Abstract: An improved fire-retarded insert for forming a fire and thermal barrier between the bottom of a fluted deck structure and the top-of-walls is disclosed. The fire-retardant insert comprises an elongated fire-retardant member and at least one intumescent member in contact with the top, bottom, side, or end surfaces of the fire-retardant member, or positioned within the interior of the fire-retardant member. The fire-retardant member and the intumescent member are circumscribed preferably by a thin flexible film, such as shrink-wrap, to fully encase the fire-retardant insert making the installation easier and safer.