April 29, 2020

Do you struggle with ways to mix up your water features edge treatment? Are you looking to combine a patio and pond with a seamless transition? Have you been looking for a way to blend a pondless waterfall with an existing concrete patio?

If you said yes to any of these questions, then you need to try using flagstone to take your water feature's edge game to the next level!

You are probably thinking, "Flagstone? Really? On a pond's edge? That's what DIY'ers do around their pond and in their waterfalls!" Yes, flagstone can look bad if installed poorly, but I'm talking about using stacked flagstone walls to create an entirely different dimension to your water feature.

Anyone who has ever owned a water feature knows that the serene sound of water attracts all living things. Especially us! People are drawn to it and want to be near it as much as possible. By creating an outdoor living space that is part of the pond, you are inviting someone to be part of that experience.

As professional pond installers for over 20 years, we have experimented and searched for all types of ways to make the water feature and the "hang-out" spot become one cohesive unit. We have found that the stacked flagstone method to be the most fluid and structurally compatible way to accomplishing this. It has been tested, molded, and re-tested over the past ten years into the following steps.

Here is our step-by-step guide on how we install stacked flagstone pond edging:

Design & Layout

  1. The patio should extend over into the pond or stream.
  2. It is best to have the stacked wall curve into a boulder as opposed to a liner edge. 
  3. If using a softer stone, design a smooth and curved edge. If using a denser rock that doesn't cut as efficiently, you may need to make straighter edges.

Excavation and Liner Preparation

  1. Allow at least 12-16" of space between the inside wall and the outer side of the wall. 
  2. t's better to over dig and backfill if needed.
  3. The ground in which the flagstone will sit, needs to be as level as possible.
  4. Once the liner is in, set the boulders and paint the outer edges of the patio onto the liner.

Breaking the Flagstone

  1. Choose a sizable piece of flagstone with smooth and even sides.
  2. Break the large piece of stone by using the weight of a sledgehammer.
  3. Some of the pieces may need to be re-hit into smaller ones.
  4. Look for pieces that are 5-8" in length. Too small and it is hard to secure, too large and its hard curve.

Stacking the Flagstone

  1. When stacking, look for clean vertical edges that will match up evenly. If necessary, you can chip and hit the ends with a hammer. If a hammer doesn't work, a hand grinder may be needed.
  2. Use a thin layer of pea gravel when setting the first layer.
  3. Follow your painted line with the first layer, paying close attention that the vertical joints match up.
  4. Level the flagstone pieces as you go.
  5. We prefer to dry stack the layers, but you could use a small bead of waterfall foam if you need the extra stability.
  6. Just like with laying bricks, or setting tile, be sure to alternate the vertical joints as much as possible for a more secure wall.

Securing the Wall

  1. Once two to three layers have been stacked, it's time to secure them into position. We've used both waterfall foam and concrete. If time permits, we prefer concrete for a more secure wall. However, if you are working on a time crunch and can't wait for the concrete to dry, ample amounts of foam will hold up just as well.
  2. Place foam or concrete along the backside of the wall. We also place concrete or foam along the base of the front edge of the first layer.
  3. Once the first layers are secure, begin stacking the additional layers and spreading the concrete as you go.
  4. It is not necessary to fill the entire area between the inside of the stacked and liner wall with concrete or foam. Backfilling with pea gravel or 1" minus is our preferred rock for backfill.

Matching the Wall Height with the Patio

  1. Matching up the stacked wall with the predetermined patio height can be one of the trickier aspects of the entire process, especially if the patio's level is dependent on the existing concrete patio.
  2. At this point in the process, the wall height should be almost level with the outer bank and leveling height of the flagstone patio.
  3. Be sure that this height is at least a minimum of 2-3" above water level.
  4. If the patio is in front of the pond or stream, keep it low, so you don't block the pond or waterfall. 

Picking and Setting the Top Pieces

  1. Selecting the thickness of the top piece of flagstone is critical, especially if you need multiple pieces that share the same wall. 
  2. If matching to an existing concrete pad, the final stacking height, and the top piece will all need to be taken into account to determine the final height of the wall.

Cutting the Top Edge

  1. Use chalk or a pencil to mark the curve of the top cut. Be sure to cut through the entire stone for a clean visible edge.
  2. Outside curves are much easier to cut.
  3. Keep inside curves long and clean.
  4. If the piece is small and hard to get steady, it may be necessary to foam underneath to secure the stone in place.

Additional Tips

  1. The Saw: We prefer the Bosch circular saw, combined with a 7.25" diamond blade. We've tried the large paver saws, but have not been able to duplicate the tighter curves. They are big and awkward to manipulate when cutting curves. We have found that we can cut much more efficiently with the smaller saws. We use two guys to cut flagstone, one for cutting and one for spraying a small stream of water. The water keeps the blade from overheating and keeps the dust down. When using large pieces of flagstone, a second person is essential for moving and manipulating the stones.
  2. Flagstone Types: We prefer softer stones like Arizona buff, because of the ability to cut flowing curves. We also use some of the denser stones such as Colorado buff, Arizona Red, and Idaho buff. 
  3. ‚ÄčPatio Base: For the patio base, we use a structural fill made of sand and pea gravel. It compacts well and allows for quick and easy leveling.

In Conclusion

The beauty of it is that the stacked wall method can be used on all different types of water features and is not just limited to ponds. Creating an outdoor space that becomes part of the pond is a big game-changer for any water garden. Stacking flagstone can be very tedious and time-consuming, but well worth the efforts. I will admit the first flagstone wall we attempted, added a day and a half onto our project. With a little practice, this method can be a very efficient strategy to add to your bag of edge treatment tricks! 

About the author 

Gregg Sawyer

Gregg is founder/partner of Sawyer Waterscaping in Cheyenne, Wyoming. He built his first pond in his parent's backyard at age 12 and has had a passion for designing and construction natural waterscapes ever since.

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