How to Build a Garden Pond

Lay Out Pond Boundary

Start by outlining your pond directly on the ground. The classic way to mark pond boundaries is with a garden hose because it naturally forms wide, gradual curves. If you wish, you can sprinkle flour or chalk dust around the hose to mark the edges of the pond.

It's a fairly common mistake to undersize a landscape pond. Most experts recommend that a healthy, balanced pond with plants and fish should be a minimum of 50 square feet (a surface area of 10 feet by 5 feet, or an 8-foot diameter, if the pond is circular). The depth of a standard landscape pond should be 18 inches to 24 inches, although depths up to 32 inches are possible in very large ponds.

Dig Pond Border

Your next order of business is to dig out the pond border. Using a shovel or spade, make cuts in the ground following the boundary outline. For grass sod, it helps to use a spade, which allows you to make narrower cuts and slide the spade under the segmented turf to remove it. Once the edges of the pond clearly marked, you can remove the hose. 

Excavate the Pond's Center

After the pond perimeter has been established, the long work of excavating the earth from the center begins. To start, remove all dirt within the boundaries of the pond, down to the same depth th/at the border strip was excavated.

Next, excavate down to the lowest point in your pond, wherever that that might be located (typically, this falls near the center of the pond). This helps you establish a baseline for your pond's depth, and no other part of the pond should be excavated deeper than this point. From the center, you can now begin excavating outward to the sides.

Create Tiers

As your excavation moves outward towards the sides of the pond, create flat-bottomed tiers, with each tier about 8 inches higher than the previous one. Concrete building blocks with 8-inch sides make perfect boundaries for these tiers. A perimeter of concrete blocks at each level will serve as a retaining wall to hold back the soil of the next higher tier of the pond.

The goal is for your pond to "step up" as it approaches the sides. A large pond with a 24-inch center depth can have as many as three tiers, each bounded with a perimeter of 8-inch tall concrete blocks; smaller ponds may require just two. Keep the walls of the tiers relatively short, since this will simplify the later step of covering the blocks with rocks. By keeping the height of the tiers short, you can span the vertical distance with one or two rocks.

Reinforce With Retaining Wall Blocks

As you approach the edges of the pond, reinforce the perimeter of the last tier with retaining wall blocks laid over the concrete blocks. This is especially important if the building site has sandy, loose soil—these blocks will help maintain the pond's shape and height. Keep in mind, small retaining wall blocks give you better flexibility and are easier to work with.

Check For Level Frequently

A laser level is a highly valuable tool when building a pond. If you only own a bubble level (or no level at all), you should purchase a laser level, if only for this one project. It's critical to check the tiers and edges of the pond frequently to make sure they remain level and flat. A pond that is slightly off-kilter can't be filled to a uniform water level. 

Lay Hardware Cloth

If your yard has burrowing animals, such as groundhogs or moles, eventually they may find their way to your pond and burrow upwards, piercing your expensive liner. To protect against this, purchase rolls of hardware cloth (1/4-inch grid) and lay it out over the entire base of the pond. Spread about at least 2 inches of dirt over the hardware cloth to cushion it.

Measure For the Liner

Pond liners are expensive, so it makes sense to wait until the excavation is complete to measure and buy a liner to fit the pond. The easiest way to do this is to use a rope to measure the pond in both directions. Begin by placing one end of the rope about 2 feet beyond the edge of the pond, then run the rope down into the pond, flush against the bottom of each tier, and up the other side of the pond, ending about 2 feet beyond the far edge. Use a tape measure to measure the rope to determine this dimension for the liner. 

Take similar measurements for the perpendicular dimension of the pond. Unless your pond is irregularly shaped, these length and width measurements are all you need to buy a pond liner that's a sufficient size to cover your pond. 

Install Pond Underlayment

Before installing the liner, lay down an underlayment to cushion and protect the liner from roots, rocks, and other objects that may damage it. Specialty pond underlayment is available from landscape supply stores, but you can also use pieces of old carpeting.

Install Pond Liner

With the help of a partner, fold your pond liner in half and lay it across the bottom of the hole. Then, unfold it so that it drapes over the sides of the pond. Be patient with this step as you slowly press the liner down onto the pond's bottom, creating folded pleats. While the bottom may have just a few pleats, all of the sides will be pleated. Don't worry about any pleats or wrinkles in the liner—they will hidden by later steps.

Trim down the edges of the liner so that no more than 1 to 2 feet of liner hang over the side of the pond. Secure the edges of the pond liner with stones to hold it in place. 

Add Rock to Pond Walls

Cover the side walls of the pond and each tier wall with natural stone. Start with large and medium-sized rocks, building up the sides until no pond liner is visible. After the walls are entirely covered, you can use smaller stones or smooth river pebbles to cover the entire bottom of the pond.

Fill With Water

Fill your pond with water using a garden hose, keeping in mind that it may take several hours to fill the pond to its maximum level. If you plan to add plants or fish to your pond, make sure to follow recommended practice for the species you are using. This may include allowing the water to stabilize for a period of time, adding chemicals, or installing filtering equipment.