If you’ve bought a new hot tub or spa and you don’t want to sit it on your lawn, building a deck is a great solution. But keep in mind the weight of a hot tub is not typical and neither will be the construction of the deck supporting it. Because of this, the section of deck supporting a spa will be able to stand alone.
In Maryland you are not required to be licensed by the state to build a deck, however you must still apply for a building permit. Each county's building specifications are different and each will supply you with a detailed guide. Here is an example of Baltimore County's deck contruction guide.
Once you have obtained the necessary permits, you may begin. Here's a general process to follow.
Mark the four footing locations. Both ends of a hot tub or spa must be positioned directly over a beam and footers, so that you will always have four footings with a hot tub or spa deck.
Dig the footings a minimum of 24 inches in diameter and down below the frost line (check your local permit office for the frost line in your area).
Pour a concrete footer into each of the four holes a minimum of 12 inches deep. Set in the anchor bolt.
Once the concrete has cured, bolt down the post standoff to the anchor bolt which has set into the concrete.
Set your 6-inch by 6-inch posts into each post standoff. Level the post and backfill the dirt into the hole.
Using a line level or water level, mark and cut all 4 posts to the height of the bottom of the 2-inch by 12-inch joists.
Nail a 2-inch by 12-inch pressure-treated lumber piece between the two posts to form the beam on one end of the tub. Then nail another 2-inch by 12-inch beam to the other side of the same two posts.
Drill two staggered holes through both beams and post and bolt all three pieces together with a 1/2 inch carriage bolt, nut and washer. Repeat for the other post of this beam.
Cut the two 2-inch by 12-inch lumber into 5-1/2 inch wide wood block spacers. Nail them every 12 inches apart between the two 2-inch by 12-inch beam members. This will form a ridged beam that will resemble a ladder from 1 post to the other.
Repeat steps 7 through 9 for the other beam.
Lay the 2-inch by 12-inch joists 12 inches “on-center” (which means they will be 12 inches apart as measured from center of joist to center of joist) and nail to beams.
Close in open ends of joists with a 2-inch by 12-inch board on each end, nailed at each joist with two to three nails.
Lay your decking and fasten.
Install a “rack brace” below the joists. This is a piece of lumber, typically a 2-inch by 4-inch board, run across the bottom side of the joists at a 45 degree angle. It must be nailed to each joist it crosses over and should run from one post to the “catty-corner” post.
Your deck is ready for the hot tub or spa. Be sure to add railing after installing the hot tub or spa if the deck is greater than 24 inches high.