Other options for pilings include plastic-coated wood and heavy-duty aluminum. Typically, pilings should be 6–8 in (15–20 cm) in diameter, but if your deck will weigh more than 10,000 lb (4,500 kg), choose 10–12 in (25–30 cm) pilings. [3] X Research source You’ll need to place a post about every 10 ft (3. 0 m) along the dock in order to support its weight. [4] X Research source

The cost of renting a water jet will vary depending on your location and the length of time you need it. These high-powered water pumps typically run on gasoline, and they come with either a 2 in (5. 1 cm) or 3 in (7. 6 cm) diameter hose. Either size will work, but since the hose gets heavy when it’s full of water, the 2 in (5. 1 cm) hose may be easier to use. [6] X Research source If you don’t have access to a water jetter, you may be able to use a high-pressure garden hose instead, but the process will probably take longer.

Burying the piling 4–6 ft (1. 2–1. 8 m) into the ground should give you a tight, secure fit.

Even in a body of water that isn’t affected by tides, the water level may still fluctuate. If you’re not sure what the maximum water line is, ask other pier or dock owners in your area. Cut the beams a little longer than you’ll need them. You can always trim them later if you need to.

If you don’t have anyone who can help you, use sturdy pieces of wood and a pulley system to create a tripod that can lift and hold the pilings in place.

Repeat this process for the remaining pilings. If the force of the water isn’t enough to remove the sand, attach a PVC pipe with a 1 in (2. 5 cm) diameter to the end of the hose to increase the pressure. Use the water jetter to push some of the dirt back into place after the piling is set.

Multiply this length by the number of beams you will need to get the total length of PVC. When you’re choosing the beams that go inside of the concrete, add another few inches to account for the height of the pier or dock above the water.

If you’re building a deck that is larger than 8 ft (2. 4 m), start with a PVC pipe of 18 in (46 cm) and a post that’s about 6 in (15 cm).

It may help to spray paint the pipe in 1 ft (0. 30 m) increments so you can tell how deep it is.

While you can use a pump to clear out the pipe, doing it by hand is safer, since you don’t have to have electrical equipment near the water. If the ground is very hard, you may need to rent a mini-excavator.

The amount of concrete you’ll need depends on the size of your project. For a PVC pipe with a diameter of 12 in (30 cm) and a post of 4 in (10 cm), estimate about 2 bags of Quikrete per 1 ft (0. 30 m) of height. If your pipe is 18 in (46 cm) in diameter and your post is 6 inches (15 cm), you’ll need about 5 bags per 1 ft (0. 30 m). It may be a good idea to rent a concrete mixer for this project.

The PVC pipe will keep the water out of the concrete as it cures.

This part of the process will take awhile, so it’s probably a good idea to get some friends to help you fill and carry buckets of concrete. You may have some excess pipe at the top. You can cut this off with a reciprocating saw after the concrete dries, if you like.