How to Make Concrete Slabs for Hot Tubs

Measure the base of your hot tub. The standard size for a drop-in tub is 6-by-6 feet. You’ll need 2-by-4 boards long enough to create a frame that completely surrounds the hot tub’s base. For a standard hot tub, get 2-by-4s at least 64 inches long. Arrange the 2-by-4s into a square and nail them together to form the frame.

Locate the place where you plan to place the hot tub. Dig down into the dirt two inches, excavating a square area large enough for the wooden frame. Place the frame inside the excavated area. It should be below the surface of the ground, not resting on top of it.

Beside the excavated area, lay the ½-inch rebar down on the ground in a grid pattern. Space each rod 12 inches apart. Fasten the rebar together using the wire ties at each point of intersection.

Place the wooden blocks inside the excavated area within the wooden frame. Space them 12 inches apart, matching the grid pattern you just made with the rebar.

Lift up the rebar grid and place it horizontally inside the excavated area. Lay it on top of the wooden blocks, so it doesn’t directly touch the ground. Nudge any wood blocks that aren’t supporting the rebar into place so each block helps to hold up the grid.

Follow the manufacturer’s instructions and create the concrete mix. Pour the mix into the wooden frame. Add it slowly, so it oozes down beneath the rebar and coats the ground there. Push it down and under each piece with the wooden smoother if necessary. Add concrete mix until the wooden frame is filled and you can no longer see any rebar.

Lay the wooden smoother on top of the concrete and drag it across the top of the mix, smoothing it out to create an even, level surface.

Wait for the concrete mix to set. Allow it to cure for a minimum of four days. Depending on the weather in your area, you could need to wait a week for the concrete to set completely.