How to Brace a Deck for a Spa

Consult a structural engineer to determine whether your existing deck can adequately support the weight of the deck. He can offer specific recommendations for how to adequately brace the deck. Plan on the hot tub adding about 6,000 pounds of weight to the load, averaging out to about 94 pounds per square feet.

Check your existing support system. Posts should be pressure-treated and 4-by-4 or 6-by-6, depending on the engineer's advice and the height of your deck. Floor joists should be 2-by-10. Replace any inadequate or rotting posts or joists.

Measure the location of your existing posts. Posts should be spaced every 6 to 8 feet. If the distance is greater, you'll need to set a post in the center of the deck. Dig a hole in the ground with a shovel at least 1 foot in depth so the post is located below the frost line.

Add additional posts, if necessary. Screw posts to the floor joists where you dug your center hole, using four 2-inch deck screws, a drill and screwdriver bit. Drill the deck screws 2 inches from the top of the post and into the center of the floor joist.

Install 4-by-4s at a 45-degree angle from the support post to create two 4-by-4s extending from the support beam to the floor joist. The three components should resemble the letter "Y." Drill pilot holes with the drill and drill bit at each butt. Place two galvanized carriage bolts countersunk through a miter's upper half in the pre-drilled holes. Add washers and nuts to the carriage bolts, then tighten with the wrench.

Continue adding 4-by-4s to each post under the deck. Add one 4-by-4 board at a 45-degree angle for corner posts and secure in place with galvanized carriage bolts and nuts.