Preformed Concrete Plank or Sections
Because of the joints between the sections, this type of subfloor requires finishing with a concrete topping before flooring is installed. The topping prevents the finished floor from cracking or loosening from the subfloor due to movement of the concrete. Trowelable underlayments are not satisfactory for smoothing preformed concrete subfloors. Concrete toppings on precast concrete must be tested for moisture as for ordinary concrete floor slabs.