The most popular wood used in the tub construction is redwood. Vertical grained all-heart redwood is strong, watertight, aesthetically pleasing and if properly maintained, will last for 15 years. Other durable and usable hardwoods include cedar, cypress, oak and teak. Redwood is extremely resistant to decay, does not splinter, and swells easily to watertightness. Cedar comes close to resistant on all counts, except it may not be as long-lasting.
Cypress is very durable and resistant to alkalis, acids and other chemicals.
Oak, a hardwood, is extremely durable if maintained properly. Teak is the most durable and decay-resistant of all, and has a natural oily smoothness. However, high price and availability may present drawbacks. Hot tubs are usually four feet deep. A standard 5' x 4' tub holds 500 gallons of water and is generally comfortable for four adults.