Cast iron tub – is made of gray cast iron, a material consisting of pig iron, carbon and silicon together with other compounds to give it additional properties of strength and shock resistance. The metal is glazed porcelain with a coating of a smooth attractive finish. The advantage of cast iron tubs is that the metal composition retains heat longer and sends it back into the water. Acrylic and fiberglass tubs do not have this ability. Keeps the water heating further reduces energy costs.
Cast iron tub normally weighs between 255 to 340 pounds, depending on size, according SunriseSpecialty website. If the average tank holds 42 gallons of water and water weighs about 8.35 pounds per gallon, it would mean that it would hold 350 pounds of water. If you add the weight of cast iron bathtub, the total weight of the tub plus water be as much as 700 pounds.
The above calculation makes clear floor beneath a cast iron tub must be able to support a large amount of weight. If there is any structural weaknesses in the tub, could a floor covering failures collapse flooring, with tub falls to the floor below. Older houses are generally built to support such fixtures because they were commonplace in the past. But water damage and rotting can weaken wood materials in the floor, so careful inspection of the structure of the floor and materials under it will ensure a safe base for cast iron bathtub. Metal shims can be placed under the claw feet of freestanding bathtub distribute weight evenly.