Frozen ground under the freezer

A freezer slab without proper insulation and underfloor heating slowly freezes the ground beneath it. Moisture in the sub-base turns to ice, expands and lifts the floor. The damage builds for years before anyone sees it.

How frost heave happens

Insulation slows heat flow; it does not stop it. Under a room held at −22 °C, the ground beneath the slab slowly cools. Once the sub-base falls below 0 °C, the moisture in it freezes. More water is drawn towards the freezing zone and forms layers of ice, called ice lenses, which grow and push the slab upwards.

The process is slow. By the time the floor cracks, the ground beneath can be frozen to a depth that takes a long time to thaw.

Why it happens in the UAE

It is easy to assume frozen ground is a cold-climate problem. It is not. The heat flow under a freezer has nothing to do with the weather outside, and some coastal sites in the UAE have high groundwater, which gives the ice more water to grow from.

What you’ll see

• A cracked or humped floor slab, often worst away from the walls
• Doors that start to bind or drag on the floor
• Racking out of level
• Walls or panels pushed out of line at the base

Designing it out

• An insulated floor build-up on every frozen and blast room: base slab, vapour barrier, insulation and wearing slab
• Heating under the insulation to keep the sub-base above freezing, using an electric heater mat, warm glycol pipework or a ventilated sub-floor
• Temperature probes in the sub-base, alarmed, so a failed heater is found in days rather than years
• Heater circuits checked on every planned maintenance visit

If your floor is already moving

Check first whether the floor heating is working. A failed or switched-off heater circuit is a common cause, and the cheapest one to put right.

• Measure sub-base temperatures, if probes are fitted
• Survey the floor level and cracking to see how far it has gone
• Restoring heating can stop further movement, but thawing heaved ground can let the floor settle unevenly, so it is done under control
• A badly heaved floor usually has to be taken up and rebuilt with insulation and heating