A spa needs a solid level foundation. A spa cannot be set on the grass! The area where the spa sits must support the weight of the spa, the water, and those who use it. If the foundation is inadequate, it may shift or settle cause severe stress to the spa’s shell and frame. Many spas filled with water and people can weigh over 5,000 pounds!
So what do I use to set my Spa on?
Well actually there are many things you can use. We are going to call all of these surfaces the spa pad. The spa pad can be made of pressure treated lumber, synthetic lumber, concrete, bricks or cement patio blocks. A solid cement pad should be no less that 4 inches thick. This is something that the average homeowner may not want to tackle. The spa pad should be at least the size of the spa. If you are going to pour cement pad put a slight slope in it so that water won’t pool under the spa. A 3/4″ slope in a 10 foot wide cement pad is adequate.
If you use bricks or patio blocks, they should set on at least a 3″ base of sand, pea gravel or crushed stone. Sod and roots must be removed before applying the aggregate base. Remember, the base must be under the entire spa. Don’t leave out every other block!!! When using bricks or blocks there is no need to slope the pad because water will drain off in between the blocks.
Building or using an existing deck
Many spas are placed on existing decks. Most newer decks that have been built to code will support all but the largest spas. It is best to talk to a licensed home builder or an architect to be sure. In general if you have a deck or are going to build a new deck the following parameters will support most hot tubs.
Always use treated deck lumber. Use 2″ x 10″ floor joists on 16″ centers and metal joist hangers to support them. Use metal lag bolts or carriage bolts for all the major joist, beam and header connections. Nails and deck screws won’t hold the load. If the span exceeds 10 feet you will want to put a center beam halfway between the span. Posts that hold up the deck are normally made from 4″ x 4″ or 4″ x 6″ treated lumber and spaced no more that 8″ apart. These posts should be cemented into the ground with a footing pad under the post. This will keep the post from sinking over the years.
There are also footing blocks that you can purchase, talk to your building supplier. For the surface boards, it doesn’t matter if you use wood boards or the new synthetic deck lumber. The choice is up to you. Remember: spas are heavy, your deck will need to support at least 140#’s per square foot, that equals a load of 6860 pounds! That sounds like a lot of weight and it is, but it’s very easy to build a wood deck to hold that weight and more. There are many books on building decks. Pick one up at your building supplier; they’re worth the cost.
Prefabricated Spa Pad
Don’t have the time or energy to build the Spa Pad yourself? There is an alternative. It’s a prefabricated portable hot tub pad. This pad is made of high density polyethylene plastic, crush tested to over 5000 pounds per square foot. The EZ Pad is rugged and durable with excellent resistance to impact and abrasion. This light grey pad requires no maintenance. You can place EZ pad on any level well-drained area, including grass, dirt, sand and gravel. It’s also a simple way to extend your patio or deck space. The pad comes in 4 pieces and will fit in most SUV’s. The pad can be assembled and be in place in less than a half hour. Start enjoying your new spa even sooner!