How to Use Mortar in Waterfalls

A backyard waterfall should look like a serendipitous natural glen that just happens to be a few feet off your patio.
Mortar fixes waterfall stones solidly in place.Mortar fixes waterfall stones solidly in place.
It’s important to keep the stone structure stable and to direct the water so it always flows over the stones and back into the pond or reservoir for re-circulation. Water sliding between stones and soaking into the ground will erode the area around a pond or falls, and the falling water level in the reservoir could damage your pump. Use pond liner and mortar to channel the water where it’s supposed to go.

Step 1

Spread flexible pond liner over the area for the waterfall mound, leaving enough to hang over the edge of the pond and end well below water level. Mix thin mortar according to the manufacturer’s instructions. The mortar should spread easily without clumping but be thick enough to remain in place.

Step 2

Apply a thin layer of mortar to the pond liner and position the base stones or boulders on it. Cover the container of prepared mortar so it doesn’t dry out while you build each level of the waterfall. Pile stones and boulders on the base stones, arranging a flat-edged stone for water to cascade over into the basin or pond. When you are satisfied with the configuration, use a putty knife to work mortar into cracks between stones and under boulders. Scrape away any mortar that is visible so the pile of stones appears natural.

Step 3

Spread a little mortar on the tops of the base stones that the next level of rocks will rest on. Stack another level of stones on the solid base you have created. Position the hose or pipe that will deliver water to the top of your falls and let all the mortar dry.

Step 4

Add a second flat rock for water to sheet over and fall on the flat rock below before cascading into the pond. Build the last level of rocks and boulders around the second flat rock and test the water flow. Note any places where water streams away from the cascade stones or between and under any rocks.

Step 5

Adjust the water pipe or hose and the top levels of stones until the waterfall spills over the flat stones and travels to the pond or basin. Use the putty knife to work a bit of mortar around any stones that water flows under or behind. Mortar the water delivery hose in place and camouflage it with stones. Let the mortar dry before turning on the falls.

Things You Will Need

  • Pail or container with lid
  • Dry mortar
  • Water
  • Paint stick mixer
  • Putty knife
  • Flexible pond liner
  • Stones and boulders
  • Water pipe or hose

Tips

  • Mortar will make your waterfall sturdy, but that means it will be much harder to reposition or redesign. Use just enough mortar to secure the stones and redirect leaks, in case you do need to break down the falls in the future.
  • Hide as much mortar as possible to avoid a waterfall that looks like a cemented rock pile instead of a natural stone formation.

About the Author

Benna Crawford has been a journalist and New York-based writer since 1997. Her work has appeared in USA Today, the San Francisco Chronicle, The New York Times, and in professional journals and trade publications. Crawford has a degree in theater, is a certified Prana Yoga instructor, and writes about fitness, performing and decorative arts, culture, sports, business and education .