5 things to know about a clawfoot tub August 21, 2013 / in DIY Blog, DIY Plumbing, Tips and Tricks, ... but a classic clawfoot tub is made of cast iron with a porcelain finish. An empty cast iron tub can weigh between 200 and 400 pounds. Add water and the weight on the floor will increase to between 500 and 900 pounds.