Ground Insulation and Frost Heave Prevention In Low Temperature Cold Storage

The floor is the part of a cold store that nobody inspects and nobody can repair cheaply. Get it wrong on a freezer and the slab lifts, the racking goes out of level and the only real fix is to take the room out of service and rebuild it.

Why frost heave happens

Below minus 18 degrees the cold penetrates the ground under the slab. Moisture in that ground freezes and expands, and the expansion pushes the floor upward. The process is slow, cumulative and essentially irreversible once it starts.

Three ways to prevent it

• Below-ground heating cables that hold the sub-base above freezing
• Ventilation gaps that let ambient air carry heat under the slab
• Raised floor structures that separate the cold slab from the ground entirely

Which one suits a site depends on ground conditions, water table, available floor-to-ceiling height and whether the building is new or existing. Heating cables are the most common choice in new industrial builds because they need no extra height and can be zoned and monitored.

Insulation practice follows the temperature

Ground insulation practice differs based on storage temperature. A plus 4 degree chiller has a very different floor build-up from a minus 25 degree freezer: thickness, moisture barrier and frost protection all scale with the temperature difference across the slab.

Three things designed together

Load bearing, insulation thickness and moisture barriers must be designed comprehensively for each project rather than specified separately. Insulation that cannot carry forklift and racking loads will crush; a moisture barrier in the wrong plane will trap water inside the build-up, where it will freeze.