Decks and hot tubs: What you need to know before you build

By:  Fiberon Composite Decking

Have you considered adding a hot tub to your outdoor space? A hot tub is a relaxing addition to any home, however, you must be cautious when planning the installation. The structural support necessary for the hot tub must be considered and all the required electrical components must be safely installed. Fortunately we are here to offer you some guidance and insight based on tips we found on and

Before installing your hot tub be sure to verify local building codes and contact the services of as many licensed professionals as needed. Remember that safety is the number one priority during the installation


What to look for when purchasing a hot tub

While many people will use the terms “hot tub” and “spa” as though they are the same thing you should remember that if you are installing a device with circulating jets then this will be referred to as a spa. No matter what addition you are looking to make the first thing to do is decide on which hot tub or spa works the best for you.

Two-person spas on average will cost $2000. If you are looking to seat 4-8 people then the cost can increase to anywhere from $2,500 to $10,000, according to While the various bells and whistle such as integrated cup holders, and stereo systems may be appealing, the first to consider is something called “full-foam” insulation, experts say. This high-densitypolyurethane foam acts as a barrier between the spa’s outer cabinet and inner shell, and will also muffle noise also well as decreasing heat loss.

Most importantly you must remember that shipping and installing a hot tub is no small task. These massive units can be quite cumbersome. Speak with decking contractors and the hot tube company about the delivery ahead of time. Plan ahead accordingly for the best possible outcome.


How to calculate the necessary structural support

The best place to install your new hot tub is a flat and level surface like a concrete slab. A 3-1/2 to 4 inch slab will usually be capable of supporting the hot tub, according to industry experts.

But how do you determine the necessary structural support? Simply determine the tub’s dry weight and add the total amount of water weight. (1 gallon of H2O equals roughly 8.3 lbs.) and the number of occupants by the average weight for a person.
Here’s an example from

  • A 56-sq ft. hot tub with a dry weight of 855 lbs. can hold 420 gallons of water and seat 6-7 people (average weight per person = 185 lbs.).
  • 855 lb. tub + 3500 lbs. water + 1295 lbs. for 7 occupants = 5655 lbs. total weight.
  • 5655 lbs. divided by 56-sq ft. = 101 lbs. /sq. ft. = design load the framing must be able to support

After calculating the structural weight you will need to hire a structural engineer to determine how to best install the hot tub.


How to determine the ideal spa location

Even on a small deck, there must be enough room around the hot tub for the cover lift to function and air to circulate. On a larger deck, consider traffic flow around the space.


Other builder recommendations:


  • Wind and rain can ruin any outdoor day in your hot tube. Strategically position the unit in a place with less exposure to harsh elements.
  • Make sure to consider the location of the sun and trees.
  • Privacy is very important! A simple privacy screen around your hot tub can be all it takes.
  • A quick path inside is a must have when the temperature starts to dip during the winter


Power up your hot tub safely


  • Determining the best electrical source is the first step to enjoying your new hot tub. Make sure to leave the installation up to a licensed contractor.
  • Install a ground-fault circuit interrupter (GCFI). The units prevent electrocution by monitoring the current flow in your hot tub.
  • Most zoning laws will require an emergency cut-off switch.


Other safety considerations

The recommended height of your spa is 17-24 inches. This allows guest easier entry into your spa or hot tub. While spas that are flush with deck surfaces can be an attractive option you must remember that this can be quite dangerous. Children and pets can slip and fall into your hot tub by unknowingly stepping on the cover. Of course it is worth investing in a cover with a lock if you have small children at home.


Think about service

Always install access panels or removable steps for easy entry to the hot tub motor.  Leaving at least one side exposed will allow for easier maintenance and service in the future.

If carefully planned a hot tub can be a relaxing and welcomed addition to any home. Hot tubs may require some maintenance but are a wonderful way to get away from it all while staying at home. For further safety tips and information visit the Association of Pool and Spa Professionals website.