How to Figure the Concrete for a Sauna Tub

A sauna tub (hot tub) is larger than a regular tub, holding four or more occupants. It is fitted with high-pressure jets extending from the side. These jets massage the skin and circulate hot water at greater than 104 degrees Fahrenheit. Because of its size, it must be placed onto a concrete pad for optimal stability. Figuring the concrete to a high degree of accuracy will save you time and money. You can calculate the concrete required for a sauna tub in one to two hours, depending on the size and scope of the project.

Tape measure
Calculator

Instructions

- 1
  Measure the length and width of the sauna tub and record those measurements onto a writing pad.
- 2
  Determine the water and occupant capacity for the tub. This is essential in figuring the concrete for the tub slab because the thickness of the slab depends on the overall weight of the tub. Since one gallon equals 8 pounds, you can determine the weight capacity of the sauna.
- 3
  Multiply the total gallons times eight (1 gallon equals 8 pounds). If the tub holds 500 gallons, then multiply eight times 500 to get the total weight of water, which is 4,000 pounds. Take the total weight of the tub, total weight of occupant capacity and total water weight and combine them.
- 4
  Calculate the needed thickness of concrete by taking the total weight (5,500 pounds), dividing by 1,000 (pounds per 2 inches of thickness) and multiplying by 2 (inches of thickness per 1,000 pounds). For example, the above weight of the water is 4,000 pounds. Imagine that the occupant total weight capacity is 1,000 lbs. (based on instruction booklet) and the tub is 500 pounds. Combine these to get a total weight of 5,500 pounds (5,500/1,000x2=11). Round the 11 inches to 12 inches.
- 5
  Multiply the length times the width of the tub to get the total square footage of the concrete slab. For example, if the tub is 8 feet long and 8 feet wide, you have 64 square feet.
- 6
  Multiply the total square feet times the slab thickness to get the total cubic feet of concrete. For example, 64 square feet times 1 foot equals 64 cubic feet of concrete needed. Convert the 64 cubic feet to cubic yards by dividing 64 by 27 to get 2.37 yards of concrete.
- 7
  Round the cubic yards off to 2.5 cubic yards since you cannot order concrete in less than half yards.

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