How to Lay a Concrete Pond Liner

Laying a foundation for a pond can be quite challenging. This task should be completed with the utmost care to ensure that all of the construction is done the correct way, thereby limiting any future patch work that must be completed due to wear and tear issues.

Shovel

Spray paint

Level and scrap pieces of wood

Flat stones or tiles

Flexible plastic or PVC pond liner

Waterproof concrete

Sand

Microfiber/fiberglass secondary concrete reinforcement

3/4-inch wire mesh

Rebar or tie rods

Gravel

Rubber-based pool paint (optional)

Vinegar

Clear the ground in the area around the future pond. Spray paint the shape of the pond onto the ground. Lay scrap wood across the pond space and check the level of the pond. Use your shovel to make small adjustments to the ground level. The pond should be completely level in all directions. If laying a pond on a hill, specialized landscaping will be necessary to level the area.

Touch up the spray paint border if necessary. Dig a shelf on the outside of this border about 2 inches deep and about as wide as the border stones/tiles.

Dig out the pond to a depth of 16 inches to 30 inches. The sides should slope into the middle.

Lay flexible pond liner in the bottom of the pond. Try to remove as many wrinkles as possible. Let the pond liner drape over the outside of the exterior shelf. The excess can be removed later. Pond builders in areas that get severe frosts may wish to line it with gravel before setting the concrete on top of the flexible liner.

Cover the flexible pond liner with the wire mesh. If building a larger pond, rebar or tie rods should be used as well. Be careful not to puncture the flexible liner. Shape the mesh to the approximate shape of the pond. If it hovers an inch or so above the liner in places because it is oddly bent, that’s good. Don’t lay the mesh over the outer shelf, only in the pond.

Mix the concrete and sand in a ratio of 1:3 (cement to sand). Add the secondary concrete reinforcement as well. The mixture should be slightly stiff. If the mixture is too runny, add more cement to get the right texture.

Starting in the center of the pond, spread the concrete at least 3 inches thick over the liner and wire mesh. Be sure to cover the wire mesh completely. Spread the concrete from the center outward, up the sloping sides and into the outer shelf. Do this all at once, not over several days or hours. Add another layer of concrete if there is still exposed wire mesh showing. Use a scrap piece of wood rather than a metal trowel to smooth the concrete. Wood is less likely to puncture the liner. Place the border stones into the shelf. Press them into the concrete.

Fill the pond with water once the concrete becomes firm. Do this slowly and gently so the water pressure does not deform the concrete. Using a scrap piece of flexible liner over the wet concrete can be helpful. Remove this after the pond is filled so the water contacts the concrete directly.

Drain the pond after one week. Cure the pond by filling with water and vinegar. The correct ratio is 200:1. For instance, a 200-gallon pond would require 1 gallon of vinegar. Allow the pond to cure for three days. This will draw lime out of the concrete, because lime can be harmful to some aquatic creatures. Drain the pond again and fill it with clean water. Add fish, plants or other aquatic life after 48 hours.

Try to perform this task when there is supposed to be good weather for at least a week straight to limit interruptions in its construction.