Rock Backyard Landscaping Ideas
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Rock Backyard Landscaping Ideas

Building A Garden Pond Is A Fun & Rewarding DIY Project

Our small garden pond is tucked between an outcropping of natural granite boulders and under several large oak trees. While most guides for creating water gardens and backyard ponds recommend building garden ponds on a flat, level area in full sun and away from trees and rocks (and this is very good advice), our yard does not offer such optimal conditions. But this did not stop us from building a successful, unique and beautiful garden pond that is filled with healthy plants and fish, and rewarded us with years of enjoyment.

Left behind from the retreating glacier that covered the Northeast during the last Ice Age, the granite ledge and large rock outcroppings in our backyard provided a dramatic backdrop for building a little garden pond. A gap between two boulders left a natural trough that was perfect for building a little stream to trickle down towards the pond, cascading over the edge of a waterfall and then spilling into a small pond that we dug out between the rocks and contained with a cinder block retaining wall.

Building this small garden pond in an area surrounded by ledge and boulders, under trees and on a slight slope was a challenging project, but it was a lot of fun too.

Preparing the Site

We used a garden hose to layout the perimeter of the pond. When building your garden pond, outline as large an area as possible; though the pond may seem huge initially, most pond owners wish that they had made their pond a little larger and a bit deeper. Our small garden pond is a teardrop shape, approximately 11 feet long and six across at the longest and widest points, and almost three feet deep.

Since we were digging the pond into a slight slope and around huge chucks of immovable granite rock, we marked the highest point that would indicate the surface of the pond, and then used a string with a line level to determine which sections of the pond’s edge were below this point. This gave us an idea of the angle of the slope, and the height of retaining wall need to contain the low end of the garden pond.

The low point of our garden pond was nearly 24 inches below the highest point near the water fall. To contain the water on the low end, we built a low retaining wall with full sized and half sized concrete block, and covered the concrete block wall under a berm of dirt. Low block walls can be dry stacked, but use mortar for any block wall more than two courses high.

Digging In

Digging the hole for our small garden pond was a manual effort, one shovel full of dirt at a time. Though a renting or hiring backhoe would have made the job easier, locating our pond between the large boulders made it difficult to position a backhoe around the rocks to help with the digging. The end result was a lot of shoveling by hand.

We dug down as deep as we could, until we hit a ‘floor’ of ledge rock. We used the dirt removed from the hole to backfill the outside of the retaining wall. Dig your pond down at least 3 feet deep (and deeper, if possible), especially if you live in area with cold winter seasons. If you plan to keep fish in your pond, the extra depth prevents the pond from freezing solid during the winter. Deeper water also stays cooler during the summer months, and the fish can hid in the depths from predators such as herons and raccoons.

Laying the Pond Liner

Layer the bottom and sides of the hole with thick layers of newspapers and old carpet padding to protect the pond liner from tree roots and sharp rock. Then, stretch out a thick rubber liner along the bottom, ensuring enough of the liner extends over all of the edges around the pond and above the high water mark. The bottom of our garden pond is layered with a thick rubber roofing liner, purchased from a commercial roofing company that we found online, and completely overlaps the retaining wall.

Started at the bottom edge of the cinder block retaining, we added layers of field stone to create a rock wall inside the pond with shelves for plants and crevices for fish to hide. Slowly, we added water to the pond, adjusting and smoothing the pond liner for a custom fit.

The waterfall and stream was lined with more of the rubber liner, cut with a razor knife and fit with sections of rubber liner. We used a specially formulated exterior grade rubber adhesive (often used for rubber roofing) to glue all of liner seams together, creating a watertight seal. We used the rubber adhesive to glue the rubber liner in place along the rock outcroppings. The rubber adhesive bonds very well with the rough texture of the rock, and has held up well for many years.

Add Water

We continued adding field stone to cover the liner and to disguise both sides of the retaining wall. The spillway for the waterfall was created by carefully selecting and positioning smaller rocks. Adding smaller rocks and pebbles filled in the gaps between the larger rocks, further disguising the retaining wall. Planting patches of moss softened the hard look of the rock, and the small patches of moss spread quickly.

Filling the pond slowly with water (a garden hose works fine), we paid close attention to the liner. Keeping the liner taunt and pressing the liner down against the bottom and up along the sides of the pond as it slowly begins to fill with water reduces unsightly folds. Tucking the liner under the rocks that form the capstones along the top edges of the pond holds the liner in place and finishes the edges with a natural look.

The water might be mucky when you turn on the pump and filter, but the sediment will settle and the water should clear up after a few days. Wait at least a week before adding any fish, especially if using city water. The waiting period allows chlorine and other additives to evaporate, and for the water temperature to moderate to your local climate.