Concrete slabs that are designed as freezer section areas must be built specially for such purpose by using insulating material below the concrete slab, between the subgrade and the concrete slab itself. The reason for this is because a concrete slab that is part of a freezer section will also get as cold the temperature of the inside of the freezer itself. This causes the subgrade (soil usually) below the concrete slab to also get cold, which in turn expands the subgrade (soil). Eventually though, if this soil looses enough moisture at any given time, the soil will contract again and the constant expansion and contraction of the subgrade beneath the concrete slab will damage the concrete slab itself. Concrete slabs for freezer sections should be specially designed and planned for high temperature variability.