Installing a Spa on Your Deck
Evaluate the cost of purchasing, installing, and maintaining an outdoor spa to decide if it’s a worthwhile addition to your deck.
Hot tubs and spas come in an array of shapes and sizes and can be equipped with scores of accessories. Accordingly, they have a wide range of prices.
Choosing the right spa depends on its intended use, how big your deck is, and what structural alterations will be required for your deck. In addition, you’ll need to know the cost of installation, day-to-day expenses, and how much you can expect to recoup on your investment should you sell your home.
Different Types of Spas and Their Costs
It started with that icon of laid-back living, the redwood hot tub. Before long, fiberglass versions with circulating jets appeared called “spas.” Today the terms “hot tub” and “spa” are used interchangeably, but because most units are jetted, spa is the term more commonly used.
The most popular spas for decks are 4- to 8-person models costing from $3,000 to $18,000.
Choosing a spa can be challenging. You’ll need to select from a dazzling number of accessories, including cup holders, colored LED lights, even waterproof keyboards.
“The gadgetry is there to catch your eye while shopping,” cautions Erich Johanson, an experienced spa installer in Olympia, Wash. He recommends choosing established manufacturers and narrowing your choice from there. “Look at the national brands and find one you like,” he says. “Then chose a model that has the features you want.”
His top recommendation is for “full-foam” insulation—a high-density, closed-cell polyurethane foam that fills the cavity between the fiberglass tub shell and the outer cabinet and helps reduce heat loss. In addition, full-foam insulation helps reduce noise and adds stability to the entire unit.
Check installation costs as well. They'll be dependent on the size of the spa and the ease of getting it where it needs to be. In some cases, limited access may require the use of a crane to lower the spa into place. For an 8-person spa, expect about $300 for delivery and setup.
Adding Structural Components to Carry the Weight
The safest—and most cost-effective — location for a spa is the lower level of a deck. A deck only a few steps above ground, if built to code, should be able to support 100 lbs per sq. ft.— a filled 8 x 8 spa at 6,000 lbs. works out to about 94 lbs per sq. ft., just within limits. Check your local codes for any restrictions governing the installation of a spa on a deck.
Even better is a reinforced concrete pad, a great option if you're planning a new deck or intend to add onto an existing deck. A 4-inch slab will safely bear 115 lbs per sq. ft.
If you want the tub on a deck more than a couple of feet above ground or on an upper level of a deck, things get more complicated. You’ll need to hire a structural engineer to provide specs for a site-specific framing structure to support the weight.
Expect to pay an engineer $300 to $500 for these services. The necessary framing for a typical backyard deck may cost only a few hundred dollars, but expect to pay much more if your deck is a high-flying structure perched on a slope.
Accessing Power and Water
Spas require a nearby source of electricity. Because water is involved, any electrical hookup for a spa must include ground-fault circuit interrupter (GFCI) protection. This nifty device shuts down the system within milliseconds if it detects the tiniest change in current flow caused by a short circuit. Some spas come with an extension cord with a GFCI built in that can be plugged into a 110-volt, 20-amp circuit.
Larger units require at least one dedicated 220-volt, 50-amp circuit. In addition, there must be an emergency shutoff within sight of the spa, but not closer than 5 feet or farther than 50 feet. A new circuit and shutoff will cost about $800.
Water access is simple; spas fill with an outdoor hose. The spa then heats and circulates the water. Insulated tub covers limit evaporation, but the tub will need occasional topping off. When it's time to empty the unit, all spas have built-in hose bibs so you can drain the water.
Getting in and out of a spa provides opportunities for mishaps. A handrail is a good idea for older—and younger—users. A cover with a lock is must if you have children.
If you plan to build your spa into the deck, it may seem best to drop it into the deck so that the rim of the tub sits on the decking. Unfortunately, this makes it easy for people to fall in or step on the cover, and also complicates getting into the tub. The ideal arrangement is to set the spa partially into the deck so the rim is 17 to 24 inches above the decking. That way, bathers can sit on the rim, swing their feet over, and enter the water.
Hot water feels great, but needs to be indulged with caution. The Association of Pool & Spa Professionals recommends keeping the water temperature between 100°F and 102°F, with 104°F as a maximum. A safe soaking duration is 15 minutes. To keep the spa free of bacteria, you must clean it regularly and add sanitizing chemicals.
Anticipating the Value of a Spa
If you live in a region with a climate moderate enough for year-round use, a deck equipped with a spa should give you a slight edge in selling a home. John Tripp, an appraiser with Foundation Trust in San Jose, Calif., says that spas “normally are assets as long as they have been properly maintained and there is no evidence of leakage or deferred maintenance.”
In other areas of the country, don’t expect much of a return. “They don’t have the payback to meet the cost,” says Richard Koestner, an appraiser with Koestner, McGiven & Associates in Davenport, Iowa. “If they do add any value it would be in the upper price range. It could be detriment if they aren't in the right market.”
People react differently to the prospect of purchasing a house that has a spa. Some buyers may ask that it be removed as a condition of sale. Others will hardly be able to wait for that first soothing soak.