The floor is the surface of the room that carries the most load and is the hardest to put right afterwards. There are two main types. The floor panel is a ready-made panel with the same polyurethane filling as the wall panel, faced on top with non-slip patterned sheet or marine plywood; it is used in small and medium rooms with pedestrian, hand-truck and pallet-truck traffic. The insulated concrete floor consists of a vapour barrier over compacted fill and blinding concrete, insulation board with high compressive strength, a separating layer and a reinforced concrete slab of 12–20 cm; it is the solution for stores with forklifts and racking.
Insulation thickness is chosen by room temperature: 50–80 mm in rooms at 0 °C and above, 120–150 mm in −20 °C rooms, 150–200 mm in blast freezers. The board used under concrete must not be crushed; XPS (extruded polystyrene) or high-density polyurethane board with a compressive strength of at least 300 kPa is laid in two layers with staggered joints. The vapour barrier is always on the warm side, that is, under the insulation, and is joined to the outer sheet of the wall panel; otherwise ground moisture works its way into the insulation and freezes.
In positive rooms floor insulation is sometimes omitted; since the ground temperature is 10–15 °C the loss appears limited, but over large areas it becomes a noticeable item of the load and causes sweating at the foot of the walls. In rooms below zero insulation is beyond debate, and what is more, underfloor heating or ventilation is needed beneath it; otherwise the ground freezes and lifts the floor. In processing rooms where work is done wet, the floor is laid with a 1–2% fall towards the drain; no drain is fitted in frozen rooms, and the defrost melt water is taken outside through an insulated and heated pipe.
Common mistakes: assuming a floor panel will stand up to a forklift (the wheel load dents the sheet and the foam is crushed), leaving the inner sheet uncut at the wall-to-floor junction and so creating a thermal bridge, interrupting the insulation at the door threshold, and leaving the concrete joints open so that wash water escapes into the insulation. As a surface finish, food plants use an epoxy- or polyurethane-based, non-slip and washable coating. By changing the floor insulation thickness in the cooling load calculator you can see the share of the heat coming through the floor in the total load.