heating system and freezer floor.

Remember, preventive maintenance is critical—from the top of your facility, to the bottom.

If you’d like to learn more about preventing (or fixing) frost heave, feel free to email me at jjohnson@stellar.net.

 

Comments

  • Fabie Evangelista says:

    How can we eliminate frost heave in a refrigerated cold room of -33 degrees C?
    Can i use perforated pvc pipe 4 inches diameter with 3/8 inches ( 10 mm ) perforations above and pipe spaced 1 meter apart and connected to a header pipe 8 inches diameter on to an air blower?

    • Stellar says:

      Hi Fabie. Thanks for your question. Using perforated pipe is not a good idea due to the pressure loss that occurs through the perforations. This can also create other issues such as letting groundwater into the vent tubes. Furthermore, a 4-inch pipe would be too small. I would suggest you engage a mechanical engineering company with proven experience to design and engineer a vent tube system specifically for your -33 C freezer. With a tailored and efficient solution, you can feel confident that you won’t risk frost heave at your facility in the future.

  • Theodore Barber says:

    How can you remediate a converted refrigerated slab into a freezer slab after the fact?

    • Stellar says:

      Hi, Theodore. Thanks for your question. I’m assuming you are looking to convert a significant amount of square footage and not talking about something small like a walk-in cooler. Concrete slabs designed and used in an industrial cooler space that operates above 32 degrees cannot effectively be converted unless provisions were built in during the original construction to do so.

      These provisions would include: underfloor insulation for a thermal barrier, conduit for the installation of self-regulating electrical heat trace, or polypropylene tubing for a glycol system, provided you are using heavy industrial refrigeration such as an ammonia system. If the slab has vent tubes underneath the floor, then I would venture to say the original design and construction was performed with the idea to convert it into a freezer, otherwise there would have been no need for the vent tubes.

      If you are looking at converting the cooler into a freezer for long-term use, then I would suggest having a concrete floor demolition contractor saw-cut and remove the existing floor. I would then have an experienced contractor reconstruct it with insulation and an underfloor heating system.

      Also, slab loading needs to be factored in to ensure the new slab thickness will be the same as the old slab so that you can maintain the same finish floor height in the area. Be aware: Once the old slab is removed, you will need to take out an additional 9 inches of material to allow for a 3-inch sub slab and 6 inches of insulation for the new freezer floor, assuming the thickness of the new concrete is the same as the old slab. As I mentioned earlier, this is dependent on the estimated loads to be placed on the slab.

      I would be happy to discuss this further with you in detail, if you wish. Please feel free to contact me at 904-614-1702. Thanks!

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