What Are Bathtubs Made Out Of? A Materials Guide for Homeowners

The tub you choose affects everything from how long your hot bath stays hot to whether your bathroom floor needs reinforcing. If you’ve ever wondered what are bathtubs made out of, the short answer is that most fall into about six material families, each with very different costs, weights, and lifespans. A $300 acrylic tub and a $3,000 cast-iron one both hold water, but they behave nothing alike. Understanding the differences before you shop saves you from a heavy, hard-to-install mistake or a flimsy tub that flexes underfoot.

Acrylic: The Most Common Choice

Acrylic dominates today’s market for good reason. Sheets of acrylic are vacuum-formed over a mold and reinforced underneath with fiberglass, producing a lightweight tub that’s warm to the touch and holds heat reasonably well. A standard 60-inch acrylic tub weighs around 70 to 100 pounds empty, so one or two people can carry and set it without structural worries.

Acrylic resists chips, and minor scratches buff out with a polishing compound. It comes in nearly any shape, from deep soaking tubs to corner and freestanding designs. Prices run $300 to $1,500. The downside is that lower-grade acrylic can flex slightly when you step in, and harsh abrasive cleaners will dull the finish over time.

Fiberglass (FRP): The Budget Option

Fiberglass-reinforced plastic is the lightest and cheapest material, often $200 to $800. It’s molded from layers of glass fibers and resin, then coated with a gel finish. That gel coat is the weak point; it’s thinner than acrylic and prone to scratching, fading, and cracking within 10 to 15 years.

Fiberglass makes sense for rentals, secondary bathrooms, or tight budgets. It’s easy to install thanks to its light weight, but it won’t deliver the solid, premium feel of denser materials. Many tub-shower combo units use fiberglass because it molds into one seamless piece.

Enameled Steel: Affordable and Durable

Porcelain-enameled steel tubs are formed from a single sheet of steel coated with a baked-on porcelain enamel. They cost $200 to $600 and offer a harder, more scratch-resistant surface than fiberglass or acrylic. At 60 to 110 pounds, they’re heavier than acrylic but still manageable.

Two trade-offs come with steel. First, the enamel can chip if you drop something heavy on it, exposing the steel to rust. Second, steel conducts heat away from the water quickly, so your bath cools faster and the surface feels cold against bare skin until it warms up.

Cast Iron: The Lifetime Tub

Cast iron is the heavyweight champion, literally. Molten iron is poured into a mold and coated with a thick layer of porcelain enamel, producing a tub that can last 50 years or more. The enamel surface is extremely hard, scratch-resistant, and easy to clean. Cast iron also retains heat beautifully, keeping a soak warm far longer than steel or acrylic.

The catch is weight. A standard cast-iron tub weighs 300 to 500 pounds empty, and filled with water and a bather it can exceed 1,000 pounds. Many floors, especially upstairs, need reinforcement to carry that load, and installation often requires three or four people. Expect to pay $500 to $3,000 for the tub alone.

Stone, Resin, and Solid Surface

Premium freestanding tubs increasingly use cast stone or engineered stone resin, a blend of crushed natural stone and resin binders. These materials are seamless, retain heat exceptionally well, and have a smooth, matte luxury feel. Solid-surface materials like those used for countertops also appear in high-end tubs and can be repaired by sanding out scratches.

Natural stone tubs carved from marble, granite, or travertine are the ultimate splurge, sometimes exceeding $5,000 and weighing as much as cast iron. They require sealing to prevent staining and almost always need floor reinforcement. Stone-resin tubs offer most of the look at a fraction of the weight, typically $1,500 to $4,000.

Copper and Other Metals

Copper tubs bring a striking, antique-meets-rustic look and have a useful trick: copper is naturally antimicrobial and conducts heat so the whole tub warms with the water. A hand-hammered copper tub develops a living patina over the years. These are specialty pieces, generally $2,000 to $6,000, and need gentle, acid-free cleaning to protect the finish. Cast bronze and stainless steel show up occasionally in ultra-modern designs but remain niche and expensive.

Heat Retention: Which Materials Keep a Bath Warm

If you actually soak rather than just rinse, how well the tub holds heat may matter more than any other factor. Materials with high thermal mass, cast iron and stone, absorb heat from the water and then radiate it back, keeping a bath warm 15 to 30 minutes longer than thin materials. Acrylic and fiberglass sit in the middle: they feel warm immediately because they don’t pull heat from your skin, but they don’t store much, so the water cools at a normal rate. Enameled steel is the worst for retention, drawing heat away quickly and feeling cold underfoot. Stone-resin tubs offer some of the best heat retention without the crushing weight of solid cast iron, which is a big part of their appeal in the freestanding category.

Maintenance and Cleaning by Material

Each material asks for slightly different care. Acrylic and fiberglass scratch easily, so skip abrasive powders and scour pads; a soft cloth with a mild cleaner keeps the finish glossy. Porcelain enamel on cast iron and steel is far tougher and shrugs off most cleaners, but avoid dropping heavy objects that can chip it. Natural stone and copper need the gentlest treatment, mild, pH-neutral cleaners and occasional sealing or waxing to protect the surface and patina. Factoring in the upkeep before you buy keeps your tub looking new for years rather than dulling or staining within a season.

How to Choose the Right Material

Match the material to your priorities and your house. A quick framework:

• Tight budget or rental: fiberglass or enameled steel.
• Best all-around value: acrylic, for its balance of warmth, weight, and price.
• Heat retention and longevity: cast iron or stone resin, if your floor can handle the weight.
• Statement freestanding tub: stone resin or copper.

Before buying anything over 200 pounds, confirm your floor joists can carry the filled weight, especially on a second story. Measure your doorways and stairwells too, since a 5-foot cast-iron tub that won’t fit up the staircase is an expensive lesson. Knowing what bathtubs are made out of turns a confusing showroom into a straightforward decision based on the things that actually matter to you.