What should you know before buying a concrete bathtub?

How much does a concrete bathtub weigh?

It varies by mix and size. Native Trails lists the Avalon 62 in tub, 62 x 36 x 21 in outside, at 650 lb with a 65 gal capacity. It calls the material 40% lighter than standard concrete. Fiber and lightweight mixes exist because ordinary concrete is very heavy for a tub.

Water adds to that. At 65 gal, a full tub holds roughly 540 lb of water, which is 8.34 lb per gallon, before the bather. That puts a brim-full Avalon near 1,190 lb, almost double its empty weight. Solid stone is heavier again: our 67 x 31 x 22 in marble oval is about 1,150 lb empty and about 1,960 lb filled with a 200 lb bather. See the weight guide. Check floor support with a structural engineer.

Does a concrete bathtub need sealing?

Yes. Concrete Decor says proper sealing is critical for any concrete piece and absolutely essential for wet areas like tubs and showers. The most common technique is several coats of a penetrating sealer such as water-based polyurethane. Some fabricators use epoxies or two-part products.

Native Trails seals the Avalon with its own product, NativeStone Shield, for protection from stains, scratches and cracks. Sealers wear and are reapplied on the maker's schedule, which varies by product. Ask which sealer was used, how long it lasts, and what to buy for touch-ups. Stone has its own sealing needs. Honed marble is absorbent and benefits from a sealer, as the care guide explains.

Do concrete bathtubs crack?

They can develop hairline microfissures. Concrete Decor reports that fine cracks appeared after demolding on one bath project, and that the builder did not treat them as a moisture problem because a reactive penetrating sealer was used.

Treat fine surface lines as a feature of the material and large or growing cracks as a defect. Ask the maker how it classifies each, what the warranty covers, and how repairs are made. Native Trails lists a limited warranty on its own page, so read the exact terms for any tub you consider.

Does a concrete bathtub keep water warm?

Thick walls help, according to the maker. Native Trails says the Avalon's thick walls provide insulation to keep a deep soak hot. Engineering ToolBox lists dense concrete at 1.0–1.8 W/m·K, a little below marble at 2.08–2.94, so concrete conducts heat somewhat more slowly than marble, though it is nowhere near as good an insulator as wood or acrylic.

Thick walls and a deep basin (the Avalon has a 19 in interior depth) do the work. For stone, see do stone bathtubs keep water warm.

What does a concrete bathtub cost?

The one published price we could confirm is a retailer listing for the Avalon 62 in tub. Custom and large-format concrete tubs are priced by quote, so we do not state a range.

How does a concrete bathtub compare with a solid stone tub?

Concrete is lighter, usually less costly and can be cast to almost any color or texture. It is a modern, matte material and sits well in a minimal room. Solid stone is carved from one natural block, so its pattern and body are one material with no sealed coat to maintain. Stone is much heavier, and marble etches in acid. Concrete wants regular sealing.

See also stone vs acrylic and stone resin vs solid stone. Pietra Fonte makes made-to-order stone bathtubs, inspected with photos or video before shipping, with exact dimensions and weight in every quote.