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The Spa Specialist Inc.

12910 N.  Zuni, Westminster, CO 80234
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Installing A Portable Spa

Part II
Installing On And In Decks

No matter what is written here, the final authority on deck construction is your local building officials.

If you decide to install your spa on a wooden deck (or a trex deck), the structural integrity of the platform is very important to insure a long and enjoyable spa experience. There are only a handful of cheaply made spas that can sit on the bare ground. Those are usually made of Centrex or Rovel ( co-extruded thermoplastic) as it is sometimes called.

Because modern acrylic backed by structural fiberglass is the best known material to make a spa that will last, the shell must not be flexed as the spa is sitting on the deck. Thousands of pounds of water on a weak platform will stress the shell and cause cracks. I once took in a used spa that was sitting on top of a floor drain in a basement. The spa worked fine, but it had cracks all around the upper lip of the shell. As the spa sat there it sank in the middle around the footwell and put a lot of pressure on the walls of the shell. This also greatly lowered the value of the spa.

According to the Deck contractors I have talked with and building inspectors the minimum for a spa deck structure is 2 X 12 framing, usually pressure treated fir on 15 inch centers or 2 X 10 on 12 inch centers. The end plates where the floor framing joists are attached should be double 2 x 12 or triple 2 x 10 for structural integrity. The whole frame should be on top of five concrete pillars about 18 inches square by 24 inches deep, or 12 inch round by 48 inches deep; with the top of the concrete at ground level. Place 4x4 vertical structural supports on top of the pillars. At the center 4x4 support attach a 2X10 under at 90 degrees to the floor joist across the entire spa.

The average spa weighs over 4000 Lb. full of water. The standard is about 80 pounds per square foot.

There is some controversy here among deck builders, partially, I believe, due to the type of woods being used. If you use redwood for the frame, it is not quite as strong as the pressure treated fir. The spa will also be sitting there for a long time, so some of the weaker constructs that seem OK now will start to sag with time.

So far I have never heard a building inspector say that the deck needs to be fixed because it is too strong.

One of my favorite ways to install a spa is to put the spa on a concrete slab, or on a strong sub decking and build up decking around the spa's skirt. Because of the inefficiency of taking a spa shell without the insulated skirt and placing it down in a deck, it is not recommend except in only very warm climates. There is just too much wasted energy doing it that way. I have seen many older spa installations built this way, and they all are expensive to operate, even the ones with three inches of foam sprayed on the outer wall of the shell. Some of the customers tell me horror stories of $150 per month or more in the winter.

Even though the deck level spa lip looks very nice, I do not recommend placing the spa all the way down to the level of the deck for several user friendly ( ergonomic) reasons. I recommend placing the spa about 10 or 12 inches above the decking, and using a spa with a step in area or a high seat. Placing the spa at a height so that the step in is level with the decking makes for the easiest entry and exit. When people soak in hot water to relax, they usually don't like having to "do push-ups" or climb stairs to get out. Also, exiting the spa so you wind up with your butt on the ground is not very ergonomic. It is simply much better to step out over the lip of the spa at ground level, with very little height difference from one foot to the other.

Some people, for aesthetics, will put the spa in the ground, or fully down in the deck. In that case, you must have a spa with steps or a high seat. Many people are now learning the hard way that their stepless spa is hard to get in or out of after spending tens of thousands to get it constructed that way!

There are some rather clever designed spas with a high seat that is a great step for entering the spa. You be the judge if it will work in a deck.

Placing the spa at 10 or 12 inches above the deck also has other advantages. It is much easier to get water samples for testing if you do not have to get down on your knees, bending down to get the elbow length dip, necessary for proper testing. With the spa slightly above the floor level, you can sit on the edge and not get your knees in the snow, dirt, concrete or hard decking. Isn't the whole idea of a spa "comfort and relaxation", not more work!

Removing the cover is a lot easier if you do not have to bend down to ground level. I had a hot tub that was totally in the ground. Getting the cover off was a pain. A cover remover would have made it easier, but it was still too low.

Having the ability to attach the cover straps straight down to the side of the cabinet also has two other advantages. It allows a much stronger hold on the cover by the straps or tie-downs. When the tie-downs are at 90 degrees of angle to the top of the cover it is a much stronger hold against wind than having the straps stretched out and away from the cover. The other advantage is the cover skirt can be much better put to use in keeping dirt out of the spa. I have opened up many spas with the straps stretched out on the deck and found lots of dirt blown in under the cover. In high wind areas it gets really bad.

If the spa has approximately 3 inch rise on the acrylic above the deck, you can make a cut-out in the decking where the tie-downs attach and the cover skirt can be tucked down along the side of the spa. You can also attach grommets to the skirt, anything to keep the dirt out.


In order to install a spa in a deck, the spa must NOT be sealed up so that the spa is not repairable. It is not good to place decking right up to the spa and leave no access. (I do not like spas with no removable panels for access all the way around the spa. I would never consider owning one because that is just too stupid!) I once went out on a custom installed jetted bath, in which the equipment was sealed inside a tiled structure with no access. As far as I know the tub is still not working. I would have had to destroy an expensive and beautiful bathroom in order to fix the pump. Just recently, we had a customer with an indoor spa all sealed up in tile; leaking through to the carpet. I told them to hire a contractor to cut an access so we could work on it. The spa now just sits there empty.

There is not one single spa warranty that covers removing the spa for repairs. If there is no access to the equipment, you will have to pay extra to make the spa accessible. I have been involved with a repair where the spa was leaking, and had to be extracted by eight strong guys lifting it out, at a cost of over $400 to remove and replace it for a warranty repair job.

If you place a spa below the deck, the best way to allow access is with removable decking pieces. I have seen this many times and it works very well.
The decking can be supported by removable floor joists, that are not nailed in place, but are just sitting in a support. It is recommended to have access all the way around, or at least on two sides. If the spa has a problem on either of the other sides, it can be slid over in the hole created by removing the decking.

Another way to install the spa is up against an existing deck. This works quite well, and even better if the spa is 10 or 12 inches above the deck.

The cover lifter or cover remover is a great thing to have. The most popular are ones that keep the cover down and below so the cover is not an obstruction to the view. In order to achieve this some planning is important.
Your spa can be a real pleasure if the cover is easy to operate. If the cover is in the view, it is not the best. Our favorite cover lifter is the Super Lift2 by Ideal Cover company. It allows the easiest removal, and has a lifetime warranty.

There are many ways to install a spa. The common problems with spa installation is just plain lack of forethought.

When you plan for the cover removal device and intend to put the spa in a deck, you can allow cut-outs for the actuating arms on the side of the spa. We have helped customers set a spa this way. The cover can fit down into a recessed area, beside the back of the spa. These spas are usually set on or close to the end of the deck. The cover can actually be mounted so it sits below the top lip of the spa.

The spas mounted in a deck with no possibility of using a SuperLift, can use a Cover Lift or other type of cover remover that lifts the spa cover, folded in half, straight up at a 90 degree angle from the top of the spa.

Any time you can use a cover lifter, you add ease to your spa use, and help the cover last much longer. The constant scuffing and rubbing caused by putting a loose cover on and off the spa, will wear through the cover's plastic seal over the foam core. Once the core is open to the spas water, is starts to become saturated by water. Once the core is soaked, it becomes worthless for insulation, and very heavy. The shortest life on a spa cover is guaranteed if a small person is putting a large cover on the spa and struggling with it. The cover gets abused quickly this way.

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Next month; "Installing an energy efficient spa in the ground"

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