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. A 6' x 4' tub holds 700 gallons of water and is generally comfortable for six adults. Teak is more expensive with prices depending on location and availability of wood. While it is possible to cut cost by using wood of lesser quality than heartwoods, you risk the possibility of splintering and leaks. The Spa Various materials ranging from concrete to hard plastics have been used in constructing spas.