While versions of the orginal wooden tubs are still around today, outdoor spas are more common. Aboveground spas, also referred to as “portable,” were introduced to the market about 20 years ago. Portable spas differ from hot tubs in that they are equipped with many more jets (they might contain 20, 30, even 40, depending on the spa size) and have an acrylic fiberglass, or thermoplastic shell and skirting. Between the tub itself and the exterior cladding are the piping, filters, and controls.

By the early 1990s, custom-made in-ground spas were being crafted for upscale homes and over the following years, spa designs have become increasingly architecturally sophisticated. “We’re no longer dealing with the basic, off-the-shelf tub on the deck,” says Doug Jones, principal architect with Keith LeBlanc Landscape Architecture; “the 1970s trend has morphed into something much different.”

The majority of in-ground spas are made out of the concrete form of gunite, which is sprayed into a steel-reinforced form, similar to the way in-ground pools are constructed. “The advantage with gunite spas is that they are much more elegant than above-ground models,” says Katherine Field, a landscape architect who runs her own Rhode Island-based firm. Most spas, she says, are conceived with a great deal of consideration to the landscape of the site on which they are located and have sleek, contemporary designs with intricate tiling, brick, or stone features along the edges and interiors.

“With customized spas, you can control all of the standards. There’s a lot you can play around with,” says Doug Jones. For custom-designed spas, clients are able to select the size, shape, and depth of the spa, and the location and placement of the benches. The average spa seats five to six adults, yet some are made to accommodate as few as two or as many as ten. One of the greatest benefits of a custom-designed spa is that the interior may be designed to fit any ergonomic specifications. It’s not uncommon today for a 6-foot tall male to be married to a woman who is 5-feet, 3-inches tall,” says Richard Johnson, a principal landscape architect with Stephen Stimson Associates. “Obviously, their should heights are much different, and want both of them to be comfortable.”

Katherine Field designed a spa for a family where the husband was very tall. His measurements were taken and the spa was customized to fit his dimensions. “If he were to sit on a normal-size bench, the upper half of his body would be out of the water. We made one of the benches lower for him, so his shoulders were able to be massaged by the jets, and kept the other benches at a more standard height for his wife and children.”

There are usually between eight and ten jets in a custom spa, significantly less than the number found in a portable spa, and Johnson says that is one of the few advantages portable spas have over in-ground models. “If a client is interested in and intensive spa therepy, it’s hard to beat the prefabricated types because they have so many different jets at various positions,” he explains. “It’s difficult to be that elaborate with a custom spa.” However, he continues, placement of the jets is also a customized feature, so while there are may be fewer of them, clients are able to select ideal jet positions in order to target specific areas of the body.

For example, Johnson cites a spa he designed for an older female client who was active in tennis and golf. “She was aware that her hips were very sensitive, so she asked that we position the jets so she could stand in one spot and have jets massage both of her hips,” he describes.

Not only are spas equipped with the components to provide wonderful massage, they may offer health benefits as well. The typical spa is heated to about 104 degrees Fahrenheit and according to the National Pool and Spa Institute, water that warm not only relaxes muscles, but also causes the blood vessels to dilate, lowering blood pressure. The buoyancy of water counteracts gravity, so sitting submerges to your shoulders can make your heart 10 to 20 percent more efficient. Buoyancy also reduces the strain on muscles and joints.

Jones says that the popularity of custom spas has risen recently as people are not spending more time outside and devoting more energy to creating comfortable and unique outdoor living areas. “People are building really elaborate recreation spaces, outdoor game areas, tennis courts, and pools. And the majority of the pools we design are accompanied by a spa,” he says.

While pools and spas are often located on the same site, the considerations behind the exact placesment of a spa are different from those affecting the positioning of a pool. “When designing pools, you’re most concerned with where people will be sitting around it-where the terrace or patio is situated,” says Johnson. “Where the pool itself is oriented is not nearly as important because swimmers don’t generally take in the view of the horizon. People sitting in spas do.”

When selecting the exact spot for a spa it’s vital to remember its purpose; that it serves as a place to be calm. “A pool is an active thing,” emphasizes Field. “A spa is for relaxing. In a spa, you have a much slower observation pace; it should be oriented to where you can have the best view of the property. You want to be able to site in the spa and watch the sunset, absorb the natural surroundings, enjoy a glass of wine,” she says.

However, not all customized spas are located on properties that have expansive views. jones says that some of his clients prefer their spas to be placed in more concealed settings. “For some people, it’s less important to have a beautiful horizon view. They want something private, in an introspective setting,” he explains. “For one of our projects, the client wanted us to put the spa inside a structure, so we enclosed it within a gazebo where it was still possible to connect with the outside elements, but hidden as well.”

Johnson, who does the majority of his spa work for Cape and Islands coastal sights in combination with a pool, says that he also occasionally has clients who request stand-alone spas built in more unique locales. He notes one particular spa he designed that was far behind the house on a knoll in the woods. A rock patio surrounded the tub and a wood-plank wall enclosed the area on one side, so the space really had the feel of being an oudoor room. “The homeowner tells me that it’s a truly amazing experience to sit in the spa on a snowy winter night and look up at the stars,” he says.

Spas typically measure 6 feet by 6 feet and generally are about bathtub depth. However, Jones says he’s often asked to design slightly larger spas known as “plunge pools” or “swim spa” that are up to 4 feet deep and have dimensions of about 7 feet by 11 feet. These oversized spas have benches on the sides and function basically the same way as a typical spa. And while you can’t swim laps in one, you’re able to plunge and swim in place,” he says. He adds that some plunge pools are equipped to move water to produce a current that offers a slight resistance, enabling you to engage in aerobic exercise and light hydrotherapy.

“There aren’t many things nicer than being in the spa in the snow,” says Jones. Many spa owners agree and opt to keep their spas operational all year round. For pools and spas located on the same site, Field recommends that owners have separate equipment for their pool and spa. While it’s possible-and may seem less complicated- to have both share a common filtration system and heater, she says, “If the spa in connected with the pool equipment, you have to manually turn on the main system every time you want to use it and that can be a real hassle. When the spa has its own smaller circulation systems, it’s able to function all year round, and you only have to turn on a switch that gets the heat and jets going before you use it.” Some spas, she adds, even have manual controls in the house, so you can get it ready without even having to go outside.

“Spas are interesting,” says Johnson. “When spas are mentioned, people tend to think of the romantic, of something you enjoy on vacation every once in a while. But really, spas are great things to use on a daily basis. They help you to relax, let you step outside of yourself for a little while. Hey,” he continues with a chuckle, ” I wish I had one in my yard.”